Novice's first TV restoration - Bush TV53 - 63

[Mike Phelan]

Chris
Is your HT supply OK? Are the scan coils pushed right forward against the CRT flare?
I think the setting-up you have already done is fine; what effect does moving the focus lever have (thing in diagonal slot near scan coils)? It should vary the gap on the two annular magnets.

There may be two faults - lack of width (PL or PY?) and poor focus. Or just low HT.

[ChristianFletcher]

Adjustment of the focusing magnets has no effect on the picture quality. I had previously removed the focus assembly from the tube and cleaned it greased it as it was jammed originally.


Regards Chris

[BassoonBloke]

Hi Chris,

Looking good so far. A quick question - did you remove the magnets from the assembly, if so, did you put the magnets back the same way as they came out. I believe (though i stand to be corrected on this ! ) that there are 2 magnets in the assembly and that they should be magnetically opposing each other, if they are not put back the same way you will not get effect on the beam that you need.

Keep up the good work,

Alan.

[Heatercathodeshort]

Picture looks a lot better than I had expected, Chris.

The focus magnet slider should be quite critical in its adjustment, peaking around mid travel. It's odd that it has no effect, and I can only think that something mechanical is out of line.
It should have a very noticeable effect.

The EHT looks about right, maybe a bit low but this will not stop the focus unit from doing something! Let's see if we can get this correct first. I jumped to Alan's conclusion of a fault in the assembly or reversed magnets but it seems we must rule that out.

Focus magnets surprisingly seem to keep their strength even after 50 years.

Regards, John.

[Mike Phelan]

Chris
John beat me to it, but I am beginning to suspect that there is a mechanical problem with the focus mechanism.

Just a thought - is the CRT pushed back as far as it should be?

[ChristianFletcher]

I would say that the focus lever is doing nothing even though I can see the magnets moving together and apart as the lever is adjusted. The magnets do not feel very strong if I put metal screw driver to them.

The actual positioning of the focus assembly where it is held to the wooden cross-member is very critical. If I move the complete focus assembly the picture disappears completely. This is adjustable via a jacking screw assembly.
Perhaps this is not set up correctly since I removed the focus unit.

Regards Chris.

[ChristianFletcher]

My checks on the EHT indicated that it was low. So I decided to take a shotgun approach and replace everything connected with the LOPT.

I ordered the EY51 as indicated on the Trader Sheet and this is not the type of valve fitted in my set. Could someone please advise on what type of rectifier is required as its clearly not an EY51.

The small valve pictured on the left is the EY51 and the larger valve with a number starting with a C is fitted in this set. The actual number is unreadable.

I have replaced PL81 and the raster is much brighter and now full screen width. I am fairly sure that the focus unit is as fault. But it would be useful if someone with this set could measure the position from the back of the tube to the focus unit as I am sure its position on the tube neck is important.

Regards Christian.

[jim_beacon]

Looks like a DY or an EY (forget the number) to me. I suspect the only way to tell the difference is to measure the filament resistance (preferably hot, using a bench PSU), and consult the data books.

DY is a 1.2v heater, EY 6.3V

Jim.

[Heatercathodeshort]

Hello Christian,
The B9A valve in your set is an EY86. It is the plug in replacement for the EY51 in later receivers.
It won't be faulty as the picture will swell up [bloat] as you increase the brightness if it is low emission. I am still puzzled by that focus unit. Good suggestion to measure the distance. I still think something is mechanically wrong with it but time will tell.

Regards, John.

[beery]

Hi Chris,
two things to check.
Changing the PL81 for a new one will probably increase the EHT which in turn could highlight a Corona discharge problem. Corona discharge can cause lots of interference. Leakage could be around the EHT retifier, the tube anode cap or the breaking down of the heater winding for the EHT rectifier.

A washed out picture could be caused by... faulty AGC, low boost (A1 on the CRT) voltage or by a problem with the vision interferance limiter. Make sure that the vision interferance limiter is turned fully anti-clockwise.

Cheers
Andy

[Mike Phelan]

Chris
If this is because the CRT is low emission, it an unmistakable symptom, once seen, never to be forgotten.
The highlights have a "silvery grey" appearance with poor focus around the edges (but I still think you have a mechanical fault with the focus assembly)
One point - I cannot remember if the TV53 has an "interference limiter" or "black spotter" control? Anyone? This will clip the highlights if there is a fault or it is turned up too far.
HTH

[ChristianFletcher]

The limit adjustment on the set does not have much effect but I will set this as you advise. I think the noise is down to the DVD I get snow all over the screen but there is also I defined band of noise across the middle of the screen. These look a bit like artifacts on a digital image. I cleaned all around the Tube and EHT sections and the noise goes away when I turn off the DVD player.

[Mike Phelan]

Chris
It was the lack of contrast, rather than the noise that I was referring to. The noise limiter is simply a peak-white limiter - the effect is that interference "spots" are reduced, or on some sets, inverted. If the control is wrongly adjusted, you get grey peak whites, a bit like a failing CRT, but without the "bleeding" on edges.

[ChristianFletcher]

I just wanted to take a moment to thank everyone again for their patience, assistance and encouragement to keep going.

I have worked in and around the electronics industry for many years and have done some design work. All the text book learning counts for very little when compared to the hands-on experience. So, many thanks again. You're all very welcome to tea and a chat if your ever in West Yorkshire.

That’s the crawling over; back to matters in hand.

I think I will put the interference issue to one side for now, apart from saying it is certainly coming from the DVD player.
The greatest proportion is being conducted and it occurs even with the power to the Aurora disconnected.
However, I don’t think the noise was there originally, so perhaps some decoupling has failed.
I don’t, however, have another video source at the moment apart from the test card.

I am going to try tapping the tube to see about any change in brightness.

Regards Chris