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Old 3rd Apr 2018, 9:37 pm   #41
Philips210
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Default Re: Philips G23T210A

Hi

I had a look though another servicing article in Television magazine again by Les Lawry-Johns, this time on the single standard version (300 chassis) and Les states that when there's an interwinding short, it gives the impression that the boost capacitor is short. The article is in the June 1974 issue and can be found at the link I provided in post #29.

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Old 3rd Apr 2018, 9:40 pm   #42
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Default Re: Philips G23T210A

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Originally Posted by space_charged View Post
I agree its a nice set, though I confess to being biased! I'm a great fan of Philips stuff and have loads of it. G6 (single standard version) a couple of G11s, two 17TG100s (one restored).
Hi.

Is your G6 working? It would be great to see some pics of this set, maybe in another thread.

Regards
Symon
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Old 3rd Apr 2018, 9:44 pm   #43
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Default Re: Philips G23T210A

Hi Symon,

Yes when I first measured the boost capacitor in circuit, it does indeed read short. I thought I had found the fault, but out of circuit it was fine. Looking at the circuit, it shouldn't read low resistance due to anything across it. In fact it reads 23 ohms.
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Old 3rd Apr 2018, 9:47 pm   #44
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Default Re: Philips G23T210A

One other trouble spot on the 210/300 is the heater winding for the EHT rectifier. I remember it used to arc away due to insulation breakdown. The EHT lead could also breakdown as well. It's worth replacing this with good quality EHT cable. I used to save the EHT leads etc from duff diode split LOPTs as it came in handy for repairs to vintage equipment.

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Old 3rd Apr 2018, 9:58 pm   #45
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Default Re: Philips G23T210A

It's looking like the LOPTx unfortunately.
The group of windings DEF should be isolated from the group GHJKL. It would seem there's breakdown in the insulation between these windings. Rule out any other external influences first before finally condemning the LOPTx.

Regards
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Old 3rd Apr 2018, 10:10 pm   #46
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Default Re: Philips G23T210A

Yes Simon, from my reading of the circuit these groups of coils should not be connected. I did resistance checks against the service information shortly after I got the set, but I only checked the coils with published resistances.

I'll check and isolate the transformer from the rest of the set to prove, one way or another, if it is the LOPT.

I'll be back (after I've done that)...

Actually, I can't see any components that could possibly produce 23 ohms across the boost capacitor. There could be some sort of short in wiring insulation but its very improbable. I'll look of course.

Last edited by space_charged; 3rd Apr 2018 at 10:22 pm.
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Old 3rd Apr 2018, 10:26 pm   #47
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Default Re: Philips G23T210A

Hi Charles,

Can I just bring up the comment from Dazzlevision about the two 8.2Meg resistors.

In fact there are also a couple of other high value carbon resistors in the same area I think from memory 1.2Meg and either 1.5 or 1.8Meg

I strongly recommend that you replace these resistors with specifically high voltage resistors before you do anything with the LOPT.

They absolutely MUST be high voltage types. I used Farnell 3Kv rated resistors.

I fell fowl to this problem on a 210 and it took a great deal of time and several good LOPT's before I revisited the brand new resistors that I had fitted, only to find that they were not up to the voltage requirements and had failed. Of course you do not then check them again because you have already changed them.
These resistors must be well within tolerance otherwise the feedback will not be correct and it is this feedback that makes the line circuits do their job in the 210 chassis.

If after everything you are sure it is the LOPT, I still have a spare good tested one here.

Mike...
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Old 3rd Apr 2018, 10:53 pm   #48
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Default Re: Philips G23T210A

Certainly on a G6 with a defective LOPT there's absolutely no line whistle on 625 lines with the PL509 glowing with the boost volts no higher than 30V or so.
Switching to 405 gives clear loud line whistle however!

I can still hear 625-line whistle so this was obvious.

I'd imagine the 210 will be the same. Sadly it seems Philips sets from the Style 70 series to the G8 are prone to LOPT failure.

Brian
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Old 3rd Apr 2018, 11:08 pm   #49
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Default Re: Philips G23T210A

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If after everything you are sure it is the LOPT, I still have a spare good tested one here.
Well I'm now down to removing ALL the wires on the LOPT tags and then checking that the short (about 23 ohms) remains. Assuming the short remains, and if you are offering, I'd like to discuss that (privately) with you.

As to the 8.2Meg resistors, yes I was warned about those and that they need to take a high voltage. I will heed what you say about the additional ones you mention.

The stabilisation loop does depend on these and also of course the vdr which is the reference for the whole feedback loop. Where does one get replacements for those in these days of microprocessors I wonder. My service information gives no details about what they are. Their closest living relatives are power zeners I'd guess. In fact I put a 12V power zener across the VDR that sabilises the LT for the transistors, just in case.
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Old 3rd Apr 2018, 11:25 pm   #50
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Default Re: Philips G23T210A

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I'd imagine the 210 will be the same. Sadly it seems Philips sets from the Style 70 series to the G8 are prone to LOPT failure.
I got my G6 as a leaving presie from a holiday job at a TV repair workshop. It had LOPT failure (surprise). The G6 got its EHT directly, no tripler. As a result, the overwind was a highly stressed component very prone to failure. It was also a fairly high impedance soure, so was stabilised by the infamous shunt stabiliser triode (otherwise known as an X-ray tube). I ripped it out along with the massive overwind. I then wound a MUCH smaller overwind which drove a tripler. I've still got the set to this day.

