Carbon composite in place of carbon film

[TinCanAlley]

As many of you know, I'm trying to fix jail bars on my Zenith Avanti (yes, still). With the help of a few here, I'm about to replace the resistors, diode and transistor in the blanking circuit. I managed to get an NOS Zenith diode and transistor, but the resistors weren't available. I ordered the replacements from Mouser and they arrived on Saturday. When I went through them, I noticed for the 100K 1/4w 5% carbon film I ordered the 100K 1/4w 5% Carbon Composite. I was ordering the 33K and 82 composites and I must have zoned out and kept in that section when ordering the 100Ks.

Anyway, I've searched and read lots on the internet and found the composites are not as stable as film. Now, granted, most sites were in regards to music amps and such, and talked about noise as well. So what I need to know is if I should use them or run out to Radio Shack and get the metal. Only issue with RS is they don't list a manufacturer, so I don't know the quality.

Anyway, thanks for any input.

[marty59]

Since you have them handy I'd use 'em. While true that carbon comp's can drift, become noisey, etc. you do have some new ones at your disposal. Not all carbon comp's go bad "just because" and I'm sure there are still lots out there operating just fine including my sets and equipment too.

[TinCanAlley]

Originally Posted by marty59

Since you have them handy I'd use 'em. While true that carbon comp's can drift, become noisey, etc. you do have some new ones at your disposal. Not all carbon comp's go bad "just because" and I'm sure there are still lots out there operating just fine including my sets and equipment too.

Cool. Just wasn't sure if they would be a fit in that circuit. I know they're all over the bottom of the chassis, but there's also lots of carbon films as well. Can't figure out the logic behind using two different types unless the characteristics of each type fit the intended use.

Thanks for the input.

[DaveWM]

good luck with it I hope it fixes the problem. Try the transistor 1st as its just a plug in IIRC.

[DaveWM]

oh and if it was me I would prob just j hook in those parts to avoid stress on other stuff. I am pretty sure the diode is silicon but I would put a heat sink on it any way.

Do yourself a favor, check the NOS parts before installing thats the diode and transistor.

[TinCanAlley]

Originally Posted by DaveWM

good luck with it I hope it fixes the problem. Try the transistor 1st as its just a plug in IIRC.

You read my mind. I have the transistor in front of me and am about to test it. If it tests okay, it goes in and I fire her up. If that doesn't help, I flip her over and start the resistors and diodes.

[DaveWM]

BtW, does your schematic give you voltage readings for that transistor? if so it would not hurt to check them. Make sure you check the notes regarding without signal, line voltage etc...

Be VERY careful reading voltage with SS parts, a slip of a prob can instantly destroy a diode or transistor.

[andy]

...

[TinCanAlley]

Originally Posted by andy

I would be looking at the G2 supply. The fact that you can't get a setup line indicates that there is a problem. You should be able to easily get a setup line on all 3 guns. Ignore the exact voltages in the service manual as they will vary from one CRT to another. What is the maximum G2 voltage you can get? It should generally be around 700-900v with the controls at maximum.

I wasn't able to get a setup line on my CTC40, and it turned out to be a bad HV diode in the circuit that supplies the G2. In my case, it also caused the focus range to be off.

During testing, the range for each G2 control was roughly 450 to 729. The reading was taken directly from the output tap on the G2 pot.