Problem with Philips PM5131 generator

Joined 2003
Paid Member
Hi guys.

My old generator developed a fault over night.
The frequency cannot be adjusted with the big dial anymore. It appears to be stuck at the low end of the dial. It can still be changed with the 3 range selection switches, but still stuck in the low end of the respective range.

When the unit is switched On, the frequency starts high and the drops over the first 1-2 seconds. The drop looks very "controlled" and well behaved. - I'm suspecting the the error is around the sweep function, but none of the other controls vary the frequency.

The output signal looks perfect and amplitude can be adjusted.

I know that a few components look very hot, but I think they are located in the amplifier section and I'm pretty sure that they looked burnt the past few years ( should replace them, yes..).

Any ideas?

I have the service manual, but I cannot figure out where to start looking. I would really like to restore this beauty. Look at the internal build quality.

Kind regards TroelsM



  • pm 5131 philips generador.pdf
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Joined 2003
Paid Member
Reading a bit of the service manual yesterday and apparently the frequency is set by summing currents from different sources, - the pot (R650) being one of them. - I'm thinking that if any of the current-sources goes to max for some reason it will clamp the freq to one extreme. It should be possible to find the individual currents and see if any one of those are (too) high.