Congo Bongo died, pcb brings 5v down

thanks guys i scrounged around yesterday and couldn't find anything i could safely use to give the ps a load and see if it dropped 5v

that is still my next thing to do once i do

as mentioned above, original power supply, 12v measures fine and works enough to cause a speaker pop when powering off, -5v works for the coin door lights but doesnt go to the board, and -12v tests fine with no load as its not even pinned to the harness
 
you know what's crazy is the [working] Zaxxon at work is still running the original power supply and the caps tested better than new Nichicons so I just left it in there as is. I recapped the whole sound section and did the weird resistor mods to make the new caps caca like the original ones to make all the sound lines work properly.

I think there's too much resistance between +5V and ground to signify there being anything amiss at the game board. in my very very early jedi training it was suggested that +12V can fail on switching mode power supplies, because that circuitry is just a byproduct of +5V load (hence the need for the load and the "switching" aspect of SMPS)... the power supply could have just given up the ghost. I've swapped a Happ PowerPro in that Zaxxon but decided after the fact that there was nothing wrong with the original one so I'll use that. the holes where you screw it in will be the only real difference, and pay attention to where you're taking the wires from. Sega colors are different, yellow is +5V, red is +12V, and white is ground usually... I can't visualize Zaxxon's wiring now. that was thousands of missions ago.
I just got my 💖ZAXXON💖 earlier thIs year... I've played a few games on it before I put it in storage... it works fine(except the damn ship crashing into EVERYTHING!), so I haven't had it opened up enough to see if it still has the OG P/S setup or if it's been replaced ¯\_(ツ)_/¯ lol

@gwarble I hadn't seen before that you still have the OG P/S... that being the case, a fault on the 12V side shouldn't shut down the 5V side, as they're independent of each other. It's still back to a P/S problem or a PCB problem ... or still possibly a wiring problem.

I'm interested to see what you find.

D
 
thanks guys... good info and I'll keep you posted once I find a bulb or resistor to simulate the load, and/or pump a different 5v in and see what happens.

also good to know the 12v and 5v are totally separate on this original G80 power supply
 
thanks guys... good info and I'll keep you posted once I find a bulb or resistor to simulate the load, and/or pump a different 5v in and see what happens.

also good to know the 12v and 5v are totally separate on this original G80 power supply
wait, is not a switcher? post pictures
 
heat camera is a tool i don't have unfortunately

Use the back of your finger instead.

Check for bad/hot chips on the board that could be bringing the 5V down.

Also, if this PS uses 2N3055's (or similar) for the 5V, you might have just blown one. Most of these early linear supplies are a similar design as the AR-II, and should have their transistors replaced for the same reason as the AR's.
 
Use the back of your finger instead.

Check for bad/hot chips on the board that could be bringing the 5V down.

Also, if this PS uses 2N3055's (or similar) for the 5V, you might have just blown one. Most of these early linear supplies are a similar design as the AR-II, and should have their transistors replaced for the same reason as the AR's.
or the bridge rectifier. I don't see any 2N3055s on the sheet

https://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/Congo Bongo Schematics.pdf page 23

I wasn't aware they had linear power supplies also. my bad, world.
 
"I wasn't aware they had linear power supplies also. my bad, world."

Be smarter next time else it gets the hose 😆
 
yes sorry I wasn't clear, its the original Sega G80 linear power supply, same one used in the G08 vector games

would TIP141 be the transistor in question if it is the power supply?
 
or the bridge rectifier. I don't see any 2N3055s on the sheet

https://arcarc.xmission.com/PDF_Arcade_Manuals_and_Schematics/Congo Bongo Schematics.pdf page 23

I wasn't aware they had linear power supplies also. my bad, world.
It looks like a TIP141 does the 5V "heavy lifting" as is comparable to the '3055 on other supplies.

However, when I suggested a 12V short shouldn't take down the 5V side on this power supply vs a switcher... I didn't realize there could be two different power supply systems in this cab. I was looking at this originally:
Screenshot_20251103_105809_Adobe Acrobat.jpg

Which has 2 "switching modules", one for each voltage... which would be independent of each other.

After @gwarble stated it was an OG G80 P/S I looked a little closer and found this:
Screenshot_20251103_105722_Adobe Acrobat.jpg
Which would be the linear with the TIP141. Looking closer at the schematic:Screenshot_20251103_110921_Firefox.jpg
It appears a shorted 12V still wouldn't bring the 5V down too, unless the input of the +12V reg somehow shorted to ground, bringing the input of the LM723 Vregulator on the 5V side down also.

