Fender 600 champion reissue complete rebuild

[Mark]

Nice, problem is that the 600 champ reissue has noting in common with the first model. The new one sounds very much like a silver face champ with the fixed eq.

Not necessarily, my one has the tone controls removed and is more or less a 5F1 amp. The breakup is much better.

[Mikante]

Same with mine, i removed the tone stack and it was the first mod.
This amp has a lot of gain and without the fixed eq even more.
Then i changed the negative feed back value from 2.2k to 22k, to be “tweed” correct and the amount of gain increased even more. Too much distortion at this point and the sweet spot is simply not there anymore.
So i removed the second stage cathode cap, a 22uf, in order to tame the distortion a little bit. I didn’t like it.
This amp is biased hot as hell and it is driving the 6v6 too hard. This is from the factory, i don’t know why.
I need to check on this when my rebuild will be done, if i ever manage to

[Mark]

I did the Mercury Magnetics mods to my Champ 600, and to summarise, I wouldn’t recommend their mods. The mods weren’t well thought out and were weird.

The input choke and the output transformer were great, the amp was quieter and fatter sounding. The Weber speaker was better than the stock speaker but it took a very very long time to break in.

The power transformer was just crazy, I had a 115/120vac power transformer and needed a 240 to 115 drop-down transformer. I was amazed when I saw the volt meter reading 450VDC. The first thought was, in which parallel universe can a 6V6 handle that sort of voltage in class A. I emailed Patrick about it in case the transformer was faulty, he said it was normal and they hadn’t had in issues with the amp at MM.
needless to say the power transformer came out.

The amp was a 5F1 amp with an input choke power supply with the stock dropping resistors. I found this was hard on 6V6’s. I put it down to the 1K choke resistor. I remember placed the 1K resistor with a 10K and end of problem.

With the Mercury output transformer I don’t have an issue with biasing the 6V6, it’s pretty much spot on. I was going to replace the bias resistor with a wire wound variable resistor. (I have used one on an AC-30 and they work well.)
As the bias is spot on I have no need to replace the resistor.

That’s where my Champ 600 is at. On the outside it looks stock but that’s about it. I didn’t bother about the “grill cloth mod” as I didn’t it would achieve anything.

The 6SJ7/EF86 thing is about as far as I wish to go with the amp. I like it’s simplicity.

[Mikante]

The stock transformers work fine for me. The ot is a paper bobin, nowday you pay more for that yes they are cheap but i will not replace them.
The MM are too expensive in europe to have, there are a kot of other good options if i ever decide to upgrade the irons Tad makes a good one for the purpose and not for too much money.
So you did tweek the bias a little bit. On the 5f1 the choke resistor is 1k anyway if I remember correctly.
On the 600 reissue there is a 470ohm resistor there and this brings up the plate dissipation way over a good operating point.
I really need to check this once I got the amp up and running.

[thetragichero]

if you ask me, mercury magnetic transformers are too expensive here in the states too

[Mikante]

if you ask me, mercury magnetic transformers are too expensive here in the states too

That, plus shipping and taxes.

[Mark]

The MM are too expensive in europe to have, there are a kot of other good options if i ever decide to upgrade the irons Tad makes a good one for the purpose and not for too much money.
So you did tweek the bias a little bit. On the 5f1 the choke resistor is 1k anyway if I remember correctly.

TAD postage to Australia is prohibitively expensive, so that puts Mercury back into the equation.

I didn’t tweak the bias at all, I still the original 470 ohm resistor. You are incorrect the choke resistor is 10K the black and silver face Champs have 1K choke resistors.

https://www.thetubestore.com/lib/thetub ... ematic.pdf

https://www.thetubestore.com/lib/thetub ... ematic.pdf

[Mikante]

The MM are too expensive in europe to have, there are a kot of other good options if i ever decide to upgrade the irons Tad makes a good one for the purpose and not for too much money.
So you did tweek the bias a little bit. On the 5f1 the choke resistor is 1k anyway if I remember correctly.

TAD postage to Australia is prohibitively expensive, so that puts Mercury back into the equation.

I didn’t tweak the bias at all, I still the original 470 ohm resistor. You are incorrect the choke resistor is 10K the black and silver face Champs have 1K choke resistors.

https://www.thetubestore.com/lib/thetub ... ematic.pdf

https://www.thetubestore.com/lib/thetub ... ematic.pdf

Sorry, my bad, I was referring to the cathode resistor.
Dropping down the value of the choke resistor to 1k from 10k, as you did, what will that do?

[Mark]

Sorry, my bad, I was referring to the cathode resistor.
Dropping down the value of the choke resistor to 1k from 10k, as you did, what will that do?

It drops the voltage to the grid and preamp stages while also limiting current to the screen grid.

I personally liked the implementation of the 5F1 circuit in the amp, though I do have a larger output transformer.

[Mikante]

I didn’t want to spend too much money for my first project, so i am using the stock transformers and of course i m building back the champ 600 as it was with just the choke upgrade and some better components.
Thank you for the infos.
Lets hope i can start this project soon and then you ll hear a lot from me

[Mikante]

Hello,
I m relocating irons and tube in order to make space for the point to point turrets (a real p to p) and also to move the output transformer a little away from the pt.
Let me know your thoughts about this layout.

image.jpg

This is inside the chassis.
I have space under the chassis before the speaker so i am not concerned about that, just trying to have a proper layout design before to start.

[martin manning]

I would slide the choke and OT over closer to the PT. Which of those components are already located bt existing mounting holes? PT? Tubes?

[sluckey]

The OT is in a bad place. I would move it away from the preamp and put it close to the 6V6.

[ChopSauce]

If you're doing real P2P - not turrets but isolated/boardless ones - I suggest you reconsider moving any transformer especially closer to V1/the inputs.

In either case I'd take much care of Martin's & sluckey's suggestions.

[Mikante]

I would slide the choke and OT over closer to the PT. Which of those components are already located bt existing mounting holes? PT? Tubes?

Only the power transformer is in the stock position.
I thought moving the ot away from the power supply was more important. I guess i was wrong.