5F1 in a Champ 600 box... but I need some help

[Reece86]

Hi all

New to amp building, but I thought I would give it a shot. Used to work in a guitar shop so I got two Champ 600's that had died. Transformers and speakers are still good.
I have gutted the amps, made boards and wired up the 5F1 circuit. Everything is hand wired, but I used the original tranny. As such, I had to use the solid state rectifier from the amp. Amp has a volume / power, added the external access to the fuse.

I have one all wired up and it turns on, but the jewel light does not turn on and it sounds kinda weird. Plugged it into an extension cab to check if it were the speaker, but that is not it. I'll include some pics cause I think it looks pretty cool, aside from having multiple grounding points (I have since been told that is a bad idea? I'll fix it before doing more work).

Also, how do I safely discharge the caps after plugging the thing in?

[Blackburn]

I'm quite familiar with these things...

https://tubeamparchive.com/viewtopic.php?t=21601

Heaters are not center tapped, gotta get two resistors to ground on each side. I gotta say, I'm very curious how you're halting the B+ to allow warm up. Did you keep the brimistor?

David

[Reece86]

I'm quite familiar with these things...

https://tubeamparchive.com/viewtopic.php?t=21601

Heaters are not center tapped, gotta get two resistors to ground on each side. I gotta say, I'm very curious how you're halting the B+ to allow warm up. Did you keep the brimistor?

David

Hey David. No idea what a brimistor is. This was more a project to see if I could make sense of it all. A friend I know looked it over to make sure I wouldn't die from turning it on, but mostly I was on my own. I just tried to make it as close to a 5f1 as I could. And the pic does not show, but I have two resistors coming off the heaters at the V1 to ground. Thanks for pointing that out though because I did not understand why I had those there.... I am a total novice and do not do anything with the amps on until it has been looked at by friends of mine, but they are making sure it is safe, not doing the build for me.

[Blackburn]

Also, how do I safely discharge the caps after plugging the thing in?

A resistor to ground. You can use a smallish value (I use a 10K 1W), tie it to ground and short the caps. Be sure you don't physically touch the positive side of the caps!

If you don't know how to use a meter as well, I'm not sure you should be building/working on amps yet. This is a good place to learn.

[Reece86]

If you don't know how to use a meter as well, I'm not sure you should be building/working on amps yet. This is a good place to learn.

I agree lol. I am reading lots of threads but finding some hard to understand it all. I understand this stuff in theory, but there are obvious gaps in my understanding and I have not actually done much of it before. I just don't know where to take this project now that the caps have stored charges.

[Blackburn]

A brimistor provides a 'slow start' for the tubes and can be used instead of a standby switch. Fender used one in these amps. I used a three position monster that barely fit, since I tend to have those around. It isn't a good idea hitting those plates with voltage instantaneously before the heaters have warmed up.

Point is, you need to have a thorough understanding of safety before doing anything with tube amps. I wouldn't even operate it again until you have a little more knowledge under your belt. Ask any and all questions you have. Many minds here that are more knowledgeable than mine.

[xtian]

Learn to discharge your caps, and to measure them with voltmeter.

http://billmaudio.com/wp/?page_id=1150

You do not need a standby switch.

http://www.valvewizard.co.uk/standby.html

[Blackburn]

You do not need a standby switch.

With a tube rectifier.

[martin manning]

You do not need a standby switch.

With a tube rectifier.

You are worried about cathode stripping? That is not an issue for audio tubes.

[M Fowler]

That filament wiring doesn't look right at the pilot light.

[Blackburn]

That filament wiring doesn't look right at the pilot light.

I saw that too. There's a resistor and a diode, seemingly in series.

[martin manning]

That filament wiring doesn't look right at the pilot light.

I saw that too. There's a resistor and a diode, seemingly in series.

In the Champion 600 schematic the jewell lamp is actually an LED. The pictures posted above are not very good, so it's hard to tell what is going on there and why it doesn't glow.

Re the need for delayed HT to prolong tube life, Blencowe has this to say in the article linked above:

"Contrary to popular belief, the standby switch is not there to prolong valve life-span. The theory is that if the HT is applied while the cathodes are cold they will be 'stripped' by ions crashing into the unprotected cathode. However, this simply does not happen. It is an urban myth borrowed from transmitter and cathode-ray tube technology NOT ordinary 'receiving' valves."

[Blackburn]

And here I thought diodes always needed one... Could've saved a good bit of labor on wiring switches!

[Reece86]

Learn to discharge your caps, and to measure them with voltmeter.

http://billmaudio.com/wp/?page_id=1150

Thank you!

I put the resistor and diode on the lamp from the original schem. Should I take those out and go straight to the lamp from the transformer?