Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: stingray_65 on August 07, 2011, 10:06:49 pm
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Hey guys,
I scored an old amp out of a Baldwin organ.
It was a hybrid, solid state tone generators and a tube amp.
Tube compliment is 5U4 recto, 2 12AX7's and PP 5BQ5's
The point to point wiring makes re capping and converting it a bit daunting, so I planned on gutting it for parts.
I'm Thinking I'd like to build an 18Watt, and Doug's Stout has had great reviews, But I'm not sure if the PT is sufficient.
It's putting out 315-0-315 unrectified. I've not measured it after the 5U4, I don't want any of those cap cans spewing hot electrolyte around (paper ones look a bit pregnant)
Is this going to be high enough for the Stout?
I also do not have a choke for it, I might find one laying around here that may be OK but for now I'm not planning on using one.
The OT is kind of largish too (compared to a Marshall) but will be used regardless.
Any opinions are welcomed.
Ray
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Hi Ray!
Are you sure they're not 6bq5s instead? I don't seem to see any "5bq5" tube info available.
I bet that PT is likely over-rated and fine for doing whatever you'd like. Unloaded tranny's voltage ratings are usually around 91.5% of what you measure when unloaded. You also could put a 20Va or 25Va load on it to get more of an actual voltage if desired but it's not necessary. It's common for organ amp tranny's to be 290-0-290 which is what I think you have there. Perfect for an 18w or similar.
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It's putting out 315-0-315 unrectified.
it seems as that it's probably a 300-0-300V loaded @ around 150-250mA?. a something that uses a 5Y3 would likely use a PT with a rating of 125mA or less.
PSU designer formulates that there is 370VDC filtered with 100mA load using a 5U4-G recto coupled to a 300-0-300 rated at 150mA. i'd bet it's close.
should make a nice stout PT. just be sure to use a 5U4.
is it a 2 channel 6BQ5 P-P or mono. to me it seems that most of the baldwin 6BQ5 based amps i've run across are 2 channel with some being 3 channel.
does it look like this one? (http://cgi.ebay.com/Baldwin-Organ-71L-Tube-Amplifier-5U4GB-6BQ5-12AX7-/290594549068?pt=LH_DefaultDomain_0&hash=item43a8c8ed4c)
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It's putting out 315-0-315 unrectified.
is it a 2 channel 6BQ5 P-P or mono. to me it seems that most of the baldwin 6BQ5 based amps i've run across are 2 channel with some being 3 channel.
does it look like this one? (http://cgi.ebay.com/Baldwin-Organ-71L-Tube-Amplifier-5U4GB-6BQ5-12AX7-/290594549068?pt=LH_DefaultDomain_0&hash=item43a8c8ed4c)
It is 2 channel , at least from following the layout, had a separate chassis to drive the wacky spring reverb.
Looks VERY similar to that pic on ebay, exceptions being mine had one gain pot not two, and the auxiliary connections are on the top instead of the sides.
The tranny's are likely identical.
WOW! second look and they are very different. OT on mine is Z mounted and the tube compliment is doubled on the ebay item.
I'm sure the current capabilities of the PT is fine, It's the voltages I'm concerned about. In my limited experience guitar amps like to be driven at higher voltages than other amps that try to eliminate as much distortion and overdrive like HiFi and Organ amps do.
Hi Ray!
Are you sure they're not 6bq5s instead? I don't seem to see any "5bq5" tube info available.
OOPS!
6BQ5,s
Any advise about not using a choke ?
thanks
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It's putting out 315-0-315 unrectified.
is it a 2 channel 6BQ5 P-P or mono. to me it seems that most of the baldwin 6BQ5 based amps i've run across are 2 channel with some being 3 channel.
does it look like this one? (http://cgi.ebay.com/Baldwin-Organ-71L-Tube-Amplifier-5U4GB-6BQ5-12AX7-/290594549068?pt=LH_DefaultDomain_0&hash=item43a8c8ed4c)
It is 2 channel , at least from following the layout, had a separate chassis to drive the wacky spring reverb.
Looks VERY similar to that pic on ebay, exceptions being mine had one gain pot not two, and the auxiliary connections are on the top instead of the sides.
The tranny's are likely identical.
WOW! second look and they are very different. OT on mine is Z mounted and the tube compliment is doubled on the ebay item.
I'm sure the current capabilities of the PT is fine, It's the voltages I'm concerned about. In my limited experience guitar amps like to be driven at higher voltages than other amps that try to eliminate as much distortion and overdrive like HiFi and Organ amps do.
Hi Ray!
Are you sure they're not 6bq5s instead? I don't seem to see any "5bq5" tube info available.
OOPS!
6BQ5,s
Any advise about not using a choke ?
thanks
JEEZE!
I got to have coffee before replying!
It is a mono output no doubt, 2 channels, one input for the organ, one for the DELAY not reverb. The delay is a separate chassis with 2 12AX7's, no xformers, 3 what look like RF coils on an old radio, and a label that calls it a "Dynamic Tone Converter", Also it says it is for a model 71. above the RCA jacks is labeled Delay in and out.
The "Delay" spring is hanging from an 18" perf board and is maybe 30" long, about an inch in diameter and very soft. It hangs through a protective loop.