It's OK to power up an amp with no speakers IF there are no power tubes installed at the time.
Shiny blue capacitors are good. Paktrons sound good and almost never ever fail. It's the brown caps that earn no love.
I have stashes of both Blue Bullet and Paktron capacitors for Fender repair work. I've never actually found a bad one of either type.
'74 was the first year of the master volume if I'm not mistaken.
All the filter caps have to go. Put in new ones. I recommend BMI capacitors available from Mesa/Boogie's online shop. (Search for capacitors.) Otherwise, Sprague Atoms are a great choice.
Yeah, F&T is an option but Sprague Atoms are more "correct" for a Fender amp.
I would not hesitate to take the entire removed board and stick it an oven at 240 degrees for an hour, to bake out any absorbed moisture. That temperature is low enough to do no harm to any part on it but will dry it out. And then rewax the board to provide moisture protection. Use regular paraffin wax and a heat gun.
'74 Fender Silverface Twin Reverb Project (w/MV)
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Matthews Guitars
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
MV appeared in '72. The switch on the MV appeared in '73.Matthews Guitars wrote: ↑Tue Mar 08, 2022 6:24 am '74 was the first year of the master volume if I'm not mistaken.
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Matthews Guitars
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
I guess that also depended on the model. My '73 Pro Reverb did not have an MV. My '76 Pro Reverb did. My '78 Twin had the MV.
Re: '74 Fender Silverface Twin Reverb Project (w/MV)
I am curious. You suggest waxing the board? I bought new boards and was going to avoid wax since it seems like it was a bad idea. The wax will eventually crack and delaminate and creates reservoirs for moisture - which is the exact opposite of the problem is is trying to address. I think the particular amp I am repairing saw an extraordinary amount of moisture and water. Probably stored in a barn exposed to the elements and wild temperature swings.Matthews Guitars wrote: ↑Tue Mar 08, 2022 6:24 am I would not hesitate to take the entire removed board and stick it an oven at 240 degrees for an hour, to bake out any absorbed moisture. That temperature is low enough to do no harm to any part on it but will dry it out. And then rewax the board to provide moisture protection. Use regular paraffin wax and a heat gun.
Is waxing still recommended?
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Matthews Guitars
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
The wax penetrates into the vulcanized fiber board and makes it (mostly) waterproof. That's why Fender did it in the first place.
Take a new piece of dry fiberboard and it soaks up a lot of water and becomes very conductive. Now take a piece and wax it, at a high enough temperature that it soaks in, and then the board won't take on water. To salvage the original board you'd rewax it in this manner.
You don't need to have wax piled high on the board, in fact you want a very thin layer on the outer surface, as little as possible, but you do want the wax to penetrate and waterproof the board.
Take a new piece of dry fiberboard and it soaks up a lot of water and becomes very conductive. Now take a piece and wax it, at a high enough temperature that it soaks in, and then the board won't take on water. To salvage the original board you'd rewax it in this manner.
You don't need to have wax piled high on the board, in fact you want a very thin layer on the outer surface, as little as possible, but you do want the wax to penetrate and waterproof the board.
Re: '74 Fender Silverface Twin Reverb Project (w/MV)
***March 13 Update***
I was pretty busy last week so not too much time on amp. I was on my first work trip in three years!
I used to down-time to order components and stuff. I continued to clean the chassis, transformers, choke, and power supply cover, which were pretty corroded. I decided to get rid of the power tube sockets. The lugs were in bad shape. Whoever did the initial build on this amp really sucked. My 13 year old could do a better job. I ordered some extra Dremel sanding attachments.
All parts came in while I was in Miss. Then I removed all the tube sockets. I finished removing the rust via sanding and polishing. My Dremel got hot to touch. I taped everything off and it is ready for painting. We are supposed to have a mini heat wave up here in a couple of days, so I should be able to paint.
After that the reconstruction begins. I decided against applying wax to anything. Old boards were made from paper. Newer ones are some type of pre-preg that already is coated. As someone that worked in microelectronics for a long time, I cannot imagine a worse insulator/moister preventer than paraffin. I can see how poorly it worked on this particular amp. The water and corrosion was driven to the weak points. As it fails and cracks, wax drives water (and subsequent oxidation) to the most vulnerable points. It also is a great collector of dirt and debris.
This particular amp spent many a year neglected and stored in a barn. The damage is pretty bad, but repairable. If any future owner after me decides to do treat it poorly, well then....
Here are some pictures:
I was pretty busy last week so not too much time on amp. I was on my first work trip in three years!
