Where to find 6000uF 50V replacement cap cans??

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Play it.

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[RG100ESROX]

Play it.

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Ought!!! You may be just a bit premature...?🤷

But, I like your optimism.👍🏻

[RG100ESROX]

Well, I thought I would change the power transistors to see if this would make any improvement in the tone. And after I changed em, and while bringing it up to voltage, the (100W) light bulb started to glow at about 40/45VAC. Its never done this before, so, I shut her down.

Why would it do this? I tested the power transistors I replaced with the diode tester, and they all tested just like the new one I compared em to...

Now what???

If you're as fed up as I am, I wouldn't blame ya for disappearing. Seriously.

Anyway....🤷

[Miyagi_83]

You most probably know all of this and you probably think the same, but the thing that I would do is the following:
1. reread this thread,
2. write down (I'd do that on paper) all suggestions provided by the pros (g1, Loudthud, et al.),
3. try to recall everything that led to the amplifier's working properly, or at least to an acceptable degree.

Once you've discovered where you fouled up, maybe it'll be possible to undo the changes that caused the amp to misbehave.

Unfortunately, I can't offer much assistance because solid-state amplifiers are still beyond me.
Good luck!
M.

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Are they supposed to be insulated like with mica 

[RG100ESROX]

Are they supposed to be insulated like with mica 

They are; yes.

[RG100ESROX]

This morning I decided to try it again. So I powered her up and I pushed past the 45 to 50 VAC mark and the lightbulb went out and everything went back to normal. Well, somewhat normal.

So I'm not sure what goes on around that voltage point, but there seems to be a large current draw at the 45 to 50 VAC for some reason. Maybe someone can explain this to me?

At this point, the amp seems to be fine with the exception of it sounds like it has crossover distortion in it, But the weird thing is if I adjust the bias up some, it seems that it gets worse, not better. So I don't know what that's all about.

What is the absolute highest mV I should see being dropped across the .62R resistors used to bias this thing even if it's just for a minute or two? I'm wondering if it's just not high enough yet to get me to the original tone.

It seems to be getting a little better the higher I bias it. I have been as high as 105mV with no apparent detriment to the amp, but some improvement to the tone.

INTERESTING NOTE.: if I unground the 'effects return' jack. My sound goes away, and I get a pretty good hum out of the speaker. I don't believe this is normal at all. Is this any indication of what might be wrong with amp???

[RG100ESROX]

You most probably know all of this and you probably think the same, but the thing that I would do is the following:
1. reread this thread,
2. write down (I'd do that on paper) all suggestions provided by the pros (g1, Loudthud, et al.),
3. try to recall everything that led to the amplifier's working properly, or at least to an acceptable degree.

Once you've discovered where you fouled up, maybe it'll be possible to undo the changes that caused the amp to misbehave.

Unfortunately, I can't offer much assistance because solid-state amplifiers are still beyond me.
Good luck!
M.

Thank you for the input.

I may have to do just that. Ugh....🫤

[Miyagi_83]

At this point, the amp seems to be fine with the exception of it sounds like it has crossover distortion in it

Are you sure it's the power amp making this kind of sound? It can be checked fairly easily, I think, provided this model has an effects loop (I haven't checked and can't remember from this thread, sorry) and you've got another known good amp.

First, I would run the Randall's preamp out / effects loop send into the input of another amp to see if it's not the preamp that's to blame.

If the preamp is fine, you could plug your guitar straight into the power amp in / effects loop return and play it like that. Be careful, though, because the master volume might be in the preamp, so it might get loud.

Again, I don't know if your amplifier has an fx loop. If not, I'm sorry for bothering you and you can disregard this post.

[RG100ESROX]

At this point, the amp seems to be fine with the exception of it sounds like it has crossover distortion in it

Let me check. I'll be back...

Yep. She sounds just fine from the FX send into another amp. That's a relief.

So, we now know that the preamp section is fine, and the issue is in the power section???

Great idea!!

[g1]

You are going to blow up your amp if you try to bias it for tone.
Stop replacing parts that you have not proven defective.

Post data everytime you make an adjustment.  Scope shot of the waveform, and DC readings across the .68 resistors with no signal.

Start by turning the bias all the way down and posting a pic of the scope showing the crossover notch so we can be sure we are talking about the same thing.
Get an output the same level as post #192 but turned the trimmer full CCW so you get the crossover notch.  Post the picture of the scope.

[RG100ESROX]

You are going to blow up your amp if you try to bias it for tone.
Stop replacing parts that you have not proven defective.

Post data everytime you make an adjustment.  Scope shot of the waveform, and DC readings across the .68 resistors with no signal.

Start by turning the bias all the way down and posting a pic of the scope showing the crossover notch so we can be sure we are talking about the same thing.
Get an output the same level as post #192 but turned the trimmer full CCW so you get the crossover notch.  Post the picture of the scope.

Here ya go.

Most recent bias reading and sine wave. I hope the sine Vpp isn't too low.

Q: Is there a reason my sine wave is so jittery?? I have to pause the sine wave to get you a photo. I have a dummy load at 8 Ohms plugged in, and it doesn't change even if I don't use the dummy load.

[Miyagi_83]

Yep. She sounds just fine from the FX send into another amp. That's a relief.

So, we now know that the preamp section is fine, and the issue is in the power section???

That's how I understand it.

... if I unground the 'effects return' jack. My sound goes away, and I get a pretty good hum out of the speaker.

You mean you disconnected the ground connection on the return jack, correct? If so, the hum could be a normal thing, kinda like if you plugged a cable into the input, but no guitar. I'm just speculating here, though.

[RG100ESROX]

Yep. She sounds just fine from the FX send into another amp. That's a relief.

So, we now know that the preamp section is fine, and the issue is in the power section???

That's how I understand it.

... if I unground the 'effects return' jack. My sound goes away, and I get a pretty good hum out of the speaker.

You mean you disconnected the ground connection on the return jack, correct? If so, the hum could be a normal thing, kinda like if you plugged a cable into the input, but no guitar. I'm just speculating here, though.

That was a great idea by the way.

The hum when I unground the return jack is pretty substantial. So, not quite like an amp without the guitar plugged it. I was just curious if that was normal, because I don't know.

[Miyagi_83]

Q: Is there a reason my sine wave is so jittery??

What do you mean?