The partial Fisher 50-AZ schematic below shows an interesting feature in the power amp circuit. Fisher used a transformer between the push-pull driver cathodes and the power amp grids. According to Bruce Rozenblit, the transformer is 1:1. It appears that the transformer is being used like any other IT; to isolate the positive DC voltage at the driver - usually at the anodes, but in this case, cathodes - from the negative bias at the grids. What I'm not sure of is the purpose for C10 and C11. I think they're intended to impose a load on the secondary, rather allowing it to operate into an open circuit. Perhaps the transformer "misbehaves" when the secondary is operated with no load. Anyone have any other ideas regarding the purpose of these parts, or maybe practical experience with this arrangement?
This post is made possible by the generous support of people like you and our sponsors:
Topic - Purpose of these Caps? - Triode_Kingdom 23:42:32 08/27/16 (22)
- RE: Purpose of these Caps? - JKT 13:18:10 08/28/16 (10)
- Good Info! - Triode_Kingdom 14:57:00 08/28/16 (2)
- RE: Good Info! - JKT 15:19:54 08/28/16 (1)
- RE: Good Info! - Triode_Kingdom 15:51:18 08/28/16 (0)
- RE: Purpose of these Caps? - Chip647 14:43:24 08/28/16 (6)
- RE: Purpose of these Caps? - Tre' 16:40:37 08/28/16 (4)
- RE: Purpose of these Caps? - dave slagle 16:53:18 08/28/16 (3)
- RE: Purpose of these Caps? - Tre' 18:51:02 08/28/16 (2)
- RE: Purpose of these Caps? - dave slagle 20:58:15 08/28/16 (1)
- RE: Purpose of these Caps? - dave slagle 21:37:54 08/28/16 (0)
- RE: Purpose of these Caps? - JKT 15:06:32 08/28/16 (0)
- Cary did something like this in the 805 - Chip647 07:12:28 08/28/16 (2)
- LRC circuit? (n/t) - FenderLover 07:34:31 08/28/16 (1)
- RE: LRC circuit? (n/t) - Chip647 08:20:07 08/28/16 (0)
- RE: Purpose of these Caps? - dave slagle 06:29:44 08/28/16 (0)
- RE: Purpose of these Caps? - coffee-phil 00:05:50 08/28/16 (6)
- RE: Purpose of these Caps? - Triode_Kingdom 09:31:18 08/28/16 (5)
- Here is the bottom of one of my 55A Fisher amps which are the same circuit. - Michael Samra 14:37:11 08/28/16 (0)
- RE: Purpose of these Caps? - Tre' 14:06:21 08/28/16 (3)