12-07-2017, 05:49 AM
i've been replacing a load of electrolytics. The designers have made some rather odd choices of values and voltges but most are utterly non-critical.
Oddities include some (relatively) close tolerance electrolytics in the frame timebase and strange values like 75uF 9V on the EHT board. That got repalced by a 100uF as I can't see any reason for a closer tolerance. There are also quite a few tantalum beads which are now replaced with ordinary aluminium parts. A fair number of caps listed as tants in the manual are actually horrible black Callins. Tants are expensive so why on earth were they using them at all where it obviously didn't matter.
A fair number of 0.5uF low voltage electrolytics were used. All have now been replaced by polyester which happen to fit very nicely in the holes. At the time of manufacture, electrolytics would have been cheaper and smaller so fair enough.
The line timebase board that belongs to the set has the original square output transistors. It has also suffered a bit of a burn up around the line shift and A1 supply areas. There are missing components and somebody has clearly abandoned a repair. Probably many years ago. Judging by the soldering somebody has also remvoved and replaced the jellypot LOP transfomers. I also have a spare line timebase PCB that uses the alter transistors. Looks much cleaner though it has an odd looking mod that was clearly done at the factory. There's what looks like a small diode soldered directly across the top of one of the WW resistors and an electrolytic wired to one end. The cap is supported fairly crudely on top of the system switch solenoid. I haven't yet traced the circuit but it's definitely not in the manual.
Oddities include some (relatively) close tolerance electrolytics in the frame timebase and strange values like 75uF 9V on the EHT board. That got repalced by a 100uF as I can't see any reason for a closer tolerance. There are also quite a few tantalum beads which are now replaced with ordinary aluminium parts. A fair number of caps listed as tants in the manual are actually horrible black Callins. Tants are expensive so why on earth were they using them at all where it obviously didn't matter.
A fair number of 0.5uF low voltage electrolytics were used. All have now been replaced by polyester which happen to fit very nicely in the holes. At the time of manufacture, electrolytics would have been cheaper and smaller so fair enough.
The line timebase board that belongs to the set has the original square output transistors. It has also suffered a bit of a burn up around the line shift and A1 supply areas. There are missing components and somebody has clearly abandoned a repair. Probably many years ago. Judging by the soldering somebody has also remvoved and replaced the jellypot LOP transfomers. I also have a spare line timebase PCB that uses the alter transistors. Looks much cleaner though it has an odd looking mod that was clearly done at the factory. There's what looks like a small diode soldered directly across the top of one of the WW resistors and an electrolytic wired to one end. The cap is supported fairly crudely on top of the system switch solenoid. I haven't yet traced the circuit but it's definitely not in the manual.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
