Baldwin C-1

[clguy]

Here is the copy of the schematics from Arkansas and a picture of the output amp area. If I get the model with aluminum heatsinks they may stick out the back. If I get the LM3886 without the heatsink it may be bolted to the Baldwin's chassis/heatsink were the TO3's are.

[J M Fahey]

Now that I look at the PSU, I'm thinking that there is a better way to use this amp.
The PSU (never seen it before) does supply + and - 43V.
They filter properly (2200uF x 50V?) the negative side, because they feed the power amp from it, but lightly (500uF x 50V) the positive side because they use it only for the preamp.
The regular LM3886 needs around +/- 30V or less so you have *way* too much.
To use it as the original amp, you would need to filter properly the +43V side (no big deal, just add a 2200 or 4700uF x 50V capacitor) *but* you must also mod the amplifier to work with a single supply.
It can be done, but it may confuse you, it's complex .
Tracks in the PCB should be cut, wire jumpers added, etc. *or* you would need to make your own special PCB . Complex.
Now I'm thinking about 2 options instead.
1) repair the amp "as is" but modding it for PNP silicon transistors instead of the PNP germaniums it used originally.
Least work, and probably cheapest too.
I've been googling around and this seems to be the preferred way to repair these.
A guy who did it offered to mail details, but his account is dormant since 2005 so ....
Anyway, I can calculate the value of the 2 resistors needed , no big deal.
I suggest you follow this path, fast and relatively cheap.
2) another option would be to straight mount there a regular discrete (sorry, too much voltage for chipamps) beefy power amp, which handles the +/-43V rails, and drives the speakers which should be connected in series to show 8 ohms.
Nice turbocharging but relatively complex and expensive.
I suggest you mod the original amp instead.
It's the solution used on VOX Thomas SS amps, same vintage, same outdated germanium technology.
Read this. Well, not all of it, but the part about going silicon.
I can calculate the bias resistor values for you, but will need a couple measurements from your actual amp.
www.geofex.com/Article_Folders/Thomas Vox/Thomas Vox Replacements.pdf

[J M Fahey]

I'm answering in your *other* thread.
It gets confusing.
Please joecool join both threads into one.
Thanks.

[clguy]

The Thomas organ paragraph about TO3's (Output Transistors/paragraph 5) was the problem. The old TO3's grease dried out, two overheated and shorted. I need new mica washers and dielectric grease and maybe new sockets?

The premise of the article (Output Transistors/paragraph 1) is the old Germaniums are $20 each and  matched pairs are hard to find. I can get them from "guitarampsky" for $50 with shipping  (eight with a foot of fusewire.

I will still need a new driver transformer ($35 with shipping), even for the silicone replacement fix.

[J M Fahey]

Well, Mr guitarampsky seems to have access to old original Baldwin stuff.
If that's so then probably you can rebuild it.
Remember to *always* use the lamp limiter and not connect any speaker until you are sure and have measured that everything is fine.
Go step by step.
Good luck.

[joecool85]

I'm answering in your *other* thread.
It gets confusing.
Please joecool join both threads into one.
Thanks.

Done.