Deluxe Reverb Microphonic?

[johnwilliamhunter]

Hi All,

I'm having trouble with my Deluxe Reverb Reissue, looking for some advise.

It was working fine, then I replaced v4 with another 12ax7 and when I would play I would get ringing noise attached to my guitar notes. Tapping the amp cabinet forced this ringing noise through the speaker too. I figured the tube was microphonic so I put the oringinal one back in, but the problem was still there. I replaced all the tubes back with the original ones, but still the same problem. Didn't matter which tube I used, they all sounded microphonic in v4 and were all fine in v1 or v2. Eventually after swapping tubes for a while the problem went away.

Turned it on the next day and I got microphonic feedback from the speaker even with no guitar plugged in. I pulled all the tubes out and put them back in the same sockets, microphonic feedback was gone, but the amp made a lot of noise, hissing, humming, static etc.

I pulled the chassis out and checked for bad connections, couldn't find any, I retensioned the tube sockets, they all look clean, as do the tube pins. Turned it back on and it's still noisy but now my v1 and v2 posistions are acting microphonic, swapped the tubes around a bit more, doesn't help, the microphonics are staying with the sockets, not the tubes. It's still making a lot of idle noise too, much more than normal.

Mainly the problem is my v4 position was microphonic regardless of the tube I had in there. Now my v1 and v2 positions are microphonic regardless of which tubes I have in there. And there's a lot of idle noise coming out of the speaker.

The volume and tone knobs affect the sound, the effect knobs don't.

This is weird and confusing me, any one have any suggestions? They would be much appreciated.

Thanks, John.

[badams]

This may sound weird to you but the trouble may be coming from your guitar cord and not the amp at all?

[johnwilliamhunter]

Yes that would be weird considering there's no guitar cable plugged in ;-).

Edit: but I did try it with cables plugged in, just to rule out that the ground short contacts in the jacks weren't to blame, didn't help at all so I guess they're ok.

[johnwilliamhunter]

This is weird. I had the amp on, same problems as I described below, then I put it on standby for a minute, then off standby, and now all the microphonics are gone, and the idle noise is much reduced, although it's still noisier than normal. But I played the guitar through it and now it doesn't sound so good, bad distortion even at low volume. Just keeps getting weirder!

EDIT: I checked all the voltages between the tube plates and ground etc. and they're all 100% normal.

[PRNDL]

Tubes are usually the first suspect, beginning with the preamp and then the power tubes. A fresh set usually is all that's needed, along with setting the bias for the power tubes.

The power supply electrolytics can also cause this when they begin to go bad. Sometimes they fail slowly with the amp sounding progressively worse and odd things happening. They usually last about 10-15 years depending on how often and hard the amp was played.

How old is your amp?
When was the last time you put in new tubes?

[johnwilliamhunter]

Hi, thanks for the reply,

The amp is only 2 years old, maybe 1000 hours on it at moderate, 4-6 volume.

I have 10 12ax7 tubes and they all sounded microphonic in v4, but not in v1 or v2, then later the problem moved and they all sounded fine in v4 but microphonic in v1 and v2, now none of them show any signs of micophonics in any position. So I think that rules out the tubes. The power tubes aren't too old and I checked the bias is ok, they don't make any noise, I think they're fine too.

I wouldn't suspect the power filter caps after only 2 years, but maybe that's the cause.

Is there a way to test the caps? To prove they are to blame?

thanks again for the reply,

John.

[PRNDL]

The amp is only 2 years old, maybe 1000 hours on it at moderate, 4-6 volume.
I wouldn't suspect the power filter caps after only 2 years, but maybe that's the cause.
Is there a way to test the caps?

I agree.

This site has a lot of great ways to test amps.
http://www.geofex.com/ampdbug/ampdebug.htm

[lowell]

Hi are the 10 preamp tubes you own brand spankin' new?

[Enzo]

If it is only 2 years old, it is under warranty - take it in for warranty repair.

[johnwilliamhunter]

Thanks for the replies, I'll check that site out.

No, the tubes aren't new, 4 are about 2 years old and 6 are about 40 years old, at least 7 of them were all working well a few days ago, I can't believe they would all go so bad overnight. Anyway if it was the tubes why would the microphonics come and go? I don't think they can fix themselves if the parts inside are loose.

No no warranty, I already tried, aparently the shop have to write the amps serial number on the receipt for Fender to honour the warranty.

[johnwilliamhunter]

I might try some contact cleaner on the tube pins and sockets, although they look clean and shiny.

Any suggestions for a good contact cleaner?

[johnwilliamhunter]

Ok, switched the amp back on today and it's working perfectly well... I didn't do anything, it just fixed itself... I guess it will break again one day 'though, who knows...

[johnwilliamhunter]

I played through it for about an hour, no problem at all, swithced it off, and later back on, still fine, then I put it on standby for a couple of minutes, back on, and the microphonics had returned to v1 as well as a bit of noise, I've been poking around in the chassis with a stick for a while, I can't get anything to make any noise or make the problem worse or better at all.

The problems only seem to come and go and change when I flick it from standby to on, never occurs or changes or anything while it's on, I can't get it to if I try, just randomly happens when going to on from standby, does that help narrow it down at all?

[johnwilliamhunter]

Well the amps dead now, hah, although I probably killed it, I pulled it apart and resoldered some things that looked suspect, put it back together, it was fine on standby, took it off and a power tube screen grid resistor started frying.

Oh well, god knowns what I've done to it. I think I'll rebuild it like a 60s model, I don't like playing with it with the wires soldered to the circuit board, and it's such a pain to pull apart to resolder anything, or even check the input jacks.

But I think I'll buy some books about about amp building first, I'll just live without it for a while. Thanks for all the help 'though.

[PRNDL]

No no warranty, I already tried, apparently the shop have to write the amps serial number on the receipt for Fender to honor the warranty.

IMHO, that is complete BS (although I may be wrong).

It sounds more like they are fed up with these amps, or with fixing other peoples messes.
Did you ask questions about the amp and let them know you were doing things yourself?

I recommend looking for another repair shop that does Fender warranty repairs, or calling Fender directly (to ask about their receipt policy, and to find a reputable repair center).

Also, keep a good copy of the original receipt, just in case.