Help with circuit

[Kee22]

Still a newbie but learning, I bought what i thought was a 5f6a but it turns out it isn't. Ive rebuild it from the original board but changed the layout so everything is on top. The 470k resistor is missing because I got the wrong value so Im just waiting for it to arrive. Cant figure out how the NFB works with the resistor and feed from the the first pin (from the right). Anyone with some help or input is much appreciated.

[Stevem]

Well you first need to learn about what negative feedback is and what it does to the tone and response of a amp.

To save someone from from having to type up a 25 minute reply to you take stroll over to the Aiken amp site, go into his white paper listing and there you will find 2 articles on negative feedback.

You will likely find many other articles you will want to print off and have on hand also.

So if your build is not a 5f6a then what is it?

[Kee22]

I know the basics of what negative feedback is what I cant figure out is what the leads and resistor to the right of the PI is doing. Shouldn't just the NFB go from 4ohm tap back to the PI? So why the feed from the other side. Regarding the circuit Its not my original build and Im still trying to figure out exactly how it works I know its based on a 5f6a.

[pdf64]

... The 470k resistor is missing because I got the wrong value ...

I guess you're referring to the missing V3 LTP cathode bias resistor?
Its typical value is 470 ohms.
A 470k resistor is 470,000 ohms.

At the V1 end of the board there's a 270k resistor. If that's intended to be a cathode bias resistor (?), it should be 2k7.

I know the basics of what negative feedback is what I cant figure out is what the leads and resistor to the right of the PI is doing

Get you head around the Aiken documents mentioned previously and it might become apparent eg https://www.aikenamps.com/index.php/des ... e-feedback

I cant figure out is what the leads and resistor to the right of the PI is doing. Shouldn't just the NFB go from 4ohm tap back to the PI?

See the series feedback resistor Rf in the above linked document.

[Kee22]

Ok Im going to do some reading 470k resistor is a typo it should read 470 just as you mentioned. I really don't know what the 2k7 resistor on the board does but thats how the original layout was wired. Should mention that there's only one input on the amp.

[WhopperPlate]

Ok Im going to do some reading 470k resistor is a typo it should read 470 just as you mentioned. I really don't know what the 2k7 resistor on the board does but thats how the original layout was wired. Should mention that there's only one input on the amp.

https://robrobinette.com/How_Amps_Work.htm

[sluckey]

I really don't know what the 2k7 resistor on the board does but thats how the original layout was wired.

There is no 2K7 resistor in a 5F6A. That red wire should not be there.
Show us the layout you are trying to copy.

[Kee22]

Its not a 5f6a that's my conclusion but probably based on it. The cap i actually correct because of the original board layout. This is the front and back.

[Ten Over]

Its not a 5f6a that's my conclusion but probably based on it. The cap i actually correct because of the original board layout. This is the front and back.

The picture of the bottom is incomplete.

[sluckey]

Its not a 5f6a that's my conclusion but probably based on it.

It's impossible to help with the circuit since we have no idea what it should be. Parts of it resemble a 5F6A. Other parts of it do not. And without seeing any interconnecting wires to control panel, tube sockets, power supply, etc., it becomes even more impossible to say what's right or wrong.

[Phil_S]

Not your question...it looks like you can use some basic help on how to solder. Attached has an excellent tutorial. Some of those solders are fine, others need to be redone. Also, clean off the flux with 90% isopropyl alcohol with a rag or q-tip.

[Kee22]

Its not a 5f6a that's my conclusion but probably based on it. The cap i actually correct because of the original board layout. This is the front and back.

The picture of the bottom is incomplete.

The last wire is connected to NFB resistor 28k and is connected to the 8 ohm tap.

[Kee22]

Its not a 5f6a that's my conclusion but probably based on it.

It's impossible to help with the circuit since we have no idea what it should be. Parts of it resemble a 5F6A. Other parts of it do not. And without seeing any interconnecting wires to control panel, tube sockets, power supply, etc., it becomes even more impossible to say what's right or wrong.

I get it just wanted to get a presence control in there but somehow the robrob version of it canceled out all the guitar signal. My guess is that it has something to do with it wiring on the back of the original board. But I'm still learning.

[Kee22]

Not your question...it looks like you can use some basic help on how to solder. Attached has an excellent tutorial. Some of those solders are fine, others need to be redone. Also, clean off the flux with 90% isopropyl alcohol with a rag or q-tip.

Thanks for the tip, im working on it this is my first time with amp building so I know there's room for improvement.

[Phil_S]

Not your question...it looks like you can use some basic help on how to solder. Attached has an excellent tutorial. Some of those solders are fine, others need to be redone. Also, clean off the flux with 90% isopropyl alcohol with a rag or q-tip.

Thanks for the tip, im working on it this is my first time with amp building so I know there's room for improvement.

It's all good. We all start somewhere. After the first one, I had trouble stopping. Expect this. After about a dozen amps, I was able to move on. You'll be acquiring tools. You'll be needing one of these soon enough. This is a good brand. https://www.ebay.com/itm/276335982165?i ... R4yvqa7FYw