EEVblog

Tragedy in the EEVblog lab as the arcade machine releases the magic smoke.
Claytons repair time.
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#Repair #Arcade
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[@MrZenerTech]

Somewhere around halfway through the video I had guessed the problem to be a bad solder joint. There were two clues to suggest I was probably correct. The first was the horribly faulty solder joints found to early on. My experience has shown that when I find joints like that on a board, it's very probable that other joints will be faulty/suspect as well. The second clue was the very fragile and intermittent nature of the faults. Some joint(s) "teetering" on the edge of conductivity. Later in the video, I had a second guess that a transistor may be at fault. Thinking maybe spurious oscillations or ripple activity across a faulty p-n junction happening within the conductivity threshold region. I figured either scenario may make the transistor sporadically conduct.

[@speekergeek]

Pretty much same for me, except immediately I suspected a faulty solder joint, about halfway I thought maybe it was the 16 pin or so IC...

[@fcweng]

Thanks Dave ! Even you can't find the exact fault but it is still an outstanding PSU diagnostic ever with scope and explaination thrown in it. Great video ! PC supply is a way to go since a cooler is an added bonus.

[@andrewhannay]

Re-soldering suspect joints has never worked for me especially in my early days unless I can see a physical crack and sparking around the joint :-)

[@jam99]

Yet again, it's not a work of art so Dave condemns it as bad. Appearance is not everything, Dave. What a surprise. The joints on the main connector do not necessarily look dry at all, it just looks like too much solder has been used, and that does not affect the function. Some flux smells nasty and leaves residue; that's life. The IC is not obviously badly soldered, it's just that the flux has not been cleaned off so it does not look pretty, but those solder joints, upon first inspection, do not look suspect. You are getting a little too arrogant these days, Dave. Maybe have a refreshing look at your really old videos where you had a little more humility. You're very good at your thing; you don't need to show off. I don't disagree with your final microcrack / dry joint theory, but it's simply not often obvious. Electrolytic cap ageing is also a suspect. SMPS are often a complete pig to diagnose and fix. Most mass produced stuff is only just on the right edge of working; the components are getting hammered and it's all just nasty.

[@nicholasroos3627]

@@andrewhannay I try to narrow down the options first. That's an absolute last resort for me as touching around without intention has always lead me to more problems than solutions...

[@Mrwheresmyhouse]

"Dry as a dead dingo's donger" has to be the most Australian thing I've ever heard.

[@stevetobias4890]

Bloody oath mate. Aussie, Aussie, Aussie. Oi, Oi, Oi!

[@ElTwOJaY]

😂😂 One shock and im gone!

[@Eduardo_Espinoza]

& after the wildfire

[@tcpnetworks]

When you say "full wave bridge rectifier", I hear Mehdi Sadaghdar in my head. You know - at 135dB/80Hz.

[@thedevilinthecircuit1414]

"FOOL BREEJ REK-TI-FA-YA!"

[@Brendan_Keyport-WA7BMK]

@@Okurka. yeah, it's "FULL BRIDGE RECTIFIER!"

[@edpaparo9916]

LMAO!

[@dirk480]

As an old IBEW member, I am still learning electronics. Go figure, I thought motor control circuits was difficult during my apprenticeship but learning the ins and outs of electronics brings that to a whole new level. I just bought my first oscilloscope(a cheap Sigilent) just to learn more. Special thanks to all the commenters that help also. I am amazed by so many people and their knowledge of electronics. Keep up the videos.

[@efa666]

I'll never get sick of the Muriel's Wedding quote.

[@blapty]

Here I thought he was quoting Courage the Cowardly Dog 😁

[@mscir]

Dry as a dead dingo's donger. Who soldered that, Stevie Wonder? You can see it's just going silly-buggers. I wish I'd had this guy for my ET classes, so entertaining. LMFAO

[@volodymyrzakolodyazhny]

Everything is hanky-dory. :)

[@trevorvanbremen4718]

@@volodymyrzakolodyazhny - Purely FYI - Here in NZ it's pronounced with an 'O' as in hOnky dory. I think Aussie is the same (they ALWAYS seem to copy what we do here)

[@robbieaussievic]

@@trevorvanbremen4718 ..... Lamingtons,

[@martinkuliza]

i gotta be honest, i felt that he did a disservice to stevie wonder on that joke. I would have picked on a crack head

[@emolatur]

those power supplies are actually quite common in the arcade industry. I work at an arcade in Maine (northeast USA), I've seen (and repurposed) a lot of those.

