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Old 3rd Oct 2020, 4:22 pm   #81
AdrianH
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Default Re: My first foray into Old model TV repairs.

Need to think of what other caps I need to make up an order. On the cabinet, does anyone know what colour the varnish/stain would have been?

Also on the base of the unit I have just removed what I would have said were slide in pieces of wood! as though the TV could have had a wooden legged frame to site on, does anyone know of such?

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Old 3rd Oct 2020, 4:46 pm   #82
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Default Re: My first foray into Old model TV repairs.

Even in low voltage areas those caps are unreliable. I had problems with the flywheel sync in Perdio Portarama. I went for the diodes then noticed one of these lurking in the sync circuit, whipped it out and changed it.....perfect sync!
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Old 3rd Oct 2020, 7:00 pm   #83
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Default Re: My first foray into Old model TV repairs.

Change that cap! That is the type that are described as 'looking like resistors'. They are seriously bad! Looks good so far. J.
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Old 3rd Oct 2020, 7:10 pm   #84
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Default Re: My first foray into Old model TV repairs.

If the cap looks like a resistor, then it no doubt is by now.
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Old 3rd Oct 2020, 7:49 pm   #85
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Default Re: My first foray into Old model TV repairs.

Quote:
Originally Posted by AdrianH View Post
Tube seems a bit soft
There doesn't look to be much 'soft' about that tube!

You've been very lucky with the tube and line tranny in this set, you've done very well with it!
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Old 3rd Oct 2020, 8:48 pm   #86
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Default Re: My first foray into Old model TV repairs.

OK so a few more component changes, the small capacitors got replaced with some 2n2 Mustard caps at 400 Volts, but I also found a Brown Hunts 0.1 that I had missed just underneath the metal rectifier part of the sync circuit.

the small caps first all tested no resistance but had capacitance between 75pF and 22pf considering they should have been 2nF then I should find the gain of the tuner a bit better and I will test that later. The 0.1 was 0.122uF but had a resistance of 2M9 Ohm, so glad I finally found that. It all helps keep the set a bit more reliable for the future.

On the screen, I guess for a 66 year old set it is not bad, but I know that my camera compensates some what, I am able to go from Black to white in the grey scale, but perhaps I am just used to our Pan flat screen where the contrast ratio is prity good?

I seem to think that the vertical lines on the test card are better now and that the text is easier to read than before changing the 0.1uF cap, perhaps not. I'll have to figure what all the sections in the HH2 card are checks for.

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Old 3rd Oct 2020, 9:15 pm   #87
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Default Re: My first foray into Old model TV repairs.

Quote:
Originally Posted by Heatercathodeshort View Post
The sound I.F. mentioned by David was a known trouble spot. I changed loads of them as a young lad in the 60's.

Murphy Radio recommended that the original capacitor is replaced by a Hunts W99 type, the original crunchy brown one! I always fitted ceramics and had zero problems. Faulty decoupling can cause no end of odd symptoms. John.
On warmup the V410 emitted a sort of howl which was caused by this cap and we changed every one that passed through our hands. The V410 was a great performer and one of the best looking sets ever made. Pure class.
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Old 4th Oct 2020, 12:00 pm   #88
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Default Re: My first foray into Old model TV repairs.

It can be an advantage to print off a copy of the circuit diagram them mark the components with a highlighter as you replace them. This way you are unlikely to miss one.
The Ferguson manual gives the function of every component, a feature that is sadly lacking in many manufacturers data. I tend to write down what their function is and the symptoms of their failure. An A4 pad keeps them for future reference. This can assist when working on television chassis that may not be familiar. Let your good work continue. John.
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Old 4th Oct 2020, 5:51 pm   #89
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Default Re: My first foray into Old model TV repairs.

The biggest I can print is A4 so I tend to work from the screen for the circuit as I can zoom in. I use the printed page for the text sections in the manual and have tried to keep some notes, but I am doubt I am really fault finding, basically just replacing old caps at present, I can suspect what is causing various faults but as this is the first real time with a valved TV it is quite difficult to follow some aspects.

For example I need to understand if this is a fault in the frame output and where I should be looking.

When I turn on the TV and start to get an image the frame is not full height and is also distorted. It will take quite a few minutes to gradually get to a reasonable picture, for example:-

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This is an image when just providing a screen raster, now even with poor valves that need a bit longer to warm up and give a better emission I would expect the top and bottom of the screen to be straight and not bending as thay are.

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This is slightly later, and after a few more minutes the screen will be full but with a slight curve bottom right, I can also see a sort of screen trapezoid shape.taller on the left then the right of the screen. I do not know if this is normal although I suspect not, but what fault can give that I do not know, I am wondering if there could be an issue with the scan coils to do that, but can not figure in my head what would cause it for it to get better the longer I leave it?

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Old 4th Oct 2020, 6:14 pm   #90
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Default Re: My first foray into Old model TV repairs.

I would look at the HT voltage, see if that's correct first. Check the PY82`s to make sure they are both fairly even output and their resistors are correct.
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Old 4th Oct 2020, 6:59 pm   #91
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Default Re: My first foray into Old model TV repairs.

