Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Jatchley on November 14, 2020, 08:45:15 pm

Title: Univox U-1246 Plate Voltage.
Post by: Jatchley on November 14, 2020, 08:45:15 pm

How is this thing legal? 670V on 6L6gcs @ 117vac mains. Would 125 be more like 685v? I see the 10k primary on the OT but is it really ok? I’m afraid it’s gonna pop if I turn it on.  Customer says it burns through tubes pretty fast. Yeah no kidding. A friend suggested 6550s and I saw a tiny bit on groupdiy about it but I’m unsure if the OT would handle that. Any ideas?

Title: Re: Univox U-1246 Plate Voltage.
Post by: sluckey on November 14, 2020, 09:35:00 pm

670 on the plates but there's only 335 on the screens. Screens are setting the speed limit and keeping it legal.

Title: Re: Univox U-1246 Plate Voltage.
Post by: PRR on November 14, 2020, 11:11:19 pm

I had that amp's big brother. Six 6L6GC. I do not recall it burning tubes. 6L6 is almost an 807; the GC is a TV H-Sweep tube (6BG6) rated for very much higher plate voltage; 7027 is same-guts in taller glass; all without the top-cap needed for KiloVolts.
https://bama.edebris.com/download/gehamnews/ge1501/GEHamNews-Vol15No1-JanFeb1960.pdf page 7

Title: Re: Univox U-1246 Plate Voltage.
Post by: Latole on November 15, 2020, 04:06:34 am

Quote from: Jatchley on November 14, 2020, 08:45:15 pm

  Customer says it burns through tubes pretty fast.  Any ideas?

 What is the tubes bias ?

That is the first thing I will check.