Track & Field no audio, sheared off cap on sound board the culprit?

Cartouche

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Track & Field no audio, sheared off cap on sound board the culprit?

I got this board in the mail a couple weeks ago, not getting any audio during attract or gameplay. I noticed this sheared off cap on the sound board near the volume pot.

Are there any other switches or pots I'm missing for volume? Or is this cap likely the culprit?
IMG_9910.jpg


I'm using a Bob Roberts jamma-to-Konami board in case that matters.

Thanks,
Marc
 
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Yipe! That cap is definitely shorted out. If that's a decoupling cap like I suspect, it could be bottoming out a voltage that's important for sound. Try pulling it and booting the board without the cap present.

(If that works, I wouldn't leave it that way -- decoupling caps are a stability thing, and that cap missing WILL cause intermittent issues you'll otherwise never figure out.)
 
Damn - no dice.

Removed that cap, still no audio....

Then either that cap took something with it, or you've got an unrelated problem. Replace the cap, then start board troubleshooting. I don't know that hardware at all, so all I can really offer further is good luck. Hopefully someone that knows T&F can chime in.
 
Sound on those is run by a Z80A CPU and interfaces to the main CPU through the chip at 1C.

From looking at the schematics the board has 3 audio outputs: 76489 3-voice + noise audio generator, a VLM5030 DAC, and a poor-man's D/A converter consisting of a LS374 at 8E and a resistor ladder on its outputs.

Those 3 sources of generation use 2 different IC paths before meeting at the volume control. If you have some audio but not others then check the op-amps. If you have no audio at all then check the volume pot for proper operation (ohm readings between center and left then center and right pins while turning it) with the power off. Next check the audio output IC by putting your finger on the pins of it and see if you hear a hum.

No hum, check the amp chip. If you have hum and no audio out at all then it's time to dig into the digital part of the circuitry. Check the Z80A by substitution if you can. Check the EPROMs for dirty legs (common on these old boards) and for proper checksums. Beyond that you'll need a logic probe.

RJ

PS: That cap wasn't bad... just broken. They get that way and it generally doesn't hurt anything.
 
Thanks -The volume pot appears to be ok. I'm getting readings ranging from 0 to .95 ohms from both sides, I assume it's a 1k pot.

For the next step you mentioned: The audio output IC is the one at 1C?

Should I bother replacing the cap I removed? Hope I can remember the polarity :p

Seller said he tested it before shipping and the audio was fine. I threw another jamma board in and the audio works, so I know my cab wiring is ok.
 
Thanks -The volume pot appears to be ok. I'm getting readings ranging from 0 to .95 ohms from both sides, I assume it's a 1k pot.

For the next step you mentioned: The audio output IC is the one at 1C?

Should I bother replacing the cap I removed? Hope I can remember the polarity :p

Seller said he tested it before shipping and the audio was fine. I threw another jamma board in and the audio works, so I know my cab wiring is ok.

I don't think that cap has a polarity and it is probably just a filter cap for the ic chips. I have seen techs change the value of a cap like that by chipping away some of it.

I would replace that cap.
 
Ok, so I put the chipped capacitor back in. I'm sure it's oriented correctly, as the printing on all the other ones face the same way.

Held my finger on the IC chip at 1C on the sound board, no hum. Can someone point out where the amp chip is located on the board?

Disconnected the -5v from the switcher, no change.

Reading 13v at the switcher. I have no 12v at the jamma adaptor. Getting audio with a different board, so it's not the switcher, jamma harness, or speaker.

I just noticed, am I missing a jumper on this jamma adaptor?? There's only one for the 12v, on the parts side, no jumper on the solder side.
IMG_9913.jpg


IMG_9912.jpg
 
Reading 13v at the switcher. I have no 12v at the jamma adaptor. Getting audio with a different board, so it's not the switcher, jamma harness, or speaker.

"I have no 12v at the jamma adapter"? That may be your problem. Not all boards need the same voltages so plugging a board in and getting sound does NOT necessarily mean that everything is good for a different board.

I just noticed, am I missing a jumper on this jamma adaptor?? There's only one for the 12v, on the parts side, no jumper on the solder side.

No. Too lazy to look at the schematics to verify but the pinouts here only show one +12v in: http://www.crazykong.com/pins/Trackfield.pin.txt.
 
Kind of hard to tell from the picture, but.... Is there only one orange wire coming from your power supply into the jamma edge connector? To me, it looks like you've got the +12V from your jamma harness supplying 12V to the pin on the solder side of the Bob Roberts adapter. +12V on the Konami board needs to be supplied on the parts side of the adapter.

To test, just do a continuity check between the +12 supply on the Konami parts side of the adapter to your +12V output on your power supply (With the power off ....). If you don't have continuity, then try the +12V pin on the Jamma solder side of the connector to the power supply +12V output. If you get continuity here, then you are feeding +12 to the wrong pin.

If you can, pull the orange wire out of it's current location and move it to the same position on the parts side. If you can't pull the wire / pin out, then just jumper from the existing location to the +12V on the Konami parts side of the adapter.
 
Kind of hard to tell from the picture, but.... Is there only one orange wire coming from your power supply into the jamma edge connector? To me, it looks like you've got the +12V from your jamma harness supplying 12V to the pin on the solder side of the Bob Roberts adapter. +12V on the Konami board needs to be supplied on the parts side of the adapter.

H-sport gets the kewpie doll!

I often use one of the 12v wires to power the coin door light on a jamma cab and like a dunce, I had the sound path disconnected. The 12v wire I had connected was on the solder side.

Thanks to everyone for their suggestions.
 
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