I agree with Eli - the amplifier should
not be powered-up until at least the electrolytic capacitors have been replaced. You don't need to get exactly the same physical can-type capacitors as originally used in the amplifier - they are old-school, hard to find, and anything "old-stock" that has been sitting on a warehouse shelf for 40 years is going to be just about as bad as what you have.
Best thing is to go through the amplifier, identify the values and the voltage-ratings and order new caps from any of the vendors (Digikey, Mouser, Newark, Allied, etc.).
Be sure the caps you order have the correct voltage rating. Voltage ratings are usually stamped or marked somewhere on the capacitor.
The old carbon-composition resistors would probably be the next candidate to replace. They are the smaller dark-brown-body resistors with the color bands on them. Carbon resistors absorb moisture and values can change over the years, especially for the high-value resistors. And as you read through the threads in this forum, you will find many arguments that carbon-comps should be changed to metal-film resistors anyway...
IMHO, you can't go wrong replacing the old carbons with metal-film, 1% resistors and be done with it. They cost about the same, and have much better performance.
For the resistors, wattage rating is important. Carbon resistors are power-rated according to their physical size.The diameter and length determine the wattage-rating, it's standard for those resistors (they were built by the bazillions from the 1930s on, commonly used in electronics even today although they are slowly phasing out in favor of the film-type resistors).
You can find many references to the color codes for the resistors. "BBROYGBVGW for GSN" has a particularly useful, if tasteless, mnemonic for remembering the color codes
. It is still used even on the smaller metal-film resistors being built today. Good to know.
If you have access to a tube tester, check the tubes - it's possible you will need to get new ones, although it's hard to tell until you actually turn them on. The tubes have a silvery splotch on the sides or top that is called a "getter" - if it is not whiteish, then at least the tube hasn't cracked or leaked gas and will probably still work even if it is not at full-performance.
In the end, it is likely that you will need to replace most of the parts in this amp. Not a show-stopper, as long as the power transformer and output transformers are still good.
Which raises the question, "Do you have a way to safely test the power transformer?"
At a minimum, you should check continuity of the windings with an ohmmeter. And also, check each winding with the ohmmeter on its highest setting to make sure there are no shorts to the frame of the transformer.
It needs to be unplugged, of course, and you can just pull the tubes to check continuity and voltage. The high-voltage (HV) winding has a center-tap that connects to ground - find that wire and disconnect it from ground to do continuity and voltage testing.
The transformer has at least three AC outputs: 5VAC (to the 5u4 rectifier tube heater), 6.3VAC (to the 12AX7 / 6BQ5 heaters) and a High Voltage (HV) output (something around ~300VAC) to the 5U4 rectifier plates. The HV output will be center-tapped, with a third wire (from the transformer) attached to ground (it looks like this amp uses the chassis as ground... Another thing to address once you get it running).
For the output transformers, the easiest thing to do is a simple continuity check. It's not likely that the output transformers have a problem, but it's easy to check so why not? Same idea as the power-transformer continuity check - the windings have continuity and no shorts between any winding and the transformer frame (disconnect the output connection soldered to the chassis for this test, too)
On the topic of inputs/outputs, you will need to add RCA input jacks and some kind of speaker-connection (probably isolated binding posts) - both available and inexpensive, although you will need to drill some holes for them because the console used internal wiring (that big mess of wires attached to your amp) instead of "normal" input/output connectors.
So, in the face of all of the foregoing work, perhaps it's better to just rebuild this into a better amp using your chassis and transformers?
Perhaps - it's certainly a thing to consider. Eli has posted a good candidate-design, and there are other similar amplifiers "out there" that could be built on your chassis. The chassis you have would be a good starting point for any of the many different flavors of SET amplifier designs floating around this forum and elsewhere.
OTOH, simply rebuilding this amplifier could be a valuable learning tool for you. You could just rebuild this amp as it has been designed and get it running, test drive it for a while, and then see if you want to upgrade the performance.
Once you get the existing amp running (assuming you go that route), it's highly likely you will have hum issues since the amplifier appears to use chassis as "ground". This means that when you hook up an external source, and if that source is also grounded to the power mains, you will have ground-loops a-plenty!
However, if you hook up a battery operated device (such as a iThingie) or any device isolated from power-mains ground (such as a laptop running off a 2-wire charger or batteries) it shouldn't be a problem.
Hum itself is a whole 'nother topic, again I'd look at it as another "learning experience"
Lots of work ahead on this project, but it's a good chance to learn a LOT about tube amps! And once you get it running, it's gonna be Big Smiles (and all the hair you've torn out along the way can begin to grow back!)
Again, I cannot emphasize safety enough! The voltages inside this amplifier can be lethal and need to be respected.
The "Safety" sticky in this forum, at a minimum, is a
must-read before you plug anything into the power-mains! Nothing is worth getting hurt over, and these devices can hurt very badly if not treated with proper respect!
Good luck
~ Sam
BTW - hope you have a decent soldering-iron!
