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Futterman H-3 restoration
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Posted on March 4, 2024 at 17:51:38 | ||
Posts: 79
Location: Nor Cal Joined: June 8, 2006 |
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". |
RE: Futterman H-3 restoration, posted on March 5, 2024 at 14:09:18 | |
Posts: 513
Location: San Francisco South Bay Joined: October 20, 2014 |
The top |
RE: Futterman H-3 restoration, posted on March 5, 2024 at 14:19:07 | |
Posts: 513
Location: San Francisco South Bay Joined: October 20, 2014 |
Some in progress detail under the wires... |
RE: Futterman H-3 restoration, posted on March 6, 2024 at 18:42:41 | |
Posts: 533
Joined: February 24, 2001 |
Hi, That sounds just about right to me regarding how the temperature of the transformer behaves. |
RE: Futterman H-3 restoration, posted on March 7, 2024 at 08:39:48 | |
Posts: 79
Location: Nor Cal Joined: June 8, 2006 |
Thanks AJ, now I have confidence returning the H-3 to it's owner! |
RE: Futterman H-3 restoration, posted on March 7, 2024 at 08:43:29 | |
Posts: 79
Location: Nor Cal Joined: June 8, 2006 |
Kudos to you, excellent work and quality parts! |
Futterman H-3 square wave, posted on March 7, 2024 at 17:01:25 | |
Posts: 79
Location: Nor Cal Joined: June 8, 2006 |
Just for fun I ran some test on the amp. Here is the square wave. |
RE: Futterman H-3 hum level, posted on March 7, 2024 at 17:03:43 | |
Posts: 79
Location: Nor Cal Joined: June 8, 2006 |
Just for fun I ran some test on the amp. Here is the hum level. |
If they are going to oscillate, it will be load dependent. nt, posted on March 13, 2024 at 14:10:53 | |
Posts: 4870
Location: Minnesota Joined: April 24, 2002 |
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