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Forum 135

[Closed] Philips 563A Radio/Television Table Model

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Brian Cuff
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Thanks Marion - I've learnt a lot on this one. Most of all, take MORE notes and pictures than you think are necessary - several times I got caught, lacking a picture of a specific area but being rescued by my notes/sketches and vice-versa but there were times where I had to wing it.

Pursuing the lack of line scan, I remembered that the line oscillator and OP valve g2 volts are switched off during radio mode by a wafer on the RF chassis. This feed, of course, has to get to the TB chassis via the interconnect tag strips which were not in circuit. A croc-lead short between the appropriate pins produced the volts on the two valves and the EHT started to climb and finished at 4.5kV. This could be varied using the line hold control up to 6kV!

I bolted the two chassis together yesterday and connected the two interconnect tag strips together. So now it's testing time, firstly without the CRT. I powered it up via a Variac with a voltmeters on HT and EHT and an input signal from an Aurora. Firstly tone built up slowly followed by EHT but only 4kV. To check that the line oscillator was on frequency, I fed the 'scope CH1 with the CRT g1 video signal triggered at 2x line rate and held the CH2 probe near the line O/P valve. No lock - but with adjustment of the line hold control, the timebase pulled in and locked solid and the EHT rose to 6kV. The frame TB was also checked with the 'scope locked to frame and adjustment of the frame hold produced a solid lock. So time for the CRT!

I stood the double chassis on its end using the very heavy mains transformers as "props" and fitted the yoke and CRT base on the CRT placed at the side of the chassis. On powering up - yippee - first light!! Vision drive is OK, the two timebases lock and brightness & contrast controls work - I really am surprised at this as there are normally problems due to component tolerances etc., not to mention wiring errors. The frame scan is a bit low with height at max so that needs some investigation - it could be that the EL33 output valve is on the low side - I will check that tomorrow (after I have fitted the replacement heated towel rail in our bathroom!!). The CRT seems to be nice and bright and that after a total of 5 minutes in operation - hopefully it will improve with use.

As an aside, there are 4 or 5 original (1948) TCC low voltage electrolytics in this set and very often, these are dried out. I checked them for ESR and capacity and all 5 were in excellent condition.

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Posted : 15/06/2014 11:06 pm
Brian Cuff
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I didn't realise how long ago I last posted in this thread! This set seems to have taken ages - but I'm nearly there!
The pics show the progress so far and I'm now ready to re-mount the radio dial bracketry. I removed it because it stands about 150mm above the rest of the chassis so would have got in the way somewhat :) .

I had two outstanding problems one of which I solved - lack of control range on the brightness control - it couldn't be turned down low enough. This turned out to be the decoupling electrolytic on the cathode of the CRT (grid modulation). I had checked it for capacity and ESR and it looked OK but the leakage was such that it dragged the cathode down too far towards 0V and the picture was far too bright.
The other problem I haven't solved so I need help here.

This is the TV aerial input circuit:

The problem is that the picture suffers from random line tearing and general euch unless I ground the outer of the aerial feeder - then it goes quiet and stable. Why? I must add that this is one of the most sensitive sets I have met. It picks my sig gen up with the coax just hanging off the generator with the level set at -50dB! Any ideas genleman (and lady, of course).

Here's the chassis nearly ready for encabination!

I'll take some off-screen pictures for the next post.

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Posted : 07/07/2014 6:28 pm
AidanLunn
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I guess you could try checking the screening around the LOP stage?

 
Posted : 08/07/2014 2:02 pm
Brian Cuff
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The interference is not line locked, Aidan but of more of a random RF character! I've just noticed that there is a whole paragraph in the manual on setting up the RF stage which involves several frequencies and tweaks on the Ls and Cs around V1 so I will have a go at that this afternoon though I don't hold out too much hope.

