I was supposed to going to do some more work on @crustytv Chris's Vanden Plas yesterday but as my 10 year old's school was on strike I was on parental duties.
I get a frantic message from a friend who's promoting a 1970s event in a shop and his "vintage colour TV that he bought from Ebay about 10 years ago" has lost all colour so I end up loaning him my Pye CT450/G11 and now I have something to fix:
And erm...
That could've ended badly! 😱
Yikes, indeed it could've, EHT going sky-high (40-50kV) and a punctured CRT neck. Those Greenies are pants, even NOS ones need to be binned, as many members have found here.
Wayne, you need the correct construction type caps for that position due to the high frequency line pulses they are subjected to. I've got the special 5n1 1.6kV flyback tuning caps in stock, you'll need 4. You can have four of them F.O.C. you can collect next week.
p.s.
And you'll find these of use
https://www.radios-tv.co.uk/philips-g8-2/
https://www.radios-tv.co.uk/servicing-the-g8/
https://www.radios-tv.co.uk/vintage-electronics-blog-forum/g8-output-transistor-balancing/
p.p.s
Look in this document to identify the exact year of the G8 on your bench, that way you can tie it down to the correct circuit diagrams you need.
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These ones appear to be 2n7:
If you have any of these in stock that would be hugely appreciated! Also, I find it reassuring that those caps you have are the same type I installed in my G11!
I *think* it's a 1974, it doesn't have "VCR" as channel 6.
It's had a lot of work done to it in the past, the big mains smoothing cap has a date code of 1985. Also the LOPT is clearly a replacement:
Haven't had much of a chance to have a really good look at this set though, just an initial inspection.
These ones appear to be 2n7:
DOH! of course you're correct, I just checked mine. I could have sworn they were 5n1, I wonder what set I'm getting confused with. I don't think I have any 2n7 as the last ones I had were used on my PYE CT-219. I believe they are readily available online though.
https://www.aliexpress.com/i/4000397331049.html
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That's a lovely looking set. Can't say I've seen that particular model before, harks back to the original 520 but with 550 series panels. I'm surprised that those caps haven't blown the CRT open yet! By sounds of it he's run it a few times to have seen it with colour.
Chris - some G8s did use the 5n1s. My 26" 522 uses 2 5n1s so you're on the right track.
I think you will find that some G8's used two 5n1's in series (making 2n5). It was probably a way of reducing the line pulses across the individual caps.
I wasn't going bonkers, that is indeed what was done on the 520 series. I could be wrong, but I believe it is acceptable for Wayne to replace the 4x 2n7 with the 2 x 5n1.
First picture shows the 4 x 2n7 and below the 520 series line drive panel indicating 2 x 5n1, which is shown on the cct.
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@crustytv aha! Cool. In that case I'll definitely take you up on the offer of the 5n1 caps.
Brain currently in work mode rather than TV mode 😳
My mate also gave me a bag of bit he got from the Ebay seller:
Apart from the tube, tuner and case there's probably enough here to build another G8!
As Chris @crustytv mentioned to me, the LOPT caps look like the 2x 5n1.
For those of you playing along at home here's a few things, firstly the model number:
Note the much newer capacitor poking out of the convergence controls underneath.
The tripler seems to have a date code of 1974?
Tube seems to be an original Mullard:
It's pretty clean inside, it's had a lot of work done to it and there's the odd modern electrolytic capacitor dotted here and there.
One thing that is confusing me though is the colour scheme on the front of the case:
I haven't seen this with black surrounding the screen and wood speaker grill/controls surround in any literature. Could this be a "bitsa" TV I wonder? 🤔 Would explain why the seller had an entire extra chassis in a carrier bag.
Interesting, the G22K554/01 is stated as 1973.
Maybe the tripler was a replacement the following year. I've heard it recounted by ex trade, the G8 used to get through LOPTS and triplers.
I haven't seen this with black surrounding the screen and wood speaker grill/controls surround in any literature. Could this be a "bitsa" TV I wonder?
That's because you're not using the resources of Radios-TV 😉 There is a whole section dedicated to the G8 and no, the TV is as intended, here's the specific brochure spec page for the 554/01
The G8 resource https://www.radios-tv.co.uk/philips-g8/
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That's because you're not using the resources of Radios-TV 😉 There is a whole section dedicated to the G8 and no, the TV is as intended, here's the specific brochure spec page for the 554/01
The G8 resource https://www.radios-tv.co.uk/philips-g8/
I wouldn't care, but I've been reading both that and the stock faults page a lot! Totally missed that. 😯
Interesting, the G22K554/01 is stated as 1973.
Maybe the tripler was a replacement the following year. I've heard it recounted by ex trade, the G8 used to get through LOPTS and triplers.
The serial number suggests 32 week of 1972
Could be like cars, they introduce one in 1972 for the "1973 model year" I wonder?
@wayned Normally the model years would start at the beginning of the previous September.
I was a little confused by the layout of the four 2n7 caps on this board at first, but I think I've fathomed it out and this may help someone else in future:
Note there's a central point where the four 2n7 caps connect to. This would be test point 64 as shown in the schematic @crustytv posted above and caps 589 and 592 aren't populated when using two 5n1 capacitors. A single 5n1 is shown at cap 545 and another 5n1 at cap 546 in the schematic.
The board on the spare chassis which seems to be from a later G8 (possibly 1975) and has a different layout:
No central point but note the bottom two connection points are seperated. The top part acts as the central point, test point 64 in the schematic.
Thanks to @crustytv I now have some replacement 5n1/5100pF capacitors. It's interesting to note that these fit in place of the four 2n7 caps if you stagger them so they're both soldering to the middle but one is soldered to the top and another to the bottom:
They seem to fit better than they would in the later G8s with two 5n1s as standard.
New caps in, TV worked fine...
...untiI heard a ticking sound coming from the tripler and then no EHT! 🤣
@wayned and I were chatting about this in Ratchat, and I've sorted him with NOS G8-Tripler for next time he's over performing surgery on the Allegro.
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Rediffusion Mk1 tripler will fit the G8 if focus lead extended.
This TV is actually quite famous now! It was not only used in the artwork for the audio play "Simon Perkins' Lurgy" but the switch sounds and crackles were used as sound effects in the play itself!
Rediffusion Mk1 tripler will fit the G8 if focus lead extended.
That's good to know, cheers. Hopefully the one Chris is supplying will do the job.
