VERY Expensive Fire Alarm Power Supply | Can I FIX it?

[@TC_here]

Amazing to think the amount of expensive equipment that ends up in landfill over a 50c component. Great fix

[@BuyitFixit]

Very true! and Thanks 👍

[@StuartJ]

Reminds me of a car I once had. The wiper wouldn't park itself at the bottom of the windscreen. The official fix as per the manufacturer, was to replace the wiper control board which was in the hundreds. Turned out to be an inline fuse, which was absent from any circuit diagrams. It would blow, if anything overloaded the wipers, in this case snow!

[@theguyjt7921]

Bought a relatively new refrigerator that was not running. One silly capacitor on the control board and it was back up and running. So a $2000 fridge bought for $50 and fixed for $.03.

[@BuyitFixit]

@@theguyjt7921 I had the same on a freezer too, a few videos back. Mains dropper capacitor had gone out of tolerance causing the power to fluctuate and not drive the microcontroller correctly.

[@theguyjt7921]

@@BuyitFixit awesome. Just ran across your channel today I'll definitely take a deeper dive.

[@terrym1065]

Capacitor.... Why am I not surprised?! 👍👍Nice fix.

[@BuyitFixit]

Thanks Terry 👍

[@nixer65]

Nine times out of ten it will be a capacitor somewhere

[@JohnDoe-bd5sz]

As soon as he showed the 3842 (3845) i was instantly like "Startup capacitor". These fails often

[@bernarddier1060]

I have been an electronic technician for about 60+ years. I am always very suspicious of these electrolytics, as well as all electrolytics in general. Motorola used these caps in some 2-way radio products, and they were a constant cause of failures. This was 30 years ago. Some things do not seem to change. Brilliant trouble shooting!

[@BuyitFixit]

Thanks you 👍

[@luisderivas6005]

That's generally true, especially for equipment expected to run 24/7 in an enclosure with poor ventilation. Capacitors are rated in the number of operational hours run past a certain temperature (typically 85c or 105c). If rated at 5000hrs at 105c, that means it will survive less than a year if operated continuously beyond that temperature. It will also slowly become a resistor, allowing current to leak through.

[@raffaellobottoni871]

Normally such kind of caps wear out due the heat around it. Nice fix! 😊

[@BuyitFixit]

@raffaellobottoni871 Thanks 👍

[@esbrasill]

True, Philips made a TV where a 6.3V capacitor was used in a 10V circuit (Yes both 6.3V cap spec and 10V measure point were in the official circuit diagram!) The probably know the cap will last exactly the warranty period under that abuse.

[@mikeselectricstuff]

Electrolytics in the startup supply are an extremely common failure - maybe half the PSUs I've ever looked at have been down to this. Like this one, they're often close to a hot heatsink. I usually just replace them before looking at anything else.

[@BuyitFixit]

Thanks for sharing Mike 👍

[@JohnDoe-bd5sz]

I agree, back in the day i repaired sat dish receivers, every time there had been a powercut we would get loads of these in for repair. Always the cap on these 3842 SMPS that failed.

[@manolisgledsodakis873]

@@JohnDoe-bd5sz I was in the same business. I made a fortune from Amstrad and Pace PSUs. And Amstrad also used startup resistors (like that 220k) that were not rated for 350 volts, so they would arc and burn out. I even pointed it out to Amstrad's "Technical Manager" but he didn't believe that resistors had a voltage rating!

[@simontay4851]

14:35 That 224 resistor is the start up resistor. The start up cap is slowly charged up via it until the 3845 chip has enough voltage to drive the FET. Once the PSU is running, the chip is powered from the aux winding.

[@SamuelLaurenceJoel]

You're a PRO. The way you explain electronic is crystal clear. Even a non electronic person can learn through your videos.

[@BuyitFixit]

Cheers mate 👍

[@MrBaldypete1]

Saved myself £350 on a new washing machine years ago by changing a cap out on the control board. Also saved my company £1500 on a new hot water system return pump due to a blown capacitor that cost me £2 to replace! Always a bloody capacitor, mate!

[@BuyitFixit]

Nice 👍Yes bloody capacitors 😂😂😂

[@WMartinNI]

I've been a fire alarm engineer for over 20 years. Gent is a racket. Once their system is in place, it's impossible to replace the panel with anything different without also replacing all the field equipment. Check the price of the gent psu-72 if the price of the Nano psu shocks you! We used to be able to do in field diagnosis and repair on PCB components, but with the way everything is certified these days it puts you on very dodgy ground to replace any components. Certification costs so much and the equipment has to go through so many tests to pass that it's just not worth your while to open yourself up to the liability of someone saying your repair means the equipment is no longer certified. The best thing anyone can do is insist on open protocol systems. Gent CLAIMS to be open protocol because they can link up with bms systems for remote monitoring but REAL open protocol means having something like Apollo or Hochiki field equipment that can work across a range of panels so you can stick two fingers up at any panel manufacturer that tries to rip you off with replacement parts.

[@BuyitFixit]

Thanks for sharing 👍

[@TechOne7671]

Same as yourself mate, 30 years in F&S. we have a few small gent systems, when they develop a fault we just replace the panel and detectors with Apollo and Honeywell open protocol panels cause it’s more cost effective and you have a system you can work in in the future. However if you have a big system like a tower block or factory then they have you to ransom. Apparently they have superior algorithms for detecting fire early but that’s no good if the hardware is junk.

