Zenith System 3 CRT help

[rtsherrod81]

Hello All,

I recently acquired a Zenith System 3 console TV manufactured December 1980 (1 month older than me). Paid $75 for it as the cabinet is in good shape and still had the ultrasonic Space Command remote. It had a bright raster when I "auditioned" it so I paid the guy and took it home.

When I first tried it out with a VCR connected, I got a bright image, but with poor contrast. Tonight I connected my new (to me) CR70 tester to the factory installed Zenith 25VFCP22 and put it to the test. It passed H-K and G1 shorts tests with good to excellent emissions on all three guns with great color tracking. This issue at hand is poor cutoff. The red gun is just off the low side of the cutoff box, while the blue and green are pegged at bad with the bias at -52V and the cutoff set fully clockwise. In the extended cutoff test with the bias set to -36V, the meter reads in the upper half to one-third of the meter.

Is there any chance of improving the cutoff using some method to restore this CRT? Should I try the Auto Restore function?

I'm open to trying anything no matter the end result as this will not be a daily driver, only used occasionally for retro gaming or watching old movies. If the CRT gives up the ghost, I will just part it out selling what I can and scrapping the rest.

Any advice will be greatly appreciated.

Regards,

Bobby

[jbattles]

connect a vcr and let it play 24 hours and see if the picture is better.

[zeno]

I will assume it uses a 9-160 HV module. Its the big one at the bottom with the
HV transformer.
Looking in the back on the right rear under the focus control there is a cap, 10mfd 315 V IIRC. Change it. Will cause your problem & others.
If you have to remove the board its easy when you learn the secret.
Let us know

Dont rejuve for now. Thats last resort & using clean & balance is better
& less risk.

73 Zeno
LFOD !

[rtsherrod81]

Hello Zeno,

Yes, this does have the 9-160 HV module. I will look at replacing that cap. I need to see if I have any. If not, I will order as I have to place an order for another project.

Please advise on how to remove the board. I believe I read somewhere that there is a red retainer to remove.

Will the capacitor be enough? The at the bias setting listed in the set-up guide, -52V, I could not get cutoff. But with the bias at -36, no issue. Based on what I've read, given the good emissions, this is due to wear of the center of the cathode material and/or ion poisoning.

Also, I would not use the Rejuvenate function as that is very aggressive according to the manual. My thought was to use the Auto Restore which appears to much gentler by comparison.

Regards,

Bobby

[zeno]

Hopefully..... Its a common fix on ALL brands from the late 70's on.
Causes any, some or all:
Pix to bright
streaking
Normal pix on left to bad at right
Jail bars
Retrace lines
Looks like bad CRT often.
and probably more if I thought a bit.

Removal depends on if its been done before. Stuff dont get put back !
Pull & throw away little black things at edge connectors.
Metal or plastic bracket from flyback to frame.
Red holder at rear under board.
Red key apx center of board. Twist 90 degs & pull out.
Push down little claws on each side of board on the frame. Slide back & out.

Originally Posted by rtsherrod81

Hello Zeno,

Yes, this does yes the 9-160 HV module. I will look at replacing that cap. I need to see if I have any. If not, I will order as I have to place an order for another project.

Please advise on how to remove the board. I believe I read somewhere that there is a red retainer to remove.

Will the capacitor be enough? The at the bias setting listed in the set-up guide, -52V, I could not get cutoff. But with the bias at -36, no issue. Based on what I've read, given the good emissions, this is due to wear of the center of the cathode material and/or ion poisoning.

Also, I would not use the Rejuvenate function as that is very aggressive according to the manual. My thought was to use the Auto Restore which appears to much gentler by comparison.

Regards,

Bobby

[rtsherrod81]

Hello Zeno,

Thanks again for the information. I have pulled the HV board and found the cap you were referring to. It is a 4.7uF 315V and it has been replaced at least once before as can be seen from below. Someone got a little overzealous with the soldering iron and lifted the trace.

I noticed a label on the board that states "RE MFG IN MEX BY ZENITH" which could explain the repair. Therefore this is not the original HV board.

I need to place an order for another project and I will include this cap. Are there any others I should get as a just in case? Is the installed cap the correct value?

Regards,

Bobby

[John Adams]

There are a number of NOS Zenith modules on EBay .