[@BenHeckHacks]

Yeah and they're cheap as chips.

[@martinkuliza]

Hi mate, some advice if i could first a few questions You say you WORKED in an arcade. does that mean you operated the arcade only or you repaired machines as well I'm interested to speak to you if you have in depth repair experience and i'm happy to pay you for your time to speak i'm not new to electronics , i would just like to get the opinion of one who has repaired machines before I have an old Black and white knock off Space invaders cocktail table, Dual player obviously goes without saying... Black and White CRT on board it still works, no problem it was gifted to me vs the client throwing it in the bin. I've had a look around it, it seems like the caps could do with a replacing, all else seems ok I HAVE 2 ISSUES Initially the issue was ISSUE 1 - Upon Start up it would start normally, Expect the V Hold and H hold would be screwy. Now.. i have found 2 Pots inside that if i turn then, Obviously V and H Hold Pots, i can adjust it and it's fine QUESTION 1 - WHY, AFTER SHUTDOWN DOES THE V and H hold gets screwy again ? Now another problem developed it happened once, i disconnected the (let's call it CONNECTION BLOCK) from the game board and re connected it and it fixed the problem Now the problem has returned and won't go away ISSUE 2 - Unlike before, when the game now starts i don't see normal characters, i see Letters D's and T's Mostly i think. as if... the game didn't load up correctly simply put WHAT THE FUCK IS GOING ON LOL so as you can see.. I need some input from someone who has experience with these things. I could probably take a whole heap of time and go through it and find the issue, but it'd be cool to speak to someone with some experience as well so.. is that you, or did you just run the arcade or did you actually fix the machines

[@emolatur]

​@@martinkuliza while it is seasonal, I *believe* I /still/ work at an arcade. I mean if I show up for work in April and they tell me to go home I'll know otherwise, but unless that happens, let's be gentle with Mr. Ed. He's old and doesn't need a full ado about nothing! Barring unforseen changes, I am a tech and also an assistant manager. Now. As to your other issues. The horizontal and vertical issues are almost certainly dried out capacitors in their respective oscillator circuits. They are obviously designed to lock to the sync pulses in the input signal but in order to do that they have to be close to the correct frequency to begin with. Lots of tuned bits there: coils and caps. Any component that changes in value changes the frequency. A common failure mode of electrolytic capacitors, before they fail completely, is to become thermal: when they're cold, they're either low value or very high esr, but as they warm up, they start behaving more like capacitors again. I'm gonna guess you've got a few caps that are drying out, and you're setting the h/v hold to compensate for whatever value they are while it's running, and then it's out of spec when they cool off. The sync stuff is generic to all 100% analog raster displays, and hopefully helps. The logic issue, on the other hand, will be specific to that game board, but if manipulating the "CONNECTION BLOCK" (close enough. "connector," although there's probably a dozen and you haven't really specified which one) treated the problem before, I'd start with some electrical contact cleaner (deoxit) and a close inspection on and around said connector for bad solder joints.

[@martinkuliza]

@@emolatur " let's be gentle with Mr. Ed. He's old and doesn't need a full ado about nothing!" Understood... Do Lets "Barring unforseen changes, I am a tech and also an assistant manager." Thank you and now that Pleasantries are aside we can get to business "Now. As to your other issues." Precisely "The horizontal and vertical issues are almost certainly dried out capacitors in their respective oscillator circuits" I suspected as much, and i don't really need too much help on this front, the confirmation was enough As for the rest I was going to go around and inspect the solder joints ALL OF THEM with a microscope , very slowly. My other guesses would be, there are 2 boards, the bottom board seems to have the EEPROM's the top board seem to have i think (of memory) 8 was D.I.P. switch. and a few pots that seem to control the speed of the good ship and the aliens and the bullet speed and ship speed and alien speed and sound level. i have 2 guesses why the screen Characters are filling up with D and T all over the place. either something with the D.I.P. but.. i haven't touched it or more likely, badly seated EEPROM's, in my mind it has to have something to do with the Character ROM doesn't it ? that's what i've got so far. I suspect maybe the ROM's may need reflashing, but GUT FEELING says, Likely that won't be necessary. previously, it was working fine, other than the V and H hold and i'd adjust a board that was mounted vertically a little under the Power supply and to the right of the monitor, there was a Pot there and that'd fix the Hold, other than that. the game actually worked perfectly Player 2 button doesn't fire, but.. that's just a button replacement, Nothing to worry about, it wasn't until recently that the game upon start up produces DT T DDDDTTTDDDTT D's and T's in some spots you can see half a space invader here and there

