So, done a bit of work. Replaced a couple of Hunts capacitors that were hiding behind the UHF tuner. Hoovered out the many dead spiders! Unfortunately I've misplaced my isolating transformer so instead I'm injecting a signal to pin 8 of the video amplifier PCL84 valve using a Raspberry Pi powered from a power bank so it's completely isolated.
Note the teletext interference, I completely forgot about this! This is the same Raspberry Pi I used for Teletext 50 at Cambridge last September.
Picture is quite dim but the CRT seems to test ok. I noticed the image during the initial warm up seems quite large, the PL36 line output valve looks like it has a serious amount hours on it so could be weak.
Also, PL36?! How old is this thing?! I thought the PL36 was more of a 1950s set line output? I was expecting either a PL500 or PL504. 🤔
My mistake, it's a 30P19 with the writing mostly gone:
Also, PL36?! How old is this thing?! I thought the PL36 was more of a 1950s set line output? I was expecting either a PL500 or PL504. 🤔
Not sure how long the PL36 was in use but my Pye 11U uses one and that is 1964.
The PL36 was used in the ITT/KB VC53 chassis which is early 70s.
Crikey! According to one valve circuit book I was looking at, it was apparently considered obsolete by the early 60s. Then again, if it works...
The PL36 is the series heater version of the EL36 which crosses to the 6CM5.
In Oz, the 6CM5 was used in the first TVs in 1956. Early alternative was the 6DQ6 but even AWA moved to the 6CM5 by the early 60s.
It remained the only line output valve used in the last of the hybrids into the early 70s. By everybody!
The go-to damper was the 6AL3, apart from AWA who used the single-ended octal 6AU4
This happy state of affairs simplified the service van stock no end!
I suppose it's like when you see a 555 timer in a modern circuit. Heh, just think when the 555 was introduced in 1972 there were still hybrid sets using a variation of the PL36!
Managed to lose EHT when having a look at the 30P19. I had to remove the efficiency diode to get to it and seem to have disturbed the dryest of dry solder joints on the efficiency diode's socket:
😮
I need to install the new capacitors properly anyway so I'll take the whole board out and give it a good going over.
Good lord! The dry joints! 😱 Quite how this worked as well as it did is beyond me.
Some pins from the efficiency diode socket had jumped out of the PCB and were physically pressing the socket away so it wasn't even going to get an intermittent connection. I've sorted that.
Fully installed most of the capacitors that were tacked in. The PCB foil is really weak so even if the pads aren't lifting up I bent the legs through the hole and down the PCB track to the next component and soldered it there too.
Left a couple of caps on the solder side as there wasn't much space left for them.
Regarding the EHT, although the LOPT winding is ok I am concerned about it's longevity. I have a couple of new old stock doublers Malc Scott gave me so I might see if one works ok with this and have it as a backup if the winding eventually fails. Getting flashbacks to the Rediffusion Guildford!
@wayned I think these sets were early on in the flow solder by machine times. Certainly the previous 1959 model was with 'Doris' only fitting the larger parts. There is a youtube video that shows the trouble they went to.
GEC 405 line Television factory Coventry 1960 - YouTube
I found my BT302 needed a lot of resoldering I remember removing the frame output valve and the holder almost came with it!
I haven't forgotten about the photo of the back cover, it is just that my set is 'well stored' at the moment!
Pictures of the back cover . Hope this is helpful
Rich.
Pictures of the back cover . Hope this is helpful
Rich.
Perfect! That's exactly what I needed, thanks 😀
I'll make a template out of cardboard first. There's a few differences but I'm guessing the basic shape of the original is similar. I noticed the vertical hold etc controls are sideways on mine but there's cut-outs on the metal frame to clear the knobs on a set like yours.
Yes I think that PCB predates the wave solder technique, which when set up properly really gets the job done.
Funny to see the flux still there and the way it seems to have reacted with the soldermask. Guess they still had a bit to learn about how to make PCBs in those days.
