08-04-2015, 04:23 PM
Many thanks for your speedy response and helpful comments Keith.
It wouldn't of course be a big deal to replace all the Rs, Cs and the two diodes if need be, but I didn't want to just pull components out on the off-chance that they might be duff, when a more restrained and logical approach would be a better option. I don't think those little tubular caps and resistors are noted for being unreliable or drifting in value. Initially, I'd wondered if the diodes could be suspect, but I think that given the 118V at D2, they seem quite healthy. I could always sub them for 1N4001s to see what change if any that it makes. I've not checked the voltage on the bases of TR2 & TR3, but what's puzzling me is the lack of any change in voltage on the grid of the DM70 when the calibration dial is swung round. I think I'll have to remove the PCB again to get at some inaccessible points on the circuit to take a few more voltage checks, and perhaps remove TR2 & 3 to test them out of circuit.
Quite an innovative little firm and something of a mystery. Brings to mind the likes of Codar and Jasonkits who had their moment in the sun before it set on them.
It wouldn't of course be a big deal to replace all the Rs, Cs and the two diodes if need be, but I didn't want to just pull components out on the off-chance that they might be duff, when a more restrained and logical approach would be a better option. I don't think those little tubular caps and resistors are noted for being unreliable or drifting in value. Initially, I'd wondered if the diodes could be suspect, but I think that given the 118V at D2, they seem quite healthy. I could always sub them for 1N4001s to see what change if any that it makes. I've not checked the voltage on the bases of TR2 & TR3, but what's puzzling me is the lack of any change in voltage on the grid of the DM70 when the calibration dial is swung round. I think I'll have to remove the PCB again to get at some inaccessible points on the circuit to take a few more voltage checks, and perhaps remove TR2 & 3 to test them out of circuit.
Quite an innovative little firm and something of a mystery. Brings to mind the likes of Codar and Jasonkits who had their moment in the sun before it set on them.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
