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In Reply to: Need help on Marantz 9 posted by alltec marantz 9 on August 2, 2005 at 10:18:03:
with the calibration meter's settings inside being off. Its not usable for setting bias and AC balance. As an alternative to rebuilding the meter, I'd suggest you can get a cheap digital VOM and use in paralle with the original meter to set the bias, etc. What you'll need to know, of course, is the voltage drop across the cathode resistors, which should be in the service manual. I've even put a little banana socket in place on my Citation II to make the job easy. I've only used it once, tho.WARNING: If you're not comfortable dealing with high voltages - Don't. Just take the amp to a tube-savy service guy and have him do it. Its not hard with the expertise and the tools.
I just wouldn't indulge in tube rolling though, in this case.
Cheers,
Follow Ups:
Hi David,Thankyou for your suggestion. In fact, i don't want to drill any extra holes for the banana sockets on the Marantz 9 so i prefer to get a replacement meter. It is a good idea to connect a digital VOM in parallel with the original meter to set the bias but the meter connected a complicated calibration circuit and i don't understand the connection between the calibration circuit and the meter selector. I am not sure it can be connected in parallel with VOM or not.
Regards
I'm fortunate that the metal cage is missing and the holes for it are perfect for a banana socket.I haven't looked at a Marantz 9 schematic in over 30 years so don't know the particurlars but on the Citation, the meter is pretty much placed in parallel with the cathode resistors through a switch so I can monitor the current draw through the resistor since I know the value of each of them. In this way, then, I do my setups. The AC balance is a bit more tricky, voltage wise, but I still use the VOM for all the setups. I'm sure the same technique can be applied to the M-9.
Cheers,
Hi doodlebug,I agreed with you, the same technique should be applied to the M-9. Now, i can calibrate the bias current to 55mA across the resistor.
But, the meter without the pin looks very strange so i still want to get a replacement meter if possible.Regards,
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