1967 Marshall Super PA KT66 screen voltage question
Moderators: pompeiisneaks, Colossal
-
- Posts: 1104
- Joined: Thu Jan 23, 2014 7:32 pm
- Location: Laguna Niguel, California
Re: 1967 Marshall Super PA KT66 screen voltage question
Now I am confused. The Drake 1202-84 /4k primary impedance is the stock Marshall transformer for a quad of kt66. Same one that is in Hendrix's Monterey amp.
CW
CW
- martin manning
- Posts: 13276
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
1 others liked this
Re: 1967 Marshall Super PA KT66 screen voltage question
Yes, I edited after looking it up. It's really not a good place to be operating, but a little better at lower voltage. FWIW, Brian Wallace thinks either KT66 or EL34 will be fine with that transformer.
-
- Posts: 1104
- Joined: Thu Jan 23, 2014 7:32 pm
- Location: Laguna Niguel, California
Re: 1967 Marshall Super PA KT66 screen voltage question
Thanks Martin. Well the amp now has the Merren power transformer and the TAD KT66. I think I'll use the lower B+ 460v secondary taps.
CW
CW
Re: 1967 Marshall Super PA KT66 screen voltage question
Charlie Wilson wrote: ↑Mon Feb 28, 2022 10:21 pm Hmmm, let me rephrase my original question. Will TAD KT66 take higher than the spec sheet 400v? As far as variacs and butchering vintage amps. This amp is to be sold and I feel better selling an amp to a buyer that can plug the amp into the wall than having to get a step up or variac and hope they know what they are doing. Obviously the original transformer is included with the amp and is easily put back in if they choose. Again, I repeat, NOS GEC KT66 are $1400+ if you can find them so that is not an option.
CW
yes 500v at the plates is no problem. how much screen resistance you need depends on the voltage really. many of these amps have been running for a long time with these new tubes with original 1k screen resistors and roughly 500v at idle (which will sag significantly under load)
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
Re: 1967 Marshall Super PA KT66 screen voltage question
yes, but el34s were introduced in february 1967 with the drake 1202-119 OT (1k75 Z)Charlie Wilson wrote: ↑Tue Mar 01, 2022 3:13 am Now I am confused. The Drake 1202-84 /4k primary impedance is the stock Marshall transformer for a quad of kt66. Same one that is in Hendrix's Monterey amp.
CW
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
- martin manning
- Posts: 13276
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
1 others liked this
Re: 1967 Marshall Super PA KT66 screen voltage question
yes, this is pretty much the history of marshall 100w amps from 1967 until recently. redplating is all too commonmartin manning wrote: ↑Tue Mar 01, 2022 1:55 pm1k7 is really too far the other way, and depends upon significant voltage sag to stay out of trouble.
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
Re: 1967 Marshall Super PA KT66 screen voltage question
3k4, 3k5, 3k6 is a standard for 2*EL34, half of that for quad
Re: 1967 Marshall Super PA KT66 screen voltage question
yes, but in the case of marshall the problem is the 100w amps, not the 50w ones, due to voltage differences
www.myspace.com/20bonesband
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
www.myspace.com/prostitutes
Express, Comet 60, Jtm45, jtm50, jmp50, 6g6b, vibroverb, champster, alessandro rottweiler
4x12" w/H75s
- Reeltarded
- Posts: 9960
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
1 others liked this
Re: 1967 Marshall Super PA KT66 screen voltage question
As per my post '66 45 amps (JTM50) tube rectified or not and 34s with either OT configuration, 100s finally @1k7 like Roe says.martin manning wrote: ↑Tue Mar 01, 2022 1:55 pm1k7 is really too far the other way, and depends upon significant voltage sag to stay out of trouble.
100w magic is 2k5 and 34s.Baaaaa WAAAAHHHHHRRR
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
- Reeltarded
- Posts: 9960
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
1 others liked this
Re: 1967 Marshall Super PA KT66 screen voltage question
Roe wrote: ↑Tue Mar 01, 2022 5:14 pmyes, this is pretty much the history of marshall 100w amps from 1967 until recently. redplating is all too commonmartin manning wrote: ↑Tue Mar 01, 2022 1:55 pm1k7 is really too far the other way, and depends upon significant voltage sag to stay out of trouble.
YES this.. poor screens..
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.