HT as in 14KV or HT as in the 192 Volts measured with an Avo 8, the first is a bit above my DVM and at 11 Meg resistance I would need to find a lot of resistance for that to get up to 14KV but possible i guess.

On the normal HT I have 205 Volts from both PY82's after the 40 and 42 Ohm resistors, approx 209 and 207 on the anodes of the PY82's and 192 Volts on the 200uF cap after the choke. To be honest I have taken that value as being good as we have 235 Volts nominal mains and I am on the 240-250 Volt tap.

The part I can not understand is the curve in the frame line I would still expect it to be linear unless the frame sawtooth has a hump in it, which is possible but can not check.

I have left the TV running for some time now and this is the picture.
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So the lines are now straight but slightly shorter on the RHS. I need to check the coils are sat on the tube both sides.

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Old 4th Oct 2020, 7:34 pm   #92
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Default Re: My first foray into Old model TV repairs.

That looks a bit like the EHT charges in the CRT are not fully stabilised.
Rather like this old thing from about 02.00 onwnards

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Old 4th Oct 2020, 8:12 pm   #93
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Default Re: My first foray into Old model TV repairs.

Slight distortion of the raster could be caused by the scan coils. I doubt it will be objectionable on a normal picture. That odd effect as the set comes on, I've had that caused by residual magnetism or even a high static charge on the CRT that dissipates as the EHT comes up. Also check the earthing of the CRT (if it has any).
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Old 4th Oct 2020, 8:19 pm   #94
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Default Re: My first foray into Old model TV repairs.

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That looks a bit like the EHT charges in the CRT are not fully stabilised. Peter
You beat me to it Peter. Dampness on the CRT screen is the usual cause of this 'oil on water' effect. A slightly low tube emission that will improve with use, aggravates it. The slightly out of spec scan coils is not unusual with these 60 odd year old models. Scan coils are best left alone as disturbance may cause an insulation break down. Looks good! John.
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Old 4th Oct 2020, 8:40 pm   #95
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Default Re: My first foray into Old model TV repairs.

OK watched the video, yes it was like that at one time just nowhere near as fast to clear.
I have checked the aquadag, (if I have the correct term) and using a DVM on resistance to chassis I have typically found that any point is less than 3K Ohm to chassis so I was thinking that is OK.

One thing I have that I did not change was the EY51 diode on top of the LOPT, it seemed like a job to change it, but it is still an option.

This may be a daft question but I could series up 21 x 10 meg resistors to the DVM although how accurate that would be is anyone's guess.

If I put my hand on the front of the CRT glass I can distort the screen?

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Old 4th Oct 2020, 10:29 pm   #96
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Default Re: My first foray into Old model TV repairs.

Static charges. With a stiffer beam the symptoms do not manifest themselves. They may well vanish when the tube ages a little. J.
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Old 4th Oct 2020, 10:49 pm   #97
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Default Re: My first foray into Old model TV repairs.

Well I have just used a ladder of 10Meg resistors and I get the EHT to be 15 KV even if it was out by 10 percent it is in the correct area.. I am contemplating trying some new old stock ECL80's as the ones fitted tested low emission so would be could be slow to come to life. It also looks to fold the top and bottom of the frame if that points to anything else.

But in general I am happy with progress, I can get a picture, it does not seem as sharp as expected but again not really sure what I am expecting for the age of the TV. The cabinet is back together, now need to sand the rest down and recolour and varnish, I think a dark mahogany?

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Old 5th Oct 2020, 11:52 am   #98
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Default Re: My first foray into Old model TV repairs.

Just a quick dry fit up of the TV to the cabinet, before I do sanding, stain and varnish.
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Old 5th Oct 2020, 7:07 pm   #99
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Default Re: My first foray into Old model TV repairs.

Hello group, please I would like more information on this:-

Quote:
Originally Posted by peter_scott View Post
That looks a bit like the EHT charges in the CRT are not fully stabilised.
Peter
Quote:
Originally Posted by Sideband View Post
I've had that caused by residual magnetism or even a high static charge on the CRT that dissipates as the EHT comes up.
Quote:
Originally Posted by Heatercathodeshort View Post
Static charges. With a stiffer beam the symptoms do not manifest themselves. They may well vanish when the tube ages a little. J.
I did a test, which to me seems to confirm this? The set has now been switched on for several hours, it started off with the irregular pattern and then gradually filled out and stayed like that for some time before I shut the brightness off. Left the set running and have gone back to it and turned up the brightness and the effect is there again, if I turn the brightness up full it quickly dissipates and a full screen is again established.

Is there anything I can do for this, re-coat with Aquadag (can I even get it?) to get a lower resistance to deck presently between 1.5 and 3K Ohm, take the aquadag to under the clamp?

Reading up on the EY51 suggests if that goes faulty when the brightness is advanced the picture would expand and this is not the case.

John, You mention it may go better when the tube ages, should this be with a white raster to promote emission or with dark?

Just wondering what to try?

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Old 5th Oct 2020, 7:23 pm   #100
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Default Re: My first foray into Old model TV repairs.

I wonder if your Aquadag is properly earthed? I think there should be a beryllium-copper (or other spring) strip linking the 'dag to the chassis.

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