02-05-2012, 10:08 AM
I did a bit of digging 'round last night and found this model is suspiciously like the HeathKit V-7A, the only obvious difference being the sockets.
This also revealed that it should have a battery in it so after fitting one the resistance measurements 'work' but are not accurate; a 1KΩ resistor reads 1.2KΩ and a 10KΩ reads 18KΩ.
I've checked the HT which is only 50V across what I take to be the smoothing capacitor. This itself is fine in terms of both leakage and ESR so it looks like the rectifier is to blame. I take it a silicon diode would want a 100Ω resistor in series with it?
I've spot-checked a few of the precision resistors which all seem to be bang on - that is one job where a digital meter scores over an AVO.
More later.
- Joe
This also revealed that it should have a battery in it so after fitting one the resistance measurements 'work' but are not accurate; a 1KΩ resistor reads 1.2KΩ and a 10KΩ reads 18KΩ.
I've checked the HT which is only 50V across what I take to be the smoothing capacitor. This itself is fine in terms of both leakage and ESR so it looks like the rectifier is to blame. I take it a silicon diode would want a 100Ω resistor in series with it?
I've spot-checked a few of the precision resistors which all seem to be bang on - that is one job where a digital meter scores over an AVO.
More later.
- Joe
