@michael-dranfield If the bcl pot is burnt, then one half of the thermal cutout is o/c. The 100mfd 25v cap on the PL509 base will be u/s.
ok so I Studied the circuit diagram as as soon as I found where the beam current is sensed I knew what the fault would be , beam current is sensed at the cathode of the line output valve via a 10 Ohm 1 watt carbon resistor which is bypassed by a 150uf 16 volt Phillips capacitor and as I thought the cap was open circuit, oddly enough the 10 ohm was ok given that its 10 percent tolerance carbon but i swapped it for a metal film anyway, switched on and hey presto up comes a raster, its lacking in green with poor linearity so now I need to get the box connected to the set so i can display a picture and sort out the other faults, however that wasn't the end of the problem !!!!!!
So I tried to be clever, big mistake , I wanted a cap in keeping with the rest of the set for originality, I found a Phillips 150uf but rated at 63 volt that looked just like the one I took out, now its was in a draw of caps I have had since I was a kid in fact I can tell you where these came from , why is it I can remember things from 50 years ago like it was yesterday but i cant remember what i had for tea yesterday ?
these caps came from BI-PRE PAK in something like 1978 , the winter to be precise and it would have been a Wednesday because thats the day I didn't go to work after school, the shops in Buxton all closed half day on a Wendsday, anyway I battled through heavy snow to get home from school and when I arrived home my mum said the postmans been when I was out and has put a card through the letter box, well I couldn't contain my excitement I picked up the card and straight out back into the snow for the one mile round trip to the sorting office to collect the parcel, I think Bi pre pak called these Tebocasy parcels and cost about £4 for so many kilos or assorted random parts , many of which I still have to this day, in those days ordering stuff took about a week I first had to buy postal orders from the post office and send them off with the order .
Anyway so with my very old new capacitor fitted , you can see whats coming, about a 60 seconds after the raster appearing the capacitor exploded, I dont think it could take the current passing through and it heated up rapidly so I had to revert to a modernish Japanese cap , the voltage across the cap running is less than 3 volts , interestingly enough I have examined the etched foil of the cap and the surface is covered in micro fine black pinpricks so it would have appear to suffer some degradation over time .
these caps came from BI-PRE PAK in something like 1978
Bi-Pre-Pak goes back further than 1978 - I had a quick look at some old copies of Practical Wireless from 1978 and it was shortened to Bi-Pak by then: I ended up going back to the end of 1974 to find Bi-Pre-Pak!
However... would the cap you fitted have gone "bang" if you'd reformed it first? It's something we seem to forget to do with "modern" components.
Whilst I couldn't immediately find the acronym you mention, I think it was TECASBOTY - The Electronic Component and Semiconductor Bargain Of The Year?
@michael-dranfield Did you check the bcl side of the thermal cut out? If it is o/c this cap goes bang.
A TV restorer friend of mine Pete just picked up a HUGE cache of mostly-late-60s components, including thousands of polyesters and electrolytics. The polys (about 1/3 Mustards) will all be fine but he is expecting that he will need to check / reform most of the electros prior to use. Except for the Elna caps that almost always come up good.
Blue Philips electros of that vintage are often bad.
Pete is a single dad and it's about time he had some luck!
It could well of been earlier than 1978 yes, If I have a search round I may even be able to find the post office counterfoil for the postal orders, how about that!!!
I didn't reform the cap no, I just assumed with less than 3 volts across it and not been connected between a supply and ground the cap would reform itself if left running for a while.
before I studied the circuit too closely I realised the 10 ohm cathode bias resistor was not returned to ground and when I measured it was atcually sitting a few ohms off ground, now I see where the arrow points to I see it is returned to ground through the heating coil in the thermal cutout, so yes I had in fact allready established the cutout was OK.@michael-dranfield Did you check the bcl side of the thermal cut out? If it is o/c this cap goes bang.
I always suspect non electrolytic caps as I have loads of brand new vintage ones here that are faulty, brown hunts types which I always assumed were pretty well sealed that are leakey, and those that were used for mains suppression where the cases have cracked despite never been out the packet.A TV restorer friend of mine Pete just picked up a HUGE cache of mostly-late-60s components, including thousands of polyesters and electrolytics. The polys (about 1/3 Mustards) will all be fine but he is expecting that he will need to check / reform most of the electros prior to use. Except for the Elna caps that almost always come up good.
Blue Philips electros of that vintage are often bad.
Pete is a single dad and it's about time he had some luck!
If I have a search round I may even be able to find the post office counterfoil for the postal orders, how about that!!!
Now that takes me back - postal orders. In my case, usually going to Xeroza Radio for components...
Zerola radio, I thought I recognised the name!!!!!
Xeroza Radio (later T. Powell) were great - all the prices included postage so you could literally sent them a postage stamp to pay for a single transistor and they'd send it to you!
The first IC I bought (a 741) and LEDs came from them, as did many others.
Ah Tom Powell, I know now, use to buy a lot of semis from him when I opened the shop in the 80s, he got throat cancer and ended up with a voice box, my buisness partner got quite friendly with his sister and she use to give up updates on Tom, eventually he ended up in a nursing home where he died.Xeroza Radio (later T. Powell) were great - all the prices included postage so you could literally sent them a postage stamp to pay for a single transistor and they'd send it to you!
The first IC I bought (a 741) and LEDs came from them, as did many others.
The connector is no problem , I can make those from a couple of valve bases , I noticed in the translator box there is 5 wires connected .You'll need two pairs to connect the TV to the box, one pair have the 8.9Mhz vision and the other for the audio, those female McMurdo octal cable mount sockets are hard to find. Those boxes were designed for the version of the cable system which has an FM carrier for audio, the TV would have been used with the system that had high level AF audio distribution. Those boxes were widely available in the nineties as they were useful as TV sound tuners with little modification, getting a 1V CVBS signal needed a buffer amplifier.
ok , Looking in my box I have 5 wires connected but on the psu there is no high frequency modulator fitted and the back of the box has a single phone socket fitted also but there is no phone socket on the TV , if I connect the 5 wires to the TV will this work, or is this not the right box for the TV, I cant attach photos at the moment as I left my phone at home and im on a pc right now.
When i worked on the Rediffusion mk1 test rig the video signal fed from a Grundig FG5E pattern generator was fed direct into the S/F panel via a pad/filter.
