I replaced the output transistors in my Sherwood SEL-400 because one was bad so I replaced all four. I hooked up a turntable and headphones and it was working fine until I tried to take some voltage readings and must have shorted the test lead. A stream of smoke rose from the driver board left channel so I immediately unplugged it. Several resistors burned to a crisp, one ceramic cap is charred, at least one driver transistor is shorted and both output transistors are toast.
I'm going to use this as an opportunity to learn more about this amp and rebuild the driver board. The three transistors and three electrolytic caps (per channel) are on order but I am unfamiliar with the remainder of the components so I'm hoping to get some guidance in identifying them.
Ceramic Capacitors
Although they seem to be from the same manufacturer, they don't appear to have consistent nomenclature.
C703....schematic reads .02.....cap reads "RMC .02 20% Z5U" ( .02 uF, 20%, Z5U ? )
C704....schematic reads 820.....cap reads "RMC 820 10% Z5F" ( 820 ? Z5F ? )
C705....schematic reads 4.7.....cap reads "RMC NPO 4.7 10%" ( 4.7 uF, non-polarized, 10% tolerance, voltage? )
C707....schematic reads .01.....cap reads "RMC .01 80-20 Z5U" ( .01 uF, 80-20 ?, Z5U ? )
C720....schematic reads 47......cap reads "RMC 47N750 10%" ( 47N750 ? )
C724....schematic reads 2700..... cap reads..."RMC .0027 10% Z5F" ( 2700 pF, Z5F ? )
Red Capacitors
(what type are they?)
C701....schematic reads 10uF 35V......cap reads "10 35V" one leg has + signs
Rectangular Capacitors
(what type are they?)
C721....schematic reads "0.1"....cap reads "250 .1"
C722....same as above
Green Capacitor
(what type is it?)
C723...schematic reads "0.22 250V"....cap reads "MSH .22/K 250V"
Resistors
the values are on the schematic and I will verify the color codes, I just need to know what type they are and wattage
View attachment 1304599 View attachment 1304600
I'm going to use this as an opportunity to learn more about this amp and rebuild the driver board. The three transistors and three electrolytic caps (per channel) are on order but I am unfamiliar with the remainder of the components so I'm hoping to get some guidance in identifying them.
Ceramic Capacitors
Although they seem to be from the same manufacturer, they don't appear to have consistent nomenclature.
C703....schematic reads .02.....cap reads "RMC .02 20% Z5U" ( .02 uF, 20%, Z5U ? )
C704....schematic reads 820.....cap reads "RMC 820 10% Z5F" ( 820 ? Z5F ? )
C705....schematic reads 4.7.....cap reads "RMC NPO 4.7 10%" ( 4.7 uF, non-polarized, 10% tolerance, voltage? )
C707....schematic reads .01.....cap reads "RMC .01 80-20 Z5U" ( .01 uF, 80-20 ?, Z5U ? )
C720....schematic reads 47......cap reads "RMC 47N750 10%" ( 47N750 ? )
C724....schematic reads 2700..... cap reads..."RMC .0027 10% Z5F" ( 2700 pF, Z5F ? )
Red Capacitors
(what type are they?)
C701....schematic reads 10uF 35V......cap reads "10 35V" one leg has + signs
Rectangular Capacitors
(what type are they?)
C721....schematic reads "0.1"....cap reads "250 .1"
C722....same as above
Green Capacitor
(what type is it?)
C723...schematic reads "0.22 250V"....cap reads "MSH .22/K 250V"
Resistors
the values are on the schematic and I will verify the color codes, I just need to know what type they are and wattage
View attachment 1304599 View attachment 1304600
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Honestly, it's not cool.
If there is one amp that should not be shorted, it is this series, it is full of op circuits that cannot be found and given your questions about simple things like reading capacitor values, it is not won.
Lots of competent people here but it's going to take time and patience.
Good luck.
If there is one amp that should not be shorted, it is this series, it is full of op circuits that cannot be found and given your questions about simple things like reading capacitor values, it is not won.
Lots of competent people here but it's going to take time and patience.
Good luck.
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