[Crist Rigotti]

Hate to say it but it looks like the pix tube to me too. A brightener might help. It will raise the heater voltage slightly causing the gun to give more emissions. Low high voltage will cause blooming when the brightness is increased and loss of focus. May be a combination of both. A picture tube tester should verify, unless the tube is gassy.

It's beginning to look like the crt.  I'm going to try and get it checked again like I did at first to see what the results are.

[Crist Rigotti]

I hooked up the heater wires to my BK 467 CRT tester so I could vary the heater voltage. I varied the voltage from 6.3 to 7.5vac and saw very little changed to the "negative" effect. The CRT did get just barely a very little bit brighter. I did not want to go any higher on the heater voltage seeing it seemed to make little difference.

[mikethedruid]

the higher the heater voltage the shorter your tube life. If the 6.3 v gives sufficient brightness to view in moderate light, it is fine. These sets were not to be viewed in a bright room in those days. I remember well, the pictures were a good bit dimmer than what we are used to today.

[Crist Rigotti]

the higher the heater voltage the shorter your tube life. If the 6.3 v gives sufficient brightness to view in moderate light, it is fine. These sets were not to be viewed in a bright room in those days. I remember well, the pictures were a good bit dimmer than what we are used to today.

Mike,
Yeah, but the picture is viewable only in a very dim room.  I'm working on getting some substitute tubes and going back over my friend's house to retest the CRT in his good working chassis.  He'll also help trouble shoot the problem.  The audio is very good.  Just have to work out one bug at a time.  If I remember right, when we tested the CRT the shops lights were on and we had no problem seeing the picture.  We even thought that over time it might even get better after it "wakes up".  Thanks for the input.

[TV MAN]

You are saying the tube worked ok in another chassis? I had only read of testing. In my experience I had many times where I had tested a pix tube and it tested good on the tester, but wouldn't work well in the TV. Some others would test low, yet still produce a good picture. The old 21" round color tubes were known for that. Have you subbed the video out tube? May be back to it is just a lousy combination of small problems making a big problem.  

[Crist Rigotti]

Tim,
Yes, the tube worked a lot better in another chassis. Early next week I'll get with my friend and we'll double check the crt in that chassis and swap out a lot of the tubes, especially the loctals. They checked the weakest as a group.

[Crist Rigotti]

We had the chance to check the CRT in another chassis today. Looks like mine isn't so good. My friend's tube worked and looked really great! At least I know my chassis is good. I'm pressing on now with the cosmetic part of the restoration. I'll keep an eye out for another better CRT.

[Eliot Ness]

I guess that's kind of a good news/bad news scenario.  At least you know for sure that the CRT is weak and you're very fortunate to have a friend you could swap CRT's with for testing.  Your electronic restoration came along nicely and I hope you're able to locate a good CRT somewhere.  Good luck!  

[Crist Rigotti]

I guess that's kind of a good news/bad news scenario.  At least you know for sure that the CRT is weak and you're very fortunate to have a friend you could swap CRT's with for testing.  Your electronic restoration came along nicely and I hope you're able to locate a good CRT somewhere.  Good luck!  

Yeah, you're right.  I now know the chassis is working very well.  I'm doing the finish on it now and then the final assembly.  Then I learn a little about alignment!

[Mondial]

Be careful about attempting alignment on one of these old TV sets. Its a lot more difficult than aligning a radio. The video IF must be aligned with a sweep generator, oscilloscope and accurately calibrated marker frequency generator.

Do you have any reception problems that an alignment would correct? If you have good sound and a clear detailed picture now, its probably better left alone as it will be hard to improve by alignment and its very easy to mess up and make it worse. 

[Crist Rigotti]

Be careful about attempting alignment on one of these old TV sets. Its a lot more difficult than aligning a radio. The video IF must be aligned with a sweep generator, oscilloscope and accurately calibrated marker frequency generator.

Do you have any reception problems that an alignment would correct? If you have good sound and a clear detailed picture now, its probably better left alone as it will be hard to improve by alignment and its very easy to mess up and make it worse. 

I'm going to align the audio first.  Just as a learning experience.  I'm leaving the tuner alone!

[Radioroslyn]

Hey Crist,
> I'm k\leaving the tuner alone! 

On a lot of the old tv's (pre 51 or so used turret tuners) there is an local oscillator adjustment that can be found behind the fine tuning knob. This adjustment can be helpful if you have a situation where have a good pic and crummy sound or crummy pic and good sound. Unlike the video IF where you need equipment, this can be adjusted by sight and sound. Some folks will also dittle with the discriminator transformer (read detector for the audio) for loudest / least distortion

As Mike said about the video IF unless you know someone that has the equipment and has done many times before I'd leave it alone. The picture and sound pass through this IF circuit so if they get out of adjustment it can screw up both sound and pic all at once. In the 60's manufactures changed the IF frequency from 21 mc to 45mc. Not a great idea by the manufacturer to use 21mc for the IF as it's in a ham radio band (15mtrs). Have been given a number 45mc sweep tv generators (usually strip for parts or chuck)  but the 21 mc units may be just a little hard to come across. If you adjust the 4.5mc sound IF it won't mess with the pic.

Have fun! Not trying to scare you just help you make wise decisions.

Terry

[Crist Rigotti]

Just an update on getting the chassis up to speed. Still a little more to do.

[Image: http://i1060.photobucket.com/albums/t458...ey10oo.jpg]

[Image: http://i1060.photobucket.com/albums/t458...zs8ylu.jpg]

[Crist Rigotti]

Here is a short video of the restored chassis.

I just taped the mask into place on the CRT. I'm playing it now for an hour or so. I want to see if I get the HV fade. BTW, the video is "White Christmas".

https://youtu.be/TwwV8PGGjtc

[Arran]

 I don't think that a brightener will help much with an electrostatic tube like a 7JP4, when those tubes get dim it's because the phosphorus has become fouled not because the cathode emissions are poor. What may help is if you could increase the high voltage somehow, did you replace the HV rectifier yet? Even when these tubes were brand new they were never as bright as a electromagnetically deflected tube, and were often viewed in a darkened room. It's too bad that this set appears to have had a high number of hours and has worn out the CRT, on most of these electrostatic sets the set was retired long before the tube became unusable, probably when the owner decided to buy a 21'' set or when the high voltage caps started to fail, or both.
Regards
Arran