Tech Help Needed: Galaga Sound Prob

[John Bennett]

[ukvac] Tech Help Needed: Galaga Sound Prob
Can anyone offer a suggestion on this problem????

I have a bootleg Galaga (the blue type with 4 x Z80s) with a sound
problem.

The sound works OK but is quiet, turning the volume pot increases the
sound very slightly but greatly increases a background hum.

I've changed all the caps in the audio section, the audio amp and the
volume pot none of which has made any difference.

Any suggestions where I go from here?

TIA )

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Regards

Lee

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[invadarr]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
At 09:31 AM 11/15/99 -0800, you wrote:
>Can anyone offer a suggestion on this problem????
>
>I have a bootleg Galaga (the blue type with 4 x Z80s) with a sound
>problem.
>
>The sound works OK but is quiet, turning the volume pot increases the
>sound very slightly but greatly increases a background hum.
>
>I've changed all the caps in the audio section, the audio amp and the
>volume pot none of which has made any difference.
>
>Any suggestions where I go from here?
>
>TIA )
>
Have you tried changing the 12v supply cap C26
it sounds like a power supply fault to the amp !!!
Regards

Pete (Invadar)
>Lee
>
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[John Bennett]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
Hi Pete, thanks for your reply.

> >
> Have you tried changing the 12v supply cap C26
> it sounds like a power supply fault to the amp !!!
> Regards
>

I've changed C26 but it didn't make any difference. I replaced it with
what was already there a 25V 100uF. Interestingly the printing on the
board is a bit contradictory, on C26 there is a + symbol printed on the
board over the ground trace. The original cap ignored the printed
symbol and had its - lead into the ground trace, as it should be?!?

Thanks for your help.

Lee

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[zepromz]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
At 13:37 15/11/99 -0800, you wrote:
>Hi Pete, thanks for your reply.

Wrong pete, theres actually 2 Peter Davis's on the list!
You want: peterdavis@enterprise.net

Cheers!

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[invadarr]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
At 01:37 PM 11/15/99 -0800, you wrote:
>Hi Pete, thanks for your reply.
>
>> >
>> Have you tried changing the 12v supply cap C26
>> it sounds like a power supply fault to the amp !!!
>> Regards
>>
>
>I've changed C26 but it didn't make any difference. I replaced it with
>what was already there a 25V 100uF. Interestingly the printing on the
>board is a bit contradictory, on C26 there is a + symbol printed on the
>board over the ground trace. The original cap ignored the printed
>symbol and had its - lead into the ground trace, as it should be?!?
>
>Thanks for your help.
>
Hi Lee,
I have two blue type galaga boardsets
on the one that is working the c26 + terminal lead is attached to the
track which has the + sign on it and although this seems wrong
the board seems to work OK. it has a MB 3712 audio amp?????
the other board has this amp missing and is not working yet
I'm working on it now, but it has the cap wired the opposite way
round Weird or what?????
when I get it going I'll let you know what happens
Regards The other pete (INVADAR).

>
>
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>

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[John Bennett]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob

> >
> >I've changed C26 but it didn't make any difference. I replaced it
with
> >what was already there a 25V 100uF. Interestingly the printing on the
> >board is a bit contradictory, on C26 there is a + symbol printed on
the
> >board over the ground trace. The original cap ignored the printed
> >symbol and had its - lead into the ground trace, as it should be?!?
> >
> >Thanks for your help.
> >
> Hi Lee,
> I have two blue type galaga boardsets
> on the one that is working the c26 + terminal lead is attached to the
> track which has the + sign on it and although this seems wrong
> the board seems to work OK. it has a MB 3712 audio amp?????
> the other board has this amp missing and is not working yet
> I'm working on it now, but it has the cap wired the opposite way
> round Weird or what?????
> when I get it going I'll let you know what happens
> Regards The other pete (INVADAR).
>

Hhmmm, interesting, I did try a cap the other way round with the + lead
matching the + printed on the board. When powering the thing up the
background hum disappeared for a few seconds then the cap exploded!! A
rather scary experience ;-) When I stopped shaking, I concluded that
the board had been printed incorrectly but perhaps not? On your working
board is C26 a 25V 100uF?Mine has a MB3712 amp as well (not the usual
MB3730 of original Galagas).

Thanks again )

Lee

(P3TE this is posted to the list and not you personally ;-) )

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[junofirstman]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob

> Hhmmm, interesting, I did try a cap the other way round with the +
> lead matching the + printed on the board. When powering the thing up
> the background hum disappeared for a few seconds then the cap
> exploded!! A rather scary experience ;-) When I stopped shaking, I
> concluded that the board had been printed incorrectly but perhaps
> not? On your working board is C26 a 25V 100uF?Mine has a MB3712 amp
> as well (not the usual MB3730 of original Galagas).

I can confirm this is the case with the blue Gallag bootleg boards as I
did the same thing.. "Hmmm, thats soldered the wrong way around. I
wonder why it hasn't died"... Solder, solder... "Pop".. Hmmm

Chris

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[zepromz]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
At 03:03 16/11/99 -0800, Lee wrote:
>(P3TE this is posted to the list and not you personally ;-) )

Yeah, sorry bout that dude!, I get confused too

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[John Bennett]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
> I can confirm this is the case with the blue Gallag bootleg boards as
I
> did the same thing.. "Hmmm, thats soldered the wrong way around. I
> wonder why it hasn't died"... Solder, solder... "Pop".. Hmmm
>
> Chris
>

I'm glad I'm not the only one to fall into this trap ;-)

Was you also having sound problems with your Galaga Chris?

Lee

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[d-type]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
Hi All,

We design our own boards at work, not disimilar to retro arcade stuff (for
custom volume computer monitoring systems). Sometimes we get the screening
wrong, and it never gets fixed 'cos it causes a delay in shipping, so don't
be surprised...

Bye.
Phillip Eaton
phil@pjeaton.demon.co.uk

 

[junofirstman]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob

> I'm glad I'm not the only one to fall into this trap ;-)

... It happens to the best of us.

> Was you also having sound problems with your Galaga Chris?

Yeah. I had a fully working gallag bootleg, except the explosion sound wasn't
working. Unfortunately while I was poking around trying to work out where the
sound was generated, (anyone got schems for the 4 z80 Gallag bootleg?), I
toasted one of the cpu-cpu buffer chips. (haven't worked out which one yet)

The really sad thing is that I found the resistor which was broken about 5
minutes later! Fixed explosion, dead board

Chris

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[John Bennett]

[ukvac] Re: Tech Help Needed: Galaga Sound Prob
chris_hard-@vie.co.uk (chris hardy) wrote:
> Unfortunately while I was poking around trying to work out where the
> sound was generated, (anyone got schems for the 4 z80 Gallag
bootleg?), I
> toasted one of the cpu-cpu buffer chips. (haven't worked out which
one yet)
>
> The really sad thing is that I found the resistor which was broken
about 5
> minutes later! Fixed explosion, dead board

That's a gutter! Don't you just hate it when something like that
happens?! :-(

Well I'm not sure where to go next with mine. Changed every component
in the amp circuit and still that irritating hum, guess I'll have to
live with it for a while.

I wouldn't mind a copy of the schems if anyone has a copy?

I believe these blue bootlegs were either manufactured or distributed
by Kyugo Trading Co Ltd, Tokio, Japan. Not sure if this company is
still in existence, they appear not to have a web presence. Anyone
heard of this company or knows anything about it?

…on to my next project, getting a Section Z running... more traumas
ahead no doubt ;-)

--
Regards

Lee

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