Centipede to Jamma adapter audio amp problem??? Problem fixed...Duh!!!

[ArtMAME]

Greetings fellow arcade nerds 

I just got a Centipede to Jamma adapter off Ebay and the pot on the audio amp section was bumped around durring shipping.  The pot was still on the board but bent and shifted, though it looked like it was still solidly mounted. 

I tested it with a working Centipede board and the game displays fine, but the sound is not right.  I hear a whine if I turn up the pot.  You can hear the game playing but barely.  Also when I turn the pot half way I get some nasty grunting and distortion.  When I turn it all the way down it is quiet. 

All the components still look pretty solidly mounted on the board.  I replaced the pot with an identical 10K pot, but still did the same thing. 

Does anybody recognize this problem???

Is there anyway to hack the adapter to bypass the audio section and use a different method of amplification, such as PC speakers or something???

[ArtMAME]

BUMP... 
I found a place where the audio pin from the Centipede PCB went into the Jamma adapter, and desoldered one end of a cap on the adapter as close as I could get to the audio out of the centipede PCB.  I fed that to some hacked amplified PC speakers, and soldered the black wire from the speaker amp to a ground point on the adapter. Still no sound.

 I tried coming off the audio1 or audio2 test points on the Centipede board into the PC speakers, still nothing.

At least when I went through the audio amp on the Jamma adapter, I could hear the game but very faintly. 

Could it be a bad audio amp on the Jamma adapter,
or could it be on the Centipede board itself?. 

Or does the audio circuit on the Centipede board use some kind of voltage that disappeared when I disabled the audio amp on the Jamma adapter?

Anybody have some ideas or suggestions? 

[RayB]

Well... my Centipede shows it takes in 22v for something... And JAMMA has a maximum of 12v, so maybe that's the problem. Have you tried talking to the seller of the adaptor? I keep seeing them on Ebay...

[ArtMAME]

I have read some docs on it and the 22V is for the high score memory.  It is not really required when JAMMAing the Centipede. 

As far as the seller on Ebay, he says contact him up to 15 days after the purchase if there is a problem.  It has been longer than that, plus he is in Canada, etc.  and shipping takes a long time, etc. 

I really don't feel like messing with all that.  I paid about $15 for the adaptor, so I am not worried too much about it.

I do have a Centipede wiring harness, AR board, Atari power supply, etc.  but I would have to fugure out all the wiring and stuff.  I do not really feel like messing with all that right now.  I have other projects I am focusing on right now. 

As for the Centipede cab, I think I will just use a PC platform for now just to get it working.   Then later, much later, try to get it going using the Centipede board and dedicated parts.   

[Rocky]

I've not had much success amplifying Atari boards without using the A/R II.

I don't really care for them as power supplies, so I use a switching supply when I can, but use the A/R II to amplify the audio.

When I test boards that need amplified, I feed the signal into an open audio input on my TV. It has plenty of power to make the game sound loud.

Good luck,
Rocky

[RayB]

As far as the seller on Ebay, he says contact him up to 15 days after the purchase if there is a problem.  It has been longer than that, plus he is in Canada, etc.  and shipping takes a long time, etc.

It might be too late for an exchange, but it's not too late to ask him the questions you posted here. (Assuming the seller has technical knowledge of how those adaptors work)

[ArtMAME]

I've not had much success amplifying Atari boards without using the A/R II.

I don't really care for them as power supplies, so I use a switching supply when I can, but use the A/R II to amplify the audio.

Thanks for the suggestion.  I will try that. 

When you use the A/R board, do you feed power to it using the Atari power block, and then just use a switching power supply to feed +5, -5, and +12 Vdc power to the main PCB?

From looking at the Centipede diagram, the A/R board needs 36 Vac, and 10.6 Vdc, so it looks like the only way to do that is with the Atari power block.

[Rocky]

I've not had much success amplifying Atari boards without using the A/R II.

I don't really care for them as power supplies, so I use a switching supply when I can, but use the A/R II to amplify the audio.

Thanks for the suggestion.  I will try that. 

When you use the A/R board, do you feed power to it using the Atari power block, and then just use a switching power supply to feed +5, -5, and +12 Vdc power to the main PCB?

From looking at the Centipede diagram, the A/R board needs 36 Vac, and 10.6 Vdc, so it looks like the only way to do that is with the Atari power block.

The A/R II needs the 36vac to power the audio part of the board.  the 10.3vdc simply passes through to the main board.

