Sony HV selenium diode replacement
 

Working on a 1979 Sony TV-511, little 5" B/W set. Found the HV rectifier is shorted. Original type is given as a "MF 12" with Sony p/n 1-531-065-00.

Any recommendations on replacement? I'm not finding either original part numbers in any cross references.

It is similar to an ECG/NTE 502 or 503 selenium rectifier. I could likely make one of those work, but worry because they are about 1" longer. I assume this means they also have a higher forward voltage drop.

Would a Silicon HV diode be a better replacement? Like a 2CL72 or DD1000?

Photo of original rectifier:
https://i.imgur.com/swU5k15.jpg

Depending on what the HV is 2-4 of these in series should work fine. https://www.mouser.com/ProductDetail...gvC%2FCmVI8%3D

We meet again ! A focus rect stick may work. What is the HV rated at ?
Focus ran abt 6 KV. Following the average HV is abt 1 KV per inch.
Also the OLD ECG catalogue had break downs of device uses. If you get
an old PAPER copy it can help tons. Only considerations are FWD voltage
drop, Op freq & reverse volts the way I see it.

73 Zeno:smoke:
LFOD !

The HV is spec'd at 6kv on the schematic. Two silicon diodes in series might be the cheapest/quickest fix.

Hey Zeno, yes indeed, I figured the solid state forum here might be a better place to discuss my "modern" tv than the ARF.

I'll take a look for some focus rectifiers... any types in particular you recommend?

ECG sold them. Most console chassii from abt 1965 - 1970 used them.
HV sticks were in most B&W's. Regular rects will blow. The cant
handle the 15 khz speed & over heat.

Instead of an ECG/NTE 502 or 503, you mean something like this NTE 118?
https://www.elliottelectronicsupply....rectifier.html

Think I have it figured out. I stumbled across this 1981 RCA cross reference, and it has the MF12/1b part number from the original rectifier. This crosses to an NTE 502. I found one on eBay and ordered that. Should be just a hair longer than the original, but otherwise the same.

Will post back when I get the new part installed.

Cross reference found here: http://bitsavers.trailing-edge.com/c...Guide_1981.pdf


https://i.imgur.com/3PQqn0e.png

https://i.imgur.com/ck1IpSv.png

Either should work fine IMHO

Zeno

Got the new NTE 502 selenium rectifier last night, TV is back to working! B+ is right on spec, current is also where it should be.

Find it very odd that the old rectifier went bad after just sitting in climate controlled storage for 20 years, but who knows. Maybe it was about to fail when it got put into storage.

Only small issue is the 502 is about 2.5mm larger in diameter than the original MF12, so it doesn't fit with the rubber boot into the flyback. I'll probably insulate it with tape and heat shrink so it fits in, leave the boot off.

Many thanks for the help!

https://i.imgur.com/7u2L5Hu.jpg

https://i.imgur.com/wCfgCOi.jpg