Today, when designing a PCB, you get a lot of help from the PCB CAD tools like Altium Designer that have manufacturability rules.
Those early GEC PCB’s had a reputation for the tracks lifting with any rework, perhaps something to do with heat and age with the glue. It must have been ok in production but after a few years in the set it degraded.
It could also be the unfamiliar repair of them aswell.
Frank
@nuvistor I wonder what Racal's excuse was then? Every bit of Racal test gear I've worked on had that problem.
I despair sometimes: the Yanks had Tektronix and HP. Who did we have? Telequipment and Marconi...
Have to say, watching the GEC 405 line TV assembly line film @slidertogrid Rich posted above has certainly given me a lot more appreciation for the set. Yeah, the PCB isn't the best by today's standards but by 1960's standards it's ridiculously advanced!
I did also spot perhaps a bit of a flaw in the technique, the components being automatically cut by machine... It seems to have left a lot of things, particularly the valve bases very short and only just able to get through the PCB to be soldered, which I suspect made them prone to dry solder joints. The efficiency diode socket in particular I had to "feel" with the soldering iron in the pool of moulton solder to check it was actually getting through. Still, it's lasted the best part of 62 years...
I suspect this set is from 1962 as that's the oldest date code I've found on any of the components. A couple of valves date from 1965 but the Mullard ones look original and they have a date code of 1962.
That date would make it a very early dual standard set. The chassis design is very like the previous 405 only set. These early dual standard and convertible sets are very uncommon now. The valve UHF tuners were a bit low gain, lots of sets were never converted and became obsolete. back in the early '70's as a lad I remember seeing quite a few sets of this era dumped and the rag and bone man usually had at least one on his cart, off to burn it for the copper. The later 1000 series and 2000 series dual standard GEC models are still rare to find but are more common. Of course you will need one of each of those now... 😎
@slidertogrid yeah, I honestly thought it was a '64 as that would tie in with BBC 2's launch but it's clearly earlier than that. I suppose people bought "HD Ready" TVs long before HD was launched...
According to a guy at work a 19" TV in 1962 was serious money. Mainly because as a kid he wanted one and there was no way his parents could afford something like that. 9-12" seemed more common then.
@wayned In 1962 a 19" Murphy was 66 Guineas, a 23" 76 Guineas. Not outrageous for the time when you consider how much sets were ten years prior. However, I do find your idea of most people having 9" or 12" sets at that time somewhat fanciful - the tubes would long have died and the lack of ITV would be a major issue against them (I can only think of one 12" set with ITV and that's the Bush TV24C).
The BoE inflation calculator suggests the equivalent value of the 19" Murphy is £1,270; there were dearer Murphy radiograms for sale that same year - and by some margin.
@wayned We were installing 19 inch sets in 1962, possible 23 inch but I don’t recall them. Servicing 17inch sets seemed to be the norm with a few 21inch ones.
Some sets were being sold as convertible but many had controls on the front for 405/625 but connected to nothing, see the Bush TV105, the TV115 slightly later had the switch connected for the line speed but nothing for the tuner/IF, it needed a UHF tuner and replacement IF strip for conversion, never converted either of those models. The TV125 around 1964 just required a UHF tuner if it didn’t have one fitted from new, I think I fitted very few of those.
There was an Ekco set around 1962 that just required tuner, again I never fitted one and only saw a few of them.
Winter Hill transmitted BBC2 from late 1965, we were selling fully switchable sets by that time but interest in BBC2 was not great. Many who had bought a new set and aerial were disappointed with BBC2 at that time.
Frank
@cathovisor Ah! Now bear in mind this is up north (Gateshead, next to Newcastle) and we're talking proper working class here! ITV (Tyne Tees) didn't start until 1959 and before then not many people could justify the cost of having a TV with one channel. Sure, there were a few but for the vast majority the radio was enough.
Could also be that the guy at work was in a particularly poor area, of which there were many around Gateshead.
