Recap?

[ranzy]

I have had to do a bit of research since I got my dad's QX-747 to understand how it works and all. I have a little problem with it that I figured I would work on after I worked all the bugs out of the decoder. Well the decoder works just fine now and I am ready to try and fix the constant hiss from the amp section now. I know it is just the amp section because there is no hiss from the tape record jacks when I copy stuff to my computer. I do have the same hiss on the headphones as what comes out of the speakers, all 4 of them. You guys talk a lot about recapping old equipment and I would think that my problem is a capacitor problem but is on all 4 channels and the headphones, so I just don't know where to start. It seems to me that you guys recap your old equipment all the time. Could you fill me in on this subject a little bit.

Thanks,
Ranzy

 

[sqdave1975]

Electrolytic capacitors have an average life span of 20-25 years - with most quad gear meeting or exceeding that age the time has come to replace those leaky or weak capacitors. I recently did my Sansui QRX-8001 and quite enjoyed the process. The cost, if you do it yourself, is pretty low too.
I made a careful list of all the electrolytics in the receiver and bought replacements that met or exceeded the original specification. A service manual is a must in case any of the capacitor's values are illegible.
The result is stunning, particularly in the decoder section where the tolerances are critical.
The receiver now sounds better than ever!
I can't promise it will correct the particular problem you have, but if you will be keeping the Pioneer for a long time, then you'll be needing to do it soon or later anyway. In fact, better sooner than later - go for it !

 

[ranzy]

So, I only need to do the electrolytic capacitors? The rest of the caps don't have a shelf life?

Ranzy

 

[captainwrong]

How long did the process take you? And how complicated is it?

I'm considering doing my QRX-3000. I've got the service manual and have already replaced a transistor and an in-line fuse. I'm confortable with a soidering iron but not a master .

 

[sqdave1975]

I think it's just the electrolytics that suffer due to their construction. They use a paste, or liquid (electrolyte) inside the capacitor which dries up or leaks out and affects the value of the component.

It took me a couple of hours, but I'm pretty quick with the desolder gun. I did each board one at a time.
Most important thing is of course to pay strict attention to the polarity of the capacitors when replacing. Reversing one by mistake may cause serious damage.

If you're happy with straighforward solder/desolder techniques, you're on your way.

If you're working on boards with early integrated circuits, it's a goood idea to wear an approved ground strap to avoid static discharge damage to those irreplaceable chips!