Intermittent problem where approx -30Vdc output from right channel phono stage
(between FR104, FR106).
Power rails ok +/-31Vdc. TR110, 12, 14, 16, 18 replaced. D102 (VD1212) replaced.
Recaped, solder joints/bridges/shorts checked ok.
Approx -30Vdc on FR102 (either side), FR102 replaced with metal film
TR112 Vb-e approx 0.2Vdc
TR114 Vb-e approx 0.0XVdc
TR116 pulled, still high dc present.
TR106,8 Vb-e's look ok 0.6-0.7V, b&e voltages in line with other channel
TR104b approx 12Vdc
IC104 pin 6 approx 14.6Vdc
Plan is to replace IC104(2SK100) with other channel
Has anyone come across this problem before, ie, high dc on phono stage?
Also, 2SK100 is no longer available, having problems finding the datasheet (yamaha internal).
I would expect that these are two closely matched FETs. Any significant drawback with
replacing the IC with individual FET's? Recommendations? Donor amps are rather expensive in AU.
(between FR104, FR106).
Power rails ok +/-31Vdc. TR110, 12, 14, 16, 18 replaced. D102 (VD1212) replaced.
Recaped, solder joints/bridges/shorts checked ok.
Approx -30Vdc on FR102 (either side), FR102 replaced with metal film
TR112 Vb-e approx 0.2Vdc
TR114 Vb-e approx 0.0XVdc
TR116 pulled, still high dc present.
TR106,8 Vb-e's look ok 0.6-0.7V, b&e voltages in line with other channel
TR104b approx 12Vdc
IC104 pin 6 approx 14.6Vdc
Plan is to replace IC104(2SK100) with other channel
Has anyone come across this problem before, ie, high dc on phono stage?
Also, 2SK100 is no longer available, having problems finding the datasheet (yamaha internal).
I would expect that these are two closely matched FETs. Any significant drawback with
replacing the IC with individual FET's? Recommendations? Donor amps are rather expensive in AU.