[@AlexEatonPDPIGaming]

Old Gent equipment is solid and really good quality. New Gent stuff fails before it’s even been fitted

[@TechOne7671]

@@AlexEatonPDPIGamingthat’s the beauty of Gent being taken over by Honeywell, use the brand name and reduce quality to maximise profits. Thanks

[@kelvinobichere6586]

Good afternoon please having issue with a gent Nano addressable fire alarm panel it went blank and it not displaying on the screen . Please I need solution. Thank you

[@tomaszski9818]

Great fix, I would like to see what was the voltage on this IC after capacitor change.

[@BuyitFixit]

Thanks 👍yes totally forgot to measure it again on camera, but I did after making the video and it was 12V when the power supply was running 🙂

[@manolisgledsodakis873]

@@BuyitFixit It's best to measure that startup voltage with an oscilloscope. That way the ripple is obvious.

[@Leon-qc7fe]

Those UC3845 and PC123 were used extensively in consumer products in the US. I worked on stuff like that for 20 years. I would replace all the low value caps < 100uf in the ones I worked on weather they checked Ok or not. Those ICs rarely failed. Also Zener protection diodes on the low voltage secondary lines would short. Sometimes The switching transistor shorts. Other than that those switching supplies work well

[@BuyitFixit]

Thanks for info 👍

[@JohnDoe-bd5sz]

I agree, used extensively in sat dish receivers in Europe as well. Every time there was a brownout somewhere, we would have tons of receivers that worked fine, but would not restart after the power came back. Easy repair, that made my employer tons of money, as we charged the costumer 1 hour of labor and a 100 times markup for the capacitors compared to what we paid. Best thing, costumer was happy, because the repair price was still about 20% of the price of a new unit, and when we fixed it, it ran again for years

[@BuyitFixit]

Nice 👍I've had similar on TV's in the past where the standby light just keeps flashing and it was the bootstrap cap on the PSU.

[@Ragnar8504]

@@BuyitFixit Last year I had the same issue on an old Sony Betamax VCR.

[@Jesselovespinball]

Great work as always ! I’m a construction superintendent and work with these types of alarms . What I can tell you is that any time something has to do with fire control or life safety systems the prices go up quite a bit . I think because all of these items need to be certified by a second party in order to be used . Almost like paying for a UL listing . For example a commercial metal door frame vs. a fire rated metal door frame . The difference is literally a UL tag that says it was tested and certified for a certain fire rating ie. one hour , two hour etc . Hope this helps .

[@BuyitFixit]

Thanks 👍and thank you for the info 🙂

[@JeffHanke]

Yeah, that was my thought as well. The certification is what probably drives up the price. Be careful trying to sell a repaired one.

[@carpespasm]

@@JeffHanke That's exactly the reason they're so much more expensive. In the unlikely event of a building fire where the alarm system doesn't work, a forensic alarm tech working for an insurance company and/or fire dept will be picking over the scene with a fine toothed comb, and if they catch a repaired fire alarm component they'll be chasing down whoever they can pin to that repair, and who OKed it. It's just not worth the liability for equipment that's expected to work without failure often for decades. All the same, it's cool to see as a purely diagnostic thing, I've seen lightning strikes zombify fire alarm equipment many times where I've been curious just how broken (or not) it really was.

[@jonmarler]

@@carpespasm Nobody wants their CEO on the news trying to explain why they saved a little bit of money to have the fire control power supply repaired after it failed in the field and didn't raise an alarm for a fire. At that point, they would be more than happy to have paid the 500. It's more about perception than reality. I agree that watching the repair is entertaining and informative, but I would never put that board back into service again when lives literally depend on it.

[@BuyitFixit]

One of those power supplies could fail at any moment, should they all be changed regularly? I would think that if a future failure would occur they would sound a mains failure event in such a situation like what happened originally. Personally I would see it no different to changing the batteries or a fuse. Further faults could occur on the rest of the panel so if any fault occurs should the whole system be replaced?

[@kieranplowright7932]

I find so many blown domed caps on computer mother board's. Swop them out for new ones and all is good. Cheep caps that last max two years means company's can keep selling new models every two years. Why are we not surprised 😊 Great work great vid Nice channel

[@BuyitFixit]

Cheers Kieran 👍

[@599miata]

That was an awsome repair mate. The company is making a fortune by selling new boards to their customers.

[@BuyitFixit]

Thanks 👍Yes, you could buy an Xbox series x for the same price 😂👍

[@cajuncoinhunter]

You would think that a 400 dollar board would have a lil better quality everything on it , but you get a bad part every now and then ....

[@pileofstuff]

As son as anything has a "life safety" label on it, the price quadruples.

[@johanbenko7818]

Because the testing is more rigorous and testing has a cost! If you just count the weight of plastics and metal of your car you cannot justify the price of it...@@pileofstuff

[@johnscott4493]

​@@pileofstuffI work in the alarm/fire alarm industry and I agree. But this equipment is made to very high standards and has to adhere to strict standards to be included in these systems.

[@peterlarkin762]

Nice fault finding! I was shouting at the screen to change cap - I've seen those exact type of SMD electrolytics fail in large numbers. Very common in Linn amplifiers from the 00's.

[@BuyitFixit]

Thanks Peter 👍Yes it looked fine, wasn't bulged or anything, but then again these look similar to the caps used on the Sega "game gears" which are notorious for needing to be re-capped.

[@paulmoir4452]

@@BuyitFixit I've had failures with those Panasonic FKs in a rather expensive VFD. But I think I'm suspicious of all SMD electrolytics especially on thermally tricky to reflow boards with lots of copper and large components. Maybe new ones are OK now. I'd be interested to hear other's experiences.

