Baldwin Organ Transformers

[strongjay912]

Want to see what amp I can build from a generous donor who gave me these for helping him. Baldwin PT, Baldwin OPT, they are from a 60'S era Organ the amp model 46c had 3 channels and pushed 8) 6BQ5, 3)12 AX7 and 2) 5u4GB rectifier. Although it had 2 other small output transformers on it I don't  have them. The organ also had a big tone rack full of 44 12AU7S and its own transformer which I don't have either. The PT is massive weighing 12 pounds,# fc512-02590 I tested and puts out 290-0-290, the OPT transformer works but has not been tested. An old post on here somebody stated the OPT was 20:1 ratio 3440k @4 ohms model #ac512-025947, its a big stand up style like you might see on a Marshall JTM.

[scstill]

Wow eight 6bq5 is about 400ma on that 290vct
Why not go over the top with a 6bq5 Push Pull with four parallel plates....
could get 40 to 70watts out.
I believe that four 6BQ5 in parallel would need 2000ohm load impedance (from the single tube 8000ohm)
So if you want to use the OT from the organ (4k:4) go with two parallel tubes on each side.

[strongjay912]

I dont need one that expensive lol was hoping for a JTM 45 or a AC30 you think these would fit the bill.

[scstill]

Do you have the tubes from the organ? transformers and tubes are the pricey items.

you did not mention if the OT was SE or PP.
based on this 46H schematic (likely similar to 46C)  they did stereo PP with two parallel plate into 8ohm
The 46H OT would likely be 4k:8
https://www.whirl-asound.com/blog/baldwin-46h-stereo-amplifier-conversion
assuming your 46C organ is like this then your single OT would likely not support power from all eight tubes.

To get the 400ma I added plate current for eight 6BQ5 should have also added the eight screen and the three 12AX7 plate. That would add another 90ma or so...

AC30 and JTM45 schematics are in El34 library one uses four EL84/6BQ5 in Parallel plate PP and the other KT66 in PP. Your transformers should support these. But these do not use your dual 5U4GB which  would be a pretty cool power supply. Study the diagram from the 46H above. These are all complex builds. Have you built many guitar amps?

[strongjay912]

Yes Sir Thanks for the reply..It is the exact same Amp the one pictured and all I have is the PT and one OT there were two others under the Amp paper layered matching. Tubes yes I have quite a few and I never wanted to use 8) 6bq5s, I just wanted to go small maybe 20 or 30 Watts loud is not really what I'm after. I'm building an 18 watt from Mojo now so I'm just thinking about this for a future project. This tube Amp building is highly addicting, it's really quite a rush. The OT is push pull but only has 2 leads from the secondary shouldn't it have more. Thanks for your help again

[mresistor]

if OT is for a pp output the OT should have three leads on the input, two from the power tube plates and one center tap for the high voltage, the secondary is probably an 8 ohm lead and a ground lead.

[strongjay912]

Yes there are three leads from the primary sideI I had said it was only two from the secondary but I don't have any plates for it yet. Still fleshing out what I have as an Output transformer. Thanks for your help also.

[mresistor]

I know what you said ...   and I told you what the two leads most likely are.  Just making sure you know what the other three primary leads are for.


Post a pic of this OT. And did you say what Baldwin organ madel it was? OK  a 46C.   

[scstill]

Yes there are three leads from the primary sideI I had said it was only two from the secondary but I don't have any plates for it yet. Still fleshing out what I have as an Output transformer. Thanks for your help also.

You probably already know this but just to clarify...
The two secondary wires go to the speaker
The two primary outside ends go to the plates of the output tubes
The center of the primary goes to the B+ dc voltage from the power supply
See the 46H organ schematic provided earlier.
BTW - the organ schematic also has a negative feedback (NFB) from the secondary positive to the PI cathode

[mresistor]

scstill why do you think what I said to him needs clarification.  It's plain as day what I said.   Not appreciated.

[scstill]

scstill why do you think what I said to him needs clarification.  It's plain as day what I said.   Not appreciated.

Sorry didn't mean any harm...
I wasn't clarifying you I was clarifying him. Sounded like he was talking about plates on the secondary
since you are a moderator why don't you just delete my post.
And then hopefully we can be friends again...

[strongjay912]

Sorry for all the confusion guys I really am, I misunderstood all the small details in your replies but to clarify the OT has blue brown and whitish tan, maybe use to be red.

[Willabe]

Sorry didn't mean any harm...
I wasn't clarifying you I was clarifying him. Sounded like he was talking about plates on the secondary
since you are a moderator why don't you just delete my post.
And then hopefully we can be friends again...

scstill, your fine, your post doesn't need to be taken down. You did nothing wrong. 

[strongjay912]

Data plate

[strongjay912]

Thought about putting the Baldwin in this unit.