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1100 man · 7th Feb 2018, 12:49 am

Good evening,
I have now repaired the charred hole in the EHT overwind's former with a small drop of Araldite. After removing all the remaining traces of carbon, the former was replaced inside the overwind and the process of building up a dozen or so coats of insulating varnish began.

While this was happening, I turned my attention to the chassis and the motley collection of components that had found their way in there.
I must say, from an access point of view, it's a dream to work on. The top panel, which contains all the signals circuitry, hinges up & clips in position. The side panel with the controls & Fireball tuner, hinges outwards: they have even marked the screws to remove with arrows cut out of the metalwork. The whole thing, complete with tube, sits nicely on its side, giving excellent access to the underside wiring. All very nicely thought out: it's a bit ironic that a set with such good access rarely seemed to need fixing!!

Have a look at the first picture below. On top of the Mazda valve box is a grey object made of thick card and of a strange shape. This was taped to the top of the chassis near the speaker transformer. Does it have anything to do with this set and if so what? It looks like some sort of special tool.

Whilst dismantling the LOPT, I discovered that it's windings were not exactly as per the VT161 circuit (in R&TV servicing). It seemed to have an extra winding and was more similar to the VT157/ VT160 from the same book. The scan coupling cap was a 1.0mfd and the tuning cap a 800pf, which are also the same as the VT157/60.
Interestingly, the VT157/60, uses a very similar circuit but a slightly different valve line up. It uses a PL36 rather than the tiny PL81 but the entire thing is on two PCB's. Rather a brave move I would think!
Being in the same R&TV book, is it reasonable to assume that both chassis were in production simultaneously?
My VT161 has a large hole for a PL36 base but a plate with a PL81 valve holder has been spot welded over the top. I imagine the original design used a PL36.
All the best
Nick

7th Feb 2018, 12:49 am	#6
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: Marconiphone VT161 17" TV Good evening, I have now repaired the charred hole in the EHT overwind's former with a small drop of Araldite. After removing all the remaining traces of carbon, the former was replaced inside the overwind and the process of building up a dozen or so coats of insulating varnish began. While this was happening, I turned my attention to the chassis and the motley collection of components that had found their way in there. I must say, from an access point of view, it's a dream to work on. The top panel, which contains all the signals circuitry, hinges up & clips in position. The side panel with the controls & Fireball tuner, hinges outwards: they have even marked the screws to remove with arrows cut out of the metalwork. The whole thing, complete with tube, sits nicely on its side, giving excellent access to the underside wiring. All very nicely thought out: it's a bit ironic that a set with such good access rarely seemed to need fixing!! Have a look at the first picture below. On top of the Mazda valve box is a grey object made of thick card and of a strange shape. This was taped to the top of the chassis near the speaker transformer. Does it have anything to do with this set and if so what? It looks like some sort of special tool. Whilst dismantling the LOPT, I discovered that it's windings were not exactly as per the VT161 circuit (in R&TV servicing). It seemed to have an extra winding and was more similar to the VT157/ VT160 from the same book. The scan coupling cap was a 1.0mfd and the tuning cap a 800pf, which are also the same as the VT157/60. Interestingly, the VT157/60, uses a very similar circuit but a slightly different valve line up. It uses a PL36 rather than the tiny PL81 but the entire thing is on two PCB's. Rather a brave move I would think! Being in the same R&TV book, is it reasonable to assume that both chassis were in production simultaneously? My VT161 has a large hole for a PL36 base but a plate with a PL81 valve holder has been spot welded over the top. I imagine the original design used a PL36. All the best Nick Attached Thumbnails