HH Sound Board Amp mod/help..???

[ROLLERBALL]

Hey guys...Ok well after some playing around Ive found out why my HH sound board is not working...the Amp is dead...
I spoke to Mick and he says it could be an easy fix..but could also need a part that you cant get anymore...

I used this test on Marvin's site...and I could hear the sounds..

A set of headphones can also be used on the sound board. Hook an alligator lead to the part of the headphone plug closest to the plastic plug handle, and connect the other end of the alligator wire to ground. Now use another alligator lead and connect it from one of the other two sections of the headphone plug, to the lead of R15 (or R16) furthest away from the edge of the sound/speech board. Sounds from the sound/speech board should be heard in the headphones. If sounds can be heard in the headphones, but not at the speakers, then the sound/speech board's audio amplifier may have failed (or +30V at the sound board is low/missing).

Anyway just a thought but I checked with Mick B and he says it would probably work...I thought why cant I buy a small Amp that will run on 12v dc...run the new amp on the machines 12v power... and then run wires into it the same way I had them setup for the headphones and then plug the speakers into that amp...bypassing the busted amp on the soundboard???

Would this work??

[ROLLERBALL]

Something like this may work???

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=260455218799&viewitem=&sspagename=STRK%3AMEWAX%3AIT&salenotsupported

[The pinballist formally known as Dean Morgan]

You can do a mod and replace the AMP with a newer LM 1875.

I have done this on other System 80 games, many times.  Most recently for Tony T on this site to get his Rocky sound board working.

So Tony can also vouch for how well it works.

The info is available on the web some where, but I will PDF the article and send it to you tomorrow.  Whats your email address?

[The pinballist formally known as Dean Morgan]

Here is the link to the article,  this works VERY well and is simple

http://www.geocities.com/kirbseepe/repairAMP.html

[The pinballist formally known as Dean Morgan]

The new amp is widley available,  I buy mine here:

http://www.altronics.com.au/index.asp?area=item&id=Z2599

[ROLLERBALL]

Thanks heaps for that...

[tonyt]

Can vouch that my soundboard is working great with that amp mod, thanks Dean

[ajlaird]

Either way will work; not sure which one would be easier to implement - probably replacing the op-amp on board.

[Wotto]

Hey Paul.

I deal with Altronics !
Didnt know they sold that.

Can probably get U that for nothing if I ask nicely ( maybe  )
Want me to ask?

[ROLLERBALL]

I should be able to do the Mod...will grab the parts later today...

I just dont understand this part of the mod..???

Now that the pins are soldered to the board, you have to get +12V to pin 14 of the socket. I grab this +12V from the + side of C39. This will bias the +IN so that it won't saturate. Your amp will only work for about 30 seconds without this +12V.

Im guessing I need to find the + side of c39 and run a wire from it to pin 14..??Is that correct??

[ajlaird]

That's what it says!

So yeah, solder a wire from the + side of C39 to pin 14.

[ROLLERBALL]

All good...got all the bits i need...will get back on here in a few hours and let you know if it worked..lol

[The pinballist formally known as Dean Morgan]

I should be able to do the Mod...will grab the parts later today...

I just dont understand this part of the mod..???

Now that the pins are soldered to the board, you have to get +12V to pin 14 of the socket. I grab this +12V from the + side of C39. This will bias the +IN so that it won't saturate. Your amp will only work for about 30 seconds without this +12V.

Im guessing I need to find the + side of c39 and run a wire from it to pin 14..??Is that correct??

  Correct +ve side of C39 to pin 14.  Remeber the oriontation of the original chip is upside down.

[pinballahq]

Hey Paul,
if you want to keep the sound board and the power supply original, I've got some of the LM379s chips coming in about a week if you wanted one.
Let me know,
Anthony

[The pinballist formally known as Dean Morgan]

How did you go rollerball??