If all wiring, fuses, connections etc are good, and the pcb doesn't have an issue... looks like the TIP141 could be falling flat under load like the 3055s can

Dylan

Edited to say @gwarble and @andrewb posted re: '141 while I was compiling. What they said!

D
 
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If your fingers are as insensitive to temperature difference as mine then another method is to squirt a little alcohol on a chip and see how fast it evaporates. the hotter the chip the faster it evaporates.
 
based on the manual i think it is the 800-0170-02 or -03 assy
 

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If your fingers are as insensitive to temperature difference as mine then another method is to squirt a little alcohol on a chip and see how fast it evaporates. the hotter the chip the faster it evaporates.
I watch a guy that fixes Dell laptops that does exactly this to find shorted or bad parts.
 
If any Sega game uses what I call the "G80-style" power supply, which is the one shown three replies above, you can easily rebuild it following these steps. While not perfect (it is hard to remove the PCB for servicing) it is one of the better linear supplies from this era with one small, but critical, modification (below). The integrated sound amp is great, too. Sega used these primarily in G80 games, but I think they put them in games like Congo Bongo, Pengo, and a few others probably just using up excess inventory. But here is all you need to do to make them rock solid:
  1. Replace all capacitors. Arcade Parts and Repair has a nice kit ready to go.
  2. Reflow all the header pins. There will be cracks, trust me.
  3. Replace the TIP-141 on the +5V circuit with something beefier. The current draw on the G80 games can be high with all six logic cards and dozens of EPROMs. I have no forensics data to back it up, but I assume the TIP-141 failures are due to heat generation from that current. This is the biggest failure point of the power supply. I replace it with a 2STW100, rated at 25 A continuous collector current (TIP-141 is 10 A). No game will come close to that! The package is different so you will need to find a TO-247 mica and some longer insulated hardware to mount. I noticed 2STW100 is slated for obsolescence on Mouser's website, but you can surely find another Darlington transistor similar to that once the supply runs out.
 
thanks for that suggestion... I have to get back to this and make sure its the power supply and then will look into this upgrade... i don't know the difference in draw between the G80 games and Congo Bongo, but CB docs say 4A on the 5v so I would assume the 10A rated TIP-141 should be enough, but admittedly after years and degrading thermal contact I would still agree to blame the existing TP-141, but your #2 seems likely and I will reflow those if/once I pull it out.

With the sliding tray they were so close to making it all easily serviceable, but the end result isn't with grounding straps and terrible cable lengths preventing an easy slide. I think the older G80 convertacabs were better but I'm not sure

Still odd it was working great until moved, and gently...

first plan is to give it a simulated 5v load and see if it drops to make sure it isn't the pcb, as already suggested just haven't bought a bulb or found a resistor yet (just haven't had time, plan to follow journeyman's suggestion of the 17w bulb (3.4amps iirc)
 
The TIP-141 was probably fine when the power supply was new but in truth it is a combination of both the "on time" when heat is being generated and the thermal cycling when the substrate inside heats and cools repeatedly that both contribute to an ultimate failure. The latter is probably more detrimental to be honest. Metals expanding and contracting thousands of times over its service life will cause stress cracks and other strange things internally. Using current rating likely isn't a proper 1:1 comparison or good way to look at it engineering-wise. I just assume due to the higher current rating, the larger TO-247 package/surface area and 40 years of advancement in manufacturing that the 2STW100 will have a longer service life under the load of the PCB. If you end up taking it apart and find one of the three legs on the TIP-141 discolored (from heat) you'll know that is the culprit.
 
You can try an 1158 automotive bulb. It's a 6v dual Filament bulb that has 17/5W filaments. The 17W should draw about 3 amps.

Also, like I'd said in our PM convo the other night about the other game... don't forget to check connections on your PS fuses for poor connections. Also, connectors from the PS to the game board too.

Does it still have the OG linear supply, or has it been bumped to a switcher?

Dylan
Can't edit my OG post. Upon review, the 1158 bulb is a little more difficult to find. The voltage and wattage specs of an 1154 are the same... the pin configuration on the sides differ from each other... the pins on the 1158 are 180° opposite each other and aligned the same distance from the edge of the base, while the 1154 pins are 180° out and are different distances from the edge of the base.

I originally grabbed the 1158 out of a 6v automotive bulb chart based on the wattage spec, not the practical availability.

I apologize for any confusions.

Dylan
 
so its definitely the power supply, i hacked in 5v from a wall wart and got raster i wasn't getting before... realized i have the g80 atx adapter in space fury so swapping that over brought congo bongo back to life.

i will update this thread once i swap the tip141 but at least i have a working game in the mean time if i mount this ps and adapter
 

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