# Dear redrooster, on our case there is no std-by power supply capacitor, I've checked already, only one std-by voltage provided by T371. But you have a point, some other Yamaha models have this capacitor serial to AC power .
Attachments
Last edited:
a) how can I control DC offset of STK 403 ?
b) PS PRT - wich is normal range for it, wich is IC 242 pin for it ?
as you can see 5MS repaired and now I have display and diag mode... but still 3 errors...
DC:37% -I don't know how to control DC offset of STK 403, it is 1 V in my case
PS:16%-I don't know how to solve- all voltages seems to be ok, I don't know exactly what does it mean
THM: 490% 5 FAN-I know how to solve
IMP:6 PL:255%-I know how to solve
b) PS PRT - wich is normal range for it, wich is IC 242 pin for it ?
as you can see 5MS repaired and now I have display and diag mode... but still 3 errors...
DC:37% -I don't know how to control DC offset of STK 403, it is 1 V in my case
PS:16%-I don't know how to solve- all voltages seems to be ok, I don't know exactly what does it mean
THM: 490% 5 FAN-I know how to solve
IMP:6 PL:255%-I know how to solve
Helo,guys ! Thks for your support. Finally ... it's working... I'll tell you the whole story.
1. Power relay click-on-click-off solved by LM7812 on S12 output. S12 now is 12 V sharp instead of 13V. My power module - factory made - was without any stabiliser transistor. None. Nil.
2. Display off solved by replacing Q244 in order to have 5MS
3. Now I have display & DIAG MODE. Found all STK with DC on output. STK 403 had 1 V DC offset. STK 404 had 49V DC offset.
STK 403 DC offset corrected by double-grounded the rear panel !!! Seemed that one crocodile clip was not enough ! As a conclusion, DC offset do not depends on main power supply , nor pre - power supply due it is an AB class topology and it is affected only by it's inputs. On the other hand it is normal to be so due LIMB (pin 4 of IC 242) affect pre +BV power supply on STK 403 and the result is not a DC offest but a power control.
STK 404 DC offset still in study, I have a feeling it'n not burned.STK 404 not on board anymore.
4.DC:37% PS:16% protection becames DC:27% PS:16% - after double grounding the rear panel and seems to be NORMAL STATE due no more "protect mode"
5.THM: 490% 5 FAN becames THM: 0% 5 FAN after grounded pin 1 of STK 404 (that is no more onboard)
6.IMP:6 PL:255% seems to be NORMAL STATE due no "protection mode" on start and also clear audio power signal on output, not limited. Also 4 P93 LIMB O Power Limiter Control now is 0V on pin 4 of IC 242, that is normal a/p manual.
I'll came back to you if STK 404 was affected by wrong grounding - like STK 403 cases, altough DC +49V on output seems to be out of order.
1. Power relay click-on-click-off solved by LM7812 on S12 output. S12 now is 12 V sharp instead of 13V. My power module - factory made - was without any stabiliser transistor. None. Nil.
2. Display off solved by replacing Q244 in order to have 5MS
3. Now I have display & DIAG MODE. Found all STK with DC on output. STK 403 had 1 V DC offset. STK 404 had 49V DC offset.
STK 403 DC offset corrected by double-grounded the rear panel !!! Seemed that one crocodile clip was not enough ! As a conclusion, DC offset do not depends on main power supply , nor pre - power supply due it is an AB class topology and it is affected only by it's inputs. On the other hand it is normal to be so due LIMB (pin 4 of IC 242) affect pre +BV power supply on STK 403 and the result is not a DC offest but a power control.
STK 404 DC offset still in study, I have a feeling it'n not burned.STK 404 not on board anymore.
4.DC:37% PS:16% protection becames DC:27% PS:16% - after double grounding the rear panel and seems to be NORMAL STATE due no more "protect mode"
5.THM: 490% 5 FAN becames THM: 0% 5 FAN after grounded pin 1 of STK 404 (that is no more onboard)
6.IMP:6 PL:255% seems to be NORMAL STATE due no "protection mode" on start and also clear audio power signal on output, not limited. Also 4 P93 LIMB O Power Limiter Control now is 0V on pin 4 of IC 242, that is normal a/p manual.
I'll came back to you if STK 404 was affected by wrong grounding - like STK 403 cases, altough DC +49V on output seems to be out of order.