EEVblog

[@gglovato]

thumbs up for Dave using the old DS1052E when he has those fancy new DSOs around!

[@EEVblog]

That was deliberate. Keep'n'it real :->

[@gglovato]

EEVblog hahaha down to earth and back to the roots ;). BTW, what use will you give that filter? :D, fundamental friday experiment?

[@MrCarlsonsLab]

Hi Dave. I enjoy your videos, and have also checked out the "Live Cam" too. I also have some SRS test equipment. Not badly designed, but could have used a little more thought.... IE: my SR780 has the power switch on the back. What the heck were they thinking?? With your SRS filter.... A big part of the regulator heat issue is the missing lid while servicing, on top of the already missing heat sink problem. You can see the air gets pulled in (or pushed) through the side of the case, and would travel right over those regulators. Computer fans push or pull air in a somewhat conical fashion . This would place those regulators in the direct path of air." So they did their homework in that respect. Still..... It's a screwy design! I think EMI and RF noise are the reasons they didn't go for a switching power supply. The cost in added filtering, shielding, and "engineer brain power" was probably worth more than the linear supply they built it with. I'm sure the "bean counters" are a little to blame for design deficiencies. Take Care :^)

[@Mythricia1988]

Might not have been the most in-depth repair video, as you hoped for, but it certainly planted the idea in my head to check for missing heatsinks or keeping in mind heat in general. I am actually really surprised by the behaviour of that regulator - I would not have thought of it as a problem. But now I know!

[@superdau]

That's the overload protection of the lm78xx (or similar linear regulators). It's mentioned in the datasheets, which you should definitely always read, if you build stuff, even if you think you know your parts (like in this case it really helps in troubleshooting). Depending on the manufacturer many datasheets don't even give a "continous current" or "maximum wattage" rating, they just tell you "internally limited".

[@latengocomoburro]

These are the ones I enjoy the most.... I get lost on the complicated ones.

[@GrahamLeach]

latengocomoburro I bet you'd be surprised at how the complicated ones get a lot less complicated if you watch them 6 months later, after having watched a lot of the "simple" ones and (BETTER YET) trying to do some repairs yourself. If you have a HackerSpace nearby, go and hang out during a repair cafe day - and if they don't know what that is, organize one! repaircafe.org/

[@TomaszWota]

Graham Leach That.... sounds awesome, actually.

[@darrenjacobson7456]

Considering that this thing was held shut with different types of screws, I reckon someone has had this lying around as a parts donor, probably since after the mains filter died. Then at some point they needed a heat sink and grabbed one from in there, that'd be my guess as to why it's missing.

[@spiros1994]

Maybe the high temperatures you get are cause by the no airflow from the fan because the case is open. Try with closed case too

[@DantalionNl]

thought the same thing especially since the hole in the case is on the right side, so if you close it the air will go from front right to center crossing all the regulators.

[@KristinnVidar]

Lan Party Hosting I agree, but hard to measure stuff when closed, put an external fan to blow some air around it and check again. Box like that is of course engineered to work correctly when closed.

[@rbarkoch]

Don't even care that it was a simple repair. The repair videos are still great and really interesting. Keep them up!

[@thomaswilson4495]

Great video, Dave. Not as complicated an issue as I initially thought. Good lesson to take notice of things like missing heat sinks. Cheers.

[@TimFeleppa]

Good to see the old DS1052E still being used!

[@ChaplainDaveSparks]

Great bit of detective work on that hardware. It shows how randomly trying to diagnose/fix things often makes things worse. I remember as a teenager many attempts to repair the family vacuum tube television. Back then that would generally consist of removing all the tubes, visiting the local Rat Shack, trying inserting them one by one into the tube tester, and replacing the ones found to be defective. I'm guessing that someone with just enough electronic knowledge to be dangerous tried to fix this, randomly disassembling parts of it, then gave up and put the cover back on, minus a few components. Removing a heat sink, though, is the work of a neophyte. It's just like trying to fix an old single cylinder gasoline (petrol) engine by first adjusting the carburetor, which is usually the LEAST likely thing to be out of adjustment.

[@OneBiOzZ]

2 things, for one is the falloff better? and two, the 7805 had a silpad on it and the TIP did not and they were right next to each other were they mounted on the same heatsinc? make sure the TIP is not overheating!

[@keefebaby]

Alyx yes that’s what I was thinking probably sharing a heat sink, why else would you have an insulator on the reg if it had its own isolated heat sink

[@GrahamLeach]

Thanks very much for repairing this piece of equipment and demonstrating what it is used for. I recently got something similar and hadn't the foggiest idea of what it does, how to hook it up, what it might be used for and how to wire it. Now I am very happy that I included it in lot purchase that I made the other day. Thanks again.

