converting to solid state rectifier

[pontiacpete]

I built a bassman 20 recently with the power supply from the deluxe reverb ab763 circuit using a deluxe trafo and the bias supply set up with the adjustable pot and a standby switch. I'd like to change out the tube rectifier(gz34) and put in a bridge rectifier but I'd like to keep the adjustable bias supply. I'm having a problem figuring out the wiring. I've tried clip leading it in on a breadboard and haven't had any luck.
Is there anyone here that could help be with this?
thanks in advance.
pete

[black_labb]

a bridge rectifier could make the bias a bit difficult to put in. i'd suggest using a full wave rectifier. its the same type of rectifier as the tube rectifier, just using diodes as opposed to the tube. bridge rectifiers are suited to when you have a single winding, not a center tapped winding like you would on an amp with a tube rectifier.

otherwise there is no harm. you can upsize the first filter cap if you want to get an even tighter sound, and maybe less hum if the amp has much b+ ripple.

[pontiacpete]

not sure how to work this forum, I ended up replying with the 'quick' reply.
Anyway, the full wave rectifier seems to work well.
thanks.
I now have a static like hum like a grounding issue happening. Since the PT is from a deluxe there are the 2 yellow wires still attached to the octal socket with 5vac across them. Could this be the source of the noise?
If so, do I ground one of them? They seem to be tapped to the winding that goes off to the bias supply circuit as in the deluxe rev which in this case is the blue/red wire.
thanks for the help.
pete

[Chuck H]

DO NOT GROUND THE YELLOW WIRES!

PT death will ensue.

If all else is the same besides the rectifier, and the amp was quiet before, you may have a mistake in your bias supply wiring after tinkering.

Chuck

[pontiacpete]

Thanks, Chuck

[pontiacpete]

I actually was able to set the bias to the specs of the bassman 20 schematic, -33vdc.
Maybe I should connect the 2 yellow wires?

[pontiacpete]

That didn't work! I tried clip leading the two yellow wires and fried my clip lead.
What to do?

[pdf64]

Try waiting for an answer before you short out a winding!
I'm worried that you know just enough to be dangerous. No one here can know if you've grounded you chassis properly etc, and you are risking a major transformer failure which could make the chassis live.
Read up as much as possible on stuff you're thinking of doing,
aikenamps.com
geofex.com
Then ask questions here before you go ahead.
You need to get an understanding of why what you've done just was a bad idea.
Re bias, you need to understand why setting the bias to the specified -33V is entirely the wrong way to check it when you moved from a tube to a silicon rectifier. Peter.

[Jag]

+1

You really CAN kill yourself with this stuff.

[pontiacpete]

Dumb move on my part. I'm usually more cautious. I have it plugged into an outlet with a 100W bulb as a limiter and forgot that the limit switch was not on when of course it should have been.
No apparent harm done to the PT. It's still powering up with the loud hum.

Do I need a dropping resistor on the cathodes of the two IN4007s?
Any suggestions would help.

thanks all

[pontiacpete]

I put a 470 ohm 2W resistor on the anodes of the 2 diodes and connected the other end of the resistor to the standby switch.
This seems to have reduced the hum, maybe in half, but I still have it.
I'm thinking that maybe a higher resistor might do. No?

[pdf64]

Please stop dicking around with this.
Put it back how it was.
Learn electronics on some low voltage stuff, like effect pedals.
This is like a commentary from someone who has a blindfold on as he walks along a cliff edge. Peter.

[pontiacpete]

Thank you Peter

Point well taken. I am a newbie at electronics. I have built about 10 working effects pedals for myself. It was a great learning process. I put together a kit and built two clone amps from skratch. Gerald Webers kit, the newjoyzee, a blackface deluxe and super reverb. More great learning for me and all of them work great and have proven so for a couple of years, which included many professional gigs.
I've been doing a lot of reading and have a mentor, an electrical engineer guy helping me with theory stuff and the mathematics behind it. We worked through a number of repairs on transistor amps , i.e. GK400 , polytone brute bassamp, heathkit IP 17 some antique radios and my Scott Stereo etc, etc.
This particular thread I started is of a build I made funded by a fellow musician i.e. he paid for the parts I did the labor with the hope learning more. It was made about a half a year go and has worked fine for several gigs and rehearsals for him. He wanted a small tube amp for such.
Anyway, here's where the problem of this thread starts. I never diverged from a schametic/layout of any of the my builds so far, but on this one I tried using a deluxe PT for a bassman 20 with a tube rectifier. It that has been working. Well, my friend loves the sound but, of course, he wants it a bit louder. So I decided to put a solid state rectifier in(years ago Harry Kolbe did it for me on a 70's princeton, which I since reversed) with the thought that it might give him a bit more power. Is this true in your opinion? Nonetheless, I never have done a conversion to a SS rectifier whatsoever, and hope to learn how. Do you have any advice that would help other than trying to discourage me?
BTW, there's a really great forum that started reading about 6 months ago called Funwithtubes run by Max Robinson, a retired EE professor.
They always say to the new guys that there are no stupid questions, I hope this forum is like that too.

Best Regards,
pete

[JoeM]

I never diverged from a schametic/layout of any of the my builds so far, but on this one I tried using a deluxe PT for a bassman 20 with a tube rectifier. It that has been working. Well, my friend loves the sound but, of course, he wants it a bit louder. So I decided to put a solid state rectifier in(years ago Harry Kolbe did it for me on a 70's princeton, which I since reversed) with the thought that it might give him a bit more power.

Best Regards,
pete

Why not just get one of the SS modules that plugs in the tube rectifier socket? Then you can go back and forth with a tube rectifier (with a re-bias), without having to do any permanent mods to the amp.

[pontiacpete]

joe
Thanks. I did a search for this but haven't come up with anything. Can you send me a link?
At this point the hum problem is solved. I added 2 more diodes in series each on the primary, and the AC hum is practically gone, but I would like to have one on these plug in SS rectifiers to try on other amps.
pete