How reliable is cross referencing parts?

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Canti

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Hi everyone I have a simple question concerning cross referencing parts. I'm trying to fix my RPTV and I found a bad diode on the convergence board which is this:

https://www.ortodoxism.ro/datasheets/rohm/1sr139-400.pdf

When I went to my local electronic store they cross reference this part and gave me this instead:

https://www.nteinc.com/specs/100to199/pdf/nte116.pdf

I took a look at the specs and it seems pretty close to each other, so is it safe to use the NTE116 diode? I just don't what to cause more problems to my TV.

Kenny
 

Well your device is called a general purpose silicon diode so I don't think it's a particulary hard device to cross. Some people have had quality issues with NTE devices but the few I've used over the years worked ok.

That all being said I think you might find the 1N4007 diode a better candidate. It also is rated as 1 amp but at 1,000 volts so you would have a little better cushion on max voltage rating. Also the 1N400X series diodes are very common, very cheap and avalible everywhere and have been the industry standard 1 amp diode series for decades.

good luck
Lefty
 
I'd say it depends on the part and the application. Generally speaking it may be OK to substitute a part with better specs than the one which failed. The problem is that you may not have found the root cause of the problem and your repair will be ineffective. Trial and error is about the best shot you've got. These replacement parts are of course tens to hundreds of times more costly than the original part, but you're only buying one so who cares?
 
What would the cause the diode to fail? The bad diode that I found looked like the picture that I attached. The board looks like its burned, from the previous diode over heating. The dumb part about this is that the service tech "fixed" the problem 4 months ago and it happen again, so I don't feel like paying another 400. By the way its for a rear projection TV.

Forgot to add that I bought a service manual for my TV and this burned diode looks different from the original diode that should have been there. The D611 and the D609 (upper right hand corner of the picture) supposed to be the same diodes, according to the service manual.

Thanks.
 

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I would Also Recommend using a 1N4007.

And I would also Suggest that you DON'T install it Laying Flat to the Board.
** Raise it Up about 1/2 Inch Above the board.
This allows for Better Heat Dissipation.

Should it Fail Again, Than Replace it and do a Test to see if the Voltage and Current are within the Specs of the diode.

** You May have a Leaky Capacitor or another component, Causing problems.
 
hi canti,
When replacing a 'burnt, overheated component, its important to be sure that the new component has a 'good' resolder job.
The c**p on the copper track can easily cause a 'bad' joint when the new component is installed.

IF the last repair left a high resistance soldered joint this could be the souce of the overheating.

Its also possible, there is a design weakness in the original circuit, this does happen.
If possible, try to get some background on this RPTV model, the manufacturers sometimes post engineering change notes.

The diode may need upgrading.
 

Its funny how you mention the bad solder joint. When I took the board out and took a look at it the soldering job on the zener diode looked like s**t. The solder didn't properly melted to the copper traces on the board, it was still clump shape.

Kenny.
 

Thanks for the tip I'll do that.
 
Hi everyone I'm back. I had order the 1N4007 and replace my bad zener diode and now the TV wouldn't even turn on, not even a click. I don't know why it doesn't respond anything anymore. Could it be that the 1N4007 has a too high of a peak repetitive reverse voltage?

Before this the old diode would allow the tv to turn on and off, but with no picture or sound.

So, my next thought is to replace the old zener diode with another zener diode. What do you guys think?
 
Would it be impertinent to point out that a 1N4007 is NOT a zener diode? At least it won't zener at the same place as the original, if in fact the original was a zener diode. You should be able to make this determination from the schematic in the service manual.
 
I know that the 1N4007 is not a zener diode. The service manual shows that it has a rectifier diode which is 1SR139-400. The problem is I don't know why the service tech would replace a rectifier diode with a zener diode?

I have the service manual here:

**broken link removed**

Its on page 42 on acrobat reader. and its located on the upper right hand corner near the IC601, following pin 2
 

It's the bootstrap diode for the frame output stage - a 1N4007 should be fine, but you might try a fast recovery diode instead if it keeps failing?. I would also suggest you replace C614 (the bootstrap capacitor) these go low capacitance and high ESR, and can kill the rectifier and the IC.
 
The problem is I don't know why the service tech would replace a rectifier diode with a zener diode?
Click to expand...
None of the diodes under discussion are Zener diodes. AllVol said it looks like a Zener.

This is something like saying milk looks like wine because yesterday we served wine in that glass.
 
Are you Sure you put the diode in with the Correct Polarity?

I Double checked that part Number you quoted, in My Cross reference, and a 1N4007 should be OK.
 

Is there a way to test the capacitor with the ohm meter or does it require some special tool to do test? Also what kind of values/specs should I look for in replacing an OEM capacitor?
 
chemelec said:
Are you Sure you put the diode in with the Correct Polarity?

I Double checked that part Number you quoted, in My Cross reference, and a 1N4007 should be OK.
Click to expand...

I did check it again and it's facing the same direction as the other original diode. The band around the diode means where the arrow is pointing, like this |<-- and I matched it to the drawing on the board as well.
 
Hi Canti,

This is off topic, but I can't help appreciate the close up photo - good details, good lighting, even the ridges on the solder mask show well. It's not too often to see good photos posted on forums.

Can you please give us some details how you made this one? camera, lens, a few tehniques how to make a close-up shot? Did you make some editing?

Thanks!

added by Matmem:

Maybe you need to start another thread on photography
 
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Canti said:
Is there a way to test the capacitor with the ohm meter or does it require some special tool to do test? Also what kind of values/specs should I look for in replacing an OEM capacitor?
Click to expand...

Don't test it, replace it!, it's under a fair amount of strain, in a hot environment, and is a common source of problems - for the cost of a small electrolytic (and make sure to use a 105 degree one) it's not worth messing with.
 
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