woodhawk1
Montana59457
I just recently scored a Fisher 500b in very good shape (original cabinet included, although in pieces, all original fisher/telefunken tubes except for four sylvania power tubes), and I am thoroughly enjoying the ride. It worked well when I brought it home, although I realized that some restoration work was due. I am lucky to work with some colleagues who know their way around electronics, and so I have already updated the bias power supply and the amplifier signal path using parts from the Metalbone kit. I also added in the current limiter to protect the on-off-volume switch, which remains fully functional. And the cabinet was easy to reassemble. I am listening to my 500b right now, and it sounds mighty fine.
My question relates to typical/acceptable noise levels on a Fisher tube receiver. I noticed when I first listened to the unit prior to any restoration that there was what I would describe as white noise on the phono setting when I cranked the volume up more than halfway (5+ which is fairly loud when a record is playing). There is no hum - I have an old Knight 724 and I definitely know what hum sounds like. The Fisher is essentially silent when the volume is set to 5 or below. The white noise is a little greater in the right channel, and shifts to the left channel when I hit the channel reverse switch. So on phono there is some noise in both channels at high/highest volume settings, and it is more prevalent on the right channel. The noise is not discernible on FM, aux or tape. I can turn the volume all the way up on aux/tape settings and the unit is absolutely quiet. And all functions work great - when a record is playing the noise is not an issue even at high volumes - I don't hear it.
Anyway, after completing the few updates mentioned above (bias power supply, amp signal path) the noise is still with me (but the power transformer runs cooler! - I can still rest my hand on it for several seconds after 3+ hours of service). And so - I am wondering if it is just normal to have some background noise on the phono stage and tape head setting at high/very high volume, or if there are more parts to track down and replace. I still have components that came with the Metalbone kit that relate to the multiplex decoder section, the FM signal path, and the B+/Power supply (2 diodes and 2 .01 uf/630 v caps). My hunch is that these won't fix the noise in the phono section, assuming it needs fixing in the first place. In fact, given that the FM works great I am wondering if I even want to do the remaining updates that came with the kit (separate question I guess).
Any wisdom on this noise issue / non-issue would be greatly appreciated.
THANKS IN ADVANCE!
My question relates to typical/acceptable noise levels on a Fisher tube receiver. I noticed when I first listened to the unit prior to any restoration that there was what I would describe as white noise on the phono setting when I cranked the volume up more than halfway (5+ which is fairly loud when a record is playing). There is no hum - I have an old Knight 724 and I definitely know what hum sounds like. The Fisher is essentially silent when the volume is set to 5 or below. The white noise is a little greater in the right channel, and shifts to the left channel when I hit the channel reverse switch. So on phono there is some noise in both channels at high/highest volume settings, and it is more prevalent on the right channel. The noise is not discernible on FM, aux or tape. I can turn the volume all the way up on aux/tape settings and the unit is absolutely quiet. And all functions work great - when a record is playing the noise is not an issue even at high volumes - I don't hear it.
Anyway, after completing the few updates mentioned above (bias power supply, amp signal path) the noise is still with me (but the power transformer runs cooler! - I can still rest my hand on it for several seconds after 3+ hours of service). And so - I am wondering if it is just normal to have some background noise on the phono stage and tape head setting at high/very high volume, or if there are more parts to track down and replace. I still have components that came with the Metalbone kit that relate to the multiplex decoder section, the FM signal path, and the B+/Power supply (2 diodes and 2 .01 uf/630 v caps). My hunch is that these won't fix the noise in the phono section, assuming it needs fixing in the first place. In fact, given that the FM works great I am wondering if I even want to do the remaining updates that came with the kit (separate question I guess).
Any wisdom on this noise issue / non-issue would be greatly appreciated.
THANKS IN ADVANCE!
