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Rygar no sound

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Shinydaz View Drop Down
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    Posted: 16 Sep 2017 at 3:34pm
Ive had this one a while and wanted to take my time over it. No sound but the amp was running, replaced all the caps in the sound section made no difference. Sound rom checked out good, swapped ram out as it was socketed, no change. Started to probe around, it took me a while but I found a hex inverter at R4 with stuck output pins on the top/sound board. We now have sound, another one saved !
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Flinnster Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2017 at 4:33pm
Cool! :)

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurray Banana Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2017 at 6:26pm
nice
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Shinydaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Sep 2017 at 7:05pm
Does anyone have a copy of the schematics for this? The links I tried where dead.
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Shinydaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 07 Oct 2017 at 9:21pm
Well I thought this was fixed, I jumped the gun a bit, after resetting the game, I have no sound again. I think I've narrowed it down to the chip enable on the audio rom (4h) followed it back through a couple of chips next to it, but then the trace disappears under chips and can't find it, even with a continuaty test. Schematics would be so helpful right now If I short some chips the chip enable pulses away and the sound returns.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote favouredson Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2017 at 2:52pm
CE for 2H comes from pin4 of the 74LS139 @ 5F.
Garry
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Shinydaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2017 at 4:06pm
Yes thanks, I did trace it back through a couple of ic's but they appeared to be working ok, once I shorted pin's further back. Tried following the (ls139) enable (1) and select pins(2,3) further back, that's where it gets a bit harder to find.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote favouredson Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2017 at 6:01pm
I've just had a quick check and several of the lines end up at the Z80 @3/4J. 74LS139 A0a is tied to A14 (pin4), A1a is tied to A15 (pin5).

Where the enable line goes to the 74LS32 @ 5H the input on pin4 comes from pin4 of the 74LS04 @ 5E; the input for this (pin3) is tied to RFSH (Z80 pin 28) and the input on pin5 of the 74LS32 is tied to MREQ (Z80 pin19).

As so much is connected to the Z80 it may be worth swapping it out.
If nothing else, it will rule it out of the equation.
Garry
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Shinydaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 08 Oct 2017 at 6:11pm
Thanks for taking the time to look at this. I'll go over all of this, this week. I've already tried another z80, thanks.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 10 Oct 2017 at 3:04am
It must be on the reset circuit for the z80, if I manually send a low signal to the reset pin, it resets and the sound works.

Edited by Shinydaz - 10 Oct 2017 at 3:12am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote favouredson Quote  Post ReplyReply Direct Link To This Post Posted: 14 Oct 2017 at 3:20pm
If you haven't got round to it yet, check the 74LS08 @ 4S.

The reset line for the main CPU inputs on pin9 and outputs on pin8 to go to the sound CPU. (The input on pin10 is tied to +5V.)

As the game is running properly you know the reset line is okay up to this point.
Garry
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Shinydaz Quote  Post ReplyReply Direct Link To This Post Posted: 16 Oct 2017 at 4:07pm
Thanks for the info, I've checked that chip out, seams to be ok. I tried another z80. It worked when I swapped it out but turned it off and on again and not working again. The time in which it's held low before going high is the shortest I've seen on any board. Maybe it just not being held low enough some times?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote favouredson Quote  Post ReplyReply Direct Link To This Post Posted: 17 Oct 2017 at 11:06pm
Very odd, I have had numerous Rygar PCBs over the years and I have never come across this issue, but all the sound issues I have had have been in mixing/amplification rather than generation.
I tested one of my PCBs and the reset line stays low for about half a second.

It could possibly be that one of the other ICs connected to the reset line is faulty and pulling it high.

For the record, the (sound) reset line is used to reset/initialise the following ICs;
YM3526 @ D4 (pin 1)
74LS175 @ M2 (pin 1)
74LS04 @ H6 (pin 5)
74LS08 @ E7 (pin 2)
40HC000 @ S7 (pins 2 & 13)

I couldn't find any more when I checked but I did find that it was also connected to pin28 of the empty socket near the edge connector.
Garry
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