15-04-2012, 07:15 PM
After yesterday's success, today I've been working on my spare R200 chassis.
As soon as I bought this I knew it had been got at as one of the AF117s was missing. I'd got three AF116s out of the R600 - all had had shorts but they seemed to have cleared with due application of ziggies - so I fitted one of those. It still didn't work and I did nothing else to it until today.
I checked the electrolytic caps first and found most of them wanting so changed those. This made no odds either.
I then set about testing the transistors. None had shorts but I was getting some queer results. They all seemed to pass the usual continuity tests but putting them on the hFE test on my DMM was a different matter. One measured 500 which slowly rose to over 1,000 and was still going up but I was getting bored and thinking about my battery - say what you like about AVOs but at least if their batteries go you only loose resistance.
The other one was even odder as the meter bleeped and its dial went blank.
I finally tested them with an LED and a couple of resistors. One would fully light the LED with its Base disconnected and it glowed dimly when I repeated the test with another.
The upshot was that the radio finished up with one AF117 and two AF116s. It still didn't work.
I then got on with changing the Hunt's caps and eventually found if it was on full volume and connected to my bench amp, also on full belt, I could just hear Absolute Radio in the wrong place. I thought the trimmers looked odd as several of the cores seemed screwed out a long way and another a long way in.
The alignment proved to be spectacularly out. This was the first time I've had to do the RF side but it's now working very nicely.
All it needs now is a case - DAVID! Seriously, making that will be an enjoyable job.
So it's been an enjoyable day.
- Joe
As soon as I bought this I knew it had been got at as one of the AF117s was missing. I'd got three AF116s out of the R600 - all had had shorts but they seemed to have cleared with due application of ziggies - so I fitted one of those. It still didn't work and I did nothing else to it until today.
I checked the electrolytic caps first and found most of them wanting so changed those. This made no odds either.
I then set about testing the transistors. None had shorts but I was getting some queer results. They all seemed to pass the usual continuity tests but putting them on the hFE test on my DMM was a different matter. One measured 500 which slowly rose to over 1,000 and was still going up but I was getting bored and thinking about my battery - say what you like about AVOs but at least if their batteries go you only loose resistance.
The other one was even odder as the meter bleeped and its dial went blank.
I finally tested them with an LED and a couple of resistors. One would fully light the LED with its Base disconnected and it glowed dimly when I repeated the test with another.
The upshot was that the radio finished up with one AF117 and two AF116s. It still didn't work.
I then got on with changing the Hunt's caps and eventually found if it was on full volume and connected to my bench amp, also on full belt, I could just hear Absolute Radio in the wrong place. I thought the trimmers looked odd as several of the cores seemed screwed out a long way and another a long way in.
The alignment proved to be spectacularly out. This was the first time I've had to do the RF side but it's now working very nicely.
All it needs now is a case - DAVID! Seriously, making that will be an enjoyable job.
So it's been an enjoyable day.
- Joe
