Defender: No sound, no controls...what to check?

Kalamath

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Ok, got my new Defender cab up and running, to a degree. I have both the regular and switching power supplies, and the game will boot up, and can be run through it's diagnostics with no rom, ram, nor display errors. The coin door controls work, and I can advance credits, or put the machine into manual mode and run tests.

Issue 1: Sound will come out of the speaker in the form of static if the volume pot is worked, but no sound from the startup, nor from the on-board sound check button. Occasionally there will be some slight static after pressing the on-board sound check, but not game sounds. Test 5 runs, but no sounds are made.

Issue 2: The control panel is non responsive. I tested continuity from the switches to the widget board, and that's good. Also, I tried unplugging the CP and jumpering a player 1 start with no effect at all. Test 6 shows Advance, High Score Reset, and the Coins all working, but nothing from the CP at all.

I've run both with and without the switcher, and get the same results, which makes me think it's not a power issue. Any ideas what I can test next?

ps. This is my only machine, so I can't swap in a different sound board or widget board unless I can find new ones to buy.
 
On the control panel, make sure you have continuity between the correct I/O header pin and ground. Ground on Defender is pin 10 on each header (as opposed to pin 1 on Stargate and later games).

Also check that you have a good ground connection going through the switches. You can test this by connecting one lead of your multimeter to the ground connection on the I/O connector and the other to one of the switch connections. Then press the switch. If that works, then make sure the ribbon cable from the I/O card is connected across both sets of pins on the MPU board.

Finally make sure you have a Defender I/O board. Somebody may have swapped in a later card. They look very similar. Pictures of each can be found on http://www.robotron-2084.co.uk/techwilliamshardwareid.html#defender

If you are still not seeing results, then you will need to break out the logic probe and schematics and trace the signal path through the I/O card.

ken
 
I'm definitely working with the "later" versions, NOT early, as per the illustrations.
Using what I have so far: (need to buy a logic probe/analyzer)

Control board:
Connectivity between ground pin and chassis is good.
Connectivity between ground pin and each button and JS tested good.


Soundboard 10J1 voltages are as follows: pin2 +10.15v, pin3 +4.9v, pin5(gnd) -4.2mv pin8 -14.16v

Question: even though the RAM test said OK, could one of the 4116's be causing this? I do have a tube full of them that came with the cab. Also, perhaps the voltages coming FROM the transformer could be bad? I'll test those as well. Just fishing for ideas as I learn this stuff.
 
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I'm definitely working with the "later" versions, NOT early, as per the illustrations.
Using what I have so far: (need to buy a logic probe/analyzer)

Control board:
Connectivity between ground pin and chassis is good.
Connectivity between ground pin and each button and JS tested good.


Soundboard 10J1 voltages are as follows: pin2 +10.15v, pin3 +4.9v, pin5(gnd) -4.2v pin8 -14.16v

Question: even though the RAM test said OK, could one of the 4116's be causing this? I do have a tube full of them that came with the cab. Also, perhaps the voltages coming FROM the transformer could be bad? I'll test those as well. Just fishing for ideas as I learn this stuff.

Do not think ram is the issue.....

Most likely bad connector or backwards connection, possible bad ground.
 
As for the sound issue, bad ground is my vote. Pins 5 and 6 of the sound board should measure less than a few hundred mV with respect to the main power supply ground.
 
Sorry, that should have read milivolts...typo. Corrected.

I pulled the little interface board and tested all the ribbon wires for continuity, all good there. Reseated all the connectors, etc.
 
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Another round of testing, here's my findings:

1. grounds seem to be fine all around the board. Tested everything 10 times over.
2. voltage to the sound board is there. No sound at all from the pcb's test button or test 5. I get a speaker pop at startup, just no sounds being delivered by the board at all.
3. test 6 for controls shows every button from the CP as stuck (displayed on screen) with and without the CP being plugged in, and also with the interface board completely unplugged at the ribbon cable. All coin door switches work fine still.

Seems to me I have 2 dead boards, unless anyone has something else I can try.

I think I've done all I can for now. I have a logic probe and misc supplies on the way to do some rewiring, and hopefully a order placed with Bob Roberts for stuff to rebuild the original power supply, cap kit for the sound board, sound rom, etc.

Hopefully I can get the sound board working, but I don't know what, if anything, I'll be able to do with the interface board. Already searching the classifieds for spare sound & interface boards, just in case. PM me if you have any laying around. =)


edit: to be clear on the CP issue, the switches all work and test out for continuity on a multi meter when pressed, I also tested continuity across the ribbon cable, and that's good too. I get a positive ground when testing 3J2 pin10, as it should be.
 
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Sounds like the PIA (Peripheral Interface Adapter) chip (the big one) has died on the I/O board. And yes, PIA does also mean Pain Inthe Ass chip as well.

If you are not hearing sounds when you press the reset switch on the sound card, it is not a good sign. It could be anything from a dead CPU chip to a dead amp chip to a dead D/A chip. That is where the logic probe comes in to see what is working.

ken
 
Update: Parts from Bob Roberts arrived last week but I've been busy with other stuff. First I recapped the power supply and totally removed the switcher. That went well, and was my first real electronics repair job.

Got the PIA chip out...Pain In Ass indeed! Made my life a lot easier by taking a Dremel to the old one and cutting all the pins free first, then de-soldering. Only boo-boo was singeing the edge of the ribbon. And the heel of my left hand.

