Q*Bert missing speech

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Well, perhaps it was the success I had reviving my Blasteroids pcb, or I'm just a glutton for punishment, but I've been poking around my Q*Bert boards. I have a problem with the sound and main cpu, but thought I'd try my luck with the sound board first. I'm totally missing speech, so I've started looking at the schematic to see what I can do before I have to throw in the towel and send these things off for repair. I really want to get better with pcb repair and I figure there's no other way than to get my hands dirty. Anyway I see what I think may be the problem. At U9, pin 13, which should be the enable for the latch, it never goes high. It's constantly low and according to the data sheet, it has to go high for the data lines to pass anything through, which doesn't sound like it's doing that. Does this sound correct? I've tried tracing that signal back all the way to the 6502 and I haven't found anything wrong unless I goofed on a reading. I'm sure I'll have to go back and check that area again assuming I'm on to something. Pin 3 of the 6502 CPU chip is showing high/low activity according to my probe. Any thoughts? Thanks.
 
Okay spent a lot of time poking around with my logic probe and even tried piggybacking a few chips I thought had issues. As it turns out, I think the enable for U9 is okay. I can hold my probe in place and watch it briefly change to a high state right about the same time I would expect to hear some speech. I did note something else with U9 however. The inputs from the data bus at pins 2 and 3 both pulse, but only the output from pin 2 pulses on the other side. The output from pin 3, which is pin 15, stays at a constant high. I wasn't able to observe any state change. I'm hoping it doesn't send up being the SC-01 speech chip, but I did notice I have no activity on pin 22, which should be the output.
 
http://www.andysarcade.net/

I would talk to Andrew Welburn, he is very approachable, and has helped me with a few qBert issues

He has worked out a sync mod, pinouts and speech for the bootleg board

Maybe he knows?

he is a member here, but I can't remember his user name
Thanks I will keep that in mind. :) One thing I noticed the other day is that there is definitely a trace that is broken on the solder side. It looks like it may have been an intentional cut and there is a jumper wire going from a point near the cut up to another TTL chip. Is anyone aware of any factory mods done to these sound boards?
 
Thanks I will keep that in mind. :) One thing I noticed the other day is that there is definitely a trace that is broken on the solder side. It looks like it may have been an intentional cut and there is a jumper wire going from a point near the cut up to another TTL chip. Is anyone aware of any factory mods done to these sound boards?

Yes, they all have this. It was done at the factory.
 
FWIW, Q*Bert appears to have the same sound/speech board that Gottlieb used in Black Hole and other pins. Of course there appear to have been a couple of small factory mods, and the software it runs will be different... but there should be some information useful to you here: http://www.pinrepair.com/sys80/s80sound.htm

These are the cutest little computers... tiny little clock circuit, a 6502, a RIOT for RAM and I/O, a couple EPROMs, a little address decoder... then the DACs, the SC-01, and an amplifier. Great example of a basic 8-bit system.
 
I tried replacing U9 and U12 and still no joy. Can anyone confirm that I should be seeing activity from pin 15 out from U9? There has to be some kind of state change there. I still get nothing but a high state even after replacing those chips. The other latches before it like U18 and U11 are showing changes on both their pin 15 and pin 16.
 
Oddly enough a co-worker of mine has a Gottlieb "Spring Break" pinball machine that's also supposed to use the sound board. He's going to be nice enough to dig his board out and let me try out his working speech chip to see what happens. In a way I hope it's not the speech chip because that will set me back a good $50 or so, but it would be nice to know that my troubleshooting hasn't been way off.
 
I'm going to bet on the fault being the speech chip...

It's a common failure - even more so in Q*Bert, since, IIRC, it runs the chip at too high a voltage.

But, in general, that chip is failure-prone. It's a common failure in GORF too. That's why working chips go for so much - they're rare.

-Ian
 
I'm going to bet on the fault being the speech chip...

It's a common failure - even more so in Q*Bert, since, IIRC, it runs the chip at too high a voltage.

But, in general, that chip is failure-prone. It's a common failure in GORF too. That's why working chips go for so much - they're rare.

-Ian
Well being that it can be hard/expensive to find the SC01, I went ahead and snagged 2 NOS ones off eBay for $35 a piece. Initially I bought only one but when I thought about it, I'd have at least one spare assuming my current one is bad so I bought another. If my current speech chip ends up not being the problem, I'm sure I could sell one of these two I just bought and only keep one as a spare. I didn't want to be kicking myself later for not taking advantage of a good price for NOS ones. There's still 1 left if someone wants it.

http://cgi.ebay.com/NOS-Votrax-SC-0...801?pt=LH_DefaultDomain_0&hash=item3f0911b7f9
 
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It's a common failure - even more so in Q*Bert, since, IIRC, it runs the chip at too high a voltage.

I'd be interested in seeing the evidence/argument for that assertion. The SC-01 datasheet I found online says (near the top of p8): "Vp = 7 to 14 Vdc" The Q*Bert schematics for the Sound/Speech Assy show the SC-01 having pin 1 (Vp) connected to a regulated 12V source, thru a 3V zener, which would appear to me to put Vp at about 9V; well within the specs. If I'm wrong, I'd be very interested in hearing the details about it being operated out of specs, so I can modify my PCB to improve the longevity of my SC-01.
 
I'd be interested in seeing the evidence/argument for that assertion. The SC-01 datasheet I found online says (near the top of p8): "Vp = 7 to 14 Vdc" The Q*Bert schematics for the Sound/Speech Assy show the SC-01 having pin 1 (Vp) connected to a regulated 12V source, thru a 3V zener, which would appear to me to put Vp at about 9V; well within the specs. If I'm wrong, I'd be very interested in hearing the details about it being operated out of specs, so I can modify my PCB to improve the longevity of my SC-01.

OK, that's my fault - I misrememberd. Went back and checked the schematics... it's not the SC-01 that is running at the wrong voltage. It's the sound amplifier chip. It's running at 30v when it should be running at 25 or so.

-Ian
 
OK, that's my fault - I misrememberd. Went back and checked the schematics... it's not the SC-01 that is running at the wrong voltage. It's the sound amplifier chip. It's running at 30v when it should be running at 25 or so.

-Ian

Ahh. Well my SC-01 can rest easier...

I assume you mean the LM379. Also not plentiful ($12 from Bob, $8 from Mark). Datasheet is also a bit of a PITA to find, but the one I did locate online appears to show a supply voltage range of 10 to 35VDC, and Gottlieb uses 30V. While this is a couple of volts above the "nominal" voltage (28V), it seems to still be within specs.
 

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Ahh. Well my SC-01 can rest easier...

I assume you mean the LM379. Also not plentiful ($12 from Bob, $8 from Mark). Datasheet is also a bit of a PITA to find, but the one I did locate online appears to show a supply voltage range of 10 to 35VDC, and Gottlieb uses 30V. While this is a couple of volts above the "nominal" voltage (28V), it seems to still be within specs.

Ah. Maybe it's not so bad then. I just remember finding the datasheet and seeing that it said the input voltage was 28v. That sound amp gets hot - reducing the voltage a bit can't hurt.

-Ian
 
Received the 2 NOS SC-01-A chips purchased from eBay. Sure enough I was rewarded with Q*Bert announcing he had been powered up! :cool: It's been a bad SC-01-A the whole time apparently (other than initially when I had no sound due to a bad amp). I'm glad I got a spare chip to keep squirreled away as well. Now to go after the background graphic failure on the main board....

Edit: I also believe I had a bad A10 on the main board as I would sometimes get the coin up sound playing at power up. I replaced it with the new one purchased from Bob and so far only Q*Bert can be heard at power up.
 
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