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Posted : 08/07/2014 3:00 pm
AidanLunn
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The interference is not line locked, Aidan but of more of a random RF character! I've just noticed that there is a whole paragraph in the manual on setting up the RF stage which involves several frequencies and tweaks on the Ls and Cs around V1 so I will have a go at that this afternoon though I don't hold out too much hope.

In that case it's definitely in relation to how sensitive the TV is. Surely even a well adjusted receiver shouldn't be that sensitive? I could imagine a TV that sensitive also displaying IF harmonics and other interference from other components within the TV too if it wasn't in your capable hands :qq1

Could the interference limiter be set to medium or high? Are there any screened components where the screening could have gone missing?

Everything around the RF amp stages OK, as if I've learnt this right, the RF amp valve(s) should also increase discrimination between the wanted signals and other interference.

 
Posted : 08/07/2014 4:31 pm
Brian Cuff
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Here are a couple of pictures which demonstrate the dramatic difference between the two conditions - no need to guess which is which:

I understand what you are saying about sensitivity and harmonics etc. but internal radiation normally reveals itself as a form of moray patterning, not the dreadful spiky effect shown here. Blocks of lines are displaced by a millimeter or so in some fields but not others which suggests interference of some sort. I will examine the input components in detail - perhaps there's an open circuit in the primary of the input transformer! I'll have a look after I walked the doc :)

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Posted : 08/07/2014 6:26 pm
Cathovisor
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There's a wee bit of me still inclined towards there being some form of instability, Brian. Put a 'scope on it - and if you can, send the set "black" rather than TCC, it may be easier to spot. Sometimes TCC is too complicated when fault finding; there's a lot to be said for a plain raster or a simple staircase.

 
Posted : 08/07/2014 7:30 pm
AidanLunn
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Wow, definitely an RF fault!

For what it's worth, I do notice a pattern of the line tearing on the vertical bars of T/card C, it doesn't seem random, even though the vertical "shape" of the distortion is different between those towards the top of the pattern, and those at the bottom.

Sort of reminds me of that fault where the whites around the left and right edges of the testcard are pulling those lines to the right.

 
Posted : 08/07/2014 7:38 pm
Refugee
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I was thinking along the lines of scoping some decoupling capacitors.

 
Posted : 08/07/2014 8:16 pm
Brian Cuff
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Thanks for the suggestions, guys. Every comment helps.
If I stuff the full output of an Aurora into the set, the cr*p goes away! but with 6dB attenuation, it's back but on a reduced scale so it definitely seems to be overall gain dependent which does suggest some sort of instability. I cannot see any spurious oscillation in the RF section so I'm no farther forward. When looking at the drive on the vision output EBL31, there seems to be no jitter on the sync leading edges so maybe it's something to do with the sync separator stages. I'll have a look tomorrow as the footie will be starting soon!!!

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Posted : 08/07/2014 9:53 pm
Valvebloke
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... I'll have a look tomorrow as the footie will be starting soon!!!

30 minutes in and it's all over Brian. Are you back working on the set now :bba ?

VB

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Posted : 08/07/2014 11:09 pm
Brian Cuff
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I stuck it out for the full duration, Graeme. It did get a bit boring in the second half but at least they got one goal. So the 563A will have to wait until the morning when I can get down to it again!

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Posted : 09/07/2014 12:02 am
Valvebloke
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I stuck it out for the full duration, Graeme. It did get a bit boring in the second half but at least they got one goal. So the 563A will have to wait until the morning when I can get down to it again!

Yeah, so did I :-(.

I'm going to stick my neck out though and say that Germany weren't completely brilliant. True, their foot-to-foot passing was nearly faultless, their shape was well planned and maintained and their goalkeeper never gave you a moment's doubt (not even when he let one in, which really wasn't his fault). But they could be penetrated, they lacked drive more than once and they had some dodgy long balls. And Ozil still didn't deliver. Furthermore Brazil had some quality moments too. But when they were bad they were bad absolutely beyond belief. I've seen Didcot Town play better than that. Dear oh dear oh dear ...

VB

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Posted : 09/07/2014 12:23 am
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