Can you elaborate on that? What didn't work right?I had marginal success replacing the fifty year old cells with custom voltage NiCD packs from an RC car battery supply outfit in the Bay area.
Can you elaborate on that? What didn't work right?I had marginal success replacing the fifty year old cells with custom voltage NiCD packs from an RC car battery supply outfit in the Bay area.
..I did discover one more stablyt based supply which seems destined for the U67 called the NUK , but I cant seem to find the schematic though , maybe someone here has it ?
However, the description in the radiomuseum link specifically mentions "Special "stabilyt" voltage reference (in fact, a nickel-cadmium cell, a Georg Neumann patent) used in the heater voltage stabilizer. "I don't think that NUK power supply had NiCd batteries. Ge transistor TF80/30 is used to regulate the heating voltage.
The filtering could have been better and they wouldn't last very long before hum crept in. About a year. I think the properties of the modern batteries aren't the same as the original nicads. My other unit's had already been converted by someone to just have a 7805 circuit there. Not optimal, in my opinion.Can you elaborate on that? What didn't work right?
I would rather use an LM317/337 plus CRCRC than the 7908. Take a look at this project as an exampleI'm planning to use a 7908 voltage regulator (-8v) and CRC filter for U67 bias mics. Using a calculator I find that I would need around a 0.5W resistor(s). So would be safe to use a 1W in a long term to drop 2v in one or two resistors?
What voltage are you starting with?I'm planning to use a 7908 voltage regulator (-8v) and CRC filter for U67 bias mics. Using a calculator I find that I would need around a 0.5W resistor(s). So would be safe to use a 1W in a long term to drop 2v in one or two resistors?
Thank you!
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