(Topic ID: 66450)

Medusa Squawk & Talk: sound effects super quiet, voice super loud

By jasonbar

10 years ago


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  • 11 posts
  • 3 Pinsiders participating
  • Latest reply 10 years ago by jasonbar
  • Topic is favorited by 2 Pinsiders

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#1 10 years ago

Howdy-

I picked up a Medusa.

There is a sound issue that I can't resolve by adjusting all 3 pots (coin door master volume pot, sound effects volume pot on S&T, & voice volume on S&T).

At first, I thought that there were no sound effects at all, just voice. It turns out that the sounds are there but reeeeeeeeeeeeeeeeeeeeeeally quiet.

I've currently turned the coin door pot up to its max, turned the effects pot up to its max, & turned the voice pot down to almost nothing. This makes the effects & voice roughly the same volume as each other, but there's a good amount of hiss/whine/pop b/c the gain is up so very high.

I've semi-cleaned the 2 S&T pots (alcohol & toothbrush w/out removing pots from PCB), which removed some "crunching" when turning the pots, & I've cleaned the header pins on the S&T, & I've reseated the 2 connectors on the S&T.

What might be the problem? The speaker sounds good, the sounds sound good, the wiring seems to be good, it's just that the effects volume is pathetically low. New pot? Bad cap or resistor or something in the sound effects part of the board?

Thanks,
-Jason

#2 10 years ago

Probably one of those small 2uf caps, have you done a cap kit on it? Usually solves those types of problems:

http://bigdaddy-enterprises.com/repairkits/bally_kits.htm#b-snt1

#3 10 years ago

I had the same problem, someone said change the caps so I changed them all. No problem after that, sounds better also. There`s not many on the board.

#4 10 years ago

And honestly if one has failed, another will likely fail soon. They age and sometimes just totally drop out, others just gradually get weak. Replacing them all usually does improve the overall sound too. These are 30 years old, most people agree electrolytic cap life is about 20-25 years.

#5 10 years ago

Thanks tons for the replies. I came across Big Daddy some time ago but had forgotten about it.

I'll report back after resolution. :]

-Jason

#6 10 years ago

Big Daddy just got a lot of my money. :] Figured I'd buy lots of other goodies while I was at it.

One question/concern:

The last page of the Medusa manual ( http://mirror2.ipdb.org/files/1565/Bally_1981_Medusa_Manual.pdf ) says that the Squawk & Talk is AS-3107-6.

Big Daddy lists it as AS-2518-61 ( http://bigdaddy-enterprises.com/repairkits/bally_kits.htm#b-snt1 ), but Big Daddy's page does specify that their kit is for Medusa.

Equivalent part numbers...?

Thanks,
-Jason

#7 10 years ago

That's just specifying it's for Medusa, meaning the ROMs and maybe a few other things.
-8 Elektra,
-9 Vector
-10 Spectrum
-11 Rapid Fire
-12 Mr & Mrs PacMan

I don't have the full list handy

#8 10 years ago

Thanks, Todd!

1 week later
#9 10 years ago

I received my cap kit from Big Daddy, including the 2 trimmer volume pots.

Installation per http://bigdaddy-enterprises.com/pdf/bally-snt.pdf was straightforward, with the following minor exceptions:

1 - I had a different rev of the Squawk & Talk board from what is shown in the instructions.

2 - Therefore, a few caps were in slightly different places/orientations, but close enough to figure out.

3 - I was unsure of polarity on the big C14 capacitor--I ended up matching the silver/black ends of the new vs. old & matched the necked-down feature.

4 - For the 2 radial tantalums, the board was unclear about polarity, & the old ones that I removed didn't seem to indicate polarity either.

In any case, all done, & both sound volumes are nice & high & equal & clear. Fixed!

Thanks,
-Jason

CIMG3149.JPGCIMG3149.JPG CIMG3152.JPGCIMG3152.JPG
#10 10 years ago

You got the polarity right on the 4700uf cap, the "+" on and the ridge indicate the positive side. On the tantalums, I'm looking at two identically marked boards and surprised one has a "+" sigh on the right and one does not on ONE of the caps. Regardless, the cap should be with the plus leg on the right, and the cap itself is marked with a little "-" and ""+", but also (too late now) the + side has the longer lead. I stock another cap that has + + marked on one side, but I think in EITHER case, if you look at the cap head on the + is on the right. While it works, you may want to check that it's installed correctly.

#11 10 years ago

Thanks, again Todd.

1: 4700 cap. The +s on that cap appeared to be part of the specs text on the housing, but I see now that those 2 +s were simply hanging out nearby the other words & letters but were not actually a part of them--my oversight--thanks.

2: Tantalum @ C14: I did see the + on the PCB, but it was also close to test point TP1, so I wasn't 100% sure if the + belonged to the cap or the test point, but studying other markings on the PCB led me to believe (correctly) that the + belonged to the capacitor, not the test point.

3: Tantalum @ C16: Indeed, mine did not have any + marking here. I had installed the + lead for this cap on the left, as shown above (pic above taken showing PCB as mounted in backbox). The sound worked just fine. However, after reading your post, I went in & swapped C16 to put the + on the right. The sound board still works & still sounds the same as before the reversal. :]

Thanks,
-Jason

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