11-08-2023, 03:50 PM
This week has been a bit odd, things not going to plan, weird faults and things going pop.
It started with the Sky Queen with an odd valve. I am more convinced than ever that it was made with the wrong valve installed.
Needing a DF96 that I have not got it was time to swop to another set.
A Murphy B485 transistor. Spent a frustrating half hour getting it out of its "leather" carry case, why did they make these such a tight fit?
Removed from its plastic covers, takes two 6v batteriesPP6s not to hand but I put it on a power supply. Stone dead of course, not a peep.
Checking the output transistors revealed one dead one. Now these are a matched pair of XC131s in there own purpose designed heat sink. The manual says must be changed in pairs. Nothing suitable in stock of course. So I removed the duff one carefully. Not easy as the heat sink has two 6BA nuts and bolts firmly clamping everything together. Now only the emitter lead is sleeved, and is quite long compared with the others.
Dropping it onto the parts tray I saw the sleeving move in an odd way. Inspection showed that the wire was broken inside the sleeving and a good look with the loop at the ends showed the wire had rusted through! I knew the wires on Ediswan's transistors were steel leads but rust in one spot inside a plastic sleeve when there is no rust anywhere else in the set? Testing the transistor again revealed that it was just fine, after all that fiddling.
So refitted, still dead and time to do a bit of intuitive component checking starting with the Hunt's electrolytic capacitors. Quickly finding a 2uf and a 50uf totally useless as capacitors I replaced them with new radial ones, tested before soldering in neatly.
Switch on to see how we were doing showed 250mA draw, too much.
Suddenly a loud pop and the cap of the new 50uf went sailing across the workshop. Odd behaviour for a new part, I picked another one, tested it and fitted it. Switch on with finger and thumb on the capacitor, its getting warm!
Check, and, yes, it is connected the right way round but marked the wrong way! Turn it round and its fine, the whole of my stock, some 30 odd parts, all labelled incorrectly.
Having wasted too much time achieving absolutely nothing, it was time to call it a day, call an end to the week and come and moan on here.
What a poor week.
It started with the Sky Queen with an odd valve. I am more convinced than ever that it was made with the wrong valve installed.
Needing a DF96 that I have not got it was time to swop to another set.
A Murphy B485 transistor. Spent a frustrating half hour getting it out of its "leather" carry case, why did they make these such a tight fit?
Removed from its plastic covers, takes two 6v batteriesPP6s not to hand but I put it on a power supply. Stone dead of course, not a peep.
Checking the output transistors revealed one dead one. Now these are a matched pair of XC131s in there own purpose designed heat sink. The manual says must be changed in pairs. Nothing suitable in stock of course. So I removed the duff one carefully. Not easy as the heat sink has two 6BA nuts and bolts firmly clamping everything together. Now only the emitter lead is sleeved, and is quite long compared with the others.
Dropping it onto the parts tray I saw the sleeving move in an odd way. Inspection showed that the wire was broken inside the sleeving and a good look with the loop at the ends showed the wire had rusted through! I knew the wires on Ediswan's transistors were steel leads but rust in one spot inside a plastic sleeve when there is no rust anywhere else in the set? Testing the transistor again revealed that it was just fine, after all that fiddling.
So refitted, still dead and time to do a bit of intuitive component checking starting with the Hunt's electrolytic capacitors. Quickly finding a 2uf and a 50uf totally useless as capacitors I replaced them with new radial ones, tested before soldering in neatly.
Switch on to see how we were doing showed 250mA draw, too much.
Suddenly a loud pop and the cap of the new 50uf went sailing across the workshop. Odd behaviour for a new part, I picked another one, tested it and fitted it. Switch on with finger and thumb on the capacitor, its getting warm!
Check, and, yes, it is connected the right way round but marked the wrong way! Turn it round and its fine, the whole of my stock, some 30 odd parts, all labelled incorrectly.
Having wasted too much time achieving absolutely nothing, it was time to call it a day, call an end to the week and come and moan on here.
What a poor week.
Boater Sam.
