To start off, I just joined this forum because I have been growing in interest in amplifiers. I went to college for computers, got interested in hobby electronics, started playing guitar and soon after wanted to get inside the amp and look around. That's my story, now to the question.
I just got a hold of a Fender Deluxe Reverb Silverface amplifier that I believe to be from 1976 after some research I did. It's been sitting unused for the past 30 years. I've read quite a bit online about how electrolytic capacitors go bad over 10-20 years, so by 30 years I believe they probably need to be replaced. I'm not an expert with electronics, but I believe I have enough knowledge to work safely inside an amp. I have quite a bit of experience working with soldering onto circuit boards and such, and although it's a little different on these older amps, I'd rather gather the knowledge and do the work myself, rather then pass it of to an unknown amp tech. I believe it should be fairly straight forward. Identify the electrolytic caps, read their values. Then buy equivalent caps, and solder them into the same place.
My main question to start out with, is does it matter what kind of caps I replace the old ones with? Do I have to replace them with electrolytic caps, or would another type of cap with the same values work as well? What are some good brands to go with? What's a good place to find them?
This is a link to all the pictures of inside my amp. Am I correct that all the large blue caps, as well as the white mallory caps all are electrolytic and should be replaced?
https://onedrive.live.com/redir?resid=7E33E45F4682CBE8%21105 (https://onedrive.live.com/redir?resid=7E33E45F4682CBE8%21105)
I'd appreciate any feedback, and I would like to thank you ahead of time.
The caps that you are referencing are not electrolytic filter capacitors. They are capacitors for tone sculpting and other such functions. What you are looking to find on this amp is underneath the chassis down where the tubes plug in to the amp. Reference the pic attached. You need to understand what you are working on and how dangerous that part of the amp can be too. Do a search on draining high voltage capacitors in guitar amps and safety.
and
http://www.ssguitar.com/index.php?topic=2093.0
The question is whether you want to replace just the electrolytic filter caps, or all electrolytics.
As Doc mentioned, the main filters are on the other side of the chassis under the rectangular metal cover known as the "doghouse".
The blue caps are non-electrolytic so are not prone to the same issues and are usually only replaced when they fail or go leaky.
But the white mallory's with the + markings are also electrolytic. The ones in the bias circuit should also be considered "filter caps" and replaced. They may need to be replaced with higher voltage rated caps as they were sometimes under-rated and modern line voltages have increased.
Other than that, there are some white mallories as cathode bypass caps in the preamp, having gone this far you might as well replace them too.
Not quite sure which schematic/layout to post. Does your amp have a "boost" pull switch on the volume control?
Quote from: g1 on April 28, 2014, 12:05:55 PM
The question is whether you want to replace just the electrolytic filter caps, or all electrolytics.
I did already know about the filter caps underneath, but I was under the impression that any cap in the amp that was electrolytic was worth replacing after such a long time period as this. I'd like to hear what you guys think about that though. My overall goal is to have an amp that still sounds good and can hopefully continue to last a long time. So if replacing more than just the filter caps would be beneficial than I'm fine with that.
Quote from: g1 on April 28, 2014, 12:05:55 PMThe blue caps are non-electrolytic so are not prone to the same issues and are usually only replaced when they fail or go leaky.
What kind of cap is the blue ones? What causes them to go leaky?
Quote from: g1 on April 28, 2014, 12:05:55 PM
Not quite sure which schematic/layout to post. Does your amp have a "boost" pull switch on the volume control?
It doesn't have the boost switch. I believe that was added the year after mine.
I appreciate the information you all have provided. It's answered a lot of my questions.
I am aware the dangers exist and I don't plan on trying anything without research and precaution.
Sorry Ajax for not reading your question just right. I was thinking you were trying to reference the Main filter capacitors and I neglected to understand the question.
Those blue caps on the board are Film caps. Those caps could be mylar, polyester, polystyrene, and polypropylene film types. I think on the older amps those are polyester, but I might be wrong. There are more types of film caps than what I listed here too. Mylar film is a very common one that I see all the time these days on most amps that I am working on.
They didn't change much till the boost version so I'll attach the standard schematic and layout which should be close.
The bias filter cap is the white mallory on the little board by the pilot light. Replace it with something bigger with a higher voltage rating, like 100uf@100V. All other caps should be replaced with same value, but can be higher voltage rating.
After you have replaced the main filters, and the bias filters, there are only a few more electrolytics, so you might as well replace them too.
The blue ones are non-electrolytic. They are being used as coupling caps. They block DC voltage from getting where it is not wanted, but they let the AC signal pass through. They last much longer than electrolytics and generally don't go leaky for any particular reason. Some brands/types are more failure prone than others, the blue ones used in the old Fender amps are usually not problematic.