[@JohnDoe-bd5sz]

In general, the 3842 that does not start up, it's very often the startup cap that has failed

[@InssiAjaton]

If I recall, your data sheet for the ‘UC’ chip listed the maximum voltage where the operation HAD to start as 8.8 V. The typical (most units started) was your expected 8.5V. My experience is you better always keep in mind, and check the WORST CASE, rather than depend on a single “typical” number. Well, you got it anyway. Fine job!

[@BuyitFixit]

Thanks 👍I forgot to measure the voltage on the VCC of the IC after repairing it on the video. I did measure it a day or two later and it now reads around 12V.

[@Indiskret1]

Bad capacitors being the culprit is all too common. Just fixed an UPS, also with a failed 50V 47uF, but that was bulging so easy to see from the get go. That was also in the battery charging circuit. Thanks for a great video, subscribed!

[@BuyitFixit]

Thanks for sharing and subscribing 👍

[@waynesharp1690]

Fitted many gent panels. Once didn't realise I connected the batteries in reverse and the plug welded into that white battery socket. Amazingly the panel still worked.

[@BuyitFixit]

😂😂I did see a few diodes around that area on the rear of the board so perhaps they are reverse polarity protection.

[@doogulass]

The dreaded surface mount electrolytic caps strike again. Nice job figuring it out!

[@BuyitFixit]

Thanks 👍Much appreciated 🙂

[@mikeamirault8741]

Quite a few years ago, When i was repairing TVs, VCRs, microwaves, and just about anything electronic, I would always check the electrolytics mounted near a heat sink. The heat dries them out. The smaller values are particularly susceptible to drying out.

[@BuyitFixit]

Thanks for sharing👍

[@simonalmond1804]

I have 3 or 4 of these under my bench waiting for the day i have time to see why they fail, thanks for spoiling my fun and also thanks for saving my time lol, great video as always !!

[@BuyitFixit]

Thanks 👍well now you know what to check and hopefully it's the same issue as this one. Please let me know how you get on!

[@Dime_Bar]

Yeah I've changed my fair share of these in my time as well. Gent Honeywell must be rolling in money, a bit like Scrooge McDuck 😂

[@nikf3188]

@simonalmond1804 If you want to part with one for less than Gent I'll buy one off you to fix :) got a Vig compact in the house (dont ask, toys!) I would love to get working again!

[@c.e.g7448]

Before retiering, I repaired many hundreds of power supplies with this family of chips. The most common faults when not starting up were: 1. Chip fault. 2. Capacitor fault. 3. Startup resistor fault. 4. Zenerdiode fault. Sometimes the chip does startup, but to continue working, the 220K resistor is too high and cannot supply the power needed to keep the chip working. So the capacitor is discharged below the threshold, and the chip stops working. The capacitor is then recharged, and the chip restarts to stop again quickly. You only get small "spikes" on the output of the power supply. For that reason, there is a diode connected to one of the windings of the transformer that supplies power to the chip, so it continues working. This phenomenon happens when there is a short on the output side. It can also happen when the small capacitor, the one you replaced, is leaking too much. The voltage gets just high enough to start, but the leakage of this capacitor is too high for the voltage to rise to the normal working voltage of the chip. That usually is somewhere between 12V and 18V. That should be the voltage of the zenerdiode.

[@BuyitFixit]

Thanks very much for your detailed explanation. I thought that the black diode seemed next to the zener appeared to come from the windings of the transformer so I thought that it must power the IC once it started up. I did measure the VCC to the IC after making the video (I forgot at the time) and it measured 12V. Thanks again, best wishes Mick 👍

[@kareno8634]

Patience, knowledge, skill, and Will to Try ... *Priceless.* Thanks for it All.

[@BuyitFixit]

Thanks 👍🙂

[@theoldbigmoose]

Nicely done mate! .... it's always the capacitor! 🙂

[@BuyitFixit]

Thanks 👍😂😂😂

[@German_byte]

That was a very satisfying repair. I felt elated when the green LED lit up 😊.

[@BuyitFixit]

You and me both! 😂😂😂😂👍

[@brianwood5220]

Excellent job, you've just saved somebody hundreds. Although UK power is supplied to domestic premises at 230Volts, Ofgem allows a tolerance of +10 and -6% on what you receive at your Service Head (Meter) that's 216 V to 253 V, so 251Volts is still within what is allowed.

[@BuyitFixit]

Yes but only just within the spec. The problem is, this was late at night and pitch black outside. When the solar panels kick in, I've seen the voltage rise to 265V at which point the inverter cuts out with an error.

[@brianwood5220]

@@BuyitFixit That does need looking into. By the accent I would say your a Geordie, so that puts you within Northern PowerGrid's remit. You can contact them by calling 105 from a landline, The call is free.

[@bobsoft]

Nice job. Its crazy the price of electronics that are used in health and safety!

[@BuyitFixit]

Thanks👍 Yes I was truly shocked when I saw the price of it!

[@ToltecMerc]

Nicely done sir! Once again a cheap cap takes down an expensive piece of tech.

[@BuyitFixit]

Thanks 👍yes it's usually one small component that brings a whole item down.

[@SeanBZA]

Same issue with gate motor power supplies, which use a similar IC. I keep the output capacitors and some 47uF 63V capacitors to replace those, though they work fine with any value from 33uf to 100uF on the primary side, just replacing the capacitor there, and the 2 on the output side, will fix most of them. good as those PSU units are nearing the $100 mark now, and the fix costs under $2 to do.

