My Hitachi CP1421R smoked

[murphyv310]

Watch out for fakes of the SMPS IC Module. This was a common problem on these sets and would even show up in warranty. Also don't use poor quality electrolytic capacitors buy cheap buy twice is a definite for this TV chassis.
You need to add to the list the smoothing capacitors that are to the right of the chip in your photo, they also can cause the chip to go pop. Can't remember the circuit references for these as I closed my business in 2006 and disposed of all my manuals.

[Foneet1]

Originally Posted by Maarten

I think you only need the 470p 2kV (originally 1kV I assume), the resistor and the IC.

4700p 500V sounds as if originally 4700p 250V AC Y2 class types were fitted? Those should be left alone generally, except when faulty (if the set fails a PAT test, for example). If you want to replace them anyway, use 275V AC Y2 rated caps. They don't exist in 500V version.

Didn't the other guy say that voltage can't be lower than the original? Well, i guess i'll try replacing only those parts that blew up.

[Maarten]

Yes, voltage can't be lower than original. For some reason, I thought you had already doubled it and made the wrong guess as to the function of the capacitors.

In that case you could replace the lower voltage ones preventively, but it's usually only the one that broke in your case that really needs to be replaced (by one of the double voltage).

[Foneet1]

Do Cricklewood Electronics tell when they send out your order? It's been 4 days and it's still "Processed".

[agardiner]

Processed means it has been completed and sent. They use Royal Mail and I do find that delivery varies from 2 - 5 days but that is UK of course. I shouldn't worry, it will probably be with you in a week or so.

[Foneet1]

I've soldered everything in, but it doesn't show any signs of life. Some parts heat up, but no LED or anything else.

[Welsh Anorak]

Time to get the meter out!
is there HT on the 'cold' side of the transformer?

[Foneet1]

What does it look like? There is a little stamp thing, I think it says HH, not HT.

[Foneet1]

I poked around where it says the voltage but none of the values are right. Everything is 4V when it's on and 1V when it's off. I'm not sure I did it right though, I put the black lead in the corner where the tube is attached and poked with red.

[Foneet1]

Also i should say that I forgot to solder in the resistor before turning the TV on, could that damage anything?

[agardiner]

Hmmm, probably not but without checking the IC data sheets I don't know for sure. Probably worth just fitting the resistor and trying again.

[Foneet1]

The thing is, I already did but it didn't change anything.

There's that resistor I forgot.

[agardiner]

So it sounds like you have repaired the damage, but not the original fault that caused it to blow up. You need to check the various other components in the power supply; capacitors and diodes particularly, both primary and secondary.

[Welsh Anorak]

If you're checking the voltage on the primary side of the power supply, the meter negative lead needs to be connected to the negative of the main smoothing electrolytic (the 450v one), not chassis earth. Witht that connected, carefully measure the voltage at the IC's pins amd see what you get, starting with pin 1.

[Foneet1]

Originally Posted by Welsh Anorak

\the main smoothing electrolytic (the 450v one)

You mean the big capacitor?

[Foneet1]

Originally Posted by agardiner

You have repaired the damage, but not the original fault

No, I think that capacitor was the original fault. If it wasn't, shouldn't the new IC blow up the same way? So I guess there is something else in the power supply that isn't working.

[Welsh Anorak]

Yes, connect your meter's negative probe to the negative of the big capacitor when measuring the 'hot' side of the transformer.
Use a chassis earth connection like you have been doing when measuring anywhere else on the chassis.

[Foneet1]

Ok, just wanted to make sure.

Pin 1 shows around 30V and goes to 0.
Pins 2, 3 and 4 show 4V.
Pin 5 shows 0.
Pins 6, 7, 8 and 9 show 4V.

That's in AC mode, in DC pin 1 shows 315V and everything else is the same.

[Welsh Anorak]

All your measurements should be in DC mode.
You have voltage on pin 1 which is correct. Pin 9 is important and is obviously wrong.
I would do some more cold checks (remember to discharge the 315v HT line first with a resistor of around 5-10k)).
Your original IC will have shorted and HT will have found its way to other pins. The most likely items to have died will be D806, D808 and R804. Check these out of circuit or, ideally, replace the diodes anyway.

[Foneet1]

So the IC is dead? Man, that sucks Desoldering the first one was such a pain. Is there an easy way to do it?

or wait, original? meaning the new one is OK?