diode identification

is this of any help

On Tue, 03 Feb 2009 20:45:59 -0600, Steve put finger to keyboard and composed:

I don't know about digital sets, but a 33V supply in an analogue TV is usually required for generating tuner voltages.

For example, my Sanyo set uses a uPC574J 33V tuning voltage reference. It has a low temperature coefficient (+/- 1mV/degC) and low dynamic resistance (10 ohms). Some early Philips sets used a TAA550B.

Here is an NTE "Integrated Circuit Voltage Stabilizer for Electronic Tuner":

FWIW a ZC43 diode cross-references to an NTE5145A which is a 43V 5W zener.

See

There are also TZC43, TZC43A, TZC43B, CTZC43C, CTZC43CA, and CTZC43CB devices which cross to NTE4944 and NTE4945 "Surge Clamping, Unidirectional Transient Overvoltage Suppressors":

None of the above devices matches your stated dimensions, though.

- Franc Zabkar

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Looks like Zack hit the nail on the head.

The layout is the same as the diode I have. I've never heard of ZC series diodes before.

The voltage is labeled as Vt, so that could easily be tuner voltage. There's still something wrong w/ the set, but at least now I can put this mystery to bed.

Thanks for all the help, Steve

On Wed, 04 Feb 2009 18:15:23 -0600, Steve put finger to keyboard and composed:

It could be that your mystery diode is a protection zener that goes sacrificially short circuit when an overvoltage condition develops. Some Sharp VCRs employ a crowbar zener across the 30V rail for this purpose. IME the root cause of the problem in the case of a VCR has always been a bad electrolytic capacitor on the primary side of the PSU.

- Franc Zabkar

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