There are two kinds of things called "isolation transformers" out there. The Tripp product is a piece of equipment. It serves the isolation function, but it is way more than you need. The other thing going by the name is the transformer itself, the electronic component. essentially it is what is inside the Tripp unit.
Typically when we have an old "hot chassis" amplifier, and we want to isolate it, we buy a component iso transformer from Mouser or someone, and mount it inside the amp.
I agree with Jon, it would be very helpful if we knew the model name or chassis number, so we could look at the schematic.
Or at least the tube list.
Typically when we have an old "hot chassis" amplifier, and we want to isolate it, we buy a component iso transformer from Mouser or someone, and mount it inside the amp.
I agree with Jon, it would be very helpful if we knew the model name or chassis number, so we could look at the schematic.
Or at least the tube list.
it is a silvertone 9075, thanks in advance! i understand the whole iso in the amp thing, but didn't know how hard it'd be to install. i talked to the owner of my local guitar shop today and he explained me how to change to 3 prong, definitely seems a lot easier now than it did reading on the internet!
A three prong does not solve the problem of isolation. You CANNOT guarantee the outlet it plugs into is correctly wired. Wiring the iso is basic. One side of the iso gets the mains plug and cord, the other side of the iso gets wired to where the original plug was wired. That's it. The transformer itself can be screwed to the chassis if there is room, or it can be screwed to the wall or floor of the wood cabinet and wired to the chassis.
I HIGHLY recommend wiring in a suitable isolation transformer. The Tripp product is a good product, but it would have you plugging into it with the unisolated original amp. And that means someone else could plug it into the wall, and we are back to dangerous. Wiring in a transformer guarantees no one can plug it in and be hot.
Sorry I do not have that schematic.
I HIGHLY recommend wiring in a suitable isolation transformer. The Tripp product is a good product, but it would have you plugging into it with the unisolated original amp. And that means someone else could plug it into the wall, and we are back to dangerous. Wiring in a transformer guarantees no one can plug it in and be hot.
Sorry I do not have that schematic.
i will end up putting an iso in it, but a tripp will work for the meantime? i am the only person who will be using this amp.
Yes, as long as you have it isolated one way or another, you no longer have the direct mains connection.
Schematic 9075
If ok to post this link:
Silvertone 9075 Ch= 528.59230 Ampl/Mixer Sears, Roebuck & Co
There is info that may become useful...
Deric
If ok to post this link:
Silvertone 9075 Ch= 528.59230 Ampl/Mixer Sears, Roebuck & Co
There is info that may become useful...
Deric
According to the service manual from Radio Museum, the chassis is already isolated and there is no earth connection, it is floating so the earth lead needs to go to the chassis.
With due Respect, not exactly accurate, since you don't mention 3 wire connection, and OP might think it's fine to ground one of two wires present, specifically the "neutral" one, so we are making unsafe what today is relatively safe.
I'm certain you are an experienced Tech and know what the right way is, so need little or no instructions, but personally I prefer to err on the side of "excess instructions" if you wish, when talking with *presumed* end users, not necessarily experienced Techs.
The proper answer is:
1) you need to pull that 2 wire mains cable, but carefully noting where it was attached.
Paper tape labels and chassis markings with permanent markers are fine.
2) add a 3 wire power cord.
It might be thicker than original (which to boot might have been thin zipcord, what used to be used for desk lamps and such low power stuff) so you might have to enlarge the chassis hole for it.
Use an insulating grommet so bare metal does not touch plastic insulation (it might eventually cut through) , at least use a rubber grommet and tie a knot on the cable on the inside, so pulling it does not tear switch and fuse broken apart.
Best of course would be to punch the chassis and add an IEC connector (what computers use) but it's hard to do without proper tools and the marching Greenlee punch is expensive, not justified for a single use.
3) solder the 3 wires as:
a) new "hot/mains/live" wire to former live wire connection, usually one end of mains switch .
b) new "neutral" wire to where the old "neutral" went.
So far, we have just replaced old 2 wire cable with 2 wires out of the new 3 wire one.
c) now the green/yellow ground wire:
* drill a small hole (1/8") and firmly attach a solder terminal to chassis.
* solder the green/yellow wire there.
It's good practice to make it , say, an inch longer than the other two, so if somebody yanks the mains cable *hard* and tears it out of the amp, the last wire to be cut by the pull is the ground green/yellow one, meaning it will protect you up to the last moment.
That is correct. I did mention the third wire as the author of the question stated that a three pin plug will be employed. I thought it obvious, maybe I was wrong.
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