Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 1blueheron on January 10, 2019, 11:43:18 am
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I have a monster set of transformers out of a Baldwin Orgasonic 51P.
Have come up empty on finding a proper schematic.
Number stamped on the top of the PT is as follows: F-C512-023757C
It has a 4U5 Rectifier, 2 6L6 for output, 2 12AX7 and 2 12AU7 in the amp chassis but it also ran about 50 other 12XX7 tubes.
What I believe to be the output transformer is stamped C512-17584C
Ohmed OT out and came up with the following:
Brown/Blue= 248
Brown/Red=133.7
Blue/Red= 115.5
Yellow/Black= 1.3
Considering using to build a Fender Bassman 50.
Google turns up that the PT was reportedly 315-0-315? Cannot verify. No manufacturer info or specs.
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The monster size 9f the PT is probably to supply lots of fitment current. To me this cries out for a studio rig powering every cool preamp you can think of.
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The monster size 9f the PT is probably to supply lots of fitment current. To me this cries out for a studio rig powering every cool preamp you can think of.
What is a "studio rig"? Can you elaborate?
Here is the glassware it supported, plus another 4 or 5 tubes in a different section not listed on this chart. I'm counting almost 60-12XX7 tubes besides the 4 in the amp chassis section.
And a couple pictures of the PT and OT. have some chokes as well.
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more
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What is a "studio rig"?
a great sounding amp that weighs more than the car you have :icon_biggrin:
take it in the studio, leave it
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But then I would have to build a studio first to put it in! :l2:
My church needs a bass amp right now so that is my motivation in building the Bassman clone.
I like your idea though. The next organ I pick up that will be a strong consideration. The Baldwin and Conn organs both have "modular" units within a common chassis. Each of these modules plug in. Got me thinking, what would it be like to build an amp with a power supply and output power and then have easily swapped preamp modules. Similar to plugging breakers into a panelboard. Has any manufacturer ever experimented with modular amps? I know some of the studio console makers have done modular consoles. I have seen some old broadcast gear that used modular boards.
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here's a good start on "modular" concept;
http://sluckeyamps.com/vox/vox.htm
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Randall MTS series had modular preamps that plugged into the amp. I don't think they're in production anymore.
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Just a guess, but I believe that Output Trans will probably have a higher reflected impedance than 4K, which is generally what is used in a Bassman. Doesn't mean it will not sound good and may be preferred.
I love Baldwin Iron simply because it seems they used overbuilt components just like Hammond, maybe even more overbuilt.
You could simply build an amp that uses LTPI and 2 6L6 or El34 according to how you setup the OT then have a Fender Pre, a Marshall, A Soldano, An Ampeg (I like the B12 and B15) I know they are bass, but really sound good with guitar too. A much more less expensive way to get a variety of tones and I believe your Power Trans will do probably 10 different ones.
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Just a guess, but I believe that Output Trans will probably have a higher reflected impedance than 4K, which is generally what is used in a Bassman. Doesn't mean it will not sound good and may be preferred.
I love Baldwin Iron simply because it seems they used overbuilt components just like Hammond, maybe even more overbuilt.
You could simply build an amp that uses LTPI and 2 6L6 or El34 according to how you setup the OT then have a Fender Pre, a Marshall, A Soldano, An Ampeg (I like the B12 and B15) I know they are bass, but really sound good with guitar too. A much more less expensive way to get a variety of tones and I believe your Power Trans will do probably 10 different ones.
I like that idea, not sure how ready I am for the complexity.
I'm picturing a lot of different tube sets, a lot of different voltage requirements and a bevy of knobs. Could it be done with a common set of knobs and a common input with just a selector switch?
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Is this the same lump you had last November?
Wudda been nice to measure voltages before you broke it up.
Yes, it was, and could be, a 35W audio power amp. However you have no use for *sixty+* little tubes. So you will be carrying-around about 130 Watts of idle heater windings/core. The "liberated" B+ from all the little tubes is not really enough to power two more 6L6; also your OT is scaled for just two.
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Is this the same lump you had last November?
Wudda been nice to measure voltages before you broke it up.
Yes, it was, and could be, a 35W audio power amp. However you have no use for *sixty+* little tubes. So you will be carrying-around about 130 Watts of idle heater windings/core. The "liberated" B+ from all the little tubes is not really enough to power two more 6L6; also your OT is scaled for just two.
I've got two "lumps". One from a Conn and one from a Baldwin. The Conn amp is intact and I can power it up. Voltages and schematic are known. It is slated to become Reverberocket R212R. Working on layout and schematic.
The Baldwin I just broke up this week. You are correct it would have been good to measure voltages but when I pulled the amp plate from the chassis, all the insulation on the power cord and remote turn on cord just disintegrated leaving exposed wires. I wasn't feeling real daring to be poking around in it with those bare wires, so I just removed it. Plan to get some measurements today.
It really doesn't matter to me if it weighs a lot. It will pretty much just sit on stage at the church full time. It's not a big auditorium so a single pair of 6L6 tubes should be plenty of power.
I had planned to use some of the 12AX7 tubes as substitute for the 7025 in the Bassman 50 schematic and pretty much replicate the circuits shown there.
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Sounds like a plan.
When wired, check the VAC on the "6V" lines. Without all those tone generator bottles it may be over 6.5VAC. Figure the over-voltage and the nominal current, figure a pair of dropping resistors to get near 6.3VAC.
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Had a chance to check the PT voltages this AM
Here's what the meter had to say about it.
HT/Red>>Red=737VAC
Red>>CT(yellow red striped)=372VAC
Brn>>Brn = 6.6VAC
Grn>>Grn = 13.6 VAC
No Center tap for low voltage.
Fine for the Bassman project?