Stumbled across this, one hell of a Homebrew

[dynaman]

Wow, that's some serious DIY right there. Suhweeet.

[ChrisM]

Anyone know how he is doing that LED power tube thing? Where the LEDs if the power tubes are fine are not, if not the pair is taken out of the circuit.

[selloutrr]

Anyone know how he is doing that LED power tube thing? Where the LEDs if the power tubes are fine are not, if not the pair is taken out of the circuit.

I'm not sure what you are asking? he talks about the LED's on his website about halfway down the page.

"Close-up of one of the LED strips. These come on a roll and you can cut them in minimum increments of three LED’s. I have cut them for six LED’s on each strip. As they are 12 volts per strip, I have simply put the four strips in series and, along with the fans on a communal fuse of F250m/a, connected them to the 50 volt bias rail......"

[ChrisM]

Four bi-colour LED's (green&red) & Fuses - each pair of KT88 has its own "security
system". When one tube blows out, the fuse disconnects both of them, then the
rest works pretty fine. Green LED indicates OK status, Red means trouble

[selloutrr]

The safety fuse is similar to how the SVT's work I'm not sure if Ampeg invented it.
The Fender Sunn Modet T reissue also has a similar LED indicator circuit for good and bad.

[ChrisM]

The safety fuse is similar to how the SVT's work I'm not sure if Ampeg invented it.
The Fender Sunn Modet T reissue also has a similar LED indicator circuit for good and bad.

Can't find schematics with these features.

[paulster]

The safety fuse is similar to how the SVT's work I'm not sure if Ampeg invented it.
The Fender Sunn Modet T reissue also has a similar LED indicator circuit for good and bad.

Can't find schematics with these features.

Try a Marshall 30th Anniversary or JCM900 (I think). Schematics are at www.drtube.com

[Marvel]

I proudly announce that the amp in the first post was made in Poland by our Polish tube amp guru Tom. He runs a very informative amp-building website (in Polish only):
http://www.mif.pg.gda.pl/homepages/tom/

ChrisM -> from the above website:

[img:640:480]http://www.mif.pg.gda.pl/homepages/tom/images/safe1.gif[/img]

Regards, Marcin

[selloutrr]

I can't find a schematic for the Sunn reissue but I have a copy of the manual if interested. Page 7 talks about bias and LED's

[ChrisM]

Cool, thanks.
Why 500mA though, seems kinda high.

[PlinytheWelder]

I have a 5KV power transformer out of an old X-Ray machine... (it's about 1 cubic foot) Combined with some radio transmitter tubes... yer all screwed..

[M Fowler]

Marvel there was a lot of good data on that Polish website.

Mark

[Marvel]

Why 500mA though, seems kinda high.

1. You don't really know how much cathode current you have at full drive. I think 150mA per tube is possible. Don't confuse it with idle current.
2. When a tube is faulty (shorted) much greater current flows through it, so even a bigger fuse will blow.

Marvel there was a lot of good data on that Polish website.

Most of it is pretty international, isn't it.

Regards, M.