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Author Topic: Fender Deluxe Reverb (1976) - Replacing Capacitors?  (Read 16198 times)

g1

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #15 on: May 02, 2014, 10:41:30 PM »
Another odd fault that old Fenders can exhibit when the electros are going down is that the volume goes down to zero at about 1 or 2 on the knob, then comes back up again from there to zero.
Roly, which electrolytics cause this, cathode bypass caps or supply filters?

Enzo

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #16 on: May 03, 2014, 01:25:21 AM »
Power supply.  The filter caps for the preamp stages don't really have any ripple to smooth, they are mainly there as decoupling caps, they decouple the stages from one another.  Without those caps, the signal influence can seep stage to stage through the power supply.

Roly

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #17 on: May 03, 2014, 07:58:26 AM »
Another odd fault that old Fenders can exhibit when the electros are going down is that the volume goes down to zero at about 1 or 2 on the knob, then comes back up again from there to zero.
Roly, which electrolytics cause this, cathode bypass caps or supply filters?

Was an early Fender, may have been a Bandmaser(?), caps in an above-chassis can, one preamp HT bypass electro had gone low C.  Replacement fully fixed.  Odd symptom of unwanted feedback; listening carefully I could hear that it was a phase cancellation zero at "2", not a true attenuation zero, thus clearly unwanted feedback.

If you say theory and practice don't agree you haven't applied enough theory.

ajax11124

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #18 on: May 05, 2014, 06:01:38 PM »
Another quick question regarding this amp. One thing that really bugs me about it is that the power light doesn't work. So it could be sitting turned on and you can't even tell. The bulb itself works, and I've found that if you wiggle the bulb around it lights up. So it's something to do with how the bulb sits in the jack. Is there any hope for fixing this? Is it possible to get replacement parts for this anymore? Any ideas?

Enzo

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #19 on: May 05, 2014, 07:14:58 PM »
Even simple things like the light can bug us, you know?

The bulb runs on 6vAC, which must be there if the light ever works or indeed if the tubes light up.  And you know the bulb is OK.   So it has to be the socket.

COuld be the bulb doesn't like the socket.   Pull the bulb and briskly rub the point of its base on something like your wood bench top, or a piece of cardboard.  Something to buff it clean, also the barrel of the bulb, is that fairly free of rust?   Look into the socket, is the center thing relatively shiny and clean?

Maybe the socket just doesn;t make good contact with the bulb. Pull the bulb.  On either side there is a J-shaped slot cut into the sidewall.  The little pegs that stick out from the bulb fit into these slots.  But if you look, the J-slot forms a couple tiny flags of metal.  Gently bend those two flags inwards a bit so they will bite into the sides of the bulb base a little more - better contact.

The spring hasn;t broken?  You push the bulb into the socket, the spring pushes back?  A broken spring is REALLY unlikely.

Now the socket construction.  At the base of the socket, there are the two solder lugs, there are some little insulating discs, and a hollow rivet running through it.  Then the sprung contact for the bulb center is staked through that rivet.  It is stacked so the one solder lug is squeezed against the barrel of the socket, thus making electrical contact.  The other lug is squeezed against the rivet, making contact there.  The two lugs are splayed apart so they don't touch each other and short it out.

Sometimes that squeezin' doesn;t make all that great a contact.  A lot of times simply grasping the solder lugs and twisting them a little each direction will restore the contact

ajax11124

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #20 on: May 05, 2014, 09:58:04 PM »
Thanks for the info. Turns out I got it working with a little sand paper and WD-40. I appreciate your info. I kind of assumed it was something more technical just because of the age of the amp. Thought it might of broke over time. I'm glade it was simple like that though. This being an older style bulb though, is it even possible to find these anymore? I know it will go someday, it won't hold up like an LED would.

Enzo

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #21 on: May 05, 2014, 11:39:25 PM »
6v mini-bayonette lamps are mainly #44 and #47.   There is no more common a miniature lamp than those.  They will be the last bulbs they stop making.   Radio Shack, Home Depot, Hardware store.

Roly

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #22 on: May 06, 2014, 03:56:07 AM »
I had a long running mini-saga with a Fender pilot lamp.  The plunger that contacts the bulb center pip doesn't make reliable contact with the rest of the assembly, basically a lamp socket design fault.  I ended up soldering a curly pigtail wire bridge between the back of the plunger and the incoming power - fixed.
If you say theory and practice don't agree you haven't applied enough theory.

Drewline

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #23 on: May 13, 2014, 06:59:08 PM »
I'd recommend either F&T or Sprague Atom caps for your amp.  F&T use 22@500 for the caps in the dog house, 100@100 for the bias cap & 22@50 for the bypass caps. Sprague values: 25@500, 100@100, 25@50.  Looks like your bias has been converted to level from balance so replace the filters, set your bias & you're good to go.

