Silver sa-5030

[Alfonsol]

i'm wating for the new resistor, in the meantime i'm wondering why someone take off the resistor. perhaps a shorted output? any ideas?

 

[Alfonsol]

i tested the output transistors in the channel without the resistance, and i get around 550 measuring bc, and be in one way and infinite in the other way, iget the same results, but with inverse polarity in the other transistor. i think that is right( one is PNP and the other is NPN) . when i first put the probes with the polarity that should have infinite, i get 300, and then starts to go up until i get infinite, i think maybe is a cap charging.

 

[Alfonsol]

i'm still wating for the missing resistor, and i'm looking for a suitable replacement for the outputs if they are bad.

the outputs are 2sd588 and 2sb618.
i found mje15030 and mje15031, they are cheap and available here in chile. the specs are close to the specs of 2sd588 and 2sd618, but mje15030 and mje15031 are 50W and 2sd588 and 2sb618 are 80 watts.

the rated output of the amplifier is 50W@4ohms , and the rails of the power supply are +-33 volts.
can i use this replacements?

 

[Alfonsol]

i replaced the missing resistor. now the channel that had an offset of 30 mv stabilizes quickly to 30 mv, the channel that had 540 mv and a missing resistor now have -512 mv, but not very stable, it fluctuates between -518, and -506.

any ideas?,

this is the schematic of one channel

the wire from r414 goes to a muting circuit, wich is controlled by a overload protection circuit.

 

[Kevviek]

I know this is an *oolldd* thread, I just picked up a Silver SA5050 which is the same as the HK770, same symptoms as above. Did you ever get the unit fixed?

 

[Alfonsol]

Hi, yes i fixed it, and is still running strong. the offset on the output was because of a open fusable resistor. check those green resistors
ii sounds very good.