Modifications on Hoffman Plexi 50, sanity check

[stratomaster]

The transformer very well could be the issue.

It's not the probe I'm concerned about. You don't need a 100x probe.  It's the input capacitor on the scope itself for AC coupling.

Looks like it might be just some small ceramic caps at the input.

I wouldn't expose those to much DC at all.

[uki]

Lets say it is the transformer, could the amp still be put to use, any risks there?
One thing i've notice, volume doesn't increase after 5, only more overdrive or distortion.

[stratomaster]

Lets say it is the transformer, could the amp still be put to use, any risks there?
One thing i've notice, volume doesn't increase after 5, only more overdrive or distortion.

You can use it, but if it's the wrong transformer then you'll eat tubes, so eventually the cost to keep running it vs just buying the right transformer stops making sense. If the transformer is the issue, once you just pony up for the right part you'll wonder why you waited so long.

You can take out the transformer and do voltage tests to determine the turn ratio and make an educated guess as to what it is--if you're unsure.  I haven't read your other thread as it's information overload, and I was wanting a fresh perspective. I'm assuming no one in your previous thread caught that you were using the wrong pot taper, for example.

The behavior you've described about getting more distorted instead of louder is normal and desirable. It's what keeps tube amps around.

[uki]

I don't remember how did i came about with those numbers thou
but here it is the turns ratio:

32:1
25:1
19:1

32 * 32 = 1024    1024 * 4Ω = 4096Ω

25 * 25 = 625     625  * 4Ω = 2500Ω

19 * 19 = 361     361  * 4Ω = 1444Ω



32 * 32 = 1024    1024 * 8Ω = 8192Ω

25 * 25 = 625     625  * 8Ω = 5000Ω

19 * 19 = 361     361  * 8Ω = 2888Ω



32 * 32 = 1024    1024 * 16Ω = 16384Ω

25 * 25 = 625     625  * 16Ω = 10000Ω

19 * 19 = 361     361  * 16Ω = 5776Ω