[@martinkuliza]

@@emolatur Now.. I appreciate the advice. it's one thing to do this on you tubel like this would you be open to me paying you and us doing a zoom session or something If your'e not interested, i understand if you are , I appreciate it. let me know your thoughts . Any help is greatly appreciated. Hope you can help a big kid get his space invaders going and thus retrubition for all those lost credits and coins LOL over the years speak soon I'm a mad max fan, so I REMEMBER A TIME OF CHAOS, AND I REMEMBER THE ROAD WARRIOR , THE MAN WE CALLED "MAX" I also remember a time WHEN WE THOUGHT AS KIDS THAT IF YOU SWITCHED OFF THE SPACE INVADERS MACHINE QUICKLY AND THEN ON REALLY QUICK YOU'D GET 50 CREDITS LOL, We tried so many times The rumous was As you dropped in 20cents, Just as the 20 cent piece gives you the credit, you'd switch it off and on really fast while the owner of the arcade wasn't looking and you'd get 50 credits NEVER BLOODY WORKED :P

[@Melamamoduro]

"For Continred protection against fire" in the board.

[@jrblast]

31:45 in case anyone missed it (lots of other times too)

[@волковдмитрий-ц2ш]

LoL, never seen that until someone pointed out

[@mcflapper7591]

this type of typo on chinese products hasn't changed since '84.

[@martijnholland1714]

Who soldered that ? Stevie Wonder. My tea came out of nose while bursting out laughing :-)

[@efa666]

I'm literally lying here trying not to wake anyone else in the house I'm laughing so hard.

[@noahhunn]

I lost it at that

[@thatgoose2639]

agreed

[@leocurious9919]

The joints didnt look that bad and clearly not dry, it was just too much solder and the flux was not removed. A dry joint looks different.

[@hydrolisk1792]

I just about died at that! Great stuff. How come we didn't have dave as a teacher in collage?

[@AlexZander688]

I would so like to see Dave take on an authentic dedicated arcade game repair. Atari Tempest, Williams Defender, etc Linear power supplies, vector monitors, raster monitors, gigantic game pcbs, oh yeah! Arcade games just look better on a CRT.

[@Membrane556]

Also giant soda can sized caps in some of them.

[@BobWiersema]

@@Membrane556 That never fail.

[@101Osprey101]

@@Membrane556 Atari's "Big Blue".

[@tmd63]

Dave, There is a reason for those notches. It is an old school method of allowing wave soldering a board with missing melt-able components like connectors. The wave does not flow over the break and keeps the hole open so the connector can be manually soldered later.

[@rodrigocastro2005]

these are the type of videos I enjoy the most

[@JWalterHawkes]

I’ll never get sick of Dave troubleshooting power supplies.

[@TopRPDRvideos]

Dave you forgot the golden rule... always reflow EVERYTHING before you even start troubleshooting!

[@cuteswan]

So after 35 years of _CONTINRED_ use the power supply evolved into a Chaos Engine? Cool. Thanks for the goodtroubleshooting & explanations.

[@m4dizzle]

Glad I'm not the only one who noticed that, lol

[@stuartmcconnachie]

11:10 Get a neon bulb and temporarily solder/wire it across the mains input terminals when testing.

[@Zodliness]

@EEVblog I nearly always find dry joints responsible for many of the intermittent faults I receive. They're often a pain to diagnose especially in power supplies around transistor connections, where cheaper components have tarnished legs from initial assemsbly. Removing the unit from its case, relieves tension on the board and sometimes makes it even harder to locate a fault. Like you, I find it's less grief to simply retouch all joints with leaded solder (pre-fluxed) and repeat the soak test. Thanks for sharing. 👍

[@RS-ls7mm]

I used to repair videos while in college (80s). It was almost always the power supply (95%). They used to put in power supplies that were over loaded.

[@FnordOok]

I suspect the reason that PSU was in there originally is that some older JAMMA boards need -5VDC and I think I saw that on the supply side.

[@EEVblog]

He knew what board he was putting into the new custom made cabinet though.

[@SteveJones172pilot]

@@EEVblog Agree, but if he also deals with standard arcade stuff, he probably just stocked those in bulk.. Those power supply types are very common in that vintage arcade machine.. My Frogger machine has one, and it needs the -5v for the audio amp..

[@RenThraysk]

@@EEVblog Pretty sure ATX supply -5v too, though that PSU predates the ATX standard by a decade.

[@DaveRepairs]

@@EEVblog all iover eBay - common ... also Suzzo Happy branded ones are supposed to give us confidence

[@56kflyingtoaster]

@@RenThraysk I think modern ATX supplies have dropped that voltage rail (or maybe it was the -12V) either way i believe your modern ATX supplies have much less current capacity on the negative rails than they did back in the day.

[@tonysfun]

Nice troubleshooting! I learned something again, nice a clean commentary that I enjoy! You stay healthy and keep up the videos coming!

[@GeoffSteeleAU]

This is just as valuable as the ones where you solve it directly Dave. If only to make me (as a mere mortal) feel far better for my own troubleshooting nightmares

[@IAdryan]

This brings back memories... I've repaired this kind of things (power supply) almost 20 years. Mostly from TV's and PC monitors. In the last 6 years only my own PC monitor.

[@biasedaudio]

i feel so much better. I hate fixing switchmode PSU's. I muck around till it works. Happy to see someone much smarter than me do the same.

[@Arek_R.]

I had some modern 1kW computer SMPS that I had failed to fix, now you made me want to just go through all the joints. Though it's 5 years old at most so...

[@funnlivinit]

At the end of last year I wired all of the lights for the Apple TV series "For All Mankind". I installed over 100 of those power supplies to drive the LEDs behind every button. There are thousands in the 130 consoles that were built. Plus the various Space Shuttle and aircraft mock ups. At least 1 in 10 of the Power supplies were DoA. These things have indeed been floating around the video game world since the '80s. You can get new ones for about $25 US. But rebuilt are about $10, with a money back guarantee. Because they know that so many are junk.

[@sumatoborukiSaru]

I work with these supplies on almost a daily basis & it's not as old as you think. They are a clone of a design from the 80's by Peter Chou. Bad joins are the most common fault (especially on Wie Ya's & other chinese junk), followed by bad caps, open circuit resistors (anything 10K & above), or a bad TL474. Occasionally the mains input bridge or output transistors can also go bad.

[@mudgle]

when dave was talking about the rectifier, all i was hearing is electroBOOM saying fuuuuullbridge rectifier! :D

[@mikeissweet]

Never heard it actually

[@gromett]

Or AvE's Rectum Fryer... :D

[@aaronbrandenburg2441]

Or as I would say when I run across bad a bad full Bridge rectifier. A full Bridge rectifier that's been wrecked a fried!!!!! You know that we'll still there was two diodes fell short circuit. Is socially instead of being a diode they became a jumper link. Also one time was charging a rechargeable battery a seal when acid those wall adapter/plug packs/ wall wart. And was not careful with by alligator clips that I put on the original poured they had come on clipped and had short it and I smelled something when I went down to my shop and the case of the charger had deformed because the diodes are being overloaded due to the short it was enough to partially deformity case not a switch mode but believe or not the Transformers okay so what up were using it. Ironically the build a nicad charger.!

[@aaronbrandenburg2441]

Also yeah agreed about the electric little thing no.

[@hikariyouk]

@@gromett That's what I hear, but with Big Clive's voice.

[@MadRC]

Its always the same that, great to see it fixed.

[@speekergeek]

Loved watching this! Brought me back to my old TV repair days 😁

[@CompilerTries]

7:49 - Found one. Cracked joint on right hand side of picture around the top of joint.

[@lgk82ramgb26]

Oh i see it...you mean the small one on the thick trace with crack between the solder and the leg of some component...right?

[@williamsquires3070]

Time to stick a bone-stock gaming PC in there. Considering all the “random” PCs you’ve fished out of the dumpster, there ought to be one lying around somewhere! 😆

[@wizpin]

not if you just play a few classic arcade games, this thing instantly powers up. En you don't have to worry about shutting it down.

[@PainterVierax]

Excluding the POST (which is not a problem on an ARM board), a Linux session can usually boot in less than 10 seconds so it's not a big deal. Also, it's always possible to use a live usb in read-only or a small UPS (often built-in an SBC or a laptop board) if the power shortage is a concern.

[@101Osprey101]

I tend to agree. MAME with Hyperspin as a front end looks killer, is easy to navigate and with it being on a PC, you have the option of adding more games than what comes on that little iCade 60 in 1 board.

[@banjoguyollie]

Fixed so many of these with a simple reflow. They're so cheaply put together that, unless reflow fixes it, troubleshooting and replacing parts is often more costly than getting a new one :)

[@area51audio]

When troubleshooting something intermittent like that, I like to poke every solder joint and component with a chopstick with everything powered up and connected to a load. Most of the time the problem will present itself and it's a huge time saver.

