Zener diode question for my Tempest

jehuie

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I've just replaced two zener diodes on my Tempest monitor (K6100) because I had a low B+ reading. It was reading around 150ish rather than 180 volts that I should get. But now that I've replaced them, I'm getting about 40 volts. :(

Anyway, I got the new ones at Frys Electronics but they look physically smaller than the originals. The specs show ZD900 and ZD901 to be 13V, 1W Zeners. The ones I bought are NTE143A.

Anyway, my question is....did I somehow get the wrong thing? Because the specs look the same to me but they are much much smaller. And obviously, my voltage is worse than before.

What have I done wrong?

EDIT: Sorry, I just realized this should have been in the monitor forum. Can I move it or does someone else have to do that?
 
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you have the right part.

the 150v zener (zd902) and the 25k pot are usually the problem areas.
 
you have the right part.

the 150v zener (zd902) and the 25k pot are usually the problem areas.

Thanks. I've already replaced both of those. When I crank the pot up all the way I couldn't get more than 150 volts. Someone suggested swapping these and now this is happening.

I double checked to be sure they are not in backward. I can't figure out what I could have done wrong. I'm thinking of putting the old ones back in to see if it goes back to 150 volts.
 
I just went and lifted one leg of each of the new zeners and tested them with the diode setting on my meter. One reads .776 and the other reads .775 one way.

For fun I went and checked the old ones. One reads .553 and the other bounces all over the place and I can't get a consistent reading. So I'm assuming that one is bad.

But I'm totally stumped at how I made it worse by replacing these.
 
And, I resoldered in the ends of the two zeners and fired it up and got....

SMOKE, and lot's of it from the vicinity of R912. Well, at least it's something different. Anyone out there have a clue what I've done?
 
Doh, I figured out what I did wrong. Reading the faq helps. I accidentally put ZD901 in the D901 spot! Off to fix that.....
 
What the heck is the diode that goes in D901 and D902? The parts list calls them out only as "Silicon Diode (D901,902)". That's not very helpful.

I can try to read the code off the old ones but I'm afraid I might have mixed them up now.
 
What the heck is the diode that goes in D901 and D902? The parts list calls them out only as "Silicon Diode (D901,902)". That's not very helpful.

I can try to read the code off the old ones but I'm afraid I might have mixed them up now.

Hi,
Dont know if you still need these but they are
D901 and D902 Type ERC27-13 marked ! replace with identical type.
hope that helps.
 
lol have had one for 14 years, I am a lurker and read alot. It was this site that saved me several times and I waited a bit ... noone responded so I did.
glad ya fixed it.
got it from here.
Wells-Gardner 19K6100 Quadrascan Color X-Y Display Service Manual.pdf
 
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