The transformers would have been from old B&W TV sets. Those are long gone.RJ Guitars wrote: ↑Fri Oct 07, 2022 2:23 pmOne of my personal favorite pieces of Wreck History...
Somewhere in the archives, my own speculation about this has been published previously. It was based on a discussion with Patrick from Mercury Magnetics (A great guy no longer with us ) Patrick shared stories of working with Ken Fischer and told me of a time when Ken brought in one of his favorite old PT's, taken from a TV set. He wanted to have MM make clones of this tranny for his amplifier biz... It's impossible to know the model or the real story but my speculation was that a PT from a TV set would certainly need to support a bunch of tube heaters. Could this be the origin of the Wreck PT?
It might be kinda cool but otherwise worthless info to study some of those old TV set transformers and see if there was anything close to the Wreck specifications. I've got some old Stancor PT's that are close to the right specs for a Wreck build except for that 10 amp heater tap. It's a bit late to think of salvaging PT's from old TV's for most of us but I think it's safe to say that you could get by with a lot less power capacity on the heater tap.
Best Currently Available Express OT in 2022?
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Re: Best Currently Available Express OT in 2022?
Yours Sincerely
Mark Abbott
Mark Abbott
Re: Best Currently Available Express OT in 2022?
The power transformer does have an effect on tone in that it doesn’t sag much. I built a prototype with a power transformer with low current capability and found the amp started off bright and became more mid focused as I turned the volume up.
Yours Sincerely
Mark Abbott
Mark Abbott
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Re: Best Currently Available Express OT in 2022?
Ken’s first repairs/refinements while still working with Ampeg were for after work customers keeping their Marshalls from failing. He would outfit them with 6V6 tubes and lower the voltage with variac adding a filament transformer to keep heaters at 6.3 volts. With the express amp maybe the overkill was to ensure reliability (definitely). He attained power amp sag with the 1k screen dropper in the power supply vs using saggy power transformers. Genius!
Re: Best Currently Available Express OT in 2022?
sagging screens voltage only sounds different than sagging both plates and screens.wpaulvogel wrote: ↑Fri May 26, 2023 11:16 am Ken’s first repairs/refinements while still working with Ampeg were for after work customers keeping their Marshalls from failing. He would outfit them with 6V6 tubes and lower the voltage with variac adding a filament transformer to keep heaters at 6.3 volts. With the express amp maybe the overkill was to ensure reliability (definitely). He attained power amp sag with the 1k screen dropper in the power supply vs using saggy power transformers. Genius!
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Re: Best Currently Available Express OT in 2022?
When I was experimenting with the Express amp I found the 1K resistor caused the supply to sag by a maximum of 40VDC.Roe wrote: ↑Fri May 26, 2023 3:16 pmsagging screens voltage only sounds different than sagging both plates and screens.wpaulvogel wrote: ↑Fri May 26, 2023 11:16 am Ken’s first repairs/refinements while still working with Ampeg were for after work customers keeping their Marshalls from failing. He would outfit them with 6V6 tubes and lower the voltage with variac adding a filament transformer to keep heaters at 6.3 volts. With the express amp maybe the overkill was to ensure reliability (definitely). He attained power amp sag with the 1k screen dropper in the power supply vs using saggy power transformers. Genius!
The idea being to cause compression but not boat loads of it.
A low wattage Express needs a larger value resistor. I think 1.8K would work for amps fitted with a duet of EL84’s.
Yours Sincerely
Mark Abbott
Mark Abbott
Re: Best Currently Available Express OT in 2022?
Interesting. that indicates a 40mA current draw, with 35mA for the el34s and 5mA for the preamp roughly. That is a lot less than a marshall that can draw 140ma with a quad. But RFTs/Siemens do draw more current than many other el34s. Some of the new chinese ones draw much less screen currentMark wrote: ↑Sun May 28, 2023 1:55 amWhen I was experimenting with the Express amp I found the 1K resistor caused the supply to sag by a maximum of 40VDC.Roe wrote: ↑Fri May 26, 2023 3:16 pmsagging screens voltage only sounds different than sagging both plates and screens.wpaulvogel wrote: ↑Fri May 26, 2023 11:16 am Ken’s first repairs/refinements while still working with Ampeg were for after work customers keeping their Marshalls from failing. He would outfit them with 6V6 tubes and lower the voltage with variac adding a filament transformer to keep heaters at 6.3 volts. With the express amp maybe the overkill was to ensure reliability (definitely). He attained power amp sag with the 1k screen dropper in the power supply vs using saggy power transformers. Genius!
The idea being to cause compression but not boat loads of it.
A low wattage Express needs a larger value resistor. I think 1.8K would work for amps fitted with a duet of EL84’s.
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