[@hubaswift7640]

Yes! EEVblog doing arcade machine repair?? I'm in heaven! (I'm currently working as an arcade technician). I don't even have the time to watch this video right now but I'm looking forward to later.

[@andrewsgarage796]

Hi Dave it's Andrew from Chemtools, most problems are bad soldering joints mate, find this all the time, thia is why I run courses Best regards Andrew

[@pileofstuff]

My guess at the culprit solder join is at 7:38 right side of the frame, halfway up. The solder tent looks a bit hollow with a little knob on top of the lead.

[@juliusski345]

Check the voltage adjustment pot (near the output terminals), I got myself similar PS where with some thermals/magic woodo it become open during the operation causing similar voltage jumps (no voltage reference for error amp in 494). Replacing it with fresh multiturn pot solved the issue, and still going 2+ years!

[@EEVblog]

I checked that, wasn't it.

[@Tedybear315]

I've got about 6 of these on the shelf in my office. I've been a tech for a video arcade company for almost 30 years! Those supplies are still in use today! (Go with a Happ brand, I've had good luck with them) Well done. For those that are wondering: 12volt rail. Normally used for the audio circuits on certain games.

[@ElektronikLabor]

I find psu's often quite hard to troubleshoot; a fault in one area can have an effect on completely other area. And because of mains you can't just easily poke or probe around

[@stonent]

Years ago I picked up a Shinobi for $20 or $40 in the paper. The guy said it would work for a bit and then freeze. I got it home and whoa! 18V on the +12 and 8V on the +5. I did a quick turn on the adjustment pot and everything was find with no issues.

[@noelj62]

I usually go on the all main solder failure-points (main chopper transistors, rectifier diodes, any chocks or coils, and main HV capacitors). I've fixed many PC PSUs that way.

[@mixmasta]

You can tell by the series of the Rubycon mains capacitor, the presence of the green Panasonic capacitor and the absence of crummy tantalum capacitors that this power supply is about 20 years newer than 1984.

[@userPrehistoricman]

Must be 2084 then.

[@R3TR0R4V3]

Robotron 😎

[@PainterVierax]

2:30 according to the green plastic guide allowing 2/4/8 ways for the joystick and the mounting screw holes, it looks like from Seimitsu (a reputed brand). The screwed buttons might be too.

[@oliviergilcreest8088]

Love it. Your videos inspired me to start my own KZbin channel. Heatinggeeks. Tha ks for all you hard work and stay safe. I just fixed 2 PCBs on 2 heating boilers and up loaded it. Thanks Dave. Probably end up in your spam bin but anyway. 😊😉

[@BrekMartin]

Sticking my hand in an arcade machine cabinet is how I got my first mains shock in my 20’s.

[@dhpbear2]

10:50 - My guess for manufacturing date is around 1984. I worked on a 'switcher' back then. The 'problem' was that the voltage output would 'fold-over' if there was no load connected :) UPDATE: DING! I was correct on the year, at least :) (12:50)

[@IDPhotoMan]

"Dry as a Dead Dingo's Donga'"....... LOL

[@Brainstorm4300]

What's donga?

[@-dazz-]

@@Brainstorm4300 Dong = Penis 😂

[@mitch19636]

@@-dazz- lol

[@aaronbrandenburg2441]

Demonetized!

[@SparkyLabs]

@@-dazz- i was just going to ask, male or female bit? or is what why he says nun nunna or whatever it is.

[@johnpossum556]

I'd guesstimate that it was near that PWM chip only because I disliked the look of all that flux and not seeing proper fillets is always a clue towards a more coldly soldered joint. That heat intermittent problem is actually pretty common in a lot of devices I've worked on. I do enjoy the hunt of these kinds of videos of yours, Dave. Good work.

[@Antoniobeta]

We need more videos like this! Love how much you can learn while being entretained!

[@aloizgorjup1869]

Love the Occa. Next time throw in a few "Bonzas", "Fairdinkums" & "Drongos". Good stuff mate.

[@koffibanan3099]

Always happy to see the same things happening to someone else, who's got a ton more experience then I do. Makes me feel somewhat less inadequate. Thanks! Different power supply topologies/explanations video would also be greatly appreciated

[@gblargg]

I once fixed an Acer monitor where the vias between sides in the LED driver PCB were going open-circuit when it heated up. Took way too long to finally diagnose. I fixed by putting thin wire through them and soldering to the traces on both sides.

