Hello, I would like to have some help to adjust my MARANTZ 5220 tape recorder and more particularly the frequency response. I bought the Hanspeterroth calibration tapes but I have a problem understanding the Marantz manual service. Thank you in advance for your help.
It looks pretty easy although I'm no expert. What voltmeter are you using and where are you getting stuck?
Hello, Thank you for your message. I would like to know which tape I should use to have 0 db at the VU METER. If it is the 315 Hz cassette or the 400 Hz one. I have to use the MTT-150 cassette in the SM which is the one corresponding to 400 Hz but I am not sure. I have all the calibration tapes to do the job as well as an oscilloscope and a metrix with frequency. I would also like to calibrate the VU METRE by applying a 1Khz signal to the front microphones input but I can't make the adjustment. Thanks in advance for your help.
I want to make a couple of remarks in regard to this adjustments: 1. According to the manual, you need to load the line out with 100kohm resistors. Failing to do that will result in incorrect calibration, as voltages you measure will be higher without a load. 2. The manual should say what 0dB means in terms of RMS voltage. It usually means 0.775V or 775mV. Without knowing this, you can't know what 0dB means, as dB is not an absolute measurement unit, but it is referenced to something. In regard to the cassette, you need to find out what magnetic fluxivity you need, the frequency is not too relevant if it's 315 or 400Hz. 160nWb/m DIN tapes and 200nWb/m ANSI tapes are the most common out there. MTT-150 is a 200nWb/m tape. The service manual calls for a MTT-116U tape, but I cannot find the fluxivity of this tape. You can use a 200nWb/m ANSI tape even if the manual requires 160nWb/m DIN, but you need to adjust for 2.4dB higher voltage than the manual specifies. In regard to the VU-meter, simply adjust it so that when you have 0dB on the line out (0.775V with 100kohm load) the meter indicates 0dB. I would not use the microphone inputs as they're way too sensitive and you will need a very low voltage. Rather, use the line in to do this adjustment.