[@BuyitFixit]

Thanks for the information 👍🙂

[@giorgikasrelishvili3247]

There is no greater wealth than experience. Thanks for the example.🙏🙏🙏

[@BuyitFixit]

My pleasure 🙂

[@markrainford1219]

Though I would greatly love to experience wealth. 😁

[@BuyitFixit]

@@markrainford1219 😂😂😂😂

[@ricfair9919]

A feature film.. I was following along hoping for an epic ending. Great job using diagnostic logical thinking to solve this one!

[@BuyitFixit]

Thanks 👍Wait until you see the video I'm working on for the weekend. I spend 3 days on trying to fix it!

[@Dave64track]

That was a great fix without a circuit thanks for sharing it's surprising that quite a lot of faults are only caused by a capacitor or a resistor going open circuit or short circuit. It goes to show that in general a well designed circuit the semiconductor components are pretty reliable. I guess the cap failed because it gets the heat from the heatsink which isn't going to help it. Good job another board saved.

[@BuyitFixit]

Thanks Dave 👍

[@TechneMoira]

Good repair, intrepid repair-guy :) I like the logical thinking you used to work yourself through the problem at hand. Very clever to use your powersupply to supply the necessary voltage to get the circuits to work. To quote a famous engineer in one of my favorite shows (his name is Scotty): The right tool for the right job :) Good job all around which is worth a subscription !

[@BuyitFixit]

Thank you very much 👍I've had to come up with some quite creative things in the past when trying to repair things. Even having to delve into reverse engineering software at times too! Check out the FLIR thermal camera video I looked at, and there was the Solar inverter where I repaired it, and they wouldn't give me the service password so I had to reverse engineer the software to figure out how it was calculated. There was also the VTech baby monitor which yielded some unexpected findings!

[@NEW_INSITE]

I'm in Northeast Georgia usa. And when I was working as apartment maintenance supervisor years ago I had to fix a couple of those. I mean the company didn't want to buy them so they knew I was good at electronics and they asked me to give it a try. We had a lot of iron in the ground around us in the apartments were kind of up on a hill. We were getting hit by lightning all the time up there. It turned out it was a fairly easy fix, the ptc's were burnt out on the input protection

[@BuyitFixit]

Nice 👍 In my last video I was repairing a Dewalt 4 way charger which suffered a similar fate, although it was caused not by lightning but by the user plugging the 110V unit into a 240V outlet 😂😂

[@NEW_INSITE]

@@BuyitFixit 🤣🖐

[@robertmjr7996]

Another great video. It's probably just my DIY level experience but, I didn't see anything special that should bring a $500US price.

[@BuyitFixit]

Thanks, apparently a few have mentioned it's to do with testing and certification 🤔

[@jay1st1st]

i use the same brand system, and the expensive bit is the certifications, and of course they have the monopole for the spare parts

[@BuyitFixit]

Yes, but surely the certification is for the design and testing. Someone mentioned that repairing it would be an issue, but I fail to see why. I mean if the fuse blew on you replaced it or you replaced the batteries then it would need recertified too as those are both repairs to a unit that isn't working as intended.

[@mazafreno]

As usual unbelievable fix. Great and thanks!! Have great day!!

[@BuyitFixit]

Thanks, you too!

[@NicksStuff]

Electrolytic cap failure is very common. I'm surprised it doesn't appear more often on your channel. Maybe is it because you're generally looking at relatively recent (i.e. not old) devices?

[@BuyitFixit]

I've had a few cap failures, ones that spring to mind (fridge repair was a 3 items in 1 video) and on one of the caravan PSU's I looked at. I've looked at quite a few old handheld games from the 70s and 80s but the capacitors usually seem OK in those.

[@orion310591RS]

23:17 - Slots that you used for green and red wire are K and A, for diode testing. You need to use 1 or 2 or 3 slots as you did. You can also open device and solder wires directly inside, to prevent bad contact at lever thingy. In that way you also have wires always with device. Great findings. ESR just high enough to drop voltage to disable IC.

[@BuyitFixit]

Thanks and thanks for the tips 👍

[@Mymatevince]

Really enjoyed the fault finding and thought process on this one. Brilliant work Mick.

[@BuyitFixit]

Thanks Vince 👍🙂

[@mikecass8306]

Wow Mick well done, you have saved your customer £400!!!!! 😁

[@BuyitFixit]

Thanks 👍

[@alfredocuomo1546]

And once again it proves out the old adage, "When in doubt replace the electrolytic capacitor". It's amazing how they can screw up so many things, nice catch & as always great video.

[@BuyitFixit]

Thanks 👍🙂

[@luckywetland]

Amazing as always 👏🏻 23:09 Just a heads-up, Mick, the bottom left openings (KAA) in the components tester are used for testing Zener Diodes only, so that's why when you tested the cap it gave you funny results.

[@BuyitFixit]

@@luckywetland Thanks mate, I was just looking ar that the other day and noticed that too 😂😂😂👍

[@d614gakadoug9]

When you use a DMM on a DC range it is important to remember that most DMMs will show you a time-averaged value. For example, a square wave that swings from 0 V to +5 V will usually result in the meter displaying 2.5 volts. If the frequency is very low or the meter is "fast" the displayed voltage may be almost anything between 0 V and 5 V and "unstable." With the UC3845, the voltage reference output will be 5 volts if the Vcc for the IC is above the lower limit. If Vcc is less than the lower limit Vref is pulled down by a resistor of nominally 5k (from text description of Vref in the datasheet). The fact that Vref was reading as 1 volt very strongly suggests that the IC was repeatedly trying to run. The cap that was replaced was almost certainly charging to the turn-on threshold for Vcc. As soon as that happens the current requirement for the IC itself increases and quite a large amount of current may be required to drive the gate of the FET. Normally as soon as the circuit starts running an auxiliary winding on the "transformer' keeps the cap charged. If for any reason the supply doesn't come up quickly enough, the cap will discharge to the turn-off threshold and switching will stop. That returns the IC to requiring only very low current. The cap will charge from the input supply through the high-value resistor, the chip will turn on and another cycle starts. 1 V at Vref suggests tha 3845 was running about 20% of the time, with unknown period. Some additional information can be had with a meter on an AC range if a DC blocking capacitor is used (I think Fluke meters have one internally in most models - check by measuring a battery on AC; the AC reading would be zero if there is DC blocking). If Vref was "stuck" at 1 V you'd expect close to zero AC. If it was switching between 0 V and 5 V you'd get an AC reading of probably hundreds of millivolts or more, depending on the actual waveform and the way the meter interprets it so the value displayed is mostly just a hint of what is going on (consult meter manual). Similarly the voltage on the cap in question would have a moderate AC component (in neither case does the polarity of the voltage actually change but the meter "sees" it as true AC due to the blocking capacitor). An oscilloscope is very much more informative but you absolutely must use an isolation transformer for the AC input to such a power supply unless you have a scope that is isolated from mains ground and designed to be safe if its ground is "hot." Very few fulfill the latter requirement. With a switchmode power supply you can often get some idea of what is going on by simply holding a probe near the power components where it will pick up radiated noise. Use a clip tip for the probe so you have a bit of an antenna. Just don't drop the probe - exciting things happen if the ground on the probe touches something in the circuit and an isolation transformer isn't being used.

[@BuyitFixit]

Thanks for your detailed explanation and thoughts. Yes the meter isn't fast enough to see what's going on if the voltage is changing. I should get myself an isolation transformer so I could then hook up the device under test to it and perform measurements, although a company did just email me and asked if I'd be interested in reviewing one of their handheld scopes which would be isolated from the mains. Thanks again 👍

[@mikebruestle218]

Thanks for taking the time to write all that out! A great majority of KZbin comments on technical things don’t provide much value, but I really appreciated learning a new (to me) troubleshooting technique of using the scope probe as an antenna near parts.

[@eliasbourozrrrs8585]

Use a battery operated scope

[@elsaarmstrong-zp6ng]

You can get a small battery powered scope to measure smpsu ! It’s negative Gnd is floating and maybe up to 600 volts it can measure! Also use x10 scope probe! You get these scopes now for £ 60 - £100 ! Also useful is a ESR meter for checking capacitors to measure equivalent series resistances many about£50 ! It applies about 100khz to the cap and measures the impedance! You can also test coils, transformers with shorted coils! A very useful little device! Fraser🛠

[@steveharvey1398]

Given that the bias cap had gone high ESR, it is likely that the actual voltage on pin 7 of the UC3845 had a large AC component as the chip started, drew too much current for the startup resistor to supply, then shutdown again at perhaps 10s of hertz. Another clue was the average of 1VDC on the Vref pin which is likely to have been starting and stopping as well. I would have loved to see that signals at VCC and Vref on the scope, not just the 8.50VDC & 1VDC average readings. Another easier trick is to simply measure the AC voltage - this will give you confidence that something is not oscillating. After replacing the cap, I have a feeling that the VCC DC voltage was going to be more like 12VDC...

[@Dime_Bar]

Hi Mick just to let you know that i finally got round to looking at one of the faulty ones i had lying around and it was the exact same fault. Thanks, Mark

[@BuyitFixit]

Nice one 👍I'd imagine this is going to be the problem with the majority of them.

[@cajuncoinhunter]

While the end roll ads are running , I'll comment .... Awesome diagnostics and fix ..... I have one of those component testers and I found that if you use the bottom left pin section it will give false readings , as you know it's for zener diodes , I forgot to switch the pins to the other sections a few times ..... Mine is about 7 yrs. old and the 1 pin in the sections do not work for ESR readings , 2 and 3 are spot on , I double checked with my BLUE ESR tester ..... 1 pin works fine with 123 sections for transistors though ..... I did find an old Micronta Dynamic transistor tester 22-025 model new in the box for 20 bux on QRZ ham site ...... A sweet find for sure , I had one 30 plus years ago and it's great for matching transistors ...... You saved that some money on that repair ....... Take Care Mon Ami ......

[@BuyitFixit]

Thanks Cajun and thanks for letting me know about the component tester. I thought that you could use any of the pins. I guess I should look at the manual. I don't use it too often, as normally just use my meter but it does come in handy especially for capacitors 👍

[@gadgetmind]

Those Vcc caps can cause a few different symptoms. The resistor charges the cap, the chip starts up Vref and goes into startup, but then Vcc drops too low before the power from the auxiliary is available. As these alarms are always on, what you see is them not starting up again when power has dropped briefly. If you'd connected your bench supply and mains at the same time, it would have started up just fine, assuming bench supply fully isolated from mains.

[@haczyk84]

Fly-backs often broke like this. You can hook up scope to this cap and in most cases you will see. But your method with adding DC to Vcc of chip is also nice and checking out waveform. Maybe I will do this that way some day :)

[@BuyitFixit]

Thanks 👍

[@d614gakadoug9]

That part of the circuit should all be considered to be at mains potential. You cannot connect an oscilloscope "ground" unless you are using an isolation transformer of the scope has a SAFE floating ground. With many mains-powered scopes the ground is connected to mains ground.

