29-04-2015, 03:48 PM
The good news so far is the Ultra 1947 radio is now working fine but there were moments when I thought it wouldn't be so easy. Also, the way it sprang into life was kind of weird.
Yesterday, I built a very simple dim bulb tester and had spent a while reading up about how dim bulb testers work. I used a piece of wood, a socket, a bayonet lamp holder and 100 watt bulb. I did another Ohms test between live and neutral as well which checked out seemingly O.K.
I hadn't intended to test the radio at all today but impatience got the better of me so I made a few more checks and then placed it on a large bench in my boat and connected everything via the current limiter. Then I switched on from a safe distance. Bear in mind the last time I tested this radio, I got a bit of a fright as you will recall the mains filter capacitor started to smoke. So, I was a bit apprehensive.
After a fairly short time, the radio began to produce some noise. The lamp on the dimmer bulb showed no signs of lighting. I powered off for a bit and took a good look at the set to see if there was any sign or scent of smoke or anything unusual but it all seemed O.K. So, I powered up again and left it for a minute or so more. Finally I removed the current limiter and plugged into direct mains.
At this point it was kind of odd and I was a bit baffled as the radio seemed healthy but no stations or sign of anything. I was also kind of worried about a resistor I had re-soldered and it had gotten a bit too much heat at the time as an end cap had bubbled a bit and come off. When I tested the resistor it seemed very much on the high side although I've known anode load resistors be about 1 MegOhm so I had my doubts.
Anyway the weird thing was there was no sign of any reception at all and I was testing voltages around valve pins with my meter and then one tiny Mica capacitor sort of buzzed when I probed it and then a station came in perfectly clear. It was just some debate about the general elections and, of course, I'd not fitted an aerial at all so I was pleased to hear actual audio. I winded up making a coffee and letting the radio play for a while and it seemed all totally O.K. and working quite smoothly.
Of course, it will be necessary now to do a lot more testing, especially I need to find out if that resistor is out of spec and I'm curious about the small cap I tapped that then caused the radio to spring into life.
It's been a lot of hard work so I'm going to take a short break and relax. I have the Bush tranny to finish as well.
Yesterday, I built a very simple dim bulb tester and had spent a while reading up about how dim bulb testers work. I used a piece of wood, a socket, a bayonet lamp holder and 100 watt bulb. I did another Ohms test between live and neutral as well which checked out seemingly O.K.
I hadn't intended to test the radio at all today but impatience got the better of me so I made a few more checks and then placed it on a large bench in my boat and connected everything via the current limiter. Then I switched on from a safe distance. Bear in mind the last time I tested this radio, I got a bit of a fright as you will recall the mains filter capacitor started to smoke. So, I was a bit apprehensive.
After a fairly short time, the radio began to produce some noise. The lamp on the dimmer bulb showed no signs of lighting. I powered off for a bit and took a good look at the set to see if there was any sign or scent of smoke or anything unusual but it all seemed O.K. So, I powered up again and left it for a minute or so more. Finally I removed the current limiter and plugged into direct mains.
At this point it was kind of odd and I was a bit baffled as the radio seemed healthy but no stations or sign of anything. I was also kind of worried about a resistor I had re-soldered and it had gotten a bit too much heat at the time as an end cap had bubbled a bit and come off. When I tested the resistor it seemed very much on the high side although I've known anode load resistors be about 1 MegOhm so I had my doubts.
Anyway the weird thing was there was no sign of any reception at all and I was testing voltages around valve pins with my meter and then one tiny Mica capacitor sort of buzzed when I probed it and then a station came in perfectly clear. It was just some debate about the general elections and, of course, I'd not fitted an aerial at all so I was pleased to hear actual audio. I winded up making a coffee and letting the radio play for a while and it seemed all totally O.K. and working quite smoothly.
Of course, it will be necessary now to do a lot more testing, especially I need to find out if that resistor is out of spec and I'm curious about the small cap I tapped that then caused the radio to spring into life.
It's been a lot of hard work so I'm going to take a short break and relax. I have the Bush tranny to finish as well.