Old:
IMG_0745.JPG


New:
IMG_0746.JPG


Yes! I now have controls! Yay! Moving on to the sound board now. New caps going in.
 
Update: Parts from Bob Roberts arrived last week but I've been busy with other stuff. First I recapped the power supply and totally removed the switcher. That went well, and was my first real electronics repair job.

Got the PIA chip out...Pain In Ass indeed! Made my life a lot easier by taking a Dremel to the old one and cutting all the pins free first, then de-soldering. Only boo-boo was singeing the edge of the ribbon. And the heel of my left hand.

Old:
IMG_0745.JPG


New:
IMG_0746.JPG


Yes! I now have controls! Yay! Moving on to the sound board now. New caps going in.

Congrats,

I like to see people fix there own stuff.
 
Damn....well, replaced all the caps on the sound board, as well as the crystal, and still nothing. Time to figure out how the hell to use this logic probe. If anyone has any tips on how to trace this thing, please let me know, I'll be checking back often.
 
I know you said you could hear static, but have you checked the speaker and it's connection too? My Defender had sound issue's once upon a time and it was the connection between the card and speaker. Just a thought.
 
Yep yep...in fact I just tested the speaker out of the cabinet to make sure it was working (it is) after rewiring it with some fresh wire. Good idea though. I get a pop and hum for a couple seconds when powering on, but nada from the card still. Thanks for suggesting it though.
 
Hmm...maybe I should replace the PIA on the sound board as well...any way I can test THAT with the logic probe?

Pull the schematic for the sound card and check the following:

Go to the sound diagnostic page, and make sure the sounds are cycling (you may need to press the up/down switch to get them to cycle).

The inputs to the PIA are pins 10-17. Check that these are pulsing with the sounds. If not you will need to trace the individual input signals at the cable from the ROM board.

Check pins 5-12 of IC13 (D/A converter). Those are the digital outputs from the PIA. If they are not pulsing when the sound diagnostic is running, it may be the PIA. If they are pulsing, it may be the D/A or the amp chip.

ken
 
Yellowdog, first let me say you rock man. Simply pointing me in a direction has been hugely helpful for my self-education of how this stuff works. I was up late last night studying the logic chart, trying to understand how the board works. This morning I got up with a clear picture of how to trace the signal paths.

Latest results:
-All the lines on the 10J3 are pulsing while in sound check mode, except J3-8 which seems to stay high no matter what. So, proper signals coming from the ROM board I think.
-All in/outs on IC5 pulse, as well as J3-6's line to IC7. Exception is IC5-7 & 6, which come from J3-8, which stay steady (high iirc).
-All inputs to the IC10 PIA chip pulse, except for pin17, which is the line from J3-8...this line is dead silent, neither high nor low signal. I've traced this path where it passes through W12/13. These diodes are marked as "PB7 Status Control, W13 never used" on the assembly drawing. Signal changed from high to low, across W12. Not sure what this all means yet.
-Inputs on the IC13 are steady, no pulsing. Of note, pin 9 sets off the speaker with some slight static popping when touched by the probe.

So from this data, I'm thinking the IC10(6821) is not functioning properly, but the one thing I can't figure out is that J3-8 line, if it's working properly or not. Is it supposed to be steady high, or should it be pulsing? One thing I haven't found is a table of what signals are sent TO the sound board during a sound check so I can verify the input is correct from the start.
 
Well shoot, sound board work is on hold, the machine developed a RAM error out of the blue that I have to figure out. It was playing fine & running, then shazam...rebooting and coming up with bad ram at R1.

Voltages read out good on ram pins 1,8,9,16, tried throwing a few different chips in, tried putting it back on the switcher just in case, checked all connectors to/from the CPU/Video board...nada.

Challenging hobby indeed!
 
Defender lives again. Replaced the RC1 voltage regulator on the PS, and the three 100uf caps on the CPU board (2 were bad). Now she boots up and plays again. Had to replace one of the 4116's once I got the new components in.

Now...on to the sound board problem. I've replaced all the caps as noted previously. Now I'm going to replace the 6802 and 6821 PIA since my logic probe trace dead ended there. Of note, the controller board fired up once the PIA on that board was changed out. Wonder if something like a voltage spike killed these chips in the past.
 
Still no sound. Here's where I'm at: New 6821 & 6808 chips installed tonight. Voltages on the sound board are T1= 10.9, T2= -14, T4= 4.92

When I run the sound test and start tracing the signal, I start at the inputs on J3. Lines 6 & 8 do not pulse, but stay on High. 2,3,4,5,7 all pulse.

Looking at IC5 (where the signals go through on their way to the PIA IC10), most of the inputs from J3 pulse, except IC5-11 which is dead. No signal H or L. Oddly enough IC5-12 pulses. I checked this like 20 times cause the logic sheet shows 11->12. IC5-6/7 both stay H.

Looking at IC10 inputs, they pulse, except for IC10-18 (from J3-6) which stays H I think, and IC10-17 (from J3-8) which is DEAD...no signal H or L.

Looking at IC13-5 to 12, no pulsing. If I poke at IC13-9 I hear static from the speaker, and can adjust the volume of said static with the volume pot.

I really don't know where to go from here. Is IC5 suspect? I'm working in the dark really because I don't even know if J3-6 and 8 are supposed to be doing what they are doing (staying High) during sound test.
 
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