That schematic is very helpful, and all the information you guys have given is much appreciated. I think I have enough understanding of how to do this now. So my last step is locating the parts to do it. Do I need to make sure the caps I buy are also electrolytic? Or are there other types of caps that would be fine as well? Anyone have a recommendation as far as brand/reliability?
Ajax; I wouldn't replace the blue coupling caps until after I had the amp up and running. Then you can see if you like the tone. Changing those caps to other varieties will mildly change the tone and one of the reasons for wanting a silver faced fender amp is that sought after tone. I would definitely do the startup of this amp using a current limiter. It's not a bad idea to then bring the amp up slowly on a variac to allow the older caps to get used to having current through them again.
Yes, you need polarized electrolyic caps to replace the main filter caps and the bias cap. Be careful to ensure you replace them with correct polarity observed.
I like Sprague Atom electolytic caps and I also like F&T which are made in Germany. Spragues are more expensive than the F&T.
smacko jack
Or see "limiting lamp" thread.
http://www.ssguitar.com/index.php?topic=2093.0
If you are going to recap, the first phase should be the power supply network electrolytics.
Once that is done you can look for current-leaky coupling caps (the blue ones) and off-value, but these generally don't give trouble. Some types like waxed-paper do, but not those fitted in your amp.
Clean/replace pots and connectors would be my next step, then look at signal caps if I have odd voltages or funny sound. Don't fix what ain't busted.
Quote from: smackoj on April 28, 2014, 09:26:17 PM
Yes, you need polarized electrolyic caps to replace the main filter caps and the bias cap. Be careful to ensure you replace them with correct polarity observed.
And a reminder: The bias cap has it's positive end going to ground. This is opposite of all the other electrolytics and is normal and correct.
Before I start ripping this thing apart I was just wondering If anyone could explain what I'm looking at underneath. I took a picture and labeled the parts im curious about with numbers. Number 1 I believe is where I need to go to get the the filter caps. I'm just curious, What the other parts are. I can tell you guys have a lot more knowledge than I do, and I'm working on growing mine. So I thank you for your patients and assistance. I admit fully understanding this amp is a little over my head, but I'm trying to learn as much as I can and get a good understanding of this amp before I start taking things apart.
UPDATE: I took off the cover and found the filter caps, tested them with a multimeter all of them are showing 15V. Is this normal after discharge?
Hi Ajax,
Small resiual voltage after discharge is normal. Don't worry about it. :tu:
Having just looked at the pic of this it's obviously in immaculate condition with no sign of being on the road for years on end,,,, So I'd would check if any leaky main filter caps and if it runs normal sounds good then don't fix what ain't broke. 8)
Phil.
You identified your number 1, the rest are the various transformers that make these old amps wiegh a ton.
In order as you have them numbered,
2: Reverb transformer for coupeling to reverb unit.
3: Output transformer - on one side couples plate voltage to the 6v6 plates, the other side talks to the speaker.
4: Power supply filter choke. More ripple and transient cleanup for the DC side of things.
5: Power transformer - takes that nasty real world AC voltage and turns it loose inside your amp.
And to repeat what others have said, definitely change the power supply and bias caps. The cathode bypass electros (the white 25v 25uf polarized parts) will probably need it, one of the signs of a bad bypass cap is motorboating, but when their value changes, so will the frequency response of that stage, so that some frequencies will be amplified more than others. This changed sound may be desirable, or otherwise. Your ears will have to decide on that one, but any motorboating, just change them all. They are not expensive and the amp will thank you for it. The other caps will hardly ever go bad, although I did have a ceramic disc break a leg on one of my Bandmasters trem circuit.
All told, you could recap it, doing it yourself, for $40. And learn a bit about the design while doing so. Have fun, and respect those DC voltages. You will have somewhere north of the 420vDC the circuit originally called for depending on how much your house current varies from the old 110/220 vAC standard. Measure carefully, and use the old tech standby, keep your left hand in your hip pocket.
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.
Quote from: Roly on May 02, 2014, 02:20:16 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?
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.
Quote from: g1 on May 02, 2014, 10:41:30 PM
Quote from: Roly on May 02, 2014, 02:20:16 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.
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?
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
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.
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.
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.
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
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?
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/ (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:
Hi
DiscDoggie, welcome.
Despite the name this forum also deals with hybrid and straight tube amps.
Quote from: DiscDoggieElectrocuted
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: DiscDoggiedamp 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 (http://www.guitargear.net.au/discussion/index.php?topic=42159.0).
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: DiscDoggieThe 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.