Drewline
Drewline

DiscDoggie

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #24 on: October 01, 2014, 11:57:09 PM »
I have one of these to fix also. Happens to be a true '68 deluxe reverb. I see the silverface reissues now for $999 and think hmmmm... which way to go? Tinker for countless hours or start fresh. That's why I'm here. Yet I am aware this is a Solid State forum, and the fact is I'm new to electronics design, better at soldering than really figuring anything out. Did plenty of research on what goes, what mods are out there. The amp currently doesn't turn on and it may just be a fuse socket issue (believe it or not there has been a hair bobby-pin jammed in there for several years; just making contact between the metal surround and the end of the fuse). You guys are going to hate me. Found the "ClassicTone" transformers and similar DIY/replacement parts out there to gauge what kind of a mess I might be getting into, pricewise. Seems like there's probably some interest to be sparked by volunteering the fact that I was already shocked -- OK, fine, Electrocuted -- once, by this amp.. I wasn't working on it. My bandmate and I were playing, we both had on sandals in a damp basement, there was an acoustic electric strapped on him and I had a Parker P-38 plugged into this baby, which was propped up on a folding (metal) lawn chair. We finished a song and gave each other a high-five. Something coupled between strings and ground or the amp to the chair to the wetness of the ground to the cable to the guitar to the body touching the strings, and some (unlikely you'll think) we were struck by some kind of pulse (felt like lightning, and I've felt a 120V lamp socket for a fraction of a second and yes, my arm went numb then too), which seemed to emerge from our hands, striking like lightning from our hands, where they met for a split second. an amplified high five!

Yeah -- so I should fix this old amp, right, or hand it over to a professional?
Guitar player
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DrGonz78

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #25 on: October 02, 2014, 01:18:05 AM »
As far as fixing the amp only you know whether or not "You" are capable of such a task. The best answer to that question is always refer to a professional. I have never been electrocuted by an amp yet and never will, hopefully. Although I plan that it might happen and take all safety precautions to avoid that scenario. Learn about safety first and perhaps if this is your first amp to repair, it might prove to be too adventurous.

Juan (J M Fahey- All know him here and on MEF) posted this little bit about a horrible accident. Amps can be the danger and even an incorrect wiring to the mains power plugs in the room. Your post DiscDoggle brought back the memory or reading the post I am attaching.
http://music-electronics-forum.com/t36666/

How much experience do you have working with high voltage tube amps?

Best regards and welcome to the forum.  :tu:
“A person who never made a mistake never tried anything new.” -Albert Einstein

Roly

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Re: Fender Deluxe Reverb (1976) - Replacing Capacitors?
« Reply #26 on: October 02, 2014, 02:35:56 AM »
Hi DiscDoggie, welcome.


Despite the name this forum also deals with hybrid and straight tube amps.

Quote from: DiscDoggie
Electrocuted

No, "shocked" is right.  "Electrocuted" is derived from "electro" and "execution" ... so like all death it generally only happens once, and you are highly unlikely to be making forum posts afterwards.   8|


Quote from: DiscDoggie
"ClassicTone" transformers and similar DIY/replacement parts


Why?

It's Sydney to a half-brick that there is nothing wrong with your amp transformers.  You could easily go to the time, trouble, and considerable expense of having your transformers replaced only to find it is utterly ineffective and you are still getting shocks because they have nothing to do with it.

The transformers in an amp have to be close to the most durable part.  I've had amps pulled from 20 years under a house and the chassis and trannies are the only usable things left.

I would never replace an amplifier transformer, an output transformer in particular, unless there was something clearly wrong with it.  You want to ruin the tonality of a classic amp?  Then capriciously changing the OPT is a good place to start.

IF IT AIN'T BROKE, DON'T FIX IT.

"Should I replace X?" (where "X" may be anything, but the current fad is capacitors).

Do they test actually faulty/off spec (or physically damaged)?  Then yes.

No?  Then leave them alone.


Quote from: DiscDoggie
damp basement

This won't be the fault of the amps themselves but situational, the wiring in the basement, lack of a secure mains earth most likely, so there is nothing in the amps for a tech to fix.  You will find an extended discussion of the problem of grounding, "earth leakage", and its solution here.

The short answer is that all your band gear should be securely earthed (not something that the American power reticulation system is noted for, particularly in older buildings which may lack three-pin outlets and earth wiring).

So;
Q1. are both amps concerned fitted with three-wire leads and plugs?

Q2. are the earth pins on the basement outlets (if any?) actually and properly connected to the house grounding system?  {really needs an electrician, but does the house wiring generally, or the basement outlets in particular, have a history of giving people shocks?  Is it an older building?}

The basic reason that you both got a shock is because both amp chassis were not connected to a safety earth.  Of that much we can be certain.  All that remains is to locate why, cos something needs to be fixed pronto.


Being populated by experienced amp techs this forum operates a bit differently to most.  You will not be advised to "change everything" on spec, but to first diagnose your problem, then address that.  It is quicker, cheaper, and more effective.


Quote from: DiscDoggie
The amp currently doesn't turn on and it may just be a fuse socket issue (believe it or not there has been a hair bobby-pin jammed in there for several years

Oh we believe you.  But you wouldn't believe the extensive range of non-fuse stuff professional techs find in fuse holders.  If it will fit and conduct electricity somebody, somewhere, sometime has used it for a fuse, brass screws, nails, paper clips, alfoil ...  25 amp car headlight fuses are popular (the amp was reduced to a smoking ruin, but the fuse survived okay   :lmao: ).

Get and fit the correct fuse and see what happens.  If the amp then works you only have your grounding to sort out, if not, or it blows, then we need to do some fault-finding - don't try a second or bigger fuse.  If you have a multimeter then we can guide you through some tests, or if you don't feel up for it then you can take it to a tech.

Please post answers to the questions above.

If you say theory and practice don't agree you haven't applied enough theory.