First timer, many questions - rewiring a Silvertone 1472

[JFC]

Hey all, I'm a first time caller to these boards. I'm an electronics tech and I've played guitar for decades for whatever it's worth.

I have a Silvertone 1472 (schematic) that I'm planning to rewire. The filter caps are original; it is noisy; the tremelo doesn't work, and I've already had to replace a few resistors over the years. Also, I'd just like to clean up the wiring. I'm starting to order parts and have a few questions:

1: What can be done to tighten up the midrange and bottom end? Even on a good day, the amp sounds flabby when it starts to distort. I don't want to make any major mods, but I might make a few changes while I'm in there. It does have the original Jensen speaker, which probably has a lot to do with it.

2. Which type of resistors should I use and where? I didn't know about the love for carbon comp resistors until I started this project. Would I be right to limit their use to the inverter and output stages, where the noise is less of an issue, and where the signal is strong enough to affect the resistor? I assume that I don't need them in the tremelo circuit, or to reference the heater leads to ground.

3. How about capacitors. I was thinking of using orange drops, mainly just because. Should I try something else, and where? It currently has the original Sangamo type 33 capacitors.

4: Grounding - everything is currently grounded to the aluminum chassis. Will star wiring the ground help that much? I assume that it would if the chassis was steel.

[tubeswell]

I have a Silvertone 1472 (schematic) that I'm planning to rewire. The filter caps are original;

They probably need changing to new ones

it is noisy;

In what way?

the tremelo doesn't work

Is it switched on? Try a new trem tube. If that doesn't work try new caps (and then resistors) in the trem circuit

1: What can be done to tighten up the midrange and bottom end? Even on a good day, the amp sounds flabby when it starts to distort. I don't want to make any major mods, but I might make a few changes while I'm in there. It does have the original Jensen speaker, which probably has a lot to do with it.

Usually Higher B+ and more filtering tightens up the sound. A bigger OT (more iron) will tighten up the bass. Replacing the speaker will help too. However having said that, the amp is a geetar amp and to a certain extent is meant to sound flabby and loose - depending on taste

2. Which type of resistors should I use and where? I didn't know about the love for carbon comp resistors until I started this project. Would I be right to limit their use to the inverter and output stages, where the noise is less of an issue, and where the signal is strong enough to affect the resistor? I assume that I don't need them in the tremelo circuit, or to reference the heater leads to ground.

Yep Carbon Film and Metal Film are quieter, and better in the first stages and most other places, but CCs can enhance the PI and other high-voltage stages later in the pre-amp in situations where they are dropping a lot of swinging voltage.

3. How about capacitors. I was thinking of using orange drops, mainly just because. Should I try something else, and where? It currently has the original Sangamo type 33 capacitors.

Mostly the existing non-electrolytic caps should still be good, and unless any of them are leaky I wouldn't bother changing any of them (unless you can't otherwise get the trem circuit to work.

4: Grounding - everything is currently grounded to the aluminum chassis. Will star wiring the ground help that much? I assume that it would if the chassis was steel.

Depends on what 'help' you are talking about. Is the amp hummy at all?, and if so - what sort of hum is it? and when does it occur?. (It might not be grounding-related hum). Aluminium is an excellent conductor and this shouldn't present any extra problem for grounding (except trying to solder it)

[JFC]

Hey, thanks!

The noise is mostly hum from the filter caps (At higher volume levels, it sounds like the amp is gargling.) This problem is better on some days, worse on others.

I'm not sure if I want to replace transformers to get a higher B+. I know that its value has gone up since 1980, but it's still a cheap pawnshop amp to me. I did read another post here that made it seem like capacitor bypasses in the preamp section might help. Correct me if I'm wrong, but this seems like something to play around with.

The Sangamo caps are paper; doesn't this mean that they are also electrolytic, or did they use to make dry paper caps?

The tremelo used to work. I assume that either a cap is leaking or a resistor went open. In any case, it wouldn't be too hard to rebuild the circuit.

The amp doesn't have that much hum right now. I assume that I'll notice more as I get rid of other noise.

One thing that I didn't mention was that I want to get my kids involved, and I may reroute the wiring to make easier to see what each section is doing (i.e., putting the supply wires in a common bundle, the grounds in a seperate bundle, and making the signal path more evident.) This is going to take a lot more work, so I decided to wait to ask about it until I have a layout diagram.

[tubeswell]

I'm not sure if I want to replace transformers to get a higher B+. I know that its value has gone up since 1980, but it's still a cheap pawnshop amp to me. I did read another post here that made it seem like capacitor bypasses in the preamp section might help. Correct me if I'm wrong, but this seems like something to play around with.

You can get higher B+ in the pre-amp simply by lowering the supply resistor values - try halving (or quartering) whatever is there (having regard to screen voltage)

The Sangamo caps are paper; doesn't this mean that they are also electrolytic, or did they use to make dry paper caps?

Not necessarily. If they are electrolytic, they will typically have a '+' symbol at one end, or a '-' symbol at the other end (or both). If they are just ordinary caps, they may well be fine to continue using (depending on whether they leak or not)

The tremelo used to work. I assume that either a cap is leaking or a resistor went open. In any case, it wouldn't be too hard to rebuild the circuit.

Or the tube needs replacing - try that first

The amp doesn't have that much hum right now. I assume that I'll notice more as I get rid of other noise.

Maybe, but maybe not. Fix up the other stuff first and see.