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Mishaps In The Trade
1971 Beovision 3200
1971 Bush CTV1120
Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
1971 Bush CTV1120
G6 Update:
A break from TV's over the weekend and a bit of DIY, that's on pause now while I await some materials to be delivered, so back to the G6.
This morning I wired in the rest of the G6 circuit to the 697 LOPT and replaced R4072 with a starting value of 470K, but didn't reduce R4070 from a 22K. I wanted to see where things were, then I could adjust on test.
Feeding in B&W 625 test card, I'm back to where we were before, an unlocked test card and the waveforms are a fair bit off in amplitude.
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Not a word I use, but I'm “Gobsmacked”, I had major doubts in using that extra winding, I was expecting the line bottles to protest visibly. I’m not able to view the pics at work so can’t see how much you are short on amplitude. Do you have frame lock BTW, concentrate on achieving that if you haven’t. Excellent work!
John.
Posted by: @jayceebeeNot a word I use, but I'm “Gobsmacked”
You and me both!
Posted by: @jayceebeeDo you have frame lock BTW
No frame or line lock
Posted by: @jayceebeehow much you are short on amplitude
22 should be 25V p-p, I have 10V & 23 should be 32Vp-p, and I have 6.8V
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Just a quickie, this is the best with some adjustments to the preset controls. I'm now embarking on investigations to narrow down the cause of lock fault, but you can see just how remarkable it is to get this far.
John, you're a clever man sussing out the PYE 697 connections.👍
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Not sure about that, I'm just stealing other peoples ideas. Kudos goes to you for sheer determination.
John.
The syncs look OK-ish at the PFL200, and I sort of managed a float, but it soon starts to drift in ever-increasing speed.
Field osc
One thing that's been bugging me this evening, what impact will this PYE LOPT be having on the rest of the circuit?
Before attempting any line, flywheel balance and vertical adjustments or fault-finding, the G6 manual states the boost needs to be correct, 590V for 625 and 12.5V across R4117 for vertical bias and height.
The voltage across R4117 is only 10.5V and that had a nuts moment when checking, going O/L numerous times before settling. Boost is a whopping great 800V! Neither of these are correct with regard to the G6.
John reminded me we've changed the LOPT line stage from a G6 to a PYE so in this area the G6 is now a G6/PYE hybrid.
Therefore, checking the PYE cct for a boost value and I find that is supposed to be 790V, so the boost we have is correct. However, adjusting the G6's R5040, boost control, it only has minimal effect on boost, 811V at one end and the lowest I can get at the other, is 797V. We replaced the old R5040 a 220K with a 1M.
What's bothering me here and in a wider context of the field and line stage is the G6 manual specifically states boost needs to be set for 590V. What are the consequences on all the remaining, finely balanced G6 line and field circuits, of getting this 200V extra boost, surely this must be a problem? So where do I start? The trouble is I don't know where to start, it's so difficult to know what might or might not be an issue and what might or might not be a red herring.
I've had a chat with John, but it was getting late, so we had to cut short. As I said to John, "What sort of monster have we created". I think this is where the fun now starts, taming the beast.
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To my mind, if the boost voltage is roughly right for the Pye LOPT, then the EHT level will be correct. Reducing the boost at the LOPT will reduce the EHT. So, alternative means may be needed to reduce it after the line stage. For instance, R5034 for the frame stage, R4128 for the flyback suppression may need to be increased to allow a greater voltage drop. I am not sure where else the boost HT goes to, but some experimenting with resistor values might be needed to get it right for other circuits relying upon it ?
Increasing the feedback to the PL509 grid by reducing R5036-7 or increasing the value of C5017 might be an alternative, it may lower the actual produced boost voltage.
This is just my guessing whilst not fully understanding how it is all now operating as a whole... so please be gentle. 😊
To understand the black art of electronics is to understand witchcraft. Andrew.
I have to admit to neglecting to look carefully at the boost circuit closely, I had assumed that the feed to the frame stage wouldn't need attention. It was only when Chris mentioned his concerns I looked and found the PYE didn't use the normal PL508 but a similar design to the 2000 chassis using 2 x BD124s. I also suggested in one of our FB sessions that R5034 would need a value change and also agree that the blanking may need attention but I think the latter can be left until a locked picture is obtained.
