03-03-2013, 06:40 PM
Good evening Gentlemen.
Having tidied the Greenhouse, started up the Propagator, chopped down the Raspberry canes, applied BFB, disposed of all debris, mowed (yes it's been that warm and dry), ferried people about and eaten a light but nourishing lunch I decided I could have a go at my stuff.
So .....
Fear not young Joe, I still have the old Electrolytics so I could re-stuff them. However, I quite like the collars, and at least I didn't hang the new ones in the wiring.
Unfortunately Al your missive arrived while I was on the job, as the Bishop said to the Actress. However, I did broadly follow your approach - see below.
Yes Lawrence, it is a bit 'upside down', in fact fairly typical in my experience of the (non-electrical) DO of that era. Everything is actually joined to the right places, but not necessarily logically.
Step one was to measure the voltages properly and apply some Switch Cleaner to the pots - see attached.
After that the -150 set up OK and the -85 settled down to the correct value.
Similarly the +300 set up OK.
The +400 was a bit high but then it us 'Unregulated'.
The +365 was OK.
The +150 didn't respond to RV601 at all although the voltage on the Slider and the Grid of V607 (Pin 7) did vary. After much head-scratching and measuring I gave V607 a strong wiggle in the base and a blast of Switch Cleaner, and it all came to life and set up as it should.
I was standing there congratulating myself on a job well done when R634 started to singe. I'm not quite sure why at this stage. It measures OK and the voltage across it is about right. Possibly I'd pushed it against an adjacent Resistor as it hasn't happened again.
There are indeed a lot of high value Resistors in there which could do with checking and possible changing, along with a few Hunts and Plessey Caps. RV601 is near the end of its travel so that area in particular will warrant some investigation.
So what next? It's looking promising so I suspect some more cleaning and measuring as Al suggests is probably a good idea, followed by the EHT Generator. I can't actually measure the 8.5kV at the moment, apart from dabbing the AVO on.
Just in passing I'm working on it on the Bench upside down. As one of the characters in 'The Dambusters' said 'This is bloody dangerous'. I kept thinking 'I'll just lean my hand on the Chassis rail while I look at the meter'. That's a bad idea 'cause there's a long Tag Strip with all the HT Voltages on it above the Electrolytics and near to the edge. I've avoided it so far, but I fear it's just a matter of time
Having tidied the Greenhouse, started up the Propagator, chopped down the Raspberry canes, applied BFB, disposed of all debris, mowed (yes it's been that warm and dry), ferried people about and eaten a light but nourishing lunch I decided I could have a go at my stuff.
So .....
Fear not young Joe, I still have the old Electrolytics so I could re-stuff them. However, I quite like the collars, and at least I didn't hang the new ones in the wiring.
Unfortunately Al your missive arrived while I was on the job, as the Bishop said to the Actress. However, I did broadly follow your approach - see below.
Yes Lawrence, it is a bit 'upside down', in fact fairly typical in my experience of the (non-electrical) DO of that era. Everything is actually joined to the right places, but not necessarily logically.
Step one was to measure the voltages properly and apply some Switch Cleaner to the pots - see attached.
After that the -150 set up OK and the -85 settled down to the correct value.
Similarly the +300 set up OK.
The +400 was a bit high but then it us 'Unregulated'.
The +365 was OK.
The +150 didn't respond to RV601 at all although the voltage on the Slider and the Grid of V607 (Pin 7) did vary. After much head-scratching and measuring I gave V607 a strong wiggle in the base and a blast of Switch Cleaner, and it all came to life and set up as it should.
I was standing there congratulating myself on a job well done when R634 started to singe. I'm not quite sure why at this stage. It measures OK and the voltage across it is about right. Possibly I'd pushed it against an adjacent Resistor as it hasn't happened again.
There are indeed a lot of high value Resistors in there which could do with checking and possible changing, along with a few Hunts and Plessey Caps. RV601 is near the end of its travel so that area in particular will warrant some investigation.
So what next? It's looking promising so I suspect some more cleaning and measuring as Al suggests is probably a good idea, followed by the EHT Generator. I can't actually measure the 8.5kV at the moment, apart from dabbing the AVO on.
Just in passing I'm working on it on the Bench upside down. As one of the characters in 'The Dambusters' said 'This is bloody dangerous'. I kept thinking 'I'll just lean my hand on the Chassis rail while I look at the meter'. That's a bad idea 'cause there's a long Tag Strip with all the HT Voltages on it above the Electrolytics and near to the edge. I've avoided it so far, but I fear it's just a matter of time
