Deluxe Reverb Cap Job Done.....One Problem Remains...........

[Pastortom]

Just finished recapping with orange drops......Clean and quiet now, really nice.......

BUT, one problem remains.......When I begin to turn up the reverb, I get a little too much background "white noise" (gets more pronounced as it goes up).......Reverb sounds great except for the white noise.  Not bad, but noticeable to me.......

Any ideas on a fix ?  This has probably come up before, but I found no specific in the search.

[HotBluePlates]

This is a typical complaint with Fender amps with reverb.

I don't know of a specific fix. If I had a listening amp (a tool Doug describes in the Library of Information), I would poke around the reverb recovery stage to see if I could find the source of the extra noise.

[eleventeen]

I would replace (at a minimum) the first three "V" formations of 100K plate resistors with the 3 watt metal oxides from Doug. And while you're at it, replace the 3.3 Meg in the reverb circuit.

The 100Ks you show in your pix do not look discolored in any way so you are probably tempted to leave them as is. If you are trying to chase out hiss and "white noisy" tube sound I believe you'll achieve VERY noticeable results replacing those 100Ks. And by the way, you may think I am audio-hallucinating, but the amp will get quieter after being on for about 15-30 minutes AFTER replacing those resistors. Go ahead, call me delusional, but I just did THREE amps (SF Princeton Rev, AB763 SF Deluxe Reverb, AB763 BF Pro Reverb) that I have owned for many years. The new resistors made blazing, unsubtle, impossible to argue about differences, and got even better after cooking for a bit. On three out of three amps.

[HotBluePlates]

I wouldn't necessarily change all that stuff.

Since the noise described increases when the reverb pot is turned up, then it must be in the reverb circuit at/prior to that pot. Therefore, it is probably a waste to replace the plate load resistors for the dry signal path, since there is a complaint of excess noise from the amp with a dry signal.

The 3.3M resistor probably isn't a problem, for the same reason I mention; i.e., the dry signal is okay.

I'd be looking first at the reverb recovery stage plate load, maybe cathode resistor, maybe cathode bypass cap. I suggested the listening amp as a way to locate the noise with going on a blind chase. If the recovery stage turns out to be noise-free with the listening amp, then you would look at the reverb driver stage.

You might save parts and frustration in chasing noise by using the listening amp. I know the prevailing wisdom is to "shotgun-replace" all plate load resistors, and that sometimes works. However, I've also had cases where it didn't work, and I've had a '66 Super Reverb that does exactly what you're describing, and that amp had all new plate load resistors.

[Pastortom]

Are there any schematics denoting the reverb recovery circuit you mention in a clear fashion.......Would be helpful in my case.......

[HotBluePlates]

From the Hoffman Amps Schematic Library:

AB763 Deluxe Reverb schematic

The reverb recovery stage is the 1/2 7025 after the reverb tank, and is V4 pins 1, 2 & 3 (and associated components).

[Pastortom]

Great library..........Thanks again guys.