I have been asked to have a look at a friends amp
the amp powers on and the vu meters light up but no relay click
the operation light is not lit
you can hear the big power relay click on and off
the main power supply is working both caps test ok
i have had the board out and checked all the caps replaced two which where out of spec
replaced caps C502 / C504 100uf 6.3v and R502 which was burnt
put it back together and still the same but when switched on R502 gets very hot
i have included the manual
TECHNICS SE-A900S SERVICE MANUAL Pdf Download | ManualsLib
20200718_153233 by glenn jarrett, on Flickr
20200716_152600 by glenn jarrett, on Flickr
the amp powers on and the vu meters light up but no relay click
the operation light is not lit
you can hear the big power relay click on and off
the main power supply is working both caps test ok
i have had the board out and checked all the caps replaced two which where out of spec
replaced caps C502 / C504 100uf 6.3v and R502 which was burnt
put it back together and still the same but when switched on R502 gets very hot
i have included the manual
TECHNICS SE-A900S SERVICE MANUAL Pdf Download | ManualsLib
20200718_153233 by glenn jarrett, on Flickr20200716_152600 by glenn jarrett, on Flickr
Possible failure of the power amplifier IC.
Damaged R502. Goes to pin 13 IC501 (Page 17)
With a 100 watt protective lamp, check the voltages.
Damaged R502. Goes to pin 13 IC501 (Page 17)
With a 100 watt protective lamp, check the voltages.
Last edited:
SVI3205, pin 15 input and pin 3 output (Lch) and pin 13 input and 6 output (Rch) should be 0 and 0V respectively
If collector-emitter short in SVI Rch (check for short pin 4-6 and 5-6) V amp will try to correct it, putting high voltage (up to 102V) across R502
Example of -tr short in Rch would see +51V applied to R502 to try and correct the -51V at pin 6
It would also knock out C502 as polarities would be reversed
If collector-emitter short in SVI Rch (check for short pin 4-6 and 5-6) V amp will try to correct it, putting high voltage (up to 102V) across R502
Example of -tr short in Rch would see +51V applied to R502 to try and correct the -51V at pin 6
It would also knock out C502 as polarities would be reversed
Thanks SVI2004A
with the amp switched off
pin 5&6 are short circuit on the svi3205
pins 4&6 are ok
how do you test the other power ic rsn6000 ?
with the amp switched off
pin 5&6 are short circuit on the svi3205
pins 4&6 are ok
how do you test the other power ic rsn6000 ?
Mos V Amp RSN6000
Check for shorts
Right channel +V between pin 1 & 7 then -V between pin 2 & 5
Do swap +/- meter leads as theres diodes in paralell between these pins... if appears short both ways, new V amp ic will be needed too
Check for shorts
Right channel +V between pin 1 & 7 then -V between pin 2 & 5
Do swap +/- meter leads as theres diodes in paralell between these pins... if appears short both ways, new V amp ic will be needed too
no shorts on pins 1&7 or 2&5 on ic RSN6000 just resistance
ic SVI3205 on schematic
pin 2 = -6.3v
4 = 51v
5 = -51v
7 = -16v
9 = -4.3v
10 = -16.3v
18 = -14v
this is what i get pin
2=-6.1v
4= 41v
5= -41v
7= -9v
9= 125mv
10= -9v
18= 428mv
ic SVI3205 on schematic
pin 2 = -6.3v
4 = 51v
5 = -51v
7 = -16v
9 = -4.3v
10 = -16.3v
18 = -14v
this is what i get pin
2=-6.1v
4= 41v
5= -41v
7= -9v
9= 125mv
10= -9v
18= 428mv