29-03-2021, 12:42 PM
(This post was last modified: 29-03-2021, 12:44 PM by Murphyv310.)
Hi.
Well an early start with this set has given one step forward and ten backwards!
One of the issues I had was the Cossor HT rectifier intermittently arcing so I fitted the NOS GZ34 this morning after quickly running the set up on the existing rectifier. The first thing I noticed was the picture was considerably duller than previously with no lights on and blind closed I could only just make it out, the HT though had dropped to 190v so time to fit the GZ34 The HT was approaching its norm over 300v when bang, one of the EF50 Valve bases in the RF unit flashed over. The base is charred from the G2 to chassis, who would have thought that a plastic type base would do this. So I have now scraped off the carbonisation as best as possible and retried but bringing up the mains on the variac. All seemed OK on this attempt but seeing the screen was a nightmare so I was about to dig out the MW6-2 to get a better idea of what is now now needed when all of a sudden the line collapsed and and a whiff of smoke from the line scan transformer.
I think the set is suffering with long term exposure to damp conditions and this has taken toll of many parts, the mains transformer EHT winding was sparking initially and only by passing current through the winding and having sitting on a tubular heater did it rather surprisingly recover after a few weeks.
Right now I'm stuck as I really think we need an RF unit as I cant see that it will be reliable, it needs a CRT and also the Line scan transformer attended to, its encapsulated as well and I'm not sure if a rewind is possible. I think before spending out on rewinds that we do something with the RF unit, changing the bases is out of the question as I've never seen these PYE ones as spares and they are specials with no room for a standard base, I even looked yesterday at my late friend's stuff yesterday when I was helping out his son for anything I could use for this set.
I've put a lot of hours into this one and now feel dejected that the outcome is bad. So near but so far!!!!
Well an early start with this set has given one step forward and ten backwards!
One of the issues I had was the Cossor HT rectifier intermittently arcing so I fitted the NOS GZ34 this morning after quickly running the set up on the existing rectifier. The first thing I noticed was the picture was considerably duller than previously with no lights on and blind closed I could only just make it out, the HT though had dropped to 190v so time to fit the GZ34 The HT was approaching its norm over 300v when bang, one of the EF50 Valve bases in the RF unit flashed over. The base is charred from the G2 to chassis, who would have thought that a plastic type base would do this. So I have now scraped off the carbonisation as best as possible and retried but bringing up the mains on the variac. All seemed OK on this attempt but seeing the screen was a nightmare so I was about to dig out the MW6-2 to get a better idea of what is now now needed when all of a sudden the line collapsed and and a whiff of smoke from the line scan transformer.
I think the set is suffering with long term exposure to damp conditions and this has taken toll of many parts, the mains transformer EHT winding was sparking initially and only by passing current through the winding and having sitting on a tubular heater did it rather surprisingly recover after a few weeks.
Right now I'm stuck as I really think we need an RF unit as I cant see that it will be reliable, it needs a CRT and also the Line scan transformer attended to, its encapsulated as well and I'm not sure if a rewind is possible. I think before spending out on rewinds that we do something with the RF unit, changing the bases is out of the question as I've never seen these PYE ones as spares and they are specials with no room for a standard base, I even looked yesterday at my late friend's stuff yesterday when I was helping out his son for anything I could use for this set.
I've put a lot of hours into this one and now feel dejected that the outcome is bad. So near but so far!!!!