[@haczyk84]

@@d614gakadoug9 yes, I'm using 230/230 classic transformer and ground is disconnected,

[@Beak3er]

I love the disclaimer at the bottom.... And I can read the fine print on my 24" curved computer monitor.

[@BuyitFixit]

😂😂😂😂Nice👍

[@substandard649]

I only have a high level understanding of what you do but man do i enjoy watching you figure stuff out! Thanks for sharing

[@BuyitFixit]

Thanks 👍yes this one wasn't the standard run of the mill repair. Most people would have given up with this, but I've had a fair bit of experience over the years messing around with different devices and code so managed to find a working solution. Hopefully this video will help others with the same problem as I've put a link to the software in the video description with all of the files needed to flash, so hopefully it should be a matter of plugging it in to a USB with the button pressed, then running the program to restore the device 🙂

[@andrewwhite1793]

The startup voltage is quite often dropped from the hv dc line through high value resistors, so a little leakage through the cap will shunt it down and stop starting.

[@BuyitFixit]

Yes, spot on 👍

[@andrewwhite1793]

I have worked on a fire alarm power supply design. These have very high approval costs which does not help the price. This has prompted me to find out how much!

[@tonye4176]

Fantastic!!! You’ve got the best videos and it’s a privilege watching and learning from you, pls keep them coming

[@BuyitFixit]

@@tonye4176 Thanks Tony 👍

[@catdog726]

It was amazing how something so cheap is a good fix how many people would have replaced the power supply with a new one thanks for another great video

[@BuyitFixit]

Thanks 👍

[@killer2point057]

Great video! KZbin needs more of exactly this type of video. Thank you for your time!

[@BuyitFixit]

Thanks for commenting 👍hopefully you'll like some of my other videos too 😊

[@Voyager_2]

I upgraded from a first gen Aoyue hotair station to the Atten last year and its such a upgrade, I love that station.

[@BuyitFixit]

Nice 👍I was using one of those 858D clones, and I've only used the new one a couple of times so far but all of the reviews seemed positive 🙂👍

[@christophermarshall5765]

I was given a high end car stereo that wouldn't work. Fix was easy. When I lifted the lid, there was a capacitor rolling around inside. It fell out due to bad soldering during assembly. I found where it went, & soldered it in place. Stereo was fixed.

[@BuyitFixit]

Well done 👍nice and easy one for you 🙂

[@GlennHamblin]

Good job! I was thinking maybe a bad Zener, resistor, or cap on that start up supply. After it's running VCC for the chip is usually supplied by a small run winding on the transformer. Great troubleshooting in this, it's rarely the ic.😊

[@BuyitFixit]

Thanks, yes I did notice another diode next to the zener which seems to be fed from a tap on the transformer. I forgot to measure the supply voltage on the IC when it was running on the video, but I did afterwards and it was 12V.

I always insist to my students to use an isolation xformer when working on switching power supplies and never rely on a Voltmeter for measurements. Always use a scope. You might have switched your DVM to AC volts. I suspect AC on DC line. You might have gotten some value. Ideally should be near 0VAC.

[@BuyitFixit]

Thanks for that. I sill need to get an isolation transformer at some point, although they also come with potential risks as any ground fault isolator would not trip if there was a problem.

[@Ed_Stuckey]

Great job on finding and fixing the fault!

[@BuyitFixit]

Thanks Ed 👍

[@fouadmida2230]

the small cap near the one you changed looks cracked above the inverter 10:44, nice job as always.

[@BuyitFixit]

Well spotted, I did have a look at that one but it was just light scratch 👍

[@kevinbowes1974]

Hello mate. Down the road here in GUISBOROUGH not far from you. Just letting you know another Tech shares your frustration. And happiness when it works.

[@BuyitFixit]

Thanks mate 👍🙂

[@yang2382]

My goodness I have the exact same power supply on my lap right now, it’s from a honey well fire alarm system, I changed the pwm chip with a ca-888 and it worked fine . My goodness

[@BuyitFixit]

Nice 👍

[@darrenmarrable2530]

Excellent methodical work. Again love your content.

[@BuyitFixit]

Thanks Darren 👍

[@Dutch_off_grid_homesteading]

Heya, nice repair of 50 cents and then it's word 420 euro really nice fix

[@BuyitFixit]

Thanks 👍Someone sent me another which I've yet to look at, and to replace it is £1500!

[@mfr04]

If the electronics sometimes work, sometimes don't, suspect the electrolytic capacitor

[@BuyitFixit]

I just had similar with a Landrover Discovery 4 Bluetooth module. It was working for a while if you disconnected the battery and reconnected it, but after a while it stopped responding and caused the battery to run flat after around 2 days. I've changed two caps, and so far it seems to be working fine (apart from the bloody gearbox in the thing has now started to have problems). Tip: Don't buy a LR!

[@StevieBGoode]

What were the faulty capacitor values?...I couldn't quite make it out on the tester screen.

[@BuyitFixit]

I can't remember off hand but something like 45uF but 8ohm ESR or something like that. The new one was less than an ohm.

[@Growis83]

It’s been known for a while that it was just a dodgy cap that causes these to fail, it was still interesting to see the thought process behind finding the fault though. I’ve had to replace many of these psus over the years, and it’s amazing how many are still out there, but service engineers aren’t testing the systems correctly now because they know the system will probably die when they do it. The most concerning thing is that gent/honeywell seem know about the issue, but never issued a recall, or even admit fault, as far as I’m aware.

[@BuyitFixit]

Thanks 👍and thanks for the info.

