for mr.babin and anyone who can help

[russdeanlee]

well on the picasso on the front channels the transistors are the original motorola tip102 and tip107 but on the rear they are on semiconductor tip102g and tip107g the problem i'm having is with the bias adjustment i am not able to set it to 25mv on anyone of the channels max i can get is 10mv. i'm positive if i was to switch transistors to the motorola my problem will be fixed but i rather not have to do that is there anything else i can do to fix this maybe change some resistors or something or will putting back the motorola be my only solution. also why is it affecting both front and rear channels if the front channels have the original transistors. wouldn't only the rear channels be affected.

 

[Perry Babin]

You could try increasing the value of Rx17 to see if that helps. Start with about 8.2k ohms. When you power it up, do so through a 10 amp fuse, set the bias pot fully counter-clockwise and monitor the current draw closely.

 

[russdeanlee]

thanks again for helping not only me but everyone

picasso is complete now bias correctly set thanks again

now i'm trying to repair my soundstream reference 1000s, which as of now only one channel operates correctly while the other channel is very low volume same problem as the picasso.

with the 1000s the overload led is lit on the left channel which is the faulty channel, i tested all output transistors and they all check fine what causes the overload led to be lit possibly the feb which i don't believe is the problem and the switches i removed and jumping wires accross instead eliminating the switches

 

[AKHeathen]

The problem i had with this on a 1000, was just the driver board contacts for the channel. De-soldered and resoldered tjem and it worked like new. There is one pair of circuits i like to check on these amps while i have it apart. There are transistors that monitor the voltage across a single output of each channel. They drive another transistor and fees the power supply the reference to controll how much it drives. A fault here can overdrive the power supply section to failure. Just like a faulty ch/hv switch can. I can send you schem. On mon, if needed.
Djheathen@gmail.com
-Heath H-