Nombrex type 27 signal generator

[Bushbaby]

Hi All
I hope you are all enjoying the hot weather.

I recently bought this signal generator and its not in the greatest of condition and of course it doesn't work. I will lay money that the OC171 will be kaputt although I have some AF178 which I believe can be used as a direct replacement.

I stripped it down in the workshop today although the 30+ degree heat did get to me a little.

i am a bit concerned about earphone addition which doesn't seem correct.

Rob
               

[Crackle]

Maybe it is an input for external modulation.
The circuit and instructions are in the radio museum. https://www.radiomuseum.org/r/nombrex_ge...ex_27.html

Mike

[Mark Hennessy]

DC input, I'd say

[Bushbaby]

I've have been endeavouring to work on this and it appears that it isn't working at all. The solder joints look very crappy like some one has tinkered with it before. I'm almost tempted to write it off as a project on this basis.
One thing that is puzzling me is the schematic shows a lot more components than the part list that accompanies it. Is there any reason for this?

Thanks

Rob

[alanworland]

I got hold of one of these a while ago, it's lovely little unit. Mine has wires coming out the back for an external battery (9v) and that's what your additional wiring looks like. They use about 3mA when running.
Couldn't believe how simple they are, mine works well and is pretty accurate on frequency.
Worth persevering with!

Alan

https://postimg.cc/image/wyhyzi4uh/
https://postimg.cc/image/3w3ownnpl/

[Bushbaby]

Hi Alan
Many thanks for the reply. However, from other images that I have seen of the circuit board (our dear friend Joe Freeman posted one on another forum) it does appear that my has been 'butchered' and may have components missing. It certainly appears that it has an additional link wire?? Do you by chance have any picture of the board in your model 27?

Kindest Regards

Rob

[Mark Hennessy]

I've just sorted out the links in post #5, so now we can see one pretty decent image of the PCB now

[Bushbaby]

Thanks Mark,
I have reference point now. It does appear that Alans is different to mine, I will need to investigate further.

Best Regards

Rob

[Terry]

Hi Rob, I can't see any real difference between the two except that Alan's uses some more modern components - for example, at the top of your picture is what looks like an OCxx transistor which, in Alan's, has been replaced by a metal canned type. There are also some differences in the style of some of the components, like the two ceramic capacitors between the tuning capacitor and and the switch.

The only real difference that I can see is the red wire link along the bottom of the board on your's - toward the right.

However, as Alan's PCB looks to be a revised version of your's, I would guess that the opportunity was taken to add the missing track in place of the link.

[Bushbaby]

Thanks for your reply Terry.
I can only think that ther must be a faulty component or so on the board. I have also noted that some of the inductor cores appear to missing too.

Best Regads

Rob