OTL Asylum

RE: Futterman H-3 restoration

198.144.203.111

rogerh113

A

In Reply to: RE: Futterman H-3 restoration posted by 33dot33rpm on March 05, 2024 at 09:32:13

Attached is the spec sheet for my H3 transformer. They measured everything when taking it apart so they could accurately rebuild it. Not cheap.

I did gut the Futterman when I rebuilt it. The old parts were not useful and the wiring was pretty poorly done. Everything was replaced aside from tube sockets. I was hoping to keep the transformer, but when I started to bring up the amp on a variac it was obvious that was not to be. If you keep a bunch of old parts in there, you will likely experience death of a thousand cuts as they fail (hard or soft) one after another.

regards -- Roger

Follow Ups:

RE: Futterman H-3 restoration - 33dot33rpm 12:04:53 03/05/24 (5)
Thanks for the info Roger.

Good luck with your H-3!

I agree with you that the original build quality left a lot to be desired. My amp had been worked over by someone else and that added to the poor wiring job. In my case I decided to leave the CC resistors in place if they tested within reason. I replace all the electrolytic, paper and "plastic" caps but retained the small "dog bones". In the process of replacing the remaining diodes.

Please keep us posted on your progress as I will mine. If you have any photos of your rebuild it would be much appreciated.

Cheers Ed
- RE: Futterman H-3 restoration - rogerh113 14:19:07 03/05/24 (0)
  Some in progress detail under the wires...
- RE: Futterman H-3 restoration - rogerh113 14:09:18 03/05/24 (0)
  The top
- RE: Futterman H-3 restoration - rogerh113 14:05:21 03/05/24 (2)
  Hi Ed,
  
  Here are a couple of pics. Wired in on the bench, so access not ideal, but should give a sense of things. I have passed signal through it, so it does seem to work. Need to go through the power tubes (some bad ones in place based on voltage setting level on one side). Just have to spend some time. Can't see it, but I did install an IEC power socket.
  - RE: Futterman H-3 restoration - 33dot33rpm 08:43:29 03/07/24 (1)
    Kudos to you, excellent work and quality parts!
    - RE: Futterman H-3 restoration - rogerh113 09:14:12 03/07/24 (0)
      Thanks. My objective was to hear what a respected, period OTL would sound like if brought up to optimal (in my opinion) standards. I build a SET amp before, under the same objective, and am very pleased with the result.
      
      Hopefully I can hear the OTL soon, if a bunch of other high-priority projects stop coming up around the house. Given that I am listening to the SET, and it is unclear how that can be bettered, I don't feel under any pressure to complete the OTL.

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