GTB Raven sound issues

[Topher5001]

I unplugged the sound board connector, A6P1, & checked pin 5 of the aux. power supply to ground & got -6.56v.
I plugged A6P1 back in & on the aux. power supply, I checked resistor R7 to ground. The banded side read 13.7v & the other -6.57v. Checking the ohms of R7, I got 0.1.
Checking in diode mode, VR1 read -421 in one direction & 1 in the other. CR1 read 944 & 412; CR2 921 & 444; CR3 974 & 510; CR4 read 908 & 422.
Does this mean R7 is bad?
Edit: When I first it on, there's no sound. After playing a few games, it'll start to play the game music non-stop & sometimes make game sounds. I don't know if this means anything.

 

[sylvain]

I unplugged the sound board connector, A6P1, & checked pin 5 of the aux. power supply to ground & got -6.56v.
I plugged A6P1 back in & on the aux. power supply, I checked resistor R7 to ground. The banded side read 13.7v & the other -6.57v. Checking the ohms of R7, I got 0.1.
Checking in diode mode, VR1 read -421 in one direction & 1 in the other. CR1 read 944 & 412; CR2 921 & 444; CR3 974 & 510; CR4 read 908 & 422.
Does this mean R7 is bad?
Edit: When I first it on, there's no sound. After playing a few games, it'll start to play the game music non-stop & sometimes make game sounds. I don't know if this means anything.

If unplugging 6P1, & checked pin 5 of the aux. power supply to ground & got -6.56v, this means that the sound board is not dragging the aux. power supply -12V voltage down. Good news.

Please confirm the following two measurements. Is this a quality multimeter or a cheap one?
- resistor R7 to ground. The banded side read 13.7v (is it actually -13.7 volts?)
- ohms of R7, I got 0.1. (is this 0.1 Kohms ? if so, this would mean 100 ohms and would be fine).
- Checking in diode mode, VR1 read -421 in one direction & 1 in the other. (why a negative voltage reading in diode test mode ??? The pinball machine is OFF when you are making the measurements, correct?)

Are these voltages changing after a few games when the music starts playing?

I am starting to suspect this could be a bad cap on the aux power supply, or a bad zener diode.
But difficult to troubleshoot/help remotely with partial or inaccurate/incorrect data...

Cheers,
- Sylvain.

 

[Topher5001]

Sorry, I'm very new to this. I understand about the info & am trying to be thorough.
The DMM is a cheaper Canadian Tire one similar to this http://www.canadiantire.ca/en/pdp/mastercraft-digital-5-function-multimeter-0520060p.html#srp
Yes, the banded side read -13.7v (typo).
I had the DMM in 200k ohms when I measured the R7 resistance. I'll try it in a lower setting. I was mis-reading the DMM labels.
Yeah, my friend was writing the numbers down as I took the readings. The dash was a separating mark. It was off when I took the readings.
I thought of taking the readings once the music came in, but then I forgot. I'll try that tonight.
And thanks for the help. It's greatly appreciated.

 

[Topher5001]

I rechecked R7 with the DMM set to 200 Ohms & read 99.1. Voltages were the same as last night.
I checked VR1 in diode mode & got 301 with the red DMM lead on the banded side (top, towards the caps) & 231 with the black lead on the banded end. I triple checked this to make sure.
I'll play a few games until the music starts & check the voltages again.

 

[sylvain]

So... R7 is good (very close to expected 100 ohms).
Where are you placing the red and black probes in each direction of the zener diode test?
The readings do not seem to make sense... Pinball machine is OFF, right?
Can you measure that zener diode again with the connector removed on the aux. power supply?

 

[Topher5001]

I had the connector disconnected when I test it. I placed the leads on the legs of the diode.
The sound came on so I checked the voltages again.
On A6P1, pin 13 measured -6.5v DC (should be 12v DC), & pin 14 measured 12.8v DC (12v DC). On A5P1, pin 5 measured -6.5v DC (-12v DC). Measuring R7, I got -13.39v one way & -6.49v the other.
Edit: I thought the VR1 measurements didn't make sense either so I checked them a couple times. Last night, it measured closed in one direction (is that the right term?).

 

[sylvain]

If this was a machine under repair here, I would replace the zener diode on the aux power supply with a proper replacement and at least try to get the -12V proper, and also check the capacitor with my ESR cap tester - from the data you have provided us.

 

[Topher5001]

If that's the case, I'll take it to the place that socketed some chips for me & have them replace the cap & the zener.
I turned it off & checked the zener again & got 298 & 223. On A5P1, pin 5 measured -6.5v DC & R7 measured -13.39v & -6.49v. On A6P1, pin 13 measured -6.5v DC (-12v DC) & pin 14 measured 12.8v dc (12v DC).
Edit: When I turned it back on, the sound didn't come back on. I figure after a couple games it'll come back.

 

[Topher5001]

I'm going to take the board in & have C7 & VR1 replaced. C7 is 47UF, 50V & VR1 is a 1N4742A. Are there recommended upgrades, or just replace with the same?

 

[sylvain]

I'm going to take the board in & have C7 & VR1 replaced. C7 is 47UF, 50V & VR1 is a 1N4742A. Are there recommended upgrades, or just replace with the same?