[@hlynurstefansson9947]

Check the solder joint at 8:02 (on the right close to the bottom of frame) It is exactly the kind that will heat up disconnect and cool down and reconnect. (Brute force re-soldering the whole thing is usually the quickest way to solve these intermittent problems)

[@lelandclayton5462]

Those Power Supplies are still in production today. They were meant to be a replacement for the old Linear Power Supplies and since the Mutlicade world has taken over a lot of Multicade Builders use them. I typically replace them with Meanwell brand multi-rail 12/5v Power Supplies.

[@coondogtheman]

It's amazing how a few cold solder joints can stop anything working. I did that to a vintage ghetto blaster boombox that had low audio output and would cut out. I did what you did and re soldered any pin that looked odd, and now the radio is a lot louder. How much current does the Jamma board require?

[@Golem386]

Cold spray often does wonders uncovering these intermittant fault, whether they are in components like caps or on solder joints. But with most single sided-boards, solder joint issues are much more likely.

[@tuber2kh]

I love it when power supplies are the culprit. You can get Mean Well replacements for popular voltages for about $17 on Amazon. Never worth the time (to me) to diagnose -- just pull the supply, order a replacement, and toss the old one in a trash can! :)

[@electronic7979]

Nice repair video 👍

[@Maxxarcade]

2 things I noticed on this one. There's a joint that looks cracked at about 8:00, on the right side of the video. And there were probably some others as well. Sometimes the tin plating comes off the copper, so even though the joint looks ok, the solder is not fully attached to the trace anymore. Also, these power supplies need about 1 amp of load on the +5v to run correctly. That is probably why the waveforms on the TL494 were so odd when you first tested it.

[@EEVblog]

Nope, wasn't that joint, that's a trick of light and shadow, I specifically investigated that joint. And no it doesn't need a load, works fine without it.

[@Maxxarcade]

@@EEVblog Ah gotta love those shadows. Sometimes all you can do is resolder a bunch of stuff until you find it LOL.

[@Mike-mw4hh]

Hey Dave! I run a Sydney-based arcade company that imports parts, upgrades old machines & makes new ones. These 60-in-one's are my bread and butter along with the 700+ "street fighter" multi games so if you need any parts or upgrades, give me a burl!

[@johnjordan3126]

Thanks for breaking it down and showing the "fixed" 15V signal - that was going to bug me. :-)

[@57dent]

Reactivate the coin mechanism, you'll be able to recoupe the kids allowance!!

[@gfcwfzkm]

Reminds me hard about my work. Whenever I get a old-ish PCB from a locomotive to repair, I re-heat all solderjoints, which solve the problem in 3/4 of the cases.

[@dnorman2134]

This was a fairly common PSU for generic arcade equipment.

[@dewdude]

Yup. I kept about 4 or 5 on my truck at any given time. It's still pretty common stuff.

[@dnorman2134]

So did I.

[@101Osprey101]

Yeah, and cheap to replace. $10 - $20.00. I would never repair one of these. I don't trust their overall construction. If one component went out, others are due to follow. Replace it. It is the equivalent of the heart of your game and if it blows in the wrong way, it can damage the game board.

[@frankpitochelli6786]

Dave, as with most electronics, having been in the TV repair business for almost 40years...solder joints are always the majority of issues, well,as well as electrolytics of course, but, especially on a board with a lot of heat...and, I would wire brush any connection if possible before resoldering.

[@warrengray610]

Hi Dave, hahaha any solder joint that looked at you the wrong way!!!

[@McTroyd]

Thanks for completing the repair, even if the ultimate cause wasn't clear. The dozens of times practicing on "worthless" hardware is what pays for the repair that really counts, I think. Besides, it never hurts to have another working power supply lying around, though in your case... ;)

[@deflugs101]

Excellent vid mate! Really enjoyed it. Classic trouble shooting 👍🏻👍🏻👍🏻

[@mrlazda]

Problem is that schematic you was looking do not correspond to that power supply, it is close but that power supply is use same topology as old AT power supplies, it us BJT on primary side not FET and they have interesting way of starting, they start self oscillating (primary transistors with driver transformer (which have bootstrap winding on it, I am not sure that is correct English term for it, but it use current from main transformer to boost current to BJT)) and when control IC on secondary side get enough power it take control. This AT schematic is more closer to that supply then one you was using danyk.cz/s_atx01b.png (only AT power supply have more complicated voltage and current sensing, but main power part is same).

