22-06-2015, 11:18 AM
The 4 generations of the Sovereign are all quite different from each other, so we really do need to know which version he has.
The Gorler tuner tuner in the RP18 is very reliable - you almost certainly wouldn't need to venture in there. But as you've said, there are 4 AF114 beasties on the FM IF PCB. These are easy to remove and zap, and I've yet to have a occurrence of problems.
If it is an RP18, the electrolytic capacitors are usually of the unreliable types. If not blue Mullards, expect to replace a few.
The later sets use BF194/5 types, and are more reliable - although they can fail with low gain. Most FM faults are caused by them. Rather than get into the details here, I'll refer you to an article I wrote which discusses transistor problems: http://www.markhennessy.co.uk/articles/v...istors.htm
Signal diodes are pretty reliable in my experience - a failure of one in a ratio detector should cause distorted audio rather than no audio.
The RP25 (and RP75) had inter-station muting - make sure that's not engaged and/or misadjusted...
I've had the usual faults with passive components along the way. The switchbanks tend to be reliable enough - the FM switching is very straightforward - in most cases it just switches the power to - and audio from - each tuner (the first three generations of Sovereign use separate tuners for AM and FM - the later Sovereign IV did not).
The service manuals for these sets can be found at the Yahoo Hacker Radio group. Registration is free. I've done a fair few of the scans, as have the other mods. (please refer people to the group rather than posting the manuals elsewhere). The Sovereign IV manual isn't brilliant in image quality terms, but we're always looking for a better quality version if anyone has one.
You've said previously that Hacker (and Roberts) sets aren't your cup of tea, but of all the transistor sets out there, Hackers are the easiest to work on by a long way - and the service manuals are a revaluation compared to the others. Give it a go - you might be pleasantly surprised
Weak/no FM counts as just about the worst fault for a transistor set for me. I usually start by injecting 10.7MHz. With a known-good set for comparison, it's easy to determine if the lack of sensitivity is being caused by the front end or the IF, or both. If the front end is poorly, you have the pain of separating the PCB from the tuning capacitor - but again, as awkward as that might be, it's so much better than on other sets.
The Gorler tuner tuner in the RP18 is very reliable - you almost certainly wouldn't need to venture in there. But as you've said, there are 4 AF114 beasties on the FM IF PCB. These are easy to remove and zap, and I've yet to have a occurrence of problems.
If it is an RP18, the electrolytic capacitors are usually of the unreliable types. If not blue Mullards, expect to replace a few.
The later sets use BF194/5 types, and are more reliable - although they can fail with low gain. Most FM faults are caused by them. Rather than get into the details here, I'll refer you to an article I wrote which discusses transistor problems: http://www.markhennessy.co.uk/articles/v...istors.htm
Signal diodes are pretty reliable in my experience - a failure of one in a ratio detector should cause distorted audio rather than no audio.
The RP25 (and RP75) had inter-station muting - make sure that's not engaged and/or misadjusted...
I've had the usual faults with passive components along the way. The switchbanks tend to be reliable enough - the FM switching is very straightforward - in most cases it just switches the power to - and audio from - each tuner (the first three generations of Sovereign use separate tuners for AM and FM - the later Sovereign IV did not).
The service manuals for these sets can be found at the Yahoo Hacker Radio group. Registration is free. I've done a fair few of the scans, as have the other mods. (please refer people to the group rather than posting the manuals elsewhere). The Sovereign IV manual isn't brilliant in image quality terms, but we're always looking for a better quality version if anyone has one.
You've said previously that Hacker (and Roberts) sets aren't your cup of tea, but of all the transistor sets out there, Hackers are the easiest to work on by a long way - and the service manuals are a revaluation compared to the others. Give it a go - you might be pleasantly surprised
Weak/no FM counts as just about the worst fault for a transistor set for me. I usually start by injecting 10.7MHz. With a known-good set for comparison, it's easy to determine if the lack of sensitivity is being caused by the front end or the IF, or both. If the front end is poorly, you have the pain of separating the PCB from the tuning capacitor - but again, as awkward as that might be, it's so much better than on other sets.