Use the exact same VR1 zener diode number. For C7, you can use the same, or a 100uF 50V for better filtering if you want.

 

[Topher5001]

Thanks. I'll take it in on Monday.

 

[Topher5001]

I had C7 & VR1 replaced. I now get -12.26v DC on A6P1 pin 13 & 12.8v DC on pin 14, -12.25vDC on pin 5 of A5P1 & testing R7, I get -15.9v DC on one end & -12.26v DC on the other, so the voltages are good.
Unfortunately, there's still no sound, although it may come back after warm up. I'll have to wait.
I guess I'll start going through the procedure to test the ICs https://www.maaca.org/viewtopic.php?f=22&t=2044&sid=fbd677bce6aa7c7ac15a965ce55b9c89&start=25
Rats.

 

[Topher5001]

I finally got around to "Testing the Data Pathway".
I jumped to ground pins 2, 4, 6, & 8 of Z13 on the driver board & got nothing. The pins on A3J5 look good, but that's the one single-sided connector I haven't re-pinned because I mistakenly ordered a 7-pin connector housing instead of an 8 pin. I'll cut it off & re-pin it.
Pin 8 of that connector is for solenoid 8 & pin 2 is L2. I can't find another reference in the schematics to sol. 8 & the only reference to L2 is coming from the bottom cabinet to a motor relay. Could someone tell me what those are for? It may help me trace the problem.
I'll check Z13 when I get home. Since the game works fine other than no sound, I have a feeling it's Z13 that's my problem.
Edit: I found that solenoid 8 is the knocker. I'll set it to match instead of extra ball to see if the knocker works.

 

[Topher5001]

I went through steps 2, 3, 5 & 6 and got absolutely nothing.
I disconnected everything from the diode board & checked Z31 in diode mode. All the pins except no. 4 were in the vicinity of 0.4 to 0.7. Pin 4 measured .015. Does this mean the chip's bad? Would this stop all the sounds?

 

[Topher5001]

I tested the SB grounding pins 1, 2, 3, 5, & 8 & didn't get any sounds. Pins 4, 6 & 7 don't have any wires. Does this mean the SB's bad?
I'm not sure what to do now. Get another SB? Find someone to burn the sound ROMs?

 

[sylvain]

Have you measured the voltage from the now fixed power supply arriving on the A6 sound board?
Just in case there is a wiring or connector issue, especially after some repinning took place earlier...

On the A6 sound board:
- does the LED blinks on the sound board ?
- does the sound board have a test button that you can press to confirm sounds are working from the sound board itself?
- Make sure there is +5V measured across the C18 tantalum capacitor; confirm the polarity;
- make sure there is +12V measured across the C10 tantalum capacitor; confirm the polarity;
- make sure there is -12V measured across the C19 tantalum capacitor; confirm the polarity.

Once this is done, also check the sound board DIP switches.
I do not have the manual here, but another post on pinside for the sound board for this game shows:
DIP switch 1: ON for background sounds enabled (otherwise OFF)
DIP switch 2: not used
DIP switch 3: OFF
DIP switch 4: ON.

If all the above is correct (supply voltages and DIP switch options), and grounding sound input pins
1, 2, 3, 5, & 8 on the sound board does nothing (these pins should be at +5V when idle),
make sure the reset signal from the MPU (pin 9 it seems) is at +5V.

Make sure there are no chips running very hot on the sound board - if so, it might be bad.

At this point, I cannot help any further, sorry.
Debugging a sound board requires a logic probe, reference to the board's schematics and more advanced
electronic knowledge to trace the logic and signals properly... Cannot be done properly remotely...
And I have very little spare time...

Good luck!
- Sylvain.

 

[Topher5001]

Totally understand Sylvain.
The LED blinks correctly. There's no test for the sounds, only the beep that the MPU is working. I'll check those caps tonight. I don't think any chips get hot, but I'll be sure to check.
Depending on what I find, I'll give Al a call. When he was here looking the boot issue, he said he has a soundboard but would have to dig it up.

 

[Topher5001]

I read on a blog, http://ty-ffasi.com/repair/gottlieb-system-80b-sound-boards/ that the display could keep the SB from working & I read somewhere else that the driver board will hold the signal low & prevent the sounds from working when grounding the pins of the SB connector, so I tried both the no avail.
I'll have Z13 on the driver board socketed & replaced & if it still doesn't work, I'll call Al & see if he can dig up his SB to try out. I think that's the most likely scenario, but it's cheap to have a chip replaced.

 

[Topher5001]

I checked those cap voltages. I got 4.98v on C18, 12.72v on C10 & 12v+/- on C19.
The schematics show the positive end towards the switches (the manual shows the board upside down compared to how it's mounted in the back box). Of course, if I reverse the probes, I get -12v. Does this mean anything?
Edit: C18 & C19 are oriented the same way on the board.

 

[sylvain]

Voltages arriving on the sound board are good, including polarity across C10 & C19.
I should have been clearer in my post above, I was looking at the sound board schematics.
Connector pin 14 (arriving on + of C10) should be +12V compared to ground (- of C10),
and connector pin 13 (- of C19) should be -12V compared to ground (+ of C19).
This explains what you are measuring.