Baldwin organ amp

[Mars Hall]

My friend recently decided to get rid of his Great Grandma's Baldwin organ. I scrunged everything I could from it, including the 12' Magnavox speaker with alnico magnet, dated to 1955.

The power section has some beefy looking transformer's, similar in size as what you would see in a 100 watt Marshall. The tranny codes show 512 for the manufacturer. None of the lists I've found online show that number. Anyone aware of what kind of iron this thing may have? What kind of guitar amp circuit might I be able to make with this iron, Tweed era Fender, Marshall, etc.?

Anyone here hip to the Baldwin stuff, I would be much obliged.

[M Fowler]

You need to google the Baldwin organ model number which will yield a schematic and show some data.

Also, you can figure out the power supply data but knowing what it was powering for output tubes and preamps.

I built one Fender type amp from a Hammond and bought two more PTs on ebay to build two more Fender type amps. The iron used in these organs are great for guitar amp builds.

I have not used a Baldwin transformer however.

Mark

[Mars Hall]

You need to google the Baldwin organ model number which will yield a schematic and show some data.

Also, you can figure out the power supply data but knowing what it was powering for output tubes and preamps.

I built one Fender type amp from a Hammond and bought two more PTs on ebay to build two more Fender type amps. The iron used in these organs are great for guitar amp builds.

I have not used a Baldwin transformer however.

Mark

Thanks Mark, the power section has a pair of the funny shaped 6L6 tubes in it. I'll get the model number and search.

This thing has a ton of 6SN7 tubes, there must be at least 50.

[Mars Hall]

Model 40, not finding much for a schematic.

[Luthierwnc]

Here are the three common types I've seen most often. Two are stereo with the output transformers inside the chassis. One has all four power tubes in the same push-pull circuit. I've been tempted to mod one but never got round to it. One thing to watch is the center tap of the HV circuit goes through a choke to ground. The HV itself comes off the center tap of the heater supply. Plan your standby accordingly. sh

[M Fowler]

Running a pair of Choke bottle 6L6s that would be a great PT for about any 45w to 50w circuit you want to build. You know that the rectifier is 5v 3A so you can use 5AR4/GZ34 or 5U4 tube or go SS rectification.

You can use the octal preamp tubes or change over to 12AX7 family of tubes if you wish.

No you have to figure out what you want to build

Mark

[Mars Hall]

I found some images online the same as what I've got, mine are in better condition. This is just the power section. I'm thinking the Tweed Fender or maybe a Trainwreck build would be nice.

http://i423.photobucket.com/albums/pp31 ... 1323886273

http://i423.photobucket.com/albums/pp31 ... 1323886320

[Phil_S]

... the power section has a pair of the funny shaped 6L6 tubes in it. I'll get the model number and search.

This thing has a ton of 6SN7 tubes, there must be at least 50.

Oh how lucky you are! The organ chassis I acquired had 12AU7's. While 12AU7 is nearly equivalent to 6SN7, it can also run on a 12.6v filament supply. As luck would have it, my organ has an enormous 12.6v filament transformer. Can anyone say "doorstop?"

You are double lucky because the 6SN7 is not only a decent preamp tube, it makes a great concertina, and a great power tube. Run a pair of them at 400v+ and you'll get a great sounding amp in the 15W range. They do great clean tone. Given what you have, you probably have what it takes to do an all 6SN7 amp -- 4 preamp tubes (step up the gain if you want it) and 4 power tubes (40+W range, depending on how its done).

The old tube organs needed all those tubes to run the tone generator. At 4 per tone x 12 = 48 tubes.

You should have everything you need to build yourself a great amp and then, if you don't want the 6SN7's they can be sold, probably for $5 each untested, maybe $10-$15 each if tested and strong used.

What a find!

[leadfootdriver]

You can very carefully measure the taps with a voltmeter, but how would you calculate amperage output?

You'd need to load it somehow. I'm sure one of you mad scientists have a tester for this.

[Mars Hall]

Anyone have a clue who the transformers are made by? 512 is the manufacture code.

[M Fowler]

You wouldn't even have to remove them from the chassis just strip it down and start building nice.

[tubelectron]

Well, I don't know if this Baldwin Organ is worth to, but I would have tried to make it work first before ripping it off... A tube organ...

[Phil_S]

For starters, we can figure out the tube configuration and operating voltage. That is enough information to work out the current that was supplied in the organ circuit. How much more capacity exists is a guess based on a variety of factors, among them the DCR of the primary winding.

The problem with an empirical test is that you've got to load the PT to the point where it lets the smoke out and what good is that? But you can get a real good idea fairly easily because there is lots of information. Some of it hasn't been posted, but it can be found.

It's much more challenging when the PT is a total mystery -- when you get it without a circuit and there is no xref/part number that has any real meaning. In a case like that, you take some basic measurements, and build out a power supply with rectifier and caps. At this point, you'll have a guess at the primary VA rating and secondary rating. Then you hang a dummy load on it, starting off with more ohms than you think you need. The voltage drop across the load tells you current (Ohm's Law). You reduce the load and try again, and again, dropping the load a little each time. At some point, the PT will start to feel too hot and that's when you quit, and you quit before you let the smoke out.

[LeftyStrat]

As luck would have it, my organ has an enormous 12.6v filament transformer. Can anyone say "doorstop?"

Can't you run a couple of 6v heater power tubes in series on 12.6?

Also, I'm building a little 4 watt amp using two NOS 12sn7s. I actually have a bag full of these.

Looking through my collection, I also have this huge 120v to 6.3 transformer, I think it actually supports 6 amps. But I'd hate to lug around a head with its added weight, it's as large as your average PT.

[Phil_S]

Can't you run a couple of 6v heater power tubes in series on 12.6?

Yes, I could, but this particular organ came with a regular PT for the power amp and a 12.6 filament supply tx only for the tone generator heaters. It's a big mutha. Not practical to use it. I think it supported 60 tubes, 48 12AU7's and 12 12AV6's. For heaters, thats 48*.3 + 12 *.15 = about 15A. That should give you an idea of the weight and size. Thanks for the thought, though.