Nombrex 42 Signal Generator

[karatzdi]

Hi,
I recently inherited a nombrex 42 Generator. I am looking for a schematic and owners manual. Cannot find anything on WEB. Anyone knows anything or owns the same model and wishes to share schematic and owners manual I will appreciate it.

Thanks

[simpsons]

Good morning Nicosia

London calling!!

Are you sure that it is a model 42?

I cannot find this model in the list of models manufactured.

A photo would be helpful.

Should it be model 41 then see:

https://www.radiomuseum.org/r/nombrex_rf_signal_generator_model.html

Chris

[Chrispy57]

Hi Chris - it did exist, as confirmed by the attached photo of this one sold in 2018. Good luck tracking down the manual Karatzdi.

Cheers
Chris

[simpsons]

Thanks Chris

Looking at the control layout, I would guess that the model 42 follows the model 27 design and would start there.

Model 27 is covered on this site with internal pictures which might help.

Chris

[karatzdi]

Hello, many thanks for your replies. Yes it is indeed a Nombrex 42. Attached are photos of the issue with 100KHz and 400KHZ I anticipate.
Seems that previous owner replaced the transistor. There are 2 transistors. I am not sure if the issues with the sine waveform are transistor bias origin or this is just the way the oscillator outputs. I am trying to attach an el-cheapo frequency counter for which I made a buffer-rf amplifier to drive the frequency meter. It seems that its not counting correctly because of these distortions or ripples or glitches. If anyone knows let me know so that I do not take work further. Thank you all for replies and hope you have a wonderful new year.
For some reason I did not get any notification for your replies in the forum, so sorry for delay on answering.

[Vintage_RC]

I have a Nombrex 27 and it has similar distortion, I think it's normal for these very basic signal generators.

[karatzdi]

Originally Posted by Vintage_RC

I have a Nombrex 27 and it has similar distortion, I think it's normal for these very basic signal generators.

Good evening Vintage_RC. I think your reply is a relief. At least now I know is not just mine, and there is nothing wrong with it, although I replaced all the carbon resistors with Film ones, as they were 20% off.

Now I have managed to fine bias my Buffer/RF amp (2 Jfet and 2 Transistors) and then pass it through an 74AC14, for wave shaping. Works, it counts the nombrex frequency but up to 3 MHz. Must be the 74AC14, which is basically an Schmitt Trigger.

Thank you everyone for dipping in. Its a great forum.

[AC/HL]

https://www.vintage-radio.net/forum/showthread.php?t=224984