[@ngtflyer]

Looks like a common Peter Chou copy. When I find these bad, I just replace them with new Happ or MW supplies. That's a standard arcade cabinet supply. Some games do require -5 and even a few have to also have -12v.

[@jimbojones3012]

7:51 you can see a crack on the solder joint for a component on the right.

[@joonaknuutinen5540]

so someone else did see it too. i dont know anything about soldering, but that was my guess too..

[@EEVblog]

Nope, trick of light and shadow.

[@jimbojones3012]

@@EEVblog I thought that too, but it looks like it'd make sense if someone pried out the fuse and knocked the cap next to it.

[@ChipGuy]

I always feel a bit uneasy when I can't really tell why a unit works again. But sometimes you just have to go with it an be happy.

[@Herby-1620]

An idea for the power supply (before you throw it away!). Put a constant load on it, and try some thermal imaging on the circuit board. It might be informative!

[@analoghardwaretops3976]

Banging the disconnected board around / tapping/ flexing them has also helped .. Heating them up sensibly with a hot air blower some time accelerates the fault to show up early..

[@SaltCollecta]

Without a doubt you tested the faulty component, but the fault was in the soldering below it. Ugh, that's rough.

[@eideticex]

I kind of called it a few minutes in. Looked like one or more phases of the input were dropping in and out, hence the partial output that spiked towards nominal output. I was suspecting the foot burned off one of the transformers or at least burned loose of the solder joint. I see similar failures in PC PSU during spring every year, lightning storms really wreck power supplies and not always immediately.

[@thsinger]

Did he say “kaputt” now he start to speak German, welcome Dave.

[@gabiold]

He should learn hungarian too. Just because we actually have distinct slang words for transistors (tranyó) and transformers (trafó). 😉

[@LordWaldema]

@@gabiold "Trafo" is also used in german, never heard a german slang word for transistor though (then again I'm not often around people who use slang in electronics)

[@farbe123]

@@LordWaldema german slang for transistor is like: transe some other words: widerling for resistor kondi for capacitor poti for potentiometer And the best one of all -> Hühnerfutter for smd resistor/capacitor parts, Hühnerfutter means chicken food like grain. Engeneers often say something like: To solve this problem only two transistors and a hand full resistors / capacitors are needed. Das Problem kann man mit zwei Transen und ner Hand voll Hühnerfutter lösen.

[@gabiold]

@@farbe123 Kondi and poti are also used in hungarian.

[@damedaE90]

Habe ich auch so verstanden 😁 Genius 👍

[@BryanByTheSea]

My two cents, prefer the repair videos such as this. Keep them coming. Thanks

[@cmfrancis1]

I'm working on an original Ms Pacman cocktail right now. Still has the the factory 7/12 volt AC power supply and CRT monitor.

[@mariomionskowski6223]

The TL494 is the chip with the most power supply applications in the 80's.

[@jamesduncan2955]

You're great Dave, love your channel!

[@carsonsully3294]

Hi Dave I’m an electrician who’s moving into electronics and I’ve just discovered your vlog. I really enjoy the in-depth analysis and explanations you provide. Any advice for someone who is just scratching the surface of this field both as a hobby and professional. Anything would be helpful thank you for your time.

[@n2n8sda]

blast from the past.. i used to repair arcade machines and boards during the 90s until the early 2000s.. i dont like those multi boards, they were big about 15 years ago (if memory serves could be longer but they were really expensive compared to now) but the quality of them varies wildly and most of them are non expandable. lately the raspberry pi and retropi OS has become a good option.. will let you run most arcade games as well as many consoles with hdmi out and is easier for a power supply / using less power. you can use usb inputs for controllers or just wire your buttons to the gpio! emulators are good and have many options / cheats / etc etc that a lot of the multi boards struggle with as well as many video modes. - possible future "upgrade" video? :D

[@cordyvandenberg3699]

A lot of these old supplies would require a minimum load to regulate. Is it possible that it was fixed after the first round of resoldering?

[@SianaGearz]

It's probably not that old, parts look fairly modern and the particular 494 clone in question wasn't out till mid-late 90s. The design is ancient but it used to be pretty modern all the way back then. It also shouldn't require a minimal load, i mean why, the 494 is a fixed oscillator design, so it should always be able to start and keep running just fine.

[@cllow2020]

Power supply for TL494 are come from big switching transformer (refill power after IC kick started), some slow start circuit or kick startup resister intermittently opened. VCC voltage supply higher than expected, was due to u have changed bigger cap value.