Not sure why there is so little range in the boost adjustment, maybe some to do with the amplitude or shape of the drive waveform which is still the G6 design. I think it's OK the way it is at the moment though, if it's not possible to lock the discriminator then it might be necessary to make some major changes here. It's just a shame that the pulse windings couldn't have been lifted from the G6 LOPT as there is an empty limb on the PYE unit for them to sit on.
John.
Typo in the last post, should obviously have been .....lifted from the G6 LOPT.
Moderator note,
Corrected it for you, John. 👍
John.
I picked this not cheap, 697 LOPT this week, its brand new and the pin out appears to be identical, but it has extra windings (see photo 2) where the one I have installed in the G6 does not. Was this a later version of the LOPT? If so what were all those extra windings for? I bought it as I wondered if these additions might be useful to us.
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That new transformer looks to me like the type usually fitted to the 697, as you say just a later version. The one you have fitted to the TV looks like an alternative manufacturer, possibly Weyrad looking at it’s construction. I don’t think there will be any electrical differences though, those two small windings are I expect the +-47v pulses and EHT overwind on the other limb.
John.
It's good to have a spare should the worst happen to the one currently installed, especially the way my luck runs with this TV.
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Finally got back to the G6.
As suggested, increase the value of R5034 (560K) with R4101 at mid-point choosing a value that gave suitable adjustment at the control. First tried a 680K, not enough range, next was 820K that gave a 2" gap at the bottom which could be adjusted with R4101. Then tried 1M, that was too much, so 820K was chosen. As expected though this has no effect on the unlocked raster.
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I found that if I short R4017 to chassis and trim L4501, things improved. However, if I remove the trim tool the mess returns, yes the tool is a correct one. If I remove the short from R4071, the mess returns, after a while things return to a mess anyway. Tried the short of pin 2 of V2002 to set flywheel balance, not much joy with that either.
This video briefly shows what I mean, this is the first time I've managed to control the condition to see what is going on. As I say, it soon goes off into a mess.
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Well changing R5304 has certainly improved matters in the frame stage. You now have frame lock although slightly on edge and the linearity looks great, even the convergence is better than I expected. You’re getting close now just need the line discriminator sorting.
just one thing, the contrast level looks a bit high, it may just be the video but try dropping it slightly as it may be crushing the sync pulses.
John.
The contrast control does nothing noticeable on screen, one might even say it's not working
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Just checked the voltage on pin 7 of V2002 (EF80 line sync amp) it should be 100V for SS or 110/125V for DS, I've 218V! HT3 rail at Jnc of R2137/8/R2125 is 280V about 10V high so acceptable However, other side of R2125(6.8K 7K in circuit)/R2126(10K and tested OK out of circuit) is 255V, other side of R2126 is 218V which is where it should be 100-125V. This cannot be right surely.
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Dare I ask what's going on at the grid and anode of V2002?
More to the point, is the positive potential on the grid of V2002 there?
High voltage on the anode of a valve says to me it’s not doing anything, either nothing going into the grid or cathode not connected, or cathode resistor o/c or gone high if it has one. I’m most likely wrong though, I normally am!
Regards
Lloyd
I think its worth pointing out I'm in the unenviable position of not knowing if I have a real, existing G6 fault or a circuit problem caused by the many changes, not least of which being the PYE LOPT transplant.
Anyway, I got the voltages squared on the Line Sync amp, now I have 88V on the anode, and 12.5 on the cathode, lower than book but acceptable. The anode voltages on the PFL are also 106V and 150V. My immediate problem seems to be in the flywheel discriminator, 0V on X4140 cath and almost double on X4141 Cath at 62V. I faffed around most of the afternoon trying to fathom why, only for John to pop up and remind me this is related to the cct changes for the PYE lopt, so not a fault as such, but a cct mod issue. I now need to figure out the correct value for R4072, we started with 470K that's too low, so that's what's up next, some experimentation.
So bear with me as I work my way through all this, I'm posting this as I go and what I find, to serve to document the conversion/restoration path.
And as John said this evening in one of our FB chats
Posted by: JayceebeeI know but you're tantalisingly close, this bit was never going to be easy. If the worst comes to the worst then we will need to change to the PYE discriminator and we can probably do without that EF80 shaper stage but lets see how far we can get on this tack. Even when you get line lock there are still things to sort. Contrast for one, possible line FB blanking issues and some feed to the blue lateral coils.
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