Retubing my Jet City

[marnold***]

Fixed biased or cathode biased?

Anyway, ever consider some used (or new) old stock tubes?

It's fixed bias with a trim pot for adjustments. From what I understand they are shipped biased slightly cold from the factory. Here's a Youtube video on biasing it. If I were to do it myself, I'd rather get a bias probe.



I don't have the cash for NOS and I don't know that I really have the desire to research.

[tunghaichuan***]

It's fixed bias with a trim pot for adjustments. From what I understand they are shipped biased slightly cold from the factory. Here's a Youtube video on biasing it. If I were to do it myself, I'd rather get a bias probe.



I don't have the cash for NOS and I don't know that I really have the desire to research.

I've seen that video and it makes me cringe. That guy is sticking both hands inside the chassis at the same time. Not a good idea. At the very least you could get a nasty shock. Worst case scenario is that the current would stop your heart and kill you.

The information in that video is valid, but the technique is bad.

To do it right you need a retractable spring clip that attaches to the tip of your DMM. That way you can clip one lead where it needs to go and use one hand to probe inside chassis.

This is important enough to say again: never stick both hands inside a tube amp. You should always keep one hand behind your back or in your pocket to resist doing so.

[Tig***]

Yes, the retractable hook clips work great. Here's a set on eBay for $2.99.
http://cgi.ebay.com/NEW-Test-Hook-Cl...-/280576916134