Convergence rings on crt neck replacement - Page 1
Forum section: electronics / repair

author: kokodin
author_rank: Regular Contributor
timestamp: July 05, 2017, 07:12:07 am
content: Hello.I have question, that might be kind of strange.I do have an old crt tv with working buy cracking and falling apart static convergence rings/purity rings. And i have fairly new set of rings from a crt pc monitor.My tv have 8 rings setup and was produced domesticaly in Poland in the 80's, so the entire crt is a little bit unique (Polkolor A56-701X they were produced mostly for export by the way) comparing to the outside world constructions. But non the less, crt should work on the same principle, regardless of being socialist or capitalist product.However the ring assembly from that pc monitor have only 6 rings and is quite a bit shorter, rings themselves are thinnerThe question is:Can i use 6 ring assembly in place of old 8 ring assembly? Or should i look for 8 ring assembly?How to find the good focal point to install different kind of assembly if possible?Neck diameter is the same by the way.Those rings falling apart is a common problem for over 20 years old polish crts, but i have a fairly fresh tube and i would like to save this tv, because they were fairly common when i was small, and sentimantal value is quite high for me. Also they are getting quite rare , because it is the lowest spec model that were produced, which people were commonly throwing out, or "upgrading" with extra modules (remote controll from other domestic tv models and so on) not so long ago.edit************************************Since i have another ring assembly core from identical crt of a died tv, kind of brittle plastic but otherwise ok. There is also the option of replacing all rings on 8 rings assembly with 8 new rings from two 6 rings assemblies. They would be different thickness but with the shims included in those 6 rings assemblies overal length of a 8 ring setup could be fairly close to the oryginal one. I have no idea about magnetic poles and field strength though.

author: fourtytwo42
author_rank: Super Contributor
timestamp: July 05, 2017, 01:03:14 pm
content: I honestly cannot imagine anybody on here has experience with this! But my advice would be the time honored "suck it and see" approach as I cannot see any damage will be caused. I think replacing the existing 8 ring set with another the same is favorite, don't forget to take lot's of pictures from all angles before disassembling itThere are some vintage websites likehttp://www.vintage-radio.net/forum/index.phpthat might be able to help you more

author: Ian.M
author_rank: Super Contributor
timestamp: July 05, 2017, 01:57:58 pm
content: IIRC, convergence assemblies for delta gun and inline gun tubes aren't interchangeable, so check they have the same gun arrangement. Also the PC monitor CRT was probably manufactured with greater precision so its convergence assembly is likely to have insufficient adjustment range for the older, cruder TV CRT. I agree that internal damage to the tube is unlikely so suck it and see.

author: CJay
author_rank: Super Contributor
timestamp: July 05, 2017, 02:57:21 pm
content: Use the rings from the original 6 ring assembly on the holder for the 8 ring assembly, if there are magnets on the old holder too (sometimes they had a few small magnets on 'spikes' poking out of the convergence ring holder) you may need to swap those onto the 'new' holder too.The poles of the magnets will be different between PIL and Delta gun arrangement tubes so you'll need to swap the rings and shim them so they don't move with vibration, put masking tape under the holder so you don't over tighten the clamp..You could also silicone the rings in place on the broken holder and save yourself the hassle.I can't find a decent picture that shows the gun arrangement on your CRT but a general rule of thumb is that a 110 degree tube will have a PIL gun assembly, older, larger CRTs will have a 90 degree tube and a delta arrangement, you can confirm this visually, the guns will be 'in line' across the tube neck, a Delta will have the guns arranged like a pyramid, usually (always?) with one gun on top where 'top' is the orientation of the tube that puts the anode cap at the top.

author: tronde
author_rank: Frequent Contributor
timestamp: July 05, 2017, 03:26:55 pm
content: A56-701X is PIL. The Polcolor tube seems to be a joint veture with Thomson. From my memories some 30 years ago, the magnet ring assembly on PIL-tubes was more or less drowned in varnish to keep them fixed. It might be you can use an assembly from a different tube, but I guess you will get some funny looking colours in the picture. The "P" in PIL stands for precision and they had far less room for adjustment than 20AX or 30AX tubes.

author: stj
author_rank: Super Contributor
timestamp: July 05, 2017, 05:23:08 pm
content: i can link you to monitor manuals that cover this, but is the neck the same diameter?and does the monitor have an extra "rotation" coil between the convergence assembly and the yoke?

author: kokodin
author_rank: Regular Contributor
timestamp: July 05, 2017, 08:13:45 pm
content: The whole deflection assembly consists of coils, metalic ot ferrite collar in between, some passives and plastic casing with glued on magnets slices all over the inside, most likely for each yoke done by hand in factory. Those canot be moved. There are also 2 horisontal magnets glued on the outside and 4 screwed in magnets 1 in each corner (those magnets have sideways field polarisation) . The whole asemby is hold on back of the tube with 4 screws atached to some plastic colar permanently atached to the tube. There is no other movable parts on this assembly.On the ring piece there is 4 pairs of identical looking rings and locking plastic ring on the pc crt i had 3 pairs in a set on similar assembly and another two closer to the deflection coils, i also get those, because it might be that 4th pair on my oryginal assembly (whole part is located very close to deflection coils on that crt). i have salvaged 3 broken pc monitors that were roting in my work storage , waiting for scrapers, so i have 3 sets of rings labeled "6" 3 sets of rings labeled "4" 3 sets of rings labeled "p" and 2 set of those close to the deflection coils rings. And yes this is pil tube 110* deflection, sockets were identical as on those pc monitors , so was the neck diameter. And that why i had this idea.I will try to build my own 8 ring set and see what happens, i know where not to touch to not get shocked and how to discharge the tube.Thanks for help i will report in few days.