I’m a little bit confused. I need resistors that are not marked. Reads on the multimeter 0.530 M ohms can you give me an explanation, so that I can make sure I have it right.
I checked in our system and I was able to find one option with this value as part 13-MFR1WSDRD52-530KCT-ND. Unfortunately I am unable to confirm what wattage rating your origional resistor is, do you know if 1W will be enough?
Can you post a photo?
0.53M = 530K so it could be a 500K +/-10% or +/-20% resistor
That appears to be a very old 1% metal film resistor, probably made before 1970. The circuit context appears to be a frequency shaping control of some sort. The size implies >= 0.5W power rating that while way over specced for the apparent application was often the most economical choice 50+ years ago.
Considering all that, I suggest you try out the part that @Rob_Johnson linked above.
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Thank you that helps a lot. It’s a very old amplifier
These two big resistors get incredibly hot….what do you have to replace them……
Hello @mikecasey,
Please let us know which resistors you are referring to.
I understand the make and model information has worn off your amplifier. However, a few pictures may help us determiner narrow down the search.
Sincerely,
Aaron
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These are the resistors. What does 5PCK mean.
I’m guessing 5watts. But I just want to make sure
mikecasey,
Without knowing the series and manufacture, there is no way to be sure what each number and letter would call out.
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Mikecasey,
Part number
4506-HVLR5208F10K0K9-ND is the only 5 watt option I found for 10K ohm 1% film resistor.
Hello @mikecasey,
It looks like the resistor is connected to a rectifier tube (likely a 5U4 or 5R4). If I had to guess, the resistor provides power to the input stage of the amplifier.
- Yes, the red power resistor will get hot.
- The red power resistors do not show signs of stress
- The little resistor in this picture requires attention
The markings for the red power resistor likely indicate a 5 % tolerance.
Recommend you test the resistance using a multimeter. Replace only if significantly out of tolerance.
Happy soldering,
Aaron
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I am trying to draw this circuit so I can do more research…..is there enough info here so you can tell me which class of amp this belongs, so that I can narrow down what to look for. Also can you tell what options I have for tubes T5- T8- and T9.
And although I do have volume on channel 1. it is very low. Channel 2 is just dead no sound at all….Also it has a hum. I removed tube 8 and the hum disappeared . If you have the time, I know you’re busy, would you give me your thoughts. Mike
Hello @mikecasey,
This is a classic push-pull 6V6 amplifier with a 1940 to 1960 design.
Unfortunately, I am unable to determine the tube types from you drawing.
Recommend:
-
Purchase “The Tube Amp Book” by Aspen Pittman. This reference is full of schematics for vacuum tube guitar amplifiers.
-
Search Antique Electroncis Supply for New Old Stock (NOS) tubes.
Sincerely,
Aaron
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