[@BradMorrisKA3YAN]

Dave, You (and possibly many of your viewers) may view this as a really simple video, but that's because you have so many years of experience with this type of work. As someone who has really just begun serious electronics troubleshooting (been tinkering for many years), the simplicity of the failure mode may have eluded many of the "young players" including myself. I mean...a heat sink? Geez. BTW, thanks for posting the video!!

[@vex9060]

I'm glad watching useful videos Dave! :)

[@frankschieschke3442]

Hi Dave, i suggest that the 12V fan is connected to the +15V and the +5V. That is the reason for increase the RPMs while the +5V dropped. I also suggest, that the original heatsink was like a L-shaped sheet of aluminium, which is screwed to both the 7805 and the transistor and has cutouts for passing the fan blow through. In the upper corner you can fix the sheet to the fan holes. Frank

[@SiorusBzns]

Couple years late to the party here, but with respect to the thermal performance: Remove the stamped fan grill, replace it with a wire grill, and flip the fan around. Airflow volume isn't _directly_ related to heatsink performance; airflow velocity is. The two values are (obviously) related, but the latter is ultimately what affects heatsink performance. Running the fan as an intake will generate more directed airflow over that power supply section than running it as an exhaust would (by virtue of the fact that axial fans tend to pull air in from every direction while the output is at least somewhat collimated) and produce a significant decrease in operating temperature on those voltage regulators. I don't think this thing uses enough power for the fact that you'd be pushing pre-warmed air across the mainboards to matter; I don't really expect the temperature rise to be meaningful. In fact, if you ditch the existing grill and reverse the airflow direction you can probably run a fan that's rated for perhaps as little as half the airflow and static pressure of the current one and still improve thermal performance. I'd recommend something from Sanyo Denki; they're of markedly higher quality than EBM-Papst or Delta and they tend to be quieter for a given flow/pressure curve. Nidec would be excellent, too, but they appear to be hard to come by, at least in the states. Mouser and element14 both carry Sanyo Denki (not sure about australia-specific distributors).

[@behrensish]

I really enjoy watching your videos. You re-ignited my interest for EE. Too bad I spent so many years on computer Science...

[@leppie]

Cool :) How about a short cleaning video? Like dealing with those BNC's, writing and rust.

[@eurias-nl]

(Note ADVERTISEMENT !!!! ) To make a comparison with a competing product, as a supplier of used equipment, I can wholeheartedly recommend the Kemo VBF8. That model has approximately the same options in terms of filter characteristics. Their gain is only 0 or 20 dB, and the channels have a common power supply. Additionally the filter slope can be reduced to a Bessel-like "pulse respons" shape. But their power supplies do not have the disadvantages mentioned in this video. The power supply of the VBF8 is designed with a toroidal transformer and such a two-channel instrument consumes no more than about 13 - 15 Watts. And because they contain no LED displays or microprocessor, the VBF8 does not require a fan, and adjustment of cut-off frequencies works with mechanical rotary switches. For those who want to use such a filter instrument, Eurias can supply a number of units that were assembled in the previous century. With minor signs of use, no rusty connectors, calibrated and tested, they still function as well as when they were first put into use. In addition to variants with an elliptical response, there are also some with an 8-pole Butterworth response. And they are supplied for connection to a 120 VAC or 230 VAC mains voltage, to be specified on order. Someone else published a video on the Kemo VBF8 at : kzbin.info/www/bejne/rHemoZulZpdpfNU

[@40ishcosplay9]

Hey Dave, don't put the repair down. I think this is a great example for a beginning service tech in any field. I've been a tech for over 30 yrs and plain observation is a hugh part in repair of any item. As soon as you noticed wrong screws in the housing, you should always expect anything. Tamper damaged equipment can be a nightmare to repair so rejoice in your ability to find a solution when someone else couldn't.

[@redtails]

5:30 wow.. it's amazing that someone noticed this in the previous video, i would never have

[@PerryCodes]

Didn't see a follow-up test on whether or not switching the filters out was functioning correctly. This was one of the issues brought up in the first video.

[@1337NoMad1337]

Question: What would you imagine a non-BER kind of repair would be like? Either it''s some simple stuff like the power supply or it's some not-so-obvious stuff like dead custom parts. Just like you already said. I think BER does not apply to you: Even if the faulty device can't be repaired by you, it's still a video you can release. If it's really hard to repair(/takes really long to find out it can't be repaired): more videos for us to watch. Maybe disappointing to see we're not getting to the finish line, but I don't think the majority of people tune in to see why your device malfunctions. They tune in to see you poking around in that device. In this sense: I like that video. Keep 'em coming.