[@sleeptyper]

Can you look at the solder side with that FLIR camera and spot the bad joint before the transistors etc. warm up?

[@gregorymccoy6797]

Did electronics repair in the service for many years. Experienced the impossible every week 🙁

[@abeleski]

Yes Dave. Wr are still around in Wollongong.

[@goamarty]

I would most likely expect an intermittent joint in the internal bias supply. The high ripple comming from some continued operation from the start up circuit (high value resistor. I once had an SMPS with "unstable output voltage" it turned out that it was in a hiccup mode with about 40Hz. The reason was a broken connection from the supply winding of the transformer. The PCB had a crack - probably the unit got dropped - and someone already tried to repair it, but not successfully. Some more solder and a pice of wire fixed it. The unit is in rough operation (often transported, in the tent - rarely indoors) with my camping fridge now since several years.

[@solderstuff]

Chinese arcade parts are often built and soldered like that. I usually re-solder almost every joint, they tend to be dry even when they look ok.

[@peterschmidt9942]

When in doubt - replace the biggest chip ;)

[@s8wc3]

Those caps look like they have spent some time in the parts bin. Wouldn't be surprised if that entire power supply was made of salvaged parts

[@absalomdraconis]

Board, case, and heatsinks included.

[@analoghardwaretops3976]

A company would definitely keep stock/s of boards /modules to be replaced instead of repairing..on an otherwise sucessful working/running/selling product ..Hance the board & box looked new although the pcb was a 1984 design...

[@Arcadecomponentscom]

At 8:08 you can see a crack ring clearly around the pin's solder on the right side of the video.

[@SianaGearz]

That's just a flux ring, not a crack ring. Besides, if that was the fault, the LED would stay right on.

[@Arcadecomponentscom]

@@SianaGearz I'm talking about at the top of the solder where the pin sticks through is an obvious crack around the pin. If that was missed, so will others. ;)

[@SianaGearz]

@@Arcadecomponentscom Ooooh i can see it now! That pin appears to belong to C1 1uF X-capacitor. It would have no effect on the operation, it's purely there for EMI compliance. Clearly the faulty soldering is the culprit, but elsewhere.

[@BoB4jjjjs]

I like the phraseology 25volts and bugger all ripple lol. Yep, been there and done all that and it didn't work, so unsolder a lot of joints, re-soldered then and zilch!? Tested a lot and still no further on, Was about to give up on it when I was going to bend it to throw it in the bin. I just thought I would have another look, help my bob, it worked and ran with no problems? So I ran over the joints I hadn't soldered as they had bent over component wires on the solder side of the board. Yeah, you guessed it, it has been running ever since. That is about ten years or more now! Maybe I did get the right joint and made another poor one somewhere else. Total mystery as to what it was. Drove me nuts and I spent hours on the thing and if it had not been for myself I would have binned it long ago. Then there was a 12vdc power supply, my mate changed everything on it except the transformer, no, still played up when it felt like it. So I had a look at it, I doubled all my mates work and still it played up, the only thing was the transformer but I didn't have one. So in steps another wizard, he changed the transformer as he had one, but it still did the same, so he coated the PCB with solder in a vain effort to get it to work, not a hope. I was sick of it by his time, so was my mate, but this guy made a new circuit board for it as he was sure it had a crack in it, but, yes you guessed it, it still did it. I asked as a joke, did anyone test the mains cable? No, it is in the bloody bin! lol Three people could not find the fault in a simple power supply. It only had to drop the mains to 12vdc for a radio. The hours everyone put into it, we could have bought 12 of them!!!

[@JamesUKE92]

You forgot the obvious percussive maintenance test before reaching for the screwdriver

[@CoolDudeClem]

That soldering looks almost as bad as mine!

[@BlackEpyon]

I do happen to have an LCD that can handle the 15 KHz signal. With a simple diode/resistor network, it's easy to get 4/16 color CGA video onto it.

[@c.schandra2134]

Its an self oscillating power supply the tl494 provide pwm for running BJT and you can use computer power supply schematic to repair it is same and identical

[@custume]

yeah, had a old TV with the same problem and after changing a couple of caps the thing after some time gone berserk, I said ... F that and spend almost 4 hours re-weld all the parts that look strange the TV works great (better than before).

[@WacKEDmaN]

nice vid...thanks Dave.. hope yas are doing well down there..

[@charlesashurst1816]

The shotgun approach. Sometimes works but you can never trust it. Good work to scrap it.