Back to the 210, does anyone know why these LOPTS fail? In my 17TG100 Philips had SUCH confidence in the reliability of its LOPT that the whole thing could be replaced without a soldering iron. It was plug replaceable!
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Old 4th Apr 2018, 9:45 am   #51
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Default Re: Philips G23T210A

Hi

Where possible I use the Philips VR series of metal glaze resistors in HV circuits. They're the blue coloured resistors that uniquely use a yellow band for the tolerance designation. There was VR25 1/4W, VR37 1/2W and VR68 1W. They are excellent resistors and stand up well the high voltage. The link to the pdf for these is here https://www.google.co.uk/url?sa=t&rc...ugn1yoysEZunHo

Regarding the LOPTx in the 210/300 chassis, I am sure there was an alternative made by a different company that didn't suffer from the interwinding short problem of the original Philips transformer.

Regards
Symon.
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Old 4th Apr 2018, 10:13 am   #52
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Default Re: Philips G23T210A

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Originally Posted by space_charged View Post
The stabilisation loop does depend on these and also of course the vdr which is the reference for the whole feedback loop. Where does one get replacements for those in these days of microprocessors I wonder. My service information gives no details about what they are. Their closest living relatives are power zeners I'd guess. In fact I put a 12V power zener across the VDR that sabilises the LT for the transistors, just in case.
The VDR is a Philips/Mullard type, usually E298ZZ/06. I have some if you need one, although they very seldom fail.
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Old 4th Apr 2018, 1:18 pm   #53
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Default Re: Philips G23T210A

I used to keep a very generous stock of Philips 210. Bush 640 and Philips G8 LOPT's.

None of these transformers were expensive and replacement was quick.

The 8.2m resistors used to give a lot more trouble in the style 70 series but of course we have moved on decades. John.
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Old 4th Apr 2018, 4:12 pm   #54
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Default Re: Philips G23T210A

Thanks for the information about the VDR in the line drive stability loop. I agree they don't usually give trouble. I remember replacing one in a set (single standard Defiant I think) in the hopes it might cure a LOPT problem I was having. It made no difference. The problem was that the LOPT got HOT. Hot enough to soften the coating on it. It never failed and worked fine. Maybe they all did that, but I thought it might be a line drive problem. Line drive is one of these things that has to be right. Low is BAD, high is bad.

Very interesting the inter winding shorts were a major "feature" of this set. This type of set was my family's first TV set. We had it for three years or so until - guess what - it died of line output transformer failure. Also interesting that the short probably does NOT result in a shorted turn, just an improper joining of two sets of coils that should be isolated. This sort of short would NOT show up in the clever LOPT tester setup because (out of circuit) there need not be any damping caused buy the short. Only a CLOSED loop of wire round the core would cause damping (he he).

Today's job is to draw the LOPT connections (I always do that) and photograph it before LOPT removal. Then apply my trusty AVO 8 MkII between any of GHJKL and any of FED.

Once again, thanks to you all both for your interest and your help.
Ill be back...
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Old 4th Apr 2018, 5:28 pm   #55
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Default Re: Philips G23T210A

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The smoothing caps each have sort of blister (safety valve) with some crusted electrolyte round it. I think I'll have to replace them.
I wouldn't bother, they always seem to look a bit like that. Smoothing problems in this model tended to come from the clamp working loose; the cans of the big electrolytics are earthed through it in some versions.

One of the wires from the tube base is held in its correct place by a rubber band, this makes sure that it does not pick up stray fields which upset the picture. There was a service note for this, which went something like "bent verticals: rubber band broken". Only Philips...

From experience, all the big transformers (frame, line, sound) are problematic in this series. The frame transformer has an extra feedback winding which is in the linearity circuit, when it fails you get massive height that won't reduce.

These were the last big screen monochrome dual standard Philips sets, the 300 models (e.g. G20T300) were the later single standard version of the same basic idea. No more mono hybrids from them after that.
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Old 4th Apr 2018, 5:48 pm   #56
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Default Re: Philips G23T210A

Oooh I just LOVE the rubber band bit. I'm chuckling no end over that. You've made my day!
I think the rubber band in mine is long gone, so do you know which wire(s) it was attached to and where at its other end? Just in case I get near having any verticals to be bent!

Chas

PS, its a bit past the 1st of April
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Old 4th Apr 2018, 7:46 pm   #57
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Default Re: Philips G23T210A

See picture below, showing said rubber band (arrowed) as fitted to a similar set that I once owned.
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Old 4th Apr 2018, 8:09 pm   #58
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Default Re: Philips G23T210A

I was just about to say, but you can see from the pic in #57 its the video o/p to crt pin 7 cathode that needs support of the rubber band. Also if the linearity feedback winding on the frame o/p transformer goes o/c causing excessive height, this often causes flashover and carbonization on the back of PCL805 valve base.

Alan
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Old 4th Apr 2018, 9:15 pm   #59
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Default Re: Philips G23T210A

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Originally Posted by murphymad View Post
f after everything you are sure it is the LOPT, I still have a spare good tested one here.
OK, I have now removed the LOPT and have checked it for a short between DEF and HGJK. You can see the AVO probes on G and on D. The reading is about 23 ohms, so yes there is a confirmed inter winding short on my transformer.

Mike, I will send you a private message shortly.
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Old 4th Apr 2018, 10:49 pm   #60
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Default Re: Philips G23T210A

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I wouldn't bother, they always seem to look a bit like that. Smoothing problems in this model tended to come from the clamp working loose; the cans of the big electrolytics are earthed through it in some versions.
Yes only one of the cans has a soldered negative tag, the other relies on the clamp; not great. They both looked thoroughly nasty. Given I'd have to remove them to reform them, I just made up a board for some modern ones. OK, its a departure from authentic, but if they did go off, they'd make a fair mess of the insides of my otherwise very clean telly. These days, I don't enjoy a great big bang as much as I used to!

Also I really HATE mains hum on a telly - either vision modulation hum or timebase hum annoy me!


Thanks Alan for the picture showing where the laggy band goes! I'll be sure to fit one to my set.
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