JB 150 8417 Tube Substitute

[CollinsMan]

I was wondering if anyone has modified a "Black Cat" JB 150 to use any tube other than a 8417. Or, is there anything I can directly substitute for this tube?

I've read elsewhere that several people have had luck with EL34 or 6L6 tubes. However, I'm interested in hearing from folks here who have actually done a substitution and had long-term, reliable success with it.

The JB 150 I have is a very nice, almost new unit that I've been using with a modified Pearce Simpson Guardian 23 on 29 Mc AM. Driving an SB 220 to about 200 watts carrier, I always get good audio reports. Folks rarely believe what I'm using when I tell them, though... (I do have to watch the scope to keep it clean, however...)

Anyway, the 8417 is getting soft, and I'd definitely appreciate suggestions on a good replacement.

 

[Charlie Brown]

6L6 worked good for me. Oh course the JB I had was like mint as mint can be and one of my buds talked me out of it. I think he still runs it..

 

[ExitThirteen]

A 6550 audio tube is also a suitable replacement. Will give more power output than a 6L6, and is a bit more durable. 6550's are still common and can be bought at most guitar shops/music stores.


~Cheers~

 

[CollinsMan]

Thanks y'all! I'll give those tubes a try.

 

[Shockwave]

Yes on the 6550 over the 6L6 because the 6550 has a bias voltage much closer to the 8417. You should also check to see if your JB-150 has a 3 pole relay. If it only has a 2 pole relay like many did, it will be a consistent tube eater because the bias is locked on. While this amp doesn't use a lot of bias, it's enough to kill the tube prematurely.

Also worth mentioning is the JB can be run on a vast assortment of inexpensive tubes. I've got them running with 6DQ6B tubes that I bought NOS on eBay for like $5. If you're willing to rewire the socket and swap out the bias zener, the possibilities are nearly endless. I've also found the JB uses too much screen voltage right off the center tap of the transformer. That makes the screens turn red. Using a 200 volt zener diode and adjusting the bias makes the tube much happier.