[@EEVblog]

See my attempted DSA repair videos a while back, that looks like it's probably BER

[@jabelsjabels]

Oh hey, congrats on your 700th video Dave!!

[@DaveCurran]

Presumably the heatsink was removed to give access to the mains filter as part of previous troubleshooting efforts?

[@Tutoelectro1]

If you stop the video in 1:55 and then in 2:07 you will see that it has dimmed gradually.

[@tonyman1106]

plus both of led screen dim at the same time and rate

[@DavidTelesPortugal]

I saw you filming this video on the live feed :P

[@TheAmmoniacal]

I have watched it for one minute, nice video!

[@microteche]

Troubleshooting can be very satisfying even when someone else is doing it, good outcome.

[@JohnAudioTech]

I too see blown regulators now and then. Some are IC, others a zener and pass transistor. I can see they had a hard life because the heat darkens the board around the regulator IC/transistor. Simple calculation to find heat given off and use proper heat sink to keep temp down.

[@sal4]

Great video, enjoyed it very much. Thanks Dave =D

[@alancordwell9759]

The fan is only held in by one screw too! The phantom parts robber was here! ;) But why would the reg have a conductive pad, and all the other regs not have, unless the heatsink was bolted to.... the fan frame via the missing screw??

[@robertjung8929]

I think there was a bigger heatsing - a common one for the 7805 and the TIP for fan controll. and the common heatsink is the reason why there is a isolation silicone tab on the 7805. (why else would the tab be there with a dedicated freestanding heatsink ?)

[@bumelant]

Dave, I think you should use your Flir camera in this case.

[@boby828]

Great set of videos! I just bought an old BK-Precision O-scope and it was listed for parts or repair, so videos like this are really helpful in pointing out what I should potentially be looking for. Man, that's a pretty nice piece of test equipment! it will be much easier than breadboarding some filters, meh :(

[@drstrangelove09]

Great fun! Thank you Dave! :)

[@MrHolesVids]

Grats on 700 vids man.

[@BrackenDawson]

Why does it have the sil pad? One heatsink shared with that component to the right perhaps?

[@theinsanityunleashed]

Love the repair vids Dave!!!

[@blackIce504]

that 5volt regulator with the tip transistor next to it should be a current pass transistor as there is enough digital stuff on those boards to easily go over 1amp or maybe 2. just a thought.

[@baghayi]

because of a dash attached right after 621, youtube wasn't bringing this episode on it search result by searching "EEVblog #621". I could find if through google search engine though. thought to tell you. others may have the same issue finding it.

[@JohnBailey39]

Not a juicy repair perhaps, but a nice example of things to look out for, for us "young players".

[@C6R1S]

Nice videos, To me this looks like it may have been an Instructors/Professor equipment used to test students to see if they can determine the causes of failure. Being that all "repairs" were isolated to very generic areas. The only thing truly baffling was the front mount clean ac output not having continuity to one of the poles. Other than that the secondary wire, heat sink, and mismatched screws give it away. Had something similar in my electronics class a few years ago. Instructor changed out a 5v regulator down to 3.3 to give it a little randomness.

[@Systemrat2008]

Perhaps the temperature of these regulators would come down a lot with the lid on thus forcing air flow via the two cut outs in the front of the sides.

[@marcop3517]

Was the lithium battery changed some time ago and perhaps the person removed the heatsink and couldn't be bothered to put it back?

[@mtabernig]

7805 is only 1A can not feed all the segments on that display for too long without disipaiting the heat.. needs a power transistor to carry the load though an inverting OP

[@CrobbDawg]

Ugggh that's horrible. Chuck a decent heat sink across those 4 infront. I'm also wondering if there was a shroud for the fan to direct airflow over that area.

[@lloydieization]

I think the person trying to fix the unit originally didn't check the open circuit on the transformer and went to town trying to diagnose the transformers secondary wiring and the regulator. Another possibility was that a faulty transformer was replaced and then coincidentally the AC input filter failed, causing the repairer to give up thinking the PSU was damaging the transformer. which everyway the repairer would have been a junior like myself. My two cents

[@jamesrbrindle]

ripper! Bladdy yank design! Hehe, nice result, given me a hint on looking for a fault on something on my shelf. Always the simplest of fixes.

