Spy hunter midway 90412 power supply stumped

[detbjr]

I have two linear power supplies that both only put out 6.5 v non-adjustable. There also seems to be problem on the 12v side too - I get like 10.5v. I've done a bob Roberts kit on both. I don't see broken traces. I've also replaced c107, c108, c109. I've replaced all diodes (except the 3 really tiny ones). On both boards, resistor 216 gets burning hot. This is a one watt resistor that is on the battery circuit. Resistor readings appear in spec. I did replace a few that looked dark.

I'd send them off but I live in Mexico and shipping is a pain.

Any suggestions? Little capacitors near the regulators? There's not much else to replace...

 

[detbjr]

Progress but still high voltage

So I found part of the problem was the 4 cloth covered wires coming out of the transformer going to the fuse block were connected in the wrong sequence. I think I was running 20 volts into where there should have been 8.

Re-ordering the transformer wires has helped. So now on one of the power supply boards I get 5.2v and 12.2v. Great. Except I get that voltage when the pots are adjusted to the lowest setting. Adjusting the pots causes voltages on both to increase.

The wall voltage is actually around 130VAC. So I was thinking maybe it was that.

Items pending to replace - pots on the board (not sure that will help since the voltages are both high), little capacitors, resistors...

Any suggestion?

 

[demogo]

Is 5.2 / 12.2 with the boardset plugged in and the game working?

 

[BozoTheClown]

If a couple of the wires were wrong its possible that others are as well. Mine is sitting out waiting for cap replacements so I can take some detailed pictures if you would like to compare.

 

[demogo]

Was the 12.2 / 5.2 with the boardset hooked up? And if that was measured at the linear power board, that's good voltages because there will be a drop from there to the game PCBs.

 

[detbjr]

voltages

The 5.2 / 12.2 was measured at the linear supply board. I was concerned because those voltages were measured with the pots turned all the way down - absolute bottom of range.

 

[detbjr]

Thanks for the picture - very helpful!!

 

[detbjr]

resistors

What are the resistor values for the resistors across the big blue caps?

 

[demogo]

Det, measure the voltage across this big blue cap:

If it's around 5.0 then you're probably good. Is there something else going on that isn't right? Yep. But this may just work out for you.

 

[detbjr]

Thats one of the caps on the main stack. I get 4.75 volts. The game plays. Only i get no game sounds. Peter gunn theme plays. Dual Power amp ics get burning hot. I did replace them and the electrolytic caps on the dual power amp. I also replace the 8910 ics on the ssio board.

 

[detbjr]

Adjusting the pots on the linear maxed out give me 4.9 volts.

 

[demogo]

Adjusting the pots on the linear maxed out give me 4.9 volts.

You really don't want to do that -- you're getting a voltage drop somewhere from 5.2 to 4.75 and you're probably pumping a damaging 5.4v into your boards to get 4.9 out on the SSIO board.

I would repin the connectors on the wiring harness going from the linear power board to the CPU stack and also the connector carrying power that goes onto the cpu board. Spraying some Deoxit in the new connectors and working it on and off will likely take care of your voltage drop.

Still no sounds with your 4.9v reading on the SSIO, I assume?

 

[detbjr]

I didnt hold the 4.9 v long enough to check for sound out of fear of frying the boards. I did repin the harness connectors.

Once i get the sockets on the linear swapped we'll see.

Thank you!

 

[demogo]

I didnt hold the 4.9 v long enough to check for sound out of fear of frying the boards. I did repin the harness connectors.

Once i get the sockets on the linear swapped we'll see.

Thank you!

Make sure that you re-pin the harness connector onto the CPU board too. I think that was the big culprit on my game and now there's very little voltage drop from the power board to the cpu board and on to the SSIO board.

I assume you've done the board interconnect cables.

I'd do the sockets on the power board last and only if needed because they're supposed to be a big pain in the ass to do.

All of this will take care of your voltage drop problem but there's still something else going on -- you should be able to adjust the voltages more than what you're seeing.

 

[detbjr]

I replaced ribbon cables, power connector to the cpu, and the electolytics on the cpu boards. The voltage improved to 4.9v when I have 5.24 volts w/ no load. Still no game sounds. The csd does work but only if I route the audio feed through a separate amp. Doing same for game sound feed doesn't make any sound except white noise.

I will redo the sockets on the power board next but I don't think that will help the game sounds...

 

[demogo]

I replaced ribbon cables, power connector to the cpu, and the electolytics on the cpu boards. The voltage improved to 4.9v when I have 5.24 volts w/ no load. Still no game sounds. The csd does work but only if I route the audio feed through a separate amp. Doing same for game sound feed doesn't make any sound except white noise.

I will redo the sockets on the power board next but I don't think that will help the game sounds...

Where are you measuring the 4.9v at when you have 5.24v without any load?

 

[detbjr]

Across one of the electrolytic capacitors on the ssio board

 

[demogo]

Across one of the electrolytic capacitors on the ssio board

It's right at 4.90? It wouldn't hurt to have it higher but that's probably good enough.

I don't think the "no load" measurements means much; if you're looking to measure power loss then measure the voltage coming out of the linear power board at J4 and J5 with the game on; then measure again across the capacitor on the SSIO board that I included the picture of above. That's a much more interesting number than comparing the unloaded voltage output with what's coming off the cap on the SSIO.

If you're still not getting game sounds with the cap on the SSIO at 4.90v then it's likely either the dual amp board, an issue with the volume pots / connectors near the coin door, or something wrong on the main board stack. If it's the latter, I'd suggest pinging Cdjump here and see if he has any suggestions or ship it to him for repair and you'll get back a fully working board.

If you do end up shipping him your main boardstack, you might as well include your linear power board for him to verify...