Deluxe Reverb Mod or mix-up?

[Joynoise]

Hi,
My Deluxe reverb has a vibrato problem. I have to turn the intensity knob to 9 or 10 to get it the vibe to work. I opened it up to see if there was anything obviously wrong. The intensity pot is different from all the others and a 7025 tube slot has a 12AX7A in it, going by the tube diagram sticker. At first I thought I would just correct the tube placement error but then I noticed a pencilled note on the chassie "Mod by John McIntyre /79". He has a very solid rep, so I don't want to mess with anything until I know more.
Do you think this is part of the modification or just an error? When I bought the amp used years ago I was told that the reverb had been souped up. I wanted a more original sound so I took it to Musitech and asked to have it put back to standard config. not knowing of John's expertise with mods. It was supposed to have been retrofitted but I'm not sure if they actually removed all the mods. Any advice about what to do with it?

[Chuck H]

Hi,
My Deluxe reverb has a vibrato problem. I have to turn the intensity knob to 9 or 10 to get it the vibe to work.

Is this a new problem, or has the amp been like this since you've owned it?

The intensity pot is different from all the others and a 7025 tube slot has a 12AX7A in it, going by the tube diagram sticker. At first I thought I would just correct the tube placement error

In the modern world of tubes a 7025 and a 12ax7a are the same tube.

but then I noticed a pencilled note on the chassie "Mod by John McIntyre /79". He has a very solid rep, so I don't want to mess with anything until I know more.

Why not? If the amp isn't working to your satisfaction then service and/or modification seem like the right way to go. It's not like you'd be painting over the Mona Lisa or something. It's an amp.

Do you think this is part of the modification or just an error? When I bought the amp used years ago I was told that the reverb had been souped up. I wanted a more original sound so I took it to Musitech and asked to have it put back to standard config. not knowing of John's expertise with mods. It was supposed to have been retrofitted but I'm not sure if they actually removed all the mods. Any advice about what to do with it?

Well, If it was modded by an "expert" and then un-modded by someone else I'd say there's a chance that some shinanigans could still persist in the wiring. Is the amp a blackface or silver? This could have a bearing on whether or not you just fix it with whatever you have around or if you want to do a more thoughtful restoration. Either way it's certainly old enough to need service on certain parts IF it hasn't been done already. When did you take it to Musitech and what exactly did they do? It should be on any work order if you still have it.

The low intensity on the trem COULD be part of a mod. Are you able to follow a schematic and relate it to the actual amp wiring?

Chuck

[pontiacpete]

is it possible that the pot isn't a 50K RA-(reverse audio taper)?

[pdf64]

Good call - I like to change intensity pots to 100k lin to get a chunkier tone (and a little more gain), and that puts most of the control range in the 5-10 region of the pot rotation.
If it was changed for an even higher value (ie 220k-1M) to get even more gain, then the intensity pot would effectively become a switch, bringing the effect in on the last fraction of a turn.
I guess the next step to for the OP to check and confirm what is the value of the intensity pot is.

[Jazz P Bass]

MOD, MOD, MOD

Why oh why do people not document there mods & keep it with the amp?

[Joynoise]

Mod or Mix-up

Thanks for the responses. The vibrato was not the best when I got it back from the shop 10 years ago, but I needed the amp and my Vamp has a pretty good vibe in it. I still like the amp vibe better, so I will fix it. It has deteriorated more in the last couple of years.
I also dropped a question to Steve Ahola's site and he got back to me echoing Chuck's comment about the tubes being the same, and advising me to replace the optoisolator, so I'll give that a try.
It would be interesting to know what mods or parts thereof are still in there. I went to Steve's site to see if I could find a direing wiregram of the original and then compare it to what I have, but got a bit confused about which diagram to use. I downloaded a diagram from the the fender site for their "65 Deluxe reverb". That may help me. It's a silverface, by the way.
I love the sound of this amp, so that's why I don't want to mess with it too much. It out-performs my son's 50 watt Mesa, (according to him too).

[macpgh]

tubes

Dumb question....how old are your power tubes & how many hours are on them? Deluxes run very high voltage on the plates and its way over spec for 6V6's based on book values. So if they are old or if they are new but not NOS tubes....they might be worn out. Some of the newer tubes are not good for delux reverbs.

Are you playing old style country music to use the trem for effect?

How about your power supply caps...have they been serviced since it left fender?