Hi guys. I have been resurrecting an EBD for the last month or so and have it up and running. Generally speaking everything works great but I did work through some hacked wires and bad connectors.

Every 10th time or so (randomly) I will power on the machine from off and there will be no sounds whatsoever of any kind. If I turn it off and on again it will generally come back with sound.

All the sounds and speech are crisp clean and loud. As part of the initial resurrection I replaced all the caps on the sound board. The speaker is new. I replaced the sound pot on the front door. All the pins on the headers of all the boards have been re flowed but only a few connectors replaced. I have not been able to confirm if the no sound circumstance can be remedied by wiggling or pulling connectors.

Any help or direction would be appreciated.

Thanks

Dave

Also meant to mention that u2 u6 u8 u9 and u11 are all new

Dave

Thanks Al. All the pots have been replaced (2 on the board and 1 on the door). I will definitely check the connectors next time it comes on silently.

Dave

Thank you. Sounds like a logical idea () since this is an occasionally boot up issue.

Question: everything else works fine just no sound. Is that still a possible reset issue?

Also I don’t have a logic probe. Any other way to test ?

Dave

Ok... just checked it before leaving and it turns out there is no chip at all in u1, just the socket.

The game generally runs fine without it.... should I get one in there?

It booted up again without sound. I checked connectors and it didn't make a difference. LED on MPU glows faintly after the boot sequence. Game starts up and plays fine just no sounds of any kind.

I booted it again no sound.. started a game and then got speech and target response but no background noises.. put a two player game on and when second player started got all sounds..

Dave

Got it. Problem may be u1 on sound board.

Dave

Still have to give that a try. I don’t have a logic probe. Is that something that can be seen with a good mm?

Dave

Ok checked with the DMM. Btw pin 40 goes to TP 12 so it made it easier.

I’m not sure what I am seeing. Almost ever time it booted I could see oL and a low reading (like .134) before settling in each time between 5.15 and 5.2.

One time it booted with no sound I saw the oL and no other reading and then 5.13.

It never spiked above 5.2 VDC that I could tell.

Dave

I powered it on and off about ten times in a row. All came on with sound and each with 5 flashes. I couldn’t watch the voltage at the same time.

When you refer to the reset circuit are you talking about the MPU board?

All the caps on the sound board were replaced as well as the two big ones on the SDB.

Dave

Perfect.

I will check that out.

Dave

Latest update:

C1 is new from previous work. R1 measures 25K or so... seems in spec. I replaced CR1...

It seems though that the "reset" advice from pinwiki is about the LED being stuck on. Whether or not the sound comes on, the LED never stays lit so we are getting deeper into the boot sequence...

One time on bootup last night, I thought I only got 4 flashes (I was trying to watch the LED and the MM at the same time so I am not 100% sure) which would indicate problems with the speech chip at u8.

I pulled u8 and it was severely tarnished so I cleaned it up..

So far after about 15 cycles sound has been coming on without issue..

We'll see.

Dave