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#1
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I bridged the power supply caps made no difference but the 2 300 v caps rated at 100uf and 120 uf I had put in 2- 450 v 470 uf caps in place of the original and I thought maybe this was a problem but it shouldn't as it's just Alittle harder on the diodes when turned on.
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#2
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1. Does the hum actually get louder as you turn the volume control down?
2. Can you measure the voltage of the hum at the speaker? Quote:
jr |
#3
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Quote:
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#4
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.012 ac voltage at speaker no hz, grid on, grid off voltage is 1.662 ac at 60hz . No DC voltage grid on or off.
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#5
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Quote:
Do you measure the same voltage with different 25L6s? jr |
Audiokarma |
#6
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There was nothing on the grid pin when I measured at the speaker leads and got 1.662 volts ac.But I did use a clip wire to measure the grid with the wire on the grid. 25l6s the same. I've been going over this beast and can't find a thing out of place.
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#7
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Well still cannot find the source of the hum but is it at all possible to get a hum like this from hv, the 1b3 gets its heater voltage from the hv coil so from there I don't know. The Motorola Manuel states that there is a 22 ohm resistor between the crt and the audio amp heaters to keep audio hum down but that resistor is there.
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