Golborne Vintage Radio

Hi all
The UK company Levell Pty Ltd made some interesting vintage Null Meters and DC Microvoltmeters. I recently acquired a TM10 model through a dealer ex TAFE SA. On testing, it is way out of cal on the volts range (~12% high). Seems ok on the mV range.
I have not been able to find any manuals or info on the TM10 or any other Levell DC microvoltmeter so would appreciate any help out there.
Would also like to know how to set Z1 and Z2 correctly as well as the function of the LOG setting.
There are lots of pots on the PCB but they are all unlabelled. Also lots of transistors and one lonely IC - UA776HC.
I have posted some pix to start things off.
enut11

Welcome to Golborne.

This style of Levell instrument is common in the UK. Apart from meters they made signal generators etc. Levell Pty would presumably have been their Australian importer as we don't use "Pty" in the UK. Looking at the PCB it should be too hard to trace out the schematic if you can't find the manual. Put s trong light behind the board so you can see the tracks from the component side to do this.

The 776 opamp is nothing special by modern standards: http://www.mouser.com/catalog/specsheets...729_DS.pdf

Used to use them, The Microvoltmeter and the Oscillator, for straightforward Audio Frequency Jobs.
As I rememn seems very thin on the ground so Jeffrey's suggestion is probably for the best.
I'll ask some old colleagues.

Alan

Best I can do is the Manual for TM3 and 4. The obvious difference is that it's all Transistors.
Still, it might give you some hints.

[attachment=14110][attachment=14111][attachment=14112][attachment=14113]

Alan

Thank you Jeffrey and Alan. It is good to hear from someone who has actually heard of Levell. Looking forward to some more feedback.
I will try to nut out the circuit diagram but this can be very time consuming.
If anyone knows of a crcuit from a similar Levell meter, this might help. I would love to get this old meter working properly again.
Enut11

(29-03-2016, 06:09 AM)ppppenguin Wrote: [ -> ]Welcome to Golborne.

This style of Levell instrument is common in the UK. Apart from meters they made signal generators etc. Levell Pty would presumably have been their Australian importer as we don't use "Pty" in the UK. Looking at the PCB it should be too hard to trace out the schematic if you can't find the manual. Put s trong light behind the board so you can see the tracks from the component side to do this.

The 776 opamp is nothing special by modern standards: http://www.mouser.com/catalog/specsheets...729_DS.pdf

Hi ppppenguin. the TM10 has some soft goo on one of the switches , could be silicone grease, which I need to clean off the trace the circuit. Do I need to replace this when finished?
enut11