[@stephenrowley4171]

Is the 5volt reg the original it looks a bit wonky, I wonder if its an poorly attempted repair

[@EEVblog]

See the new link to a photo in the video description, that will explain everything in these videos - a big convoluted metal heatsink bracket is missing!

[@chrisscott1547]

If the vr is a 7805, with the tab being ground, why not omit the the insulator? Seems like without it the thermal resistance of the joint would be less and the vr would run cooler.

[@rubber20021]

The terminator BNC you are using is 72.5 ohms? closer to 75 ohms or is it 50 ohms?

[@antiekeradio]

Only one question seems tot be unanswered, does the filter in/out function actually work now? (It didn't in the first video)

[@anthonyroby296]

Now you have it working, what are you going to use it for?

[@JohnKha]

I am wondering if the filter in/out actually worked this time (from the first video it didn't look like it did anything).

[@ipullstuffapart]

245v in the lab isn't too bad, at my home being on a crap line we run at about 254 volts, and yes it does hurt our gear.

[@CoolMusicToMyEars]

The unit looks to have a massive supply voltage, is the transformer input tapping ok for your supply voltage ?

[@daviddavud5678]

EEVblog How can a simple circuit be designed using a small DC motor that is controlled by a MOSFET when the resistance of the DC motor is not known ? (In my book they usually give some known values of which you can calculate everything...) My guess is to just play with VGate of the mosfet to adjust the current in drain-source and then you can choose the speed you want. Is this correct?

[@jopjopjop]

I thoroughly enjoyed it!

[@monchiabbad]

The heating problem might have something to do with the fact that the case being open due to which the ventilator cannot cool.

[@echothehusky]

Looking at the grommet on the transformer wiring, suggests a metal cover was fitted over the mains filter, the regulator would have been attached there so it would be quite a big heatsink, the last person had to remove the screw to take the cover off to get to the mains wiring. That's my guess anyway!

[@Technical_Audio]

That is EXACTLY the problem. I didn’t read all the comments to see if anyone else caught that. Looking at another video about the SR650 shows a large aluminum shield box around the input power module. The regulators are attached to that box, which serves as a very large heatsink.

[@echothehusky]

@@Technical_Audio Wow 5 years ago, I don't even remember posting that comment :D

[@tubical71]

I think somebody went in there to change the battery and therefore needed to remove the heatsink to do this, check the datecode of the battery, and it´s may younger than the other parts with datecode... No banana reflection this time;) BTW, it´s Dave´s 700th video....cool....:)

[@DantalionNl]

Dave they maybe they knew you bought it, and wanted to have a good repair video. So the last minute took a hak at it so it would be more difficult to repair ;)

[@Razor2048]

will it help if you add some thermal compound to the heatsinks?

[@sean8081a]

I think he did put some on, you can see some white oozing out.

[@Razor2048]

Re Pretty much, mostly into the artwork :)

[@CH_Pechiar]

The regulators would be running colder when the lid of the unit is on.

[@charlessmyth]

Thermal design for power supplies of this type is seldom well executed. Especially by the spec-sheet jobsworths who should be executed for their inattention to good design sense. I once owned a Philips PM5519 that had a number of those regulators on a board that was well singed, with the excess heat. On occasion, the unit would do strange things. After I attached the heat-sinks to the regulators, that they should have had, the unit stopped giving trouble. Even so, they ran hotter than I would have preferred. If it had not been so much work, I would have replaced them with TO3 packages, mounted on the side walls of the very substantial, aluminium chassis. As for the Stanford Research unit, the layout for the three-in-a-row regulators makes it easy enough to attach a 25-mm wide strip of 3-mm thick aluminium strip, in place of the small screw on heat sinks. This should keep them a great deal cooler. Probably close to ambient. The 5-volt regulator could be attached to the same strip, with fly-leads to connect to the PCB. Heat kills.

[@tubical71]

Even on expensive lab stuff, sometimes the power supplies are just plain basic stuff like the datasheet is telling.... I got three synths here which are failing from time to time due to heat issues. Mostly rack mounted....poor power supply design, the heatsink is 90°C. The same is for the Yamaha TX7 good design for its time, but the Caps are too close to the switching transistor, getting to hot and dry or blow off... I got now three hohner RD500 digital reverb units with deat PS due to overheating. they have all the same problem, the rectifier diodes are desoldering themself.... Beeing an audio guy, i always do my own power supplies, well oversized to overcome heat issues, as it´s not very common using 78/79xx, LM317/337 or even all discrete IRF830 (highVoltage) or 2n3055 (high current) based supplies in a (small) housing with tubes inside as well, causing the temperature rising up to 70°C inside. Tube are well ok with this, while SemiCons not quite;) So i always need (or get) to know where "cold-spots" in the housing are and put the power dissipation SCs there. Otherwise the complete unit will simply fail over time. So when i do my final test stage, i just let it stay on for a whole day long with some thermal couples inside, to see what´s going on and how high the max. temperature inside is and where it is.

