Major Havoc Build - no sound (but hums nicely)

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Hi,
Got a quick question.......
Doing a MH build using a Major Havoc conversion PCB, Amp Rack and wiring harness fabricated by Ken Falta.

When power is applied, I do not get the initial "boom" and there are no sounds during game play, all tests show OK.

I checked the harness at P8-3 to P8-4 (unplugged from the ARII) and get about 2.5 ohms through the speaker connections, no shorts there. I even tried disconnecting the speakers and tried one set at a time (upper / lower) just to be sure with no difference in "hum".

I checked P20-8 and P20-9 (SEC connector) and they have continuity to P7-8 and P7-9 (at the ARII) and appear to be OK.

I tried 2 different known working AR II's with the same results.

The board that I am using is a working pull and to be sure, I tried another known good PCB with the same results.

I have never attempted to use a conversion PCB in a dedicated cab and thought that I read all there was on using one in this application but it appears that I am missing something.

Can someone shed some light on my current (one of many) predicament!?!?

Thanks in advance
Jeff
 
to me it sounds like no signal is making from the main pcb to the arii
i would looks at the schems & wiring to see where / if it is getting lost

assume adjusting the volume pot does change the volume of the hum
 
Jeff,
I have three of these with Ken's harnesses, good stuff.
Try putting it into test and see if you see anything about the pokeys giving caution. Gotta have those guys working right to have sound. Could be something simple like the quad pokey plugged onto the board backwards or something...?
Good luck!
Chris
 
Thanks for the suggestions.....

Sorry for not being more detailed in my situation, the A/RII is rebuilt as well as the other known working one..... which works - tested in another game, (as well as on the bench).

The Powerbrick has been rebuilt and tested good on my bench.

Both PCBs are good pulls and both worked before being carefully stored in anti-static bags.

I will have to get back to the game and check that +12vdc line and see what I can find......

Thanks again
Jeff
 
What type of AR-II are you using?

MH normally needs a -04, which doesn't generate +12V. The -04 generates +/-22V, which the game board regulates down, via dedicated regulators on the board, to the other needed voltages.

If you've tried two known working MH PCB's, and two known working AR's, then the issue is either the brick or the harness. Make sure the +/-22V is on the AR, and is getting to the game board.

Also, when you say 'known working', I assume you mean the audio was verified working? Power and audio are somewhat independent, so you can have AR's that put out good voltage, but messed up audio.
 
OK, checked the schematics again and as far as I know, the MH PCB only needs +5vdc, +10v unreg, +/- 22vdc which I just verified at the PCB, all 4 voltages accounted for........

These 2 conversion PCBs were both tested in my Tempest with the adapter card before being placed in storage and both were 100% working, sound included......

This is a very strange situation and I will get to the bottom of this!

Thanks for the moral support and suggestions.

Jeff
 
Well, next would be to verify that you have an audio signal going from the game board to the AR. It's possible for the LM324 audio output amp on the game board to go bad, but if you're seeing it on two separate boards, that's probably not the case.

Be sure to check wires, remembering that just because there's a wire there, doesn't mean it's actually connected, so tone everything out with your DMM. A bad crimp can cause an open connection, as well as a broken pin inside the connectors (though this applies more to the connectors on the AR, which we suspect are ok if you've verified them in other cabs.)

Are you getting hum without the game board plugged in? Can you provide more detail on the hum? The cab should be silent without the game board plugged in, else it's a power or harness issue.

Have you measured the AC ripple on the DC voltages? Definitely check them, as it's easy to do, and rules stuff out.

Also, how is the volume pot connected? Is it the correct Atari 50 ohm rheostat? See here for more info:

http://forums.arcade-museum.com/showthread.php?t=390785
 
Just a thought, maybe you could pull the POKEYs from your MH boards and install them into your Space Duel, Black Widow, Gravitar, Star Wars, Quantum, (you get the idea) just to prove that they still work.

I like previous poster's idea, scope for the audio signal at LM324 (14Q) (schematic sheet 10A) and see if it is being generated in the first place, then follow the chain.

Bill B.
 
OK, with the PCB disconnected there is no hum.......

With the utility panel disconnected, I get volume but very loud. With it connected, I get no audio and the hum........

I checked the utility panel 4X and sounded every connection 4x and they are as per the schems, also checked the 50ohm atari pots and they work properly......

No shorts on the utility panel and all connected as per MH schems at the Molex connector.

I pulled pin 8 (10vdc) in case the diodes were shorted, same........

So to sum it up, once I connect the utility panel to the harness, I loose sound and gain a hum..........
 
So to sum it up, once I connect the utility panel to the harness, I loose sound and gain a hum..........

Sounds like there may be a problem with the harness. Unplug the utility panel and test for continuity on the main harness (P29) side: pins 2, 3, 11, and 12 should all be ground, and pins 1 and 10 should not.
 
That would be the conclusion one would draw but I tested the Harness at P29 checking pins 2-3-11-12 and all are ground and do not have continuity to pins 1 and 10.

I also checked and P29-1 has 2 leads, one goes to P20-8 (SEC) and P7-9 (A/RII).


I also checked and P29-10 has 2 leads, one goes to P20-9 (SEC) and P7-8 (A/RII).

I cannot see what is causing this and it is driving me KRAZY!
 
That would be the conclusion one would draw but I tested the Harness at P29 checking pins 2-3-11-12 and all are ground and do not have continuity to pins 1 and 10.

I also checked and P29-1 has 2 leads, one goes to P20-8 (SEC) and P7-9 (A/RII).


I also checked and P29-10 has 2 leads, one goes to P20-9 (SEC) and P7-8 (A/RII).

I cannot see what is causing this and it is driving me KRAZY!

I was just looking at and comparing schematics between MH and Space Duel, Quantum, Star Wars, etc. Only SW appears identical to MH. Any chance your cab has the incorrect UT panel? If it is the correct one, could you plug it into your SW as a test? Any chance a wire has broken off of the rheostat or something?

According to the MH schematic, the UT panel rheostat or pot is a dual-ganged part and is wired parallel to the AUD1 and AUD2 signals running from the PCB to the ARII. This accounts for why you get full blast volume (on both channels?) when the UT panel is disconnected. Since you have sound in this condition, I would expect it means that the main harness from Ken is okay. I'm assuming that the UT panel wiring did not come with Ken's harness. Since you are getting sound through without the UT panel connected, I suspect there's a problem in the UT panel itself. I would start by verifying the wiring of the UT panel (MH schem sheet 3A)

Bill B.
 
I checked the panel several times and just sounded the pots and verified that they are working at J29.......

I'll pull the panel out and trace every wire again, I might have missed something.

Thanks for the suggestion.

Jeff
 
OK, I pulled the Utility Panel again and tested all the connections as per the Major Havoc SP (attached)......

I sounded all the pots again that they are operating properly and verified that there are no shorts to ground on anything:
-checked all 3 legs of each pot to GND - N/C
-checked the test switch
-checked the aux coin switch
-checked both coin counter connections and verified the diodes are working and not shorted

This is crazy...........
 

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Harness pics
 

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Just a note, although I am using 2 separate pots in lieu of the double gang, it is wired exactly as per the schems.....

If anyone can see something that I am missing, I would be very grateful to please bring it to my attention.

Thanks for all the support.
Jeff
 
What are the pots you have there rated for? I had to source the 10K pots and that was kind of a pain. I bet the pots are either bad, wrong value, or wired backwards.
 
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