22-12-2015, 06:03 PM
Hi Mike,
That's good news
Yes, that handle is original. The earlier RP25s came with that. As did the later RP18s (the original Sovereign). Then it changed to the type with the Rexine strip, but actually there were two types of those - one that pushed down like this one, and the later type that was secured by the screws. Confusing when you don't know! The later type requires you to slide off the chrome covers, and these are perfectly rectangular. Earlier ones had a distinctly tapered appearance, and that's how you can tell at a glance whether the handle pushes off or needs to be unscrewed.
It's worth saying that although the blue Philips/Mullard capacitors are generally very reliable, I note a couple of other types - probably DALY? These are known for leaking heavily. Of the two I can see, one is the decoupler for the AM IF panel - heavy leakage can bring down the HT and cause weak signals (and if the ESR goes high, it can cause whistles and squeaks as you tune across the band - and ultimately can stop LW working). I'd change this on sight, but that's obviously a personal decision. The other one looks like the output coupling capacitor. If it leaks, it'll increase the quiescent current, but hopefully won't do much harm beyond this. If it falls in value (or rises in ESR) then the audio quality will be affected. Again, I'd replace it on-spec, but that's just me
I was confused by the earlier comment regarding the treble control. That 10Ω resistor is just a protection resistor for the headphone socket, and a bad earth there should only affect the headphone itself. I suspect that was a (happy!) coincidence. One thing to watch for with these sets - I've had a loss of bass before, where the bass control has had virtually no effect on the audio. I traced it to the bass control itself. With the bass turned to maximum, there was less than 1kΩ of resistance to chassis - there should be 50kΩ or thereabouts. I took the pot out and could see nothing wrong, and it righted itself as a result of being disturbed. I strongly suspect a tin whisker!
So, I'm wondering if a similar thing was at play here? I can't immediately see how, but as I say, I can't see it being caused by that resistor...
I completely agree with your comments about the build quality. Those people who don't understand need to get one to restore. And if they are still unconvinced, they should try fixing a Roberts R707! Or, just about any other competing transistor radio from the same era.
Good luck with the rest - I'm sure it'll be good news all round before the week is out
Mark
That's good news
Yes, that handle is original. The earlier RP25s came with that. As did the later RP18s (the original Sovereign). Then it changed to the type with the Rexine strip, but actually there were two types of those - one that pushed down like this one, and the later type that was secured by the screws. Confusing when you don't know! The later type requires you to slide off the chrome covers, and these are perfectly rectangular. Earlier ones had a distinctly tapered appearance, and that's how you can tell at a glance whether the handle pushes off or needs to be unscrewed.
It's worth saying that although the blue Philips/Mullard capacitors are generally very reliable, I note a couple of other types - probably DALY? These are known for leaking heavily. Of the two I can see, one is the decoupler for the AM IF panel - heavy leakage can bring down the HT and cause weak signals (and if the ESR goes high, it can cause whistles and squeaks as you tune across the band - and ultimately can stop LW working). I'd change this on sight, but that's obviously a personal decision. The other one looks like the output coupling capacitor. If it leaks, it'll increase the quiescent current, but hopefully won't do much harm beyond this. If it falls in value (or rises in ESR) then the audio quality will be affected. Again, I'd replace it on-spec, but that's just me
I was confused by the earlier comment regarding the treble control. That 10Ω resistor is just a protection resistor for the headphone socket, and a bad earth there should only affect the headphone itself. I suspect that was a (happy!) coincidence. One thing to watch for with these sets - I've had a loss of bass before, where the bass control has had virtually no effect on the audio. I traced it to the bass control itself. With the bass turned to maximum, there was less than 1kΩ of resistance to chassis - there should be 50kΩ or thereabouts. I took the pot out and could see nothing wrong, and it righted itself as a result of being disturbed. I strongly suspect a tin whisker!
So, I'm wondering if a similar thing was at play here? I can't immediately see how, but as I say, I can't see it being caused by that resistor...
I completely agree with your comments about the build quality. Those people who don't understand need to get one to restore. And if they are still unconvinced, they should try fixing a Roberts R707! Or, just about any other competing transistor radio from the same era.
Good luck with the rest - I'm sure it'll be good news all round before the week is out
Mark
