Well... its only half the story. If they charge then they at least behave like a capacitor but it is still not 100% proof they are good. I got suspicious when you said they were all faulty.
For bigger values (like the 470uF) you can see how long that 8 volts takes to discharge into a 100k resistor. After 1 minute the voltage should be around 2.5 volts.
For bigger values (like the 470uF) you can see how long that 8 volts takes to discharge into a 100k resistor. After 1 minute the voltage should be around 2.5 volts.
well that was an easier one, couple of faulty or low value caps, few dodgy joints and some suspect wiring and a failed open resiistor R626
al sorted
you are getting to be quite the expert on all these
well i dont know about that.
i guess they are all a very simlar concept, with specific variations on the same theme, so you tend to go looking at the commonest causes first
my only concern with the last 2 is that the lamp is still on very slightly, but as you said this could be the power supply transformers.
I cant find anything wrong inside, and im not going to get paranoid over it and spend hours possibly chasing nothing.
2 transformers must be drawing at least 50mv between them
all the idle currents and centres are ok, they all wander a bit but i find that happens with all of them +/- 10ma or so i dont get too concerned about that.
its funny realy all of the different amps ive worked on and listened to, yet i still cant find one that realy matches my 3240PE, i guess im just used to it i suppose
i guess they are all a very simlar concept, with specific variations on the same theme, so you tend to go looking at the commonest causes first
my only concern with the last 2 is that the lamp is still on very slightly, but as you said this could be the power supply transformers.
I cant find anything wrong inside, and im not going to get paranoid over it and spend hours possibly chasing nothing.
2 transformers must be drawing at least 50mv between them
all the idle currents and centres are ok, they all wander a bit but i find that happens with all of them +/- 10ma or so i dont get too concerned about that.
its funny realy all of the different amps ive worked on and listened to, yet i still cant find one that realy matches my 3240PE, i guess im just used to it i suppose
Two transformers have got to cause the bulb to glow and it doesn't take all that much to get the bulb glowing a little. As long as the idle current is correct on full mains it will be fine.
Turn the bias right down on both channels and see if it extinguishes
I’ve never bothered with a lamp, either a current limited two rail DC PSU , or a variac and monitoring bias all the way up from 20VAC
That and a ‘scope component tester prior to bringing it up on the variac usually finds most of the problems , hand built for a decade or so, but nowadays I use the built in one on my R&S HMO1202
Build one if you have a ‘scope , they’re invaluable
Attachments
Last edited: