Noisy Reverb issues with Custom Vibrolux

jaytmon

Here's a link to a video clip of what is happening when I turn the reverb up on my Fender Custom Vibrolux:

https://db.tt/UmDKMz1E

It's been like this for a while. This morning it was fine, but after playing for 20 minutes or so, the noise crept in. The reverb is still working underneath it. It has also presented itself as sounding like gusty hurricane as opposed to more constant white noise.

The reverb valve has been replaced, but what's weird is when I removed it earlier and adjusted the reverb, I was still getting the noise coming through the speaker. 

I did some of the Mark Moyer mods to this amp to reduce the hissing when I first got the amp, and it was fine for ages. Maybe something it what I did finally affected it?

If anyone has any suggestions as to what I could do to try and diagnose this I'd be mightily grateful. I appreciate it might not be possible to tell what's wrong just be listening, but any pointers before I bite the bullet and pay someone to look at it...

Thanks.

DJH83004

I believe the Mark Moyer mods involve adding a NFB loop to reduce the hissing, so you shouldn't have disturbed anything around the reverb circuit. Don't forget there are two valves associated with the reverb the send (12AT7 - usually V3 A/B) and the recovery, 1/2 V4, usually V4A) so both should be swapped out, my prime suspect would be the recovery valve, especially as you say you are getting the noise with the tank disconnected.   

jaytmon

@DJH83004 thanks for this. I didn't realise there were two valves involved in the reverb circuit. I'll check it out tomorrow. V3 is the new one so that would line up with what you say about the recovery valve. 

jaytmon

@DJH83004 In a moment of rashness I decided to replace all preamp/reverb/tremolo valves, and I'm still getting these ghost noises when turning the reverb up. I've been thinking back to the mods I did, and I have a feeling there was something to do with the reverb being available on both channels but the mod changed that to just one... I'll have to check but that does imply potential fiddling with the reverb circuit. 

DJH83004

If you could point me to a link to the modifications I will happily have a look at them for you, it may give some pointers. I am still inclined to think it is associated with the recovery side, tank and /or RCA plugs and sockets - all common suspects. 

jaytmon

@DJH83004 Thanks man, much appreciated. I will see if I've got another RCA cable to test that out. I tried a bit of switch cleaner on the plugs/sockets on the amp chassis but not on the reverb tank end. 

Here is a link to the mods:
http://www.tdpri.com/threads/vibroverb-v-vibrolux.99305/#post-1131436

Note that I didn't install a bias pot or remove the surge protection diodes.

This link I used at the time too as it has some pics and tracks progress of someone else doing the mod:
http://www.tdpri.com/threads/custom-vibrolux-reverb-mod.191388/

DJH83004

@jaytmon, started reading through the threads and loosing the will to live :-) is there a schematic, detailing the changes or did you note down the changes you made?

jaytmon

@DJH83004 haha no worries dude I'll disseminate some more precise info when I get the chance. Schematic might be pushing my knowledge mind!

MattFGBI

It may be the pan or the reverb cable. If you changed the valves it doesn't leave much else. 
Do you have a spare RCA lead to try? 

jaytmon

@DJH83004 @MattFGBI ;
chaps I think you might've solved it - took the reverb tank out, evacuated the resident spiders, swapped the RCA cable and...silence! (Well pretty much, there was always a bit of residual hiss)
I am cautiously optimistic and assuming it remains that way after further testing, massively grateful!

Cheers