[alpa6]

I'm recaping my sherwood s 7700.
I have one cap that i'm not sure of.
My schematic says 47.
The cap itself says 47.
It also says 22k above it.
I have tested it and can't get a good reading.They are all over the place.
It looks like this     22k
                          47
It's orange.This cap is at the end of the feedback loop.Will the wrong value cause a loud hum?
Anyone got a idea?
I have recaped all the powersupply.
All the preamp and amp sections.
I know i didnt make a mistake.
I have a loud hum now.Before it was a small hum with a midrange buzz.
Could of replaceing all the powersupply caps with new one's caused my old electrolitic filter caps to hum more?

[Bill Thomas]

     First off, unless I'm missing something here, it sounds like you have replaced ALL of the little capacitors, but haven't replaced the electrolytic filter capacitors.  Is that correct???  If this IS the case then you haven't really replaced the capacitors in the Power supply.  Replace the electrolytics!  Then let us know what happens to the hum.

     It sounds like your amplifier is now reproducing and amplifying the hum with greater clarity due to the new capacitors.  Replacing the main filter capacitors *should* reduce the hum.

     Hope this helps.

Bill Thomas

[alpa6]

Got the filter caps on the way.Bought some sectioned can caps.I'm still worried about that cap though.I can't get a reading on my cap tester.It's all over the place.Again anyone want to guess what a cap that looks like this is?   22k
                                                                                                                             47

[alpa6]

The cap has writing on it that looks like this     22k
                                                                47

[mgalusha]

A photo would really help. If it's part of the feedback loop perhaps it's a special part that is a 22K resistor in parallel with a 47pF cap. Compensation networks such as this are often used in feedback loops. Try taking a resistance measurement on it, if it's 22K then my guess may be correct and if you really want to you could replace it with a cap and resistor. I wouldn't worry about it too much, especially before you get the electrolytics replaced and the hum squashed.

[BobM]

Definitely post a photo, but you might also ask the experts here: http://www.diyaudio.com/

Good luck,
Bob

[nodiak]

Also try the Vintage Solid State forum at http://www.audiokarma.org if you haven't yet.

[alpa6]

A photo would really help. If it's part of the feedback loop perhaps it's a special part that is a 22K resistor in parallel with a 47pF cap. Compensation networks such as this are often used in feedback loops. Try taking a resistance measurement on it, if it's 22K then my guess may be correct and if you really want to you could replace it with a cap and resistor. I wouldn't worry about it too much, especially before you get the electrolytics replaced and the hum squashed.

Wow never thought of that!That would explain the schematic!I think you figured out my problem.It's not just a capacitor.
That's why i can't get a good reading.
Now what to do?Get a 22k resistor and a 47 pf cap and wire them up?
I have the old parts but i would rather use new ones.
Will this work?

[alpa6]

Oh one more thing why do you think it's 47 pf?