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City: Fountain Hills, Arizona
I've just finished re-capping and replacing out-of-spec resistors on an Airline Model 62-425 (Montgomery-Ward). I also replaced the Metal clad resistor (R9,10 and 11) with non-metal resistors.
The radio has good sensitivity and plays just fine above 1000KHz. Below 1000KHz there is a persistent buzz that gets louder the lower the tuned frequency. Stations can be heard in this range but with the buzz.
I've tuned the IF and oscillator circuits and I tried moving wires around looking for anything that affects the buzz to no avail.
I welcome any suggestions on how to proceed.
Thank you
Don
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City: Jackson, NJ
If it is tuning-related it is some interference.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 95
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Joined: Oct 2016
City: Fountain Hills, Arizona
Other AM radios nearby do not buzz. And no, the other radios are not on when the subject radio is on.
Thanks,
Don
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All the covers have to be on the vibrator section and the radio bottom plate if it uses one. If using a line powered supply the chassis must be earth grounded as short as possible. Vibrator must be in good condition. If the vibrator has been opened and the contact blades bent, the vibration frequency may be off. Should be 115hz.
The buffer cap must be replaced with exact values and type "buffer", no subs of "yellowy" metalized will work in the power supply the metalizing will get blown away because of the spikes. No matter even if using 2.5 kv, the dv/dt is not there unless it is a buffer cap...
If it still buzzes. To prove source is vibrator supply substitute another B+ DC source, an adjustable supply of 80-100 mills, 145 volts. The radio still buzzes look for grounding and/or miss wiring in the RF/IF section...
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
Posts: 95
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City: Fountain Hills, Arizona
Morzh,
I rechecked, you are correct that the buzzing is from outside interference.
Thanks, I'll never doubt you again.
Chas,
Thank you for your response. My radio does not use a vibrator; the buzz is from outside interference.
Don
