Hi all, I brought an old LSG 11 signal generator today.

I noticed it had eye terminals instead of a plug. I pulled it a part when I got home to find the valves were missing and it had been modded by someone unknown.

I read on the internet that there was mod using a 9v battery.

So to be honest, I am unsure what to use to power and test.

I will upload some pictures to help understand and identify my dilemma.

Hi, I use one of these virtually every day even though I have much more modern equipment.
Its a great piece of equipment for radio repair/restoration.
Your unit may have been modified to operate on FETs to replace the valves, why I don't know as it was very good as is and nostalgic.
So..... I guess its modded to 9 volt operation.
Without seeing the unit.
JJ

One mandatory mod to a non-converted LSG-11 is to remove the "death caps" across active and neutral to the case.

If yours has been converted, then it may been by following this article:

https://www.emdrc.com.au/wp-content/uploads/2022/01/LSG-11-FET-Conversion.pdf

Thanks for replies.

The mains power wire goes to 317uc8632, regulator and not a transformer, I couldn't find any reference to the number, maybe its a regular LM317.

Also there is a fet where the valve used to be T1 39 2n3819, so you could both be correct with the fet conversion.

I won't apply any power until pictures are uploaded and might help in identifying what mods were done.

I guess that it won't vaporise before my eyes if its found to be low voltage DC, which appears to be the case.

GTC, I did see that article but couldn't relate it to the schematic that I found inside of the signal generator.

I have repaired a few of those, however they have remained valve. There is one here with a fried transformer. Otherwise complete. I really do not know how these got into the country? Fully metal including case ungrounded. Suicide machine if the not approved type line cap fails.

Not one of them has left the place without an earthed body.

It may have been modified to give more stability? Albeit I have never found that an issue & calibrate it with a counter. Modulation must be off.

I have the circuit for the valve LSG-11 and the Dick Smith "Tech" clone. Ideally to get maximum stability, in such devices, one regulates the HT and heater voltage. One would be interested in the tracking if its been modified.

I noted two different manufacturers. One used oil filled capacitors which are not much better than waxed paper types. They failed leakage test and were systematically transferred to the bin.

Photos uploaded.

Well, thanks for replies.

I hooked it up to a power supply and slowly wound it up to 9v it was working from about 6v.

It does appear to work but I am unsure of what the power output should be, it was around 80ma pk-pk during testing and all bands worked.

I did ramp up voltage to 10vc but I didn't notice an improvement.

I did find a few glitches but overall l am happy with it.

Here's a link to the original specs:

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Leader/lsg11.pdf

Those black caps like the one marked 0.1 are oil filled and all in LSG-11 have been trashed. Those may be ok for low volts but based on history, they will leak like sieves.