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Silly question on CR1020 output tranies

Oscar76

Oscar76

AK Subscriber
Subscriber
Good day all,
I have what may be a very silly question concerning a CR-1020 that was recently acquired with heavy damage on both amplifiers. Badly smoked emitter resistors and drivers and shorted output transistors. T614 and T613 transistors both have insulators beneath them but nothing to insulate the mounting screws from the heat sinks. I know that the case is tied to the collectors on these units so it brings to mind, where are the shoulder insulators for mounting screws or are the screws required to make the connection since there is no collector tab on this style of case?
 
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I think there's supposed to be small plastic washers for those screws, if memory serves. They don't need to be super tight either - just snug. And don't forget the grease.
 
Oscar76 said:
T614 and T613 transistors both have insulators beneath them but nothing to insulate the mounting screws from the heat sinks
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Correct.. The screws are contacting the transistor sockets -- not chassis ground. The screws complete the circuit to supply raw +/- B to the TO-3 output transistor cases.. ie collectors.
 
avionic said:
Correct.. The screws are contacting the transistor sockets -- not chassis ground. The screws complete the circuit to supply raw +/- B to the TO-3 output transistor cases.. ie collectors.
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Just to verify: No plastic shoulder insulators on these output transistors. Thank you Avionic as always!
 
avionic said:
If you would use plastic insulators the amplifiers would not work.
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I traced the path from the fuses and observed that they connect to one screw on each transistor so that would make perfect sense then that the screw indeed is the pathway for B+-. Given that T613 and T614 output transistors are shorted, what would be a good replacement since these are not available for quite some time now ?
 
Not for even a New York minute. I figured it is better to know how things work rather than just knowing they work. ‍
 
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