Home OTL Asylum

OTL, Output Transformerless Amplifier User Group.

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ OTL Asylum ]
[ Alert Moderator ]

Futterman H-3 restoration




Hi All, I've completed the restoration of a friend's Futterman H-3 amp. It was essentially non-functional, now in it's restored / repaired condition the amp sounds very good indeed.

All the operation point adjustments are spot on to the manufacture's specifications.

All the tubes where tested on a Hickok 752A and replace with new ones where necessary.

DC voltages at various points in the circuit seems reasonable.

From the available documentation the idle current for the output stage is 200ma per channel, 400ma in total which is a lot!!!

My question for the H-3 owners: During operation, is it normal for the power transformer to become hot to the touch?

Please let me know, I don't want to inadvertently destroy the transformer.

Enjoy the posted photos. I included a before and after of the "guts".

This post is made possible by the generous support of people like you and our sponsors:
  Parts Connexion  

Topic - Futterman H-3 restoration - 33dot33rpm 17:51:38 03/04/24 (24)
FAQ

Post a Message!

 Forgot Password?
Moniker (Username):
Password (Optional):
  Remember my Moniker & Password  (What's this?)    Eat Me
E-Mail (Optional):
Subject:
Message:   (Posts are subject to Content Rules)
Optional Link URL:
Optional Link Title:
Optional Image URL:
Upload Image:
E-mail Replies:  Automagically notify you when someone responds.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]