X150.5 overheating (maybe)

[barti]

hi all

would like to know if a temperature of well more than 60°C (Celsius degrees, about 140°F) measured at the heatsinks is normal when environmental temperature is about 25°C. just as an empirical check, I cannot put my hands on the heatsinks for more than 2s....

my doubt arise from the fact that this high temperature is reached even w/o any music, indicating a possible problem in idle biasing corrent

how (if possible) can I check the bias corrent?

many thanks
mike

[Blues]

Locate the Source power resistors which are usually 3W, blue and bigger of the bunch you see on the circuit board...which lines up with the heatsinks. Each power transistor would have a Source R. Power it up -with safety in mind, measure the dc voltage across one then divide it with the value of the R which on Panasonics is printed on the body. This will be your bias current.

For good measure...measure each of the Source R voltages. And if you are up to it measure the voltage across the Drain and Source pins and compare each one.

How long before the heatsinks reach 60degC when powered up w/o music?

[barti]

Originally Posted by Blues

Locate the Source power resistors which are usually 3W, blue and bigger of the bunch you see on the circuit board...which lines up with the heatsinks. Each power transistor would have a Source R. Power it up -with safety in mind, measure the dc voltage across one then divide it with the value of the R which on Panasonics is printed on the body. This will be your bias current.

For good measure...measure each of the Source R voltages. And if you are up to it measure the voltage across the Drain and Source pins and compare each one.

How long before the heatsinks reach 60degC when powered up w/o music?

thanks for the reply. I'll follow your indications and measure the bias current, what should it be by default?

the heatsinks reach a very high temperature after some 30-40 min of idle state, and after 20-30min of music at normal level (the front indicator doesn't move or moves very very slightly)

many thanks again
mike

[Blues]

The correct bias values...Mr. Pass would be able to help us with these...hopefully he sees your post, if not try to email him directly by visiting the PL website.

It sounds like it's working normally...

[Nelson Pass]

If both channels are about the same temperature, then I
would assume the amp is OK. It seems to be running hot,
but this is often a function not only of room temperature, but
ventilation and line voltage. I would try to improve the
ventilation if possible.

Also, I shouldn't have to mention, you don't want to have it
sitting above another component which puts out heat, and you
probably don't want to have it in the sun.

[barti]

Originally Posted by Nelson Pass

If both channels are about the same temperature, then I
would assume the amp is OK. It seems to be running hot,
but this is often a function not only of room temperature, but
ventilation and line voltage. I would try to improve the
ventilation if possible.

Also, I shouldn't have to mention, you don't want to have it
sitting above another component which puts out heat, and you
probably don't want to have it in the sun.

Hi Nelson, thanks for the indications and please sorry for this late reply.
yes both channels seem to be the same temp, so I suppose there's nothing wrong. the amp is sitting on the top shelf of a 3 shelves AV rack together with the pre, and is not in direct sunlight. room temp is btwn 25 and 27 °C (I do not use AC in this room), so I think I have to arrange some more ventilation around the amp, maybe a 230V fan could do the work...

thanks again
mike