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Discussion in 'Amp Central Station' started by HD28, Apr 4, 2021.
Thanks Wally. Can you suggest resources for hardware and instruction?
HD28, I am not familiar with sources for parts in Canada nor am I familiar with shipping across that border. Perhaps one of your fellow countrymen can give some advice on sources for electrolytics, resistors, etc.
Instruction? That is a large subject. I always suggest reading before stepping off into repair work. I bought books back in the day. These days, everything is free on the Internet. I advise you to read Aiken Amps Tech pages. Dave Funk’s Tube Amp Handbook, which is focussed on Fender amps but is full of general knowledge, is available in pdf form...do a search. I paid good money for it back 8n the day. Good Fender schematics. Watch a lot of Uncle Doug’s videos....after reading, imho, so as to have some basic understanding of what he is doing. Do you have soldering skills? If not, there are tutorials on that subject, as well. The Valve Wizard site is a great one.....and he sells his book. http://www.valvewizard.co.uk/Book1.html
And.....you will get all sorts of advice here or other forums.
Our friend robrob...Rob Robinette...has a site that will take you through that process, iirc. A search for ‘Rob Robinette amp’ will get you there. I advise you to start with these basics, though...do a search for ‘Vacuum tube history’ and read the Wikipedia article. This will familiarize you with tube elements. Also, bookmark Tube Data Sheet Locator. You will find pinouts and information on your tubes there. This info will give you a way to start understanding something about the schematics, which you can find at ‘Schematic Heaven’.
The Fender schemes also have the layout, which is like looking at a circuit in front of you. This is as good of advice as I can give. In short, layout out a study program...what is a tube, what is a circuit, how do tubes function in the circuit, on and on. Robrob gives info mainly through layout form, and he goes the extra step and draws out signal paths. Relating this information to a schematic br8ngs more complete understanding, imho.
Wow. Thank you very much Wally. I’ve got some reading to do!
There are canadian distributors for almost everything. Sometimes one may shop online in the US if the product or cost warrants and typically the shipping and importation of goods is seamless, for private individuals that is. F&T caps and resistors can be found up here.
Thank you for the resources!
I’ve finished and reassembled the cabinet. The pictures don’t really do it justice. It cleaned up very nicely. The tolex or vinyl constantly showed areas of separation. I thought I was done with it days ago, but every new day taking off the tape I found another patch of lifted tolex. Even today I had to use a capo as a clamp to reglue a small lift.
The pictures below show what I used, the before and after pictures.
I did not use armorall as the general consensus was that it is the devil spawn.
I hand polished metal components with rubbing compound and then polishing compound rather than buff them because I thought, as one considerate poster said, “it’s ok to have it look old”.
What bothers me, and I would like your opinions, is the grill cloth. It looks like it’s been dipped in a spittoon. I’ve cleaned the amp all up inside and out but the grill looks like an ashtray. The research I’ve done suggests that perhaps a carpet cleaner, spray on-vacuum off, may work.
My wife says leave it alone.
What do y’all think?
Anyway, here are a lot of before pictures.
And here are some after pictures.
Now I am going to focus on the electronics...
Capo as a tolex glue clamp. In a pinch, use what you got.
Imho, that cloth should never be replaced. If I were offered that amp at one price and later saw it with replacement cloth, I would offer $500 less than the first price...maybe. It would ruin the originality, ime....and it looks great just as it is. It is real.
The reverb tank was in excellent condition. Here are some pictures of my experiences with it...
Thank you Wally.
The matchbook cover found in the bottom of the amp, from “Make Your Friends Here” at the Royal Hotel, hosts Jim and Olga Pawluk, Burdett Alta, with what I assume is a license plate number on the back, is safely back in its resting place.
Silverfaces use some different value cathode bypass caps, where as 25uf-25volt is pretty much standard in the blackfaces. I just use all 25uf caps on both.
For brands I use F&T for filter caps, a 100uf-100volt F&T for bias and Sprauge 25uf-25volt for cathode bypass.
(F&T makes a double 25uf-25volt cap, but don't be tempted! It's stupid big and stupid expensive.)
I believe the first two filter caps are 70uf in these, 80uf is as close as you can get now, works fine.
Thank you. The first 2 are 70uF.
Would you replace the 5uF with a 25uF in this amp?
You could if you wanted. Truth is I use all 25s simply because I always forget to order anything else.
No other reason than that.
I have always replaced with the same value there. If one were curious as to what one would prefer, one could do a comparison. That comparison might be best done after the amp is brought to best condition.
Please advise and offer opinions as you see fit.
I think that my first step is to replace the 2-prong cord with a 3-prong. I’m fairly confident of the first black and white solder joints to the outlet and of course grounding to the chassis.
Where I need your advice is after it leaves the existing 2-prong outlet.
Uncle Doug and robrob both discuss a negative feedback switch, but I cannot figure out if this amp has the proper circuit or switch.
The 3-way switch center leg, is connected to the “death” cap to ground, the 2 other legs connect to the center (death cap) on toggle. The center position isolates the death cap from the circuit.
From the photos, hopefully you can see the path from cord to transformer. On a 2 leg circuit, it’s quite easy to my mind. But when we are looking at a NFB switch incorporated with the 3-prong cord, I’m not sure what approach to take, meaning, I don’t know what to do.
The other picture is of my grandfathers soldering tool, a Rytel’s Glo-Aid. It has a small light bulb inside it with leads attached to the hilt of the curved probe. Any insights?
One more question.
Desolder or snip?
Another question I have is, why am I not seeing 2 Mallory 25uF caps in the center of this photo?
I now see on closer examination that the Mallory 25uF cap goes from 3 to ground on the vibrato jack rather than on the board with the resistor as per the layout. Why?