Left Robotron on for about 3 hours, now it has sound issues

SteveJ

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Left Robotron on for about 3 hours, now it has sound issues

Usually I just turn on my games long enough to play them, then switch them off. This time, I left the Robotron on for a few hours, and now the sounds... sound funny. Some sounds are fine, but others just aren't the same. I assume it has something to do with leaving the game on (heat issues?).

Any ideas on what to try? Letting the game cool off has not worked. It appears to be stuck this way until I fix it.

Thanks!
SteveJ
 
My Defender had an issue like that as well. I took out the ROMs cleaned them up replaced them and the issue went away.

Might be that simple,
 
and now the sounds... sound funny. Some sounds are fine, but others just aren't the same.

i would install new electrolytic capacitors on the sound PCB.

while it's on the workstation i would reflow the solder joints on the header pins, etc.

then i would install and retest.

still have sound problems? check out/inspect the pins inside the connectors connecting to the sound PCB. is the spacing of the pin inside there, the same? no more open than others? oxidized? burnt?
if so, replace.
 
Hi Braido --

Two questions: do you mean the ROMs on the main board, and what did you clean them with?

Thanks

Just the ROM on the sound board. Normally I use a brass detailing brush (available in the auto section of Wally World or any auto parts store) and lightly brush the legs until the are clean.

In addition to Splatter's suggestions, I would try reseating the data cables and test for continuity, especially if they are the original IDC connector cables. The original wiring harness was designed to last maybe 5 years, it is absolutely amazing to me that they still work at all 30 years later.

ken
 
Thank you gentlemen ... I will start replacing caps and cleaning pins.

I will post again once I figure it out!

Cheers,
SteveJ

Hope that works for you all i had to do was clean the pins and mine came back.

good luck,
 
Metered the P/S and Vcc on the boards. Was high (+/- 6V, +14V), so I dialed it down. to 5 and 12V. Didn't make a difference.

Tried cleaning pins on the two socketed roms on the sound board (IC9, IC12), reseated them. No Joy. While the board was out, metered the capacitors, a couple read low.

Next step is to replace the caps and try again.
 
Metered the P/S and Vcc on the boards. Was high (+/- 6V, +14V), so I dialed it down. to 5 and 12V. Didn't make a difference.

Tried cleaning pins on the two socketed roms on the sound board (IC9, IC12), reseated them. No Joy. While the board was out, metered the capacitors, a couple read low.

Next step is to replace the caps and try again.

6V is a little high. It shouldn't matter to the sound card as it has its own power regulation, but it is dangerously high for the MPU board.

I assume you have it on a switcher if you are adjusting the voltage. Be aware (as you probably are now) that the voltages on switchers will drift over time and they should be metered regularly. Or just replace the original Williams linear power supply and you should be good for another 20+ years.

ken
 
6V is a little high. It shouldn't matter to the sound card as it has its own power regulation, but it is dangerously high for the MPU board.

I assume you have it on a switcher if you are adjusting the voltage. Be aware (as you probably are now) that the voltages on switchers will drift over time and they should be metered regularly. Or just replace the original Williams linear power supply and you should be good for another 20+ years.

ken

Thanks for the tip. This is my first machine with a switcher (bought it from another member), didn't know they drifted -- how often do you check them?
 
I don't. Once I realized that they would drift and the CMOS issues with Williams games (documented elsewhere) I started rebuilding PS boards and replacing the switchers with original Williams power systems.

Back to your question, some are worse than others. The original Peter Chau switchers were pretty stable (the ones that look like a vented brick). Some of the newer knockoff ones are very unstable. I pulled one from a Joust recently and it said it was manufactured in 2002. If I power it up 5 times I get 5 different voltages, ranging from 4.5 VDC to 5.4VDC. I had some open design ones that I picked up off EPay and they worked for about 6 months and then crapped out. Fortunately, it was the +12V that went and it went to +0V.

ken
 
Update: Robotron Sound Problem

So I checked the cable between the ROM board and the Sound Board, and connectivity was good. I replaced the IDC conectors with new molex connectors.

I also installed a cap kit on the sound board.

No improvement.

I'm thinking it may have to do with leaving the machine on for a long time with high PS voltages. What kind of problem might that cause?

What sort of troubleshooting can I do... as I'm not sure the problem is on the sound board at this point.

Thanks in Advance!
 
If you have a spare ROM board or know someone that has one, swap it in and see if the problems go away. If they do, it is probably the PIA on the ROM board.

ken
 
finishing up

Saw this old post of mine and realized I didn't close the loop.

Long story short, it was the 6821 PIA chip on the sound board. Most likely a pin stuck hi or lo.

Put a socket on there, slipped in the new PIA, and all is well with the Robotron.
 
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