Why does my HOT blow every 2-3 months??

Hmm, maybe you're using incorrect rated HOTranny ?

are you putting on heat sink compound?.

are you getting the exact replacement ?

is it possible it was replaced before by some one else that may have used a different number ? something they had lying around..

also, You may want to test for the load current in the B+ line, it could be exceeding and the regulator could be driving the HOT harder to keep it stable. I've seen C+ taps from the HOT have leaky caps for lower voltage supplied derived from the HOTxformer. etc.. This would cause the flyback to work harder. Also, improper adjustments to the screen controls could cause the flyback to run hotter along etc... theirs a lot of variables here.

You may also want to test the input to the HOTransistor with a scope to see if you're getting full on/off input drive and don't have some constant DC there driving the base.

tem00 ha escrito:

check the capacitors in the line drive circuit. these are often rated quite low, something like 10-47uF. In one vestel set recently which ran hot i changed the cap from 10uF to 22uf and it now runs cooler.

also check the cap across the c-e of the HOT.

faulty line o/p transformers can cause these problems too. good luck.

-B

Resolder the horizontal drive transformer and associated parts (driver transistor, resistors...) ?

Mark Z.

Just the HOT ? Do you have to replace all the other above-mentioned too ?

Graham

I'd recommend to check all the electrolytics in the set with an ESR meter. I do so always when I have to repair a many years old device and the cap test has not been done within years. There are often found some "stray bad caps", and they sometimes cause mystic semiconductor failures etc. It might take a half an hour or so to test all the electrolytics, but it gives a far lower chance of failure in near future.

-- Top-posting not supported.

This is the thing I would check first. I had that once: A small copper wire coil to the base of the HOT had a faulty solder joint on one side. If the HOT is not properly switched (i.e. too long rise and fall time of the pulse) it will be thermally overstressed and fail prematurely.

Regards, H.

Seems the op says he just replaces the HOT, not HOT section stuff.

Thanks for the input everyone.

Yes, it was only the HOT that failed, but the 2nd time it blew I replaced a lot of related parts as well in an attempt find a marginal part. They were all parts spec'd from Vance Baldwin for my unit and seemed to be the same numbers. I used proper mounting and heatsink grease. I can test the load current, but it is not specified in the service manual so I don't know what to look for.

I'll use all the suggestions here from the drive waveform to checking the copper coil legs and post if I find something.

Thanks again tem00

tem00 wrote in news:1183331401.452728.212290 @q69g2000hsb.googlegroups.com:

I had a set that would do something similar, turned out to be a bad CRT.

It sometimes arced internally at turn on before the heaters were completely heated blowing the H.O.T .

R!

Not what I wanted to hear, but thank you, I'll keep an eye on it

This sucks but I recall reading some other HOT failures because of a shorted CRT.