[@smbrob]

Nice fix, and good teardown of the working. I also see that you have a new and bigger thing to remove nasty things.😉

[@BuyitFixit]

Thanks 👍Yes I'm sure the new rework station will be used a lot in the future, although it does sound like a jet engine when it's cooling down! 😂😂😂

[@smbrob]

@@BuyitFixit made by Boeing 😀

[@BuyitFixit]

😂😂😂😂👍

[@dbryan6542]

What a skill you have. Admiration 👍

[@BuyitFixit]

Thanks 👍🙂

[@BobCumberbatch]

Brilliant diagnostic process! You have a very real talent for this. Thanks for sharing.

[@BuyitFixit]

Thanks Bob 👍

[@basecom70]

Love your work. Never saw a troubleshooter wearing kilts. Just joking, watched most of your work. Like your thinking process. Surprised not more upvotes. Keep up your sharing and thanks again.

[@BuyitFixit]

Much appreciated!👍

[@thetraindriver01]

Absolutely brilliant bit of fault finding there Mick 👏 👌 loved the meter, scope and power supply at work, I am sure that Mark will be happy about the result, nice 😊👍

[@BuyitFixit]

Thanks 👍

[@Dime_Bar]

I've literally found 2 of these rattling around in the back of the van (no packaging) so I'm assuming they are ones I've swapped out in the past, so when I've got time I'm going to have a look at them.

[@BuyitFixit]

Nice one 👍let me know how you get on 🙂

[@iNireus]

Now that was a gorgeous fix.

[@BuyitFixit]

Thank you 👍

[@wherami]

Excellent job as usual

[@BuyitFixit]

Thanks J S 👍

[@reklaw3603]

nice work! I mind fixing a samsung tv, 65", brothers mate threw it out, bridge rectifier gone, 1.25 to fix it. brothers mate was raging when he found out, as he bought a new one at 1000. ouch!

[@BuyitFixit]

Thanks 👍And well done on fixing the TV. I wonder what caused the BR to blow?

[@reklaw3603]

@@BuyitFixit Manufacturing fault i seen online

[@BuyitFixit]

Oh right, they are usually quite robust unless something fails short circuit further down the line which causes them to blow.

[@simontay4851]

Serves him right. His loss, your gain.

[@chuckbenedict7235]

Surface mount cap like that one caused my APC UPS 1500 to not be able to sense if mains was online...similar to this fault. It would have been great if you would have shown the voltage to the IC after replacing the cap. That would have doubly confirmed the fix and also have shown the impact of the ESR on the old cap on the voltage drop. Otherwise, great video!

[@BuyitFixit]

Thanks, yes I realised that after making the video. I did measure it since then, and it now shows 12V across the cap ans on the VCC on the IC 👍

[@brianvincent6266]

Well done!

[@BuyitFixit]

Thanks Brian 👍

[@meyou5092]

Nice vid. Would have loved to see a final voltage on the new cap . Cheers

[@BuyitFixit]

Yes, sorry I forgot to do it on the video, but it measured 12V as I did it a couple of days later 👍

[@matthewgriffin4761]

Thank you for this fascinating and as always, perfectly edited video.

[@BuyitFixit]

Thank you very much!

[@MuellerNick]

Great find again. I like to watch and learn from your videos. But, just in hindsight, how about changing the Zener to a 9.1 V type. It is a design flaw by the manufacturer. "It works with 8.5 V" doesn't make it work reliably, as can be seen.

[@Sydney268]

They wouldn't sell many £422 psu boards then - built in obsolescence

[@BuyitFixit]

Thank you 👍The voltage when it was running (I measured it the other day out of curiosity after making the video) was around 12V. I think the other black diode just above the zener diode feeds power from the transformer once it's started up. I'm not sure what the "start up" voltage is. It must be higher now, but it's strange as it was already DC from the main smoothing cap, so it shouldn't have really needed smoothed, so unless the internal resistance of the failed capacitor was pulling the line down which would be a viable explanation.

[@kelvinwilson4412]

I spent over 15 years testing and repairing switch modes , I was screaming aux rail cap at the TV lol.

[@BuyitFixit]

😂😂got there eventually 👍

[@LM-wq4fe]

I just had a TP Link Kasa smart switch fail for the exact thing. Capacitor on the power supply for the control chip failed causing the chip to start and reset continuously which caused the relay to turn on and off continuously. Fixed and working now.

[@BuyitFixit]

Nice 👍Thanks for sharing 🙂

[@randyscorner9434]

After fixing several of these for subwoofers, lights, etc I'm tempted to just replace those cruddy electrolytics before doing anything else. They have ALWAYS been the problem.

[@BuyitFixit]

Good advice 👍

[@georgeholme612]

Fantastic video never boring to watch always fascinating to see the end result

[@BuyitFixit]

Thanks George 👍

[@jackzhu5094]

Thanks. A good fix.

[@BuyitFixit]

Cheers 👍

[@sdjmchattie]

Would have loved if you’d checked the voltage on that pin after the capacitor swap. What is a normal startup voltage when everything is working?

[@BuyitFixit]

I forgot to measure the supply voltage at the time, but I did after finishing the video. It reads 12v now when the PSU is running.

[@sdjmchattie]

@@BuyitFixit thanks! That’s quite far away from spec then. I guess it stands to reason that it would be received by you when just barely too low to start the IC. When the IC stopped turning on, the board wasn’t working and was taken out of service.

[@krahwinkel9503]

Always these capacitors. They seem to be in spec and do what they should do, but in the end it always ends with a faulty C again.

