CPS-1 (SF2:WW) Muffled Audio Repair

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NoAffinity
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CPS-1 (SF2:WW) Muffled Audio Repair

Postby NoAffinity » February 3rd, 2017, 6:39 pm

Hardware: SF2: World Warrior 'A' Board
Symptom: Muffled Audio, Barely Audible at Full Volume, With Apparently Correct Sounds

One of my SF2: World Warrior 'A' boards developed an issue whereby it produced barely audible audio. With the volume pot set to full volume, audio could be heard, although it was barely audible and muffled. Sounds seemed to be correct, and all there. Interestingly, it also had graphics issues alongside the failure of the audio, but re-seating things seems to have fixed the graphics issues, so we will assume the two are unrelated.

I first inspected the audio circuitry - traces, amp, amp solder joints, caps, cap solder joints, Z80 solder joints. Nothing visually stood-out as a potential source for the issue.

I proceeded to replace all of the capacitors in the sound circuit (I have a list of the caps, which I will add to this thread). This produced no noticeable improvement.

I then replaced the on-board audio amp. This fixed the problem. Below is a picture of the removed/faulty amp sitting on top of the amp heat sink. The new amp is installed and working great. Note that the legs of the amp a straight, from the factory. You can look at the removed amp to determine where the 90 degree bend needs to occur, and use some needle nose plier to get the correct bends on the new amp's legs before installing.

Two screws, bending the new amp's legs to the correct 90 degree angle, and 12 points of de-solder/re-solder is all it takes to swap the amp. I found there was no thermal transfer material (like thermal paste) between the original amp and the heat sink, so I spread a small dab of Arctic Ceramique between the two prior to fully securing the new amp. A bit of additional "best practice" to hopefully aid in the longevity of the new amp.

To summarize: replacing the amp fixed the problem. Replacement amps are readily and inexpensively available on ebay, simply by searching for "amp HA13001". I found that there were multiple "secondary part numbers" associated with the HA13001. I don't know what, if any difference there is between these, but the one I used and proved is 4G1 HA13001.

Hope this information is helpful.

20170106_184802.md.jpg
Last edited by NoAffinity on February 4th, 2017, 12:33 am, edited 2 times in total.
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Asayuki
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Re: CPS-1 (SF2:WW) Muffled Audio Repair

Postby Asayuki » February 3rd, 2017, 10:58 pm

Well, done. I also had similar problems with this specific amp.
About the 3 letters/digits marking code, it just identifies the specific production lot. The silicon is identical. ;)
My 15kHz cabinet Peplos will never power up, with any item, and I am quite proud of that.
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Re: CPS-1 (SF2:WW) Muffled Audio Repair

Postby NoAffinity » February 4th, 2017, 12:27 am

Asayuki wrote:Well, done. I also had similar problems with this specific amp.
About the 3 letters/digits marking code, it just identifies the specific production lot. The silicon is identical. ;)

Thanks for clarifying. HA13001 with slightly different specs than all the others, when I was trying to figure out which to purchase, but possibly it was just incorrect information by the ebay seller.
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Re: CPS-1 (SF2:WW) Muffled Audio Repair

Postby NoAffinity » February 6th, 2017, 12:33 am

And, here is the complete cap list for the audio circuitry (all the caps surrounding the amp). It turned out to be unnecessary to replace them as part of this fix, but others have reported the same problem, and fixing it by replacing these caps.

cc14 16v 47uF
cc18 50v 4.7uF
cc22 25v 2200uF
cc23 50v 2.2uF
cc9 16v 10uF
cc13 16v 10uF
cc10 16v 10uF
cc11 16v 10uF
cc6 16v 10uF
cc7 16v 10uF
cc8 16v 10uF
cc12 16v 10uF
cc17 16v 10uF
cc15 25v 100uF
cc16 25v 100uF
cc19 25v 100uF
cc21 25v 100uF

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