Returning MS275 to service.

[motion]

Hello,

Have this MS-275 which I picked up probably 10 years ago and intend to now use it in the car.

I see what I interpret as something coming from the capacitors.

I am competent in things mechanical and am not averse to working on this but I may enlist a professional. I am seeking guidance for my next step. I also welcome any warnings or advice you may have for my particular amplifier.

I see nothing at the base of the 4700uF but I assume those would need replacement as well. If I just replace the caps will that sort it out or should I get a pro to take a look at this?

Much thanks in advance for your time. Good group of people here.

[motion]

S/N, date:


The subject:


I see some... stuff... near the solder joints for the transistors(?, left side of picture, along the line from Q9 to Q7 to D8) as well as the base of the caps


Same type of situation at the base of the caps

[Stryker]

definately capicitor replacement....DO NOT give this amp power unitl you replace them. As for the Q7-Q9 thing someone else will prolly chime in. here's the links from this very phorum:
http://phoenixphorum.com/ms-capacitor-r ... t9930.html
and
http://phoenixphorum.com/power-supply-c ... t8276.html
hope this gives you an idea on the work required.

[oldschoolfan]

Good eye. What you are seeing appears to be "The" weak spot with all early PG amps. This is super common. The larger caps almost never show this issue so you should be fine with replacing just the smaller "power supply" caps.

The links posted above should guide you nicely through the repairs. My only suggestion, and it is just my opinion, is to not use silicon under the caps. If you ever need to remove them again it would hamper removing them. When you place the new caps, just bend the two leads in opposite directions to hold them in place. Cut the leads after bending but before soldering. This way the ends of the leads will also be sealed in under the solder. Prevents corrosion on the tip of the lead.

Have fun!

[Eric D]

Good call on the silicone. I cannot stress enough how bad of an idea it is to place silicone under the caps.

1) If you do have to remove the caps, you can damage the board (I had to do this on a few amps over the past few months, and in at least one case the copper pealed from the fiberglass under it).

2) Yes the silicone will keep the fluid in the caps, but if they are breaking down, they will still internally short and catch fire. Keeping the fluid in them does nothing to prolong their life.

3) With the silicone there you can never notice in the future if they are failing. Seeing the tell tale signs of fluid near the caps is the only way to determine they are failing before they actually do. The silicone will keep you from knowing this and if they fail in the future they will do so without warning.

Using silicone to keep the caps stuck to the side of EACH OTHER is just fine, and is not difficult to remove in the future if you must do so. Ideally silicone should not touch the board if possible.