[@charlessmyth]

TubiCal Which is a major reason as to why it never seems to work between repairs :-) I used to have endless fun fixing the test gear, to then go fix what I bought the test gear to help fix. Marconi, AVO and Gould, for example.

[@locoo1]

It looks to me like they were replacing the transistor next to the regulator and forgot to put the heatsink back

[@JoeBee999]

Hm, I wonder if somebody had changed the transformer. Because of the missing nut. Maybe this is the reason for quite high input voltages.

[@bjorndethij]

I sawn you filming it on the live stream please put the mic on when you do something like this .

[@mshahabas]

Dave still no news on HP DSA?

[@Keep-Exploring128]

when the cover is on the air flow will cool it down better .....

[@irishRocker1]

Surprising he didn't mention this after his recent video with the FLIR! lol

[@DrenImeraj]

Could the reason that these regulators are running so hot and the input voltages are so high that the transformer was replaced? That thing looks fishy.

[@JustinAlexanderBell]

I was thinking it's possible just the 240VAC input causing it.

[@DrenImeraj]

Justin Bell Well, i guess both taps have the same number of windings so it would behave the same if half of that voltage was supplied in a single tap.

[@superdau]

Dren Imeraj not 240V as opposed to 120V. More like 240V (or 245V in Dave's case) as opposed to the 230V or maybe even 220V it was designed for. Mains voltages are generally higher than they were a decade or two ago. Many old devices list 220V as input (which including the mains tolerance of +-10% means you had to design for 200V). Now whack 240V at it and you got 20% more voltage on the secondary.

[@superdau]

Ronald Lijs It has quite much to do with the input mains voltage. The device was designed for 230V maybe even 220V. With mains tolerance this means the transfomer was picked to give enough output voltage at 200V. Run it at 245V and you suddenly you got a few volts more to "burn" on the secondary.

[@superdau]

Ronald Lijs 70°C isn't "super hot" for an LM78xx. They are rated for junction temperatures of 125°C (some datasheets go even up to 150). With a junction-to-case thermal resistance of around 4°C/W (typical value for TO220) you could dissipate over 12W at 70°C heat sink temperature and still be in spec. Also with the case closed the airflow would go right across the linear regulators and keep them cooler. A big part of a design process is also not to "over" design. So yeah, the best solution would sure have been a passive heatsink to the case (only if the rest of the components really don't need cooling, which is not a given btw.). Other than that there's nothing wrong with this setup with the case closed.

[@Kezat]

Anyone else screaming at Dave to touch the damn voltage regulator to check the temp? Perhaps he did off camera or was really sure that was the issue. I wonder if the voltage regulator and fan control shared a larger heat-sink, would explain why the Vreg has a sil pad on it.

Stanford Research Systems SR650 Dual Channel Filter Repair - Part 2 There is the missed heatsink

[@whuffo]

A shot of Deoxid-D5 on some 000 steel wool wiped around those BNC connectors will bring them back to just like new again.

[@cosmolv]

Put "L"shaped heatsink - so it can cover little more air from fan ;)

[@therealjammit]

I'd be the person to replace some of those regulators with three terminal switchers. Just to take some of that heat load off.

[@SomeBroski00]

all my subscriptions suck except yours Dave what does that say?

[@Kodachi123]

It's such an expensive device, but it has such an poor engineered power supply in it? :/

[@mondeo984]

Why don't you rip out this fan and put in a proper heatsink. Then you get rid of this anoying fan noice

[@FrozenHaxor]

Surprised to see you here :P

[@kTHElidd]

Awesome vid!

[@dinkc64]

They probably removed the heatsink to change the battery behind it, and forgot (or was too lazy) to put it back on.

[@Retr0id]

Nice video.

[@EEVblog]

It's been uploaded for a minute, you haven't even watched it yet!

[@Retr0id]

I have now! I was just being childish, and wanted the first comment...

[@TheOriginalEviltech]

EEVblog All your videos are nice Dave, some are even amazing! By the way i tryed to spy on you via the wireless lab cam, but it seems to be off or something...

[@simoncrabb]

Mmm Z80.

[@AccessControlForum]

Thanks, i liked!

[@IsettasRock]

Bob's not my uncle!

[@PoLoMoTo2]

Lol EEVBlog curse, its either a simple fix or unfixable