alschnier
Silver Supporting Member
- Messages
- 362
hey guys,
I'm pretty green when it comes to amp repair, but am willing to jump in. I can solder & use a meter & have done some limited reading on amps.
I have a '79 Hiwatt 100 watt (2 input) that seems to be way underbiased.
I just took a reading, using an Amphead bias checker + DM. bias current ranges from 53 mA to 61 mA across the 4 tubes, w. plate voltage ranging from 610 - 632!!
this is in line w. symptoms I'd seen when I 1st got the amp. it shipped w. Groove Tubes (S-1), & they had turned a nice shade of dark brown. when powered up, the amp got physically hot & smelled like hot wax. the tubes were scalding & too hot to handle. the previous owner had this recently serviced & it was "fixed" by mounting a fan to the cabinet.
aside from 1 bulging cap, I don't see any red flags. the amp was modded @ some point, but seems to have been returned to stock circuit (unless something is amiss).
I already have a recap kit (from VHR), as well as a fresh set of tubes & plan to dive in next week. may also replace to the orange drops w. sozos. other than that, I have no plan (or clue) as to what the source of the problem may be.
any thoughts?
more pix here: Hiwatt FL112
I'm pretty green when it comes to amp repair, but am willing to jump in. I can solder & use a meter & have done some limited reading on amps.
I have a '79 Hiwatt 100 watt (2 input) that seems to be way underbiased.
I just took a reading, using an Amphead bias checker + DM. bias current ranges from 53 mA to 61 mA across the 4 tubes, w. plate voltage ranging from 610 - 632!!
this is in line w. symptoms I'd seen when I 1st got the amp. it shipped w. Groove Tubes (S-1), & they had turned a nice shade of dark brown. when powered up, the amp got physically hot & smelled like hot wax. the tubes were scalding & too hot to handle. the previous owner had this recently serviced & it was "fixed" by mounting a fan to the cabinet.
aside from 1 bulging cap, I don't see any red flags. the amp was modded @ some point, but seems to have been returned to stock circuit (unless something is amiss).
I already have a recap kit (from VHR), as well as a fresh set of tubes & plan to dive in next week. may also replace to the orange drops w. sozos. other than that, I have no plan (or clue) as to what the source of the problem may be.
any thoughts?
more pix here: Hiwatt FL112
