LSS "Warm Up" in 5W & 15 W Modes?

[vanceen]

I recently put an NOS Tung Sol 5Y3 into my Lone Star Special. Since then, the sound drops to a very low level when I switch to 15W or 5W mode, and then comes back to normal after a couple of minutes.

It's as if the 5Y3 is having to warm up when I change to it from the 30W SS rectifier. But that never happened with the original 5Y3.

I only swapped it out because the NOS was fairly inexpensive and reputed to last a long time.

Has anyone seen anything similar to this?

 

[ricardo loma vista]

The rectifier tube shouldn't need to warm up. It should always be lit up and hot, no matter what wattage you have set.

I found that a bad 5Y3 will blow the fuse even when playing on the 30W setting. I was playing a gig on the 15W setting when the fuse blew. I suspected the 5Y3 because the drummer saw a flash from the back of my amp, so I switched to the 30 W setting. Within about 30 seconds it blew again--same flash. The 2nd time I pulled the 5Y3, and no more problems on 30W.

My guess is that the 5Y3 runs in parallel with the diode rectifier in 30 W mode, and the diode is switched out of the circuit when switching to 15W or 5 W. This means that the rectifier tube has to be operating all the time, probably to be able to handle the switch from 30 to 15 instantaneously without a volume drop.

Since you are experiencing a volume drop, it's possible that the tube is defective, so you should try another 5Y3. Also, check to see that the 5Y3 is lit up when you are on 30W. If it's not, you may have a problem in the switch.

 

[vanceen]

Thanks, that's what I suspected.

I'll try putting the old 5Y3 back in when I get home to the amp, and I'll confirm that it's lit in the 30W position.