I used to down-time to order components and stuff. I continued to clean the chassis, transformers, choke, and power supply cover, which were pretty corroded. I decided to get rid of the power tube sockets. The lugs were in bad shape. Whoever did the initial build on this amp really sucked. My 13 year old could do a better job. I ordered some extra Dremel sanding attachments.
All parts came in while I was in Miss. Then I removed all the tube sockets. I finished removing the rust via sanding and polishing. My Dremel got hot to touch. I taped everything off and it is ready for painting. We are supposed to have a mini heat wave up here in a couple of days, so I should be able to paint.
After that the reconstruction begins. I decided against applying wax to anything. Old boards were made from paper. Newer ones are some type of pre-preg that already is coated. As someone that worked in microelectronics for a long time, I cannot imagine a worse insulator/moister preventer than paraffin. I can see how poorly it worked on this particular amp. The water and corrosion was driven to the weak points. As it fails and cracks, wax drives water (and subsequent oxidation) to the most vulnerable points. It also is a great collector of dirt and debris.
This particular amp spent many a year neglected and stored in a barn. The damage is pretty bad, but repairable. If any future owner after me decides to do treat it poorly, well then....
Here are some pictures:
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
Heat wave here up north. I was able to get a few coats of paint on!
I'll probably due a few more coats for durability.
I'll probably due a few more coats for durability.
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
Painting and cosmetic work is done. Getting ready to roll up my sleeves and put it together. Turns out the boards I bought from Mojotone are punched for Blackface. I am rebuilding this to stock '74 Silverface specs. Not all the holes are in the same places. Especially the channel mix section. Have to do some modding but I am not buying any more tools (eyelet punches and such).
Also, I wonder if this amp ever worked right. So much sloppy soldering and shorted connections... Here is one example.
Also, I wonder if this amp ever worked right. So much sloppy soldering and shorted connections... Here is one example.
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
I suggest to use a proper electrical insulator material for a replacement circuit board.
My band:- http://www.youtube.com/user/RedwingBand
Re: '74 Fender Silverface Twin Reverb Project (w/MV)
The new board is made from a proper laminate and should be fine. The old board? I really don't know if it was a material failure or user failure. It is soon headed for the great big dump in the sky...
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Last edited by Basslice on Thu Mar 17, 2022 10:10 pm, edited 2 times in total.
Re: '74 Fender Silverface Twin Reverb Project (w/MV)
So as I rebuild, I note a dearth of information about the '74 Silverface w/MV. It is much maligned, but from what I can tell for no good reason. In any case, no one sells part sets for this amp and if were not for the help of Ten Over, I would not have even a schematic to work from. I am doing a DIYLC of the '74 Silverface that I will share once I assure it is correct and the amp works.
This has caused a few delays, like for instance, the new eyelet boards I bought are for a Blackface Twin. There a some important differences. I had to drill a couple new holes and improvise. In the pic above I used a butt splice and cut it into place to serve as two of the missing eyelets. I used a little cyanoacrylate to hold them in place until the build (you can see my Sharpie trace of where the vibro-bug is supposed to sit).
****Edit: After tearing into this I wonder if the hatred of the Silverfaces compared to Blackfaces has more to do with the atrocious builds - not anything to do with the inherent circuit design.... ****
This has caused a few delays, like for instance, the new eyelet boards I bought are for a Blackface Twin. There a some important differences. I had to drill a couple new holes and improvise. In the pic above I used a butt splice and cut it into place to serve as two of the missing eyelets. I used a little cyanoacrylate to hold them in place until the build (you can see my Sharpie trace of where the vibro-bug is supposed to sit).
****Edit: After tearing into this I wonder if the hatred of the Silverfaces compared to Blackfaces has more to do with the atrocious builds - not anything to do with the inherent circuit design.... ****
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
The buttsplice to B (B+2) is the only thing I don't like at this point. The existing wire was not long enough and I did not want to unwrap the preamp bundle. I think it will be ok,but def something to look at again later. The power supply is fine. Working on re-wiring all the power tube sockets and grounding them to the chassis (not with blobs of solder).
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
OK. I was so embarrassed by my crappy job on the doghouse that I went in and re-did it this morning.
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Re: '74 Fender Silverface Twin Reverb Project (w/MV)
i like the paint! this will be very nice at the end! also it is a pleasure to work when all is new painted 
Re: '74 Fender Silverface Twin Reverb Project (w/MV)
Populating the board. Just realized I am missing a couple 10pF ceramics caps. Sigh.....
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