Golborne Vintage Radio

[attachment=15714]Craig I think VR935 and Cr931 are shorted showing continuity in both directions could there be another path in this circuit to cause this not to sure.
See pic for more voltages.
Can you suggest an equivalent for CR931?

[attachment=15719][attachment=15718]Pics of waveform 1 page 173 section 11 scope setup as 8.2 in manual.
see pics.
signal was unstable walking.

OK - the table of voltages. The bases of Q954 and Q955 are connected together. But the table says the base of Q954 is 12.63V and that of Q955 is 3.30V, which is inconsistent.

And for the traces (1) where is zero? and (2) is your probe switched to x1 or x10? And the trace being unstable is just that it isn't trggered right

Craig

Regarding diodes, have you used the diode test function of your DVM? If you are, I do not necessarily think that there is anything wrong with VR935. That is because there are back to back diodes with a 10k resistor across them. Try the same test with VR937; I suspect the result will be the same.

I cannot find a path through other components around CR931. When I am faced with that sort of conundrum I desolder one leg of the diode and test it out of circuit. If it still looks duff you know you have found a fault. If it measures OK, solder it back in and continue the search.

Craig

1) Check bases tomorrow agree with you my mistake.
2) Trace zero is mid 'X' axis gnd.
3) Probe 10x.
4) Can't stabilise trigger at the settings in 8.2 manual.
5) Diodes Vr935, Cr931 tested using Dmm on continuity and diode settings. Tested other diodes in vicinity they tested ok.

For your traces to look like the ones in the manual you need to switch your probe to x1 (or x10, but increase the vertical sensitivity by a factor of 10). And you need to reference the zero to the same graticule line as each of the trace examples. The zero is marked on each of the traces - so switch your scope input to ground and adjust the vertical position to put the zero line where the trace picture shows. So on picture 1 the zero is at the 4th vertical division and on trace 9 it is on the second vertical division. On others it is at the bottom graticule line. You have to do that very clinically every single measurement you take so you can compare what you see with what the manual says you should see.

Craig

Thanks Craig, there!s another problem this old scope has two screws at the front to balance attenuation. When I set gnd, then switch to Dc then change the volts/div the x axis moves up or down when I switch back to gnd it has moved up or down.
I have exercised the pots 22kohm and lubricated them still the same not having a lot of luck with scopes.
I,ll try what you suggested might be somewhere near at least I feel I am learning how to use a scope unfortunately the years are running out ha ha.

OK - here's an idea to get the zero set. Short the probe tip and ground lead and then adjust the zero position (vertical is y, by the way and horizontal is x). Then adjust the zero position. The connect the probe to the scope under test.

You might get a better result zero setting that way with the probe set to x10, but remember to switch to 10x more sensitivity. So if the trace in the manual says 1V(per division) set your scope to 0.1V/div.

Another Q - have you read the procedure for setting the DC balance pots (the 22k ones you mention)? Page 6 of the OS1000A Manual.

Yes Craig I read the procedure, tried again just cannot get stable triggering from test points on 434.
Used different settings as you suggested was better but still flashing and walking slowly
See Pics 484, 485.
Generator in pic. sine and square nice and stable. bnc to 4mm plugs.
Other pics are waveform 1 section 11.
I have pointed out some caps can you enlighten me and what to use as replacements if faulty in future. Never seen caps like that all new to me.
So many different points of view for caps.
If the photos of waveform1 are ok let me know please and i'll attempt to do the rest.