Adding circuits to an amplifier head build

[Shrimpfarmer89]

I’ll do more reading on the subject so I don’t fry myself, I have none of the parts or anything or an amp to modify so don’t loose sleep. Thank you both for the help I’ll get back to you when I’ve got some more information.

[nosaj]

This is going to get very confusing with 2 threads running on the very same topic. nosaj can you merge this one with the other?

Yea I just attempted it not sure I'm happy with results its not the same as previous forum software.
nosaj

[vintagekiki]

... I don’t fry myself, I have none of the parts or anything or an amp to modify so don’t loose sleep ...

Don't worry about loose sleep, why you run away from the subject when are most interesting?

[Shrimpfarmer89]

I understand you, do you understand the other side?

Question

- If you have carefully studied the schematics (by the way it's an 8-page in pdf), you would notice that there are more b+ (b2, b3, b4) on page 1, so it is unclear what you mean by b+
- Where you intend to run a line the b+ on your schemaic?
- If you connect all b+ (b2, b3, b4) to one point, there will not be enough filtration, the amplifier will hum and most likely go wild (oscillating)
- Don't worry about enough power (energy) for preamp, because the PT is designed to power the entire amp with 4 x 6L6GC.
- Have you read pdf pages from 5 to 8 on your schematic?

probably run it off the b2, the b2 powers all the other filaments in the pre amp stage, but there’s multiple lines off that initial b2 line, so probably just run a line like the other lines. that I read the bottom pages it’s a bunch of explanation of mods of the amp the other guy made.

also the 5v goes to the tube rectifier. The center tap is to cut down on the hum and ground that part of the transformer. You can use two 100 ohm resistors to cut the hum and ground them. and the 6.3 v go to power the filiments in the power tubes and run through the fuse and the beginning of the tube amp. Or to a foot switch or something like that.

I wouldn’t want to connect all the b+ points to one thread I just want to tap one line the to run the two circuts in series before the fx loop.

Thanks for the info ya’ll I’m diggin the teamwork on this one. I’m finally getting some answers

I get the power amp section doesn’t need to be messed with and that it will have enough power to power the amp overall.

[Shrimpfarmer89]

Don't worry about loose sleep, why you run away from the subject when are most interesting?

I know I got cold feet for a second, I’m finally getting answers, I knew the answers to the questions about the center tap and the 6.3 and the 5v as well I just couldn’t get them immediately. I’ve watched a bunch of videos and have that Gerald Weber tube amp video and I’ve watched it and taken notes. I get the general idea of the building and how they work and how not to get fried, that’s why I’m asking questions so I can get this thing figured out!

thank you all for your help along the way!

[vintagekiki]

Viewing User Profile
There is nothing interesting there.
Everything is here (Guitar Amps)

[g1]

I think vintagekiki 's comment here may be referring to the Gerald Weber videos.

[Shrimpfarmer89]

Before Nosaj or I give you any more potentially lethal advice can you please answer these questions. If you don't know, then please stop and learn. As Nosaj said, start simple.

1. What does the 5v tap do on your PT?
2. Does your circuit use it?
3. If not, why not?
4. What does the 6.3v tap do on your PT?
5. Does your circuit use it?
6. If not, why not?
7. Does your 6.3 v wind use a CT? If so, what is it for?
8. If your 6.3 wind doesn't have a CT, what else can you do to stop that horrendous hum?
9. I am not even going to address the challenge of getting 20VDC from 5 or 6.3VAC.

I think I will sleep better at night knowing that I haven't contributed to your premature passing. I'm out. Good luck

5 volt to rectifier, 6.3 to filiments of other tubes, and 2 100ohm resistors to cut the hum, if you don’t have a grounding center tap. 6.3 and the main section of the transformer usually have CT’s, and the main and the 5v power rectifier’s filiments the and the main powers the rectifier’s cathode/anode

[Enzo]

You seem convinced to get 20v from several hundred volts in your B+. Look at the bias supply, just above the power transformer.. Page 3. MAy I suggest just duplicating that circuit, from the same tap, except reverse the polarities. Reverse the rectifier, and invert the filter caps. Why start with 400v when all you need is 20?

[Shrimpfarmer89]

You seem convinced to get 20v from several hundred volts in your B+. Look at the bias supply, just above the power transformer.. Page 3. MAy I suggest just duplicating that circuit, from the same tap, except reverse the polarities. Reverse the rectifier, and invert the filter caps. Why start with 400v when all you need is 20?

so just off the same tap from the transformer,
make the same bias circut
but flip the caps so the negative lead is on the positive side

what do you mean reverse the rectifier? Like the rectifier for the entire amp?

and how do you reverse the polarities? Thanks for the info!

[Enzo]

At the tap for the bias supply, we add another diode but facing the other way - so it make positive instead of negative supply. D10 is the rectifier diode for the bias supply. Our new diode would be wired reverse of that. Yes, the caps would be wired reverse of what we see in the bias supply

the negative lead is on the positive side

We wouldn't state it that way, it is confusing. I would use terms like connect negative side of cap to ground.

[Shrimpfarmer89]

At the tap for the bias supply, we add another diode but facing the other way - so it make positive instead of negative supply. D10 is the rectifier diode for the bias supply. Our new diode would be wired reverse of that. Yes, the caps would be wired reverse of what we see in the bias supply



We wouldn't state it that way, it is confusing. I would use terms like connect negative side of cap to ground.

that seems easy enough.

why reverse the polarities and the caps? What does this do?

Also you are correct I need around 20 volts, are the bias supplies usually 20 volts ish? Or around there? How do you know it’s the amount I need when there’s nothing that says the voltage on that part of the schematic?

much appreciated! Thank you for answering my questions I appreciate it very much.

[g1]

why reverse the polarities and the caps? What does this do?

The bias supply is a negative voltage. You want a positive voltage, yes?

[Shrimpfarmer89]

I just looked at bias information and they had everything in negatives and I said to myself it makes sense what he was saying.....to have it flipped so it’s positive.

[christarak]

This is going to get very confusing with 2 threads running on the very same topic. nosaj can you merge this one with the other?

I am definitely confused, G1. I thought it was only Nosaj and me, but now I see so much more responses. Apologies if I crossed across other people's responses.

[Enzo]

The bias supply is like maybe 60v, but that is a detail, we can adjust with a resistor or two. Just way better - in my view - to come down from 60 than 400.

[Shrimpfarmer89]

Yeah that makes way more sense. I think that would be easier to adjust to a useable voltage. I’m looking up more information on the bias windings now! Much easier to deal with.