Helo,guys ! How can I control DC loutput offset of STK 403 , I have an Yamaha-rx-v357 and all STK have 1 V DC offset on output, otherwise sound is clear if protection is deactivated...
I've found on Google : "I found that the +/- Pre voltages were very important in setting the DC offset on the output."
On Yamaha-rx-v357, what does it mean PS PRT:16% - wich is normal range for it, wich is IC 242 pin for it , wich is the reference for it ???
I've found on Google : "I found that the +/- Pre voltages were very important in setting the DC offset on the output."
On Yamaha-rx-v357, what does it mean PS PRT:16% - wich is normal range for it, wich is IC 242 pin for it , wich is the reference for it ???
If it depends on the pre voltages +/- then you better make sure that the supplied voltages are very similar (much less than a volt difference).
PS PRT:16
Power rail is down to 16% of normal value, most likely due to failed regulator (IC651,2,3
+/-12V, +5V). Might also be a tired cap (C655,6,9) but less likely. Measure dc voltage at
CB246 to work out which rail/regulator is down.
Power rail is down to 16% of normal value, most likely due to failed regulator (IC651,2,3
+/-12V, +5V). Might also be a tired cap (C655,6,9) but less likely. Measure dc voltage at
CB246 to work out which rail/regulator is down.
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.