10-06-2011, 06:03 PM
My first task on this today was fitting a proper mains lead. This was going well until the MW coil started to slip off the former. I managed to get it back and then gave it a coat of heavy shellac and have had no problems since.
After fitting the lead I made some LED dial lights up for it and have just been investigating the low HT.
I put my trusty continuity tester across the smoothing cap and didn't like the sound of it. I de-soldered it and tacked a new one in place and with that the HT was up to 190v, which is close enough for rock 'n' roll.
I connected the old one up via a 15W lamp and diode to see just what it was up to. It leaked about 7mA and the voltage across it never exceeded 280v. I left it for a bit to see if it would reform any better but after a while the leakage started to rise. It still felt cold but there's obviously something amiss with it. I also thought the it discharged rather quickly considering it was only connected to a DMM on volts.
Just for comparison I repeated this test with the new one. That leaked 0.5 mA and the voltage went up to 345v (it's rated at 450v) and took far longer to discharge.
Despite the reputation of Bush ones it looks like that's where the trouble lies. I suspect the other half of the can won't be any better but don't have a 16μF capacitor to play with. Luckily I'm not in a rush and there are other things I can be doing both on this set and others and will no doubt be ordering other bits pretty soon.
It wouldn't have been nearly as interesting or educative if it had worked first try. In fact I'm coming to the conclusion that this radio is fond of me and is making sure I spend so much on it that there's no point my thinking of selling it. This had initially crossed my mind as it's the repairing that I enjoy and it would have been a way of making a few bob to fund the next one. That said it's grown on me but the problem now is that I'm fancying a black one to complete the set!
- Joe
After fitting the lead I made some LED dial lights up for it and have just been investigating the low HT.
I put my trusty continuity tester across the smoothing cap and didn't like the sound of it. I de-soldered it and tacked a new one in place and with that the HT was up to 190v, which is close enough for rock 'n' roll.
I connected the old one up via a 15W lamp and diode to see just what it was up to. It leaked about 7mA and the voltage across it never exceeded 280v. I left it for a bit to see if it would reform any better but after a while the leakage started to rise. It still felt cold but there's obviously something amiss with it. I also thought the it discharged rather quickly considering it was only connected to a DMM on volts.
Just for comparison I repeated this test with the new one. That leaked 0.5 mA and the voltage went up to 345v (it's rated at 450v) and took far longer to discharge.
Despite the reputation of Bush ones it looks like that's where the trouble lies. I suspect the other half of the can won't be any better but don't have a 16μF capacitor to play with. Luckily I'm not in a rush and there are other things I can be doing both on this set and others and will no doubt be ordering other bits pretty soon.
It wouldn't have been nearly as interesting or educative if it had worked first try. In fact I'm coming to the conclusion that this radio is fond of me and is making sure I spend so much on it that there's no point my thinking of selling it. This had initially crossed my mind as it's the repairing that I enjoy and it would have been a way of making a few bob to fund the next one. That said it's grown on me but the problem now is that I'm fancying a black one to complete the set!
- Joe
