Questions about Philips PM 5133audio function generator

[auato]

Hi all.

I need your help to understand if my unit Philips PM5133 function generator is faulted. This unit seems ro run good (attenuator is OK, level waveforms are OK, speep OK and so on) but I do not able to reach maximum frequency of 2MHz. The maxumum frequency in normal mode is 390KHz (see vieo below)
Another strage matter: on the Service Manual I see two frequency potentiometers START & STOP with fine and coarse functionality



...and also looking the front panel two pots seem coaxial type but only the fine section turn on itself while the coarse seems locked. Can any PM5133's owner inform me about these potentiometers? (if they are really coaxial or not)

Thanks

 

[auato]

Hello.
Just an update ;-) this afternoon I tried to go deep into the matter and I undestood that two coax post have the coarse section totally locked. Not succesful to unlock them and I do not know why they are so locked. It's a very strange matter :???: I have already tried with WD40 spray.
However, tried to replace the coarse section by another 4.7K trimmer and the frequency reaches 2MHz. Now I'm worried to find two 4.7Kohm linerar coax potentiometers. These pots seem too hard to find
The genuine pots are made by Ruwido. Nothing on eBay. Please, any tip where to buy these ?

Thank you very much

 

[Chris56000]

Hi!

Are these any use? - they're very pricey I'm afraid!

http://www.audiomaintenance.com/acatalog/SF-01-038_extended_info.html

The other possibility I can suggest is they might have been locked with a tiny grub-screw etc., somewhere on the control - it certainly seems odd Philips went to all the trouble of providing inner and outer control knobs, lettering on the panel and what-not!

Unfortunately I don't have one of these gennys myself so can't offer any suggestions from my own experience I'm afraid!

Chris Williams

 

[auato]

Hi!

Are these any use? - they're very pricey I'm afraid!

http://www.audiomaintenance.com/acatalog/SF-01-038_extended_info.html

Thank you Chris.
I found these Tektronix 311-0431-00 50K from qservice.tv but many mechanical and electrical adjustments are needed.



Now I do not able to find correct nuts to fix them at panel (the old nuts have a diameter of about 1/2 millimeter larger).

 

[FvM]

Dual "coaxial" potentiometers are still used in a lot of products. They should be basically available, although many traditional vendors like Ruwido or Preh are out of business. See e.g.

https://www.alphastat.de/pdf/katalog/039-040_RD902B21F20-RD912DSF20.pdf