Silvertone 5XL / 1420

[tboy]

I couldn't find this schematic anywhere on the web, so when I stumbled onto it's hiding place in my basement I thought I'd do a quick scan and post it up here for anyone else who might be looking for it. I'll try to remember to do a better scan some other time.

[melvin]

Does anyone know what isolation power transformer would be safe/ideal for use in this amp? 50VA?

[g1]

Good to see you around Melvin.
Yes that should be sufficient. I assume you're looking at the Triad N-68X.

[melvin]

Thanks g1! Have you done this before? If so, did you install it inside or outside the chassis?

I was looking at the Triad (well priced) but would it have to be installed inside the chassis and would that be noisy? Would it be better to install a shielded one like the Hammond 169RS, http://www.hammondmfg.com/169.htm?
Although, I don't know what safety features (thermal fuse, double insulation, etc.) it has other than it is enclosed. It just says "CSA certified".

Also, I suppose the choice needs to be able to handle more than the current demanded, but I wonder if it will supply (a little) too much voltage on the secondary if not enough current is drawn? Of course, for this circuit it may not matter.

Looking for the safest and most noise-free way to isolate "hot-chassis" amps like this and would love to get some feedback before I go buying transformers.

[g1]

It's a one-to-one transformer, so the voltage will not rise if it is not fully loaded.
If you use the enclosed type, you can rig it up as a stand alone unit which allows you to use it for other amps as well (provided you observe the VA limitation).
As far as noise with the internal type, you may have to move it around to find the quietest spot, so if there is not much room I guess you could get stuck with a noise/hum issue.

[Helmholtz]

It's a one-to-one transformer, so the voltage will not rise if it is not fully loaded.

There is no reason why a "1:1" transformer could have perfect regulation. Secondary and primary have copper resistance which makes secondary voltage dependent on secondary current just as with any other transformer. In order to get a 1:1 voltage ratio at rated load, the secondary needs to have a few more turns than the primary and secondary voltage will rise at lower loads.

Might be a good idea to get the version with tapped secondary.

[g1]

There is no reason why a "1:1" transformer could have perfect regulation. Secondary and primary have copper resistance which makes secondary voltage dependent on secondary current just as with any other transformer. In order to get a 1:1 voltage ratio at rated load, the secondary needs to have a few more turns than the primary and secondary voltage will rise at lower loads.

Thanks for the correction. I was erroneously thinking that it might drop, but would not rise. What you said makes more sense. Now I'm going to have to dig out my 169 and get some real data.

[tboy]

Another 5XL Artifact

Here's a scan of the back panel label: