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Hi everyone,
I have a JC-50 on the bench that I'm trying to coax back into existence. She was working this morning (aside from a bit of hiss and pop) and I was chopsticking around and managed to short a collector of a transistor to ground.
I've been looking at the 77 schem because it seems some of the power rectification / filtering section.
So far I have identified:
I read 5 mV on the 330R 2W resistor when I should be getting almost 40 volts.
I read +39 and -39 volts on the rectifier diodes. This baffles me according to the schematic and my voltmeter impedance setting the point I measured +40 v and point I measured +5mv are common.
?
I am unable to read + or - 16 volts on the emitters of the two transistors I suspect are equivalent to Q1 and Q2. From memory there is maybe half a volt.
Also, it seems unlike this schematic there are no zeners incorporated in the JC 50s power filtering section.
So...perhaps I need to replace the one of the transistors?
Any suggestions would be appreciated.
Matt
I have a JC-50 on the bench that I'm trying to coax back into existence. She was working this morning (aside from a bit of hiss and pop) and I was chopsticking around and managed to short a collector of a transistor to ground.
I've been looking at the 77 schem because it seems some of the power rectification / filtering section.
So far I have identified:
I read 5 mV on the 330R 2W resistor when I should be getting almost 40 volts.
I read +39 and -39 volts on the rectifier diodes. This baffles me according to the schematic and my voltmeter impedance setting the point I measured +40 v and point I measured +5mv are common.
?
I am unable to read + or - 16 volts on the emitters of the two transistors I suspect are equivalent to Q1 and Q2. From memory there is maybe half a volt.
Also, it seems unlike this schematic there are no zeners incorporated in the JC 50s power filtering section.
So...perhaps I need to replace the one of the transistors?
Any suggestions would be appreciated.
Matt