The 10.3vdc is needed for the CPU on the main board to reset.  It's unregulated so it is generally 12-15vdc, so using +12vdc from the switching power supply works fine.

By using the switching power supply to feed the main PCB, and using the A/R II for only audio, there is no need to tie grounds together since no DC power is coming from anywhere but the switching power supply.

Also, DC voltages are a common failing of the Atari power blocks.  As long as the 36vac is working, you get audio amplification.

Good luck,
Rocky

[ArtMAME]

Well, thinking that I had a faulty Centipede to JAMMA adapter, I got another Centipede to JAMMA adapter from a different source and got the same result.  Same result on both Centipede PCBs that I had, So I checked the rest of my setup...

The JAMMA harness and setup that I was using came from a Capcom game, so I thought that the sound was wired correctly since it worked with the Capcom game...

Looks like it did not have the -5Vdc wired into the board connector... ... it was not even used... the -5Vdc wires were uncut, unstripped, unused, and bundled up with all the other unused inputs on the harness... and the -5Vdc contact was unpopulated on the switching power supply...

I hooked up the -5Vdc into the board then...

"Budip, budip, budip, budip, budip....
budading-didadudip, budading-didadudip, budading-didadudip...
budip, budip, budip, budip, budip...."

So now I have 2 working Centipede to JAMMA adapters... guess I got to find another project Centipede cabinet to re-build so my extra JAMMA adapter doesn't go to waste...

[fredster]

Tell me if you need a working board. I have one for you for $75 shipped!

[ArtMAME]

I apreciate the offer fredster.  I do have one working board that I am going to put in my Centipede cabinet. 

I have another board with the RAM issues that I described in the other thread.  I am trying to get this board working to keep as a spare, or to use if I ever get another empty Centipede cabinet. 

Thanks for the tips on the repairs. 

[mrclean]

Well, thinking that I had a faulty Centipede to JAMMA adapter, I got another Centipede to JAMMA adapter from a different source and got the same result.  Same result on both Centipede PCBs that I had, So I checked the rest of my setup...

The JAMMA harness and setup that I was using came from a Capcom game, so I thought that the sound was wired correctly since it worked with the Capcom game...

Looks like it did not have the -5Vdc wired into the board connector... ... it was not even used... the -5Vdc wires were uncut, unstripped, unused, and bundled up with all the other unused inputs on the harness... and the -5Vdc contact was unpopulated on the switching power supply...

I hooked up the -5Vdc into the board then...

"Budip, budip, budip, budip, budip....
budading-didadudip, budading-didadudip, budading-didadudip...
budip, budip, budip, budip, budip...."

So now I have 2 working Centipede to JAMMA adapters... guess I got to find another project Centipede cabinet to re-build so my extra JAMMA adapter doesn't go to waste...

Sorry to bump a 7 year old thread, But I also had the exact same issue with the sound being garbled with using one of those JAMMA adapters. I just kept pushing it off for a while...The adapter I have is (Product - Centipede Jamma Adapter with Sound Amplifier PCB - No. A-01 from Y-Plus Product).. http://www.arcademvs.com/ARCADE_ACESSERIOR.htm . I tried another random JAMMA board in the cabinet without the adapter and sound was perfect, so I knew the speakers were fine. I borrowed another members adapter thinking mine might be faulty, same result buzzing noise low pitch audio issues etc... So likely at that point I knew It probably wasn't the adapter when that person who lent me their adapter said their centipede sounded fine on their end. I then thought it might of been the PCB at this point, but was told it was working / tested 100%. I had the opportunity to test my PCB on other non-JAMMA set ups with original wiring on two different centipedes, I just never got around to it but I gave the seller the benefit of the doubt. Rather then ordering a new centipede pcb, I installed a new volume pot which I read on another thread that It could alleviate the issue. Unfortunately after the vol. pot was installed same result, I needed to set the audio supper low / or off to avoid any buzzing / interference so really no improvement was made by installing a new vol. pot. Finally fast forward a few years I finally said you know what it's about time to fix this thing.. Came across this thread, also noticed my -5Vdc wasn't hooked up on my switching power supply, once I stripped the wires from the JAMMA Harness and connected them (E,5) to the power supply(-5Vdc) the audio was great and working the way it should be. Although to note the tiny vol. pot on the adapter is extremely sensitive. for a long time I had a buzzing low to no volume sound which this games audio as most makes the game. I'm glad after literally a few years I came across this thread & decided to fix it. Props to the original poster for posting the solution... I must have rushed when I installed this one, it's sometimes the simplest overlooked things to get these games working.