Hi all,

I have a trash picked a 13.5" (34cm) PHILIPS 14PT132A/75R (from the 1990's), which uses a TOSHIBA A34JFQ40X CRT. The CRT seems to have some colour issues, so I'm thinking I may as well replace the CRT if possible. I've already adjusted the colour controls, in correspondence with a test pattern, but to no avail. The colours are out (red it seems) - pink is red, red is orange etc.

I have three possible candidates, but am unsure if they would be a suitable replacement?

These are:

- ORION A34JLL92X
- SANYO A34JRY24X02
- PANASONIC A34JCD91X

Does anyone have any idea if these tubes are interchangeable? I'd like to get the set fixed and up and running, and watchable (without the faces of people being a bright yellow!).

Cheers,

Chris

I don't think the CRT is at fault here.

Here is my reasoning why.
To get white on a CRT you need to mix red + green + blue. From your picture the large white square under the colour bars is clearly white which means all three electron guns are working.
Also although in the wrong place, you are getting red and blue colour bars confirming these guns work, green also appears to be OK based on the photo.

If you turn the colour control on the TV to minimum, you should have a normal B&W picture.

What is wrong with the TV is a fault in the colour decoder circuitry.

Thanks TV Collector

It never thought of the issue being linked to the decoder circuitry... Luckily this set has a full service manual available online, all 46 pages of it. Better start reading!

Anyways, are these 34cm tubes interchangeable anyways? Would there have been some kind of standard so that tubes were interchangeable? I used to have a vague idea of how to read the tube number (and get info out of it), but I've since lost the webpage with all of that.

Cheers,

Chris

Have you checked the yoke coils? I found a lot of CRT yokes with two rubber wedges holding the top but none underneath. Since it came from an American rubbish bin it could have been upsidedown and jolted. Use a wedge from a scrapped CRT. If you have to make a major adjustment your service manual will show you how to do it but setting the convergence can be very trying.
Some tubes have small magnets stuck to the back of the tube. Have any of these fallen off?

The CRT's may be interchangeable but the deflection yokes won't be.

Modern CRT's have the yokes integrated with the CRT so that the purity and convergence is factory set for the life of the tube. The CRT part number includes the yoke but I'm not sure how the numbering is decoded. I think the last two numbers relates to the yoke.

The deflection yokes can be very different between different TV chassis for the same CRT size. It is due to the characteristics of the circuit driving the yoke, manufacturers all have different ways of doing the same thing.

So unless you are really keen to have an experiment to see what will happen, I'd leave the CRT and yoke alone as they are the least likely cause of your problems and are a real pain to get set up properly again.

Yes, I'm aware of the issues with the interchangeability of yokes. For the moment, I''ll leave the tube alone. It has some colour purity issues that need fixing, so I may attach some small magnets to the tube to fix that.

I'm trying to locate the fault in the decoding circuitry, with the use of a 46 page service manual (found online!) and an oscilloscope (CRO of course!). Lucky for me, the service manual has information on everything; test points, the set parameters for the oscilloscope, how the waveform should look, everything! It's just a matter of finding the time and patience to work on it.

Chris