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Marantz PM 66SE , domestic amp of 1996

If anyone happens to have the schematic, values, ohms and watts, of R801 and R802 , for the 24V rail would be nice.

Protection circuit relay fails to click over, because no 24V rail. I was told someone has previously had a look. R801 and R802 are droppers in series from the 44V main rail down to a 24V rail TO220 pass transistor. R801 looks genuine 1R 1/2W, but R802 has the wrong lead bending (none) and different colour banding structure to other Rs on board and measures 4.7K,

1/3W which makes no sense and just a couple of volts at the pass transistor.

Replacing 4.7K with 220R the 24V relay clicks over etc Dropped voltage at the 2SC4883 is 32V for first few seconds then drops to

24.8V on big relay activation. So about 1.8W dropped over "R802" "24V" rail drops from 23.2V to 22.8V

Going down to 110R then 37.1V to 32.8V and "24V" from 23.7V to 23.6V. About

1.1W dropped over "R802"

Assuming the original was yellow green something what was the likely value resistance and wattage of presumably fusible resistor in series with the 1 ohm ? 0.47R, 4.7R, 47R ? A lot of the red and orange colour bands on other resistors have faded to brown and silver/gold bands have faded to feint

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N Cook
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Replaced it with a 1W 47R in series with a 200mA fuse. 24V rail is 24.1V with or without the large relay being powered and about 5V over the 47R.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

R801:- 1 ohm 1/2W. R802:- 47 ohm

Colin

Reply to
Colin Horsley

and

If your source shows the wattage It probably has 801 as 1 watt and 802 as

0.5W wheras it makes more sense to be the other way round , 1R of .5W and 47R of 1W, apart from seriesing 1 and 47 ohm.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook
100mA for one 24V large relay , 2 small 24V relays plus some circuitry seems reasonable. The heating of the, heatsink-less, pass transistor is the same as the one for the -18V supply so again seems reasonable current. So 0.5W dissipated in a 0.5W resistor is questionable. Hopefully a 200mA fuse and larger 47R makes more sense.

Looking on the www it seems to be a recurring problem for this otherwise respected model

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

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Reply to
N_Cook

R801 is the same as R803. R802 is the same as R804. I sent you direct a copy of that part of the circuit.

Colin

Reply to
Colin Horsley

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