[@BuyitFixit]

Yes,faulty capacitors are a fairly common problem 👍

[@cecildramat-ps9eq]

Another job very well done, thank you for you great videos or should I say tutorials . Is there not a single thing you can't fix. Cant wait for the next video.

[@BuyitFixit]

Thank you 👍

[@TheRealBobHickman]

Nice fix. Do you think it was the ESR just pulling the voltage down a bit too low for startup?

[@BuyitFixit]

Thanks 👍Yes that's the conclusion I came to. I did measure the voltage after making the video (forgot to do it at the time) and the chip now has a VCC of around 12V 🙂👍

[@wojciechbajon]

I'm saw similar case, and there in IC application note clearly was described which capacitor should be used. (and designer didn't prove correct)

[@BuyitFixit]

That sounds very similar to the Philips sound bar I looked at. A guy bought a batch of them all faulty and overheating, it was a few videos back.

[@ovalwingnut]

Very ChaLLEnging to troubleshoot a circuit when each one is unique and you know you will never see it again. A labor of love, adventure with a dash of frustration. Basically Very COoL and enjoyable to one's gray matter Thank you 4 the video. Feel free to take the next weekend off.

[@BuyitFixit]

Thanks 👍Much appreciated 🙂

[@ernieschatz3783]

Are you familiar at all with Vicor power supplies? Looking at one right now that is quite complex. It is composed of like 5 chassis mounted cards, 5 or six plug in cards, and has additional sockets for more cards. An input power board feeds 3phase 120/208 into full wave bridge rectifiers and outputs about 280vdc. From there, the power goes to a toroid on the main board and tot he source pin of a MOSFET. The MOSFET gate appears driven by a separate driver board that plugs vertically into the motherboard on the LH side, and there is a supervisory board full of a boatload of opto couplers, thermistors, dual comparitors and the like, which is plugged into the RH side of the motherboard. At the halfway point (fore-aft) of the motherboard is a backplane where several output cards of different voltages plug in lengthwise with the unit from the front. I've never seen anything quite so involved. It looks like the design avoided using inductors outside of the larger ones driven my MOSFETs.

[@BuyitFixit]

It sounds interesting and complex. I've not came across such a device.

[@PF-gi9vv]

Did you ever test the voltage supplying the chip again after changing the cap?

[@BuyitFixit]

Yes, I realised that I forgot to do it on the video, but I did do it the other day just to see what it was if anyone asked. It now reads 12V across the capacitor and to the VCC of the chip when it's running.

[@CannonballCircuit]

Great troubleshooting and fix! One question I have--do you know why the downstream circuits didn't work when you powered the IC directly from bench power supply with 8.80 V? Because supposedly the issue is that a faulty cap with a high ESR would not be able to provide good decoupling to the IC, but once you put a power supply directly to VCC on the IC, the decoupling cap becomes unnecessary right ?

[@BuyitFixit]

Thanks, been a while since I looked at this but I remember when it was running I measured the voltage on the cap and it was 12V. The faulty cap is the bootstrap cap that powers the IC until it starts oscillating, then there's a diode that is attached to a winding of the transformer that keeps the chip running after startup. The bootstrap voltage wasn't high enough to start the IC.

[@Omri.Collects]

Lovely repair 👍🏼

[@BuyitFixit]

Thanks 👍

[@MatthewHolevinski]

I clicked this video from the thumbnail because I swear I have that exact same board and it's broken, that's wild, go algorithm!

[@FrankJCarver]

Of all the defective capacitors I've changed in my time, I have never come across a bulging, or leaking one, or a bulging and leaking one.

[@BuyitFixit]

Very strange. I've came across those a quite a few times, and even recently on the smart plugs video where the bottom sealing bung had nearly been pushed out of bottom of the capacitor and the dumpster TV where the top vent was all bulging up.

[@paulmeynell8866]

Nice fix well done Jerry interesting

[@BuyitFixit]

Thanks 👍

[@jasonputtock4428]

great detective work. I wished you could have show the measurement of that cap before you removed it. I do believe that this idea would never have worked but still im curious.

[@BuyitFixit]

Thanks, usually it's best to remove components to test them as there can be other components in the circuit that skew the readings. I forgot to check the voltage across it after replacing on the video but I did check it later and it's now reading 12V.

[@jasonputtock4428]

@@BuyitFixit well, I did not know you could check the voltage. The question my wife asks me is, what does a cap do - whats its function. My answer is as best I could tell, think of a rechargable battery that but smaller. When power is needed, the power comes from here and in a stablized form with a certain amount of Mah. If specs are bad, then no power. Probably got that totally wrong but ehhhh. Im still learning.

[@BuyitFixit]

@@jasonputtock4428 Yes, I think you put it in a way that most people would understand👍

[@PhilipBryden]

Nice work, well explained and easy to follow through. Just subbed. Good to see another fixer from (what sounds like) my neck of the woods.

[@BuyitFixit]

Thanks Phil 👍I'm not sure where you're from but I used to live in the Northeast but now over in Cumbria.

[@PhilipBryden]

@@BuyitFixit yes, I'm from South Shields.

[@BuyitFixit]

Lived there most of my life, then moved to Durham about 20 years ago, then Cumbria about 5 years ago.

[@luisderivas6005]

If you want a challenge, try working on a power supply for a vintage 80's-90's digital oscilloscope. Like a TDS714L.

[@BuyitFixit]

Interesting, I do like a challenge 🙂 I've had a few such as the FLIR thermal camera I repaired or the solar inverter where I needed the service password and had to reverse engineer their software or the recent video I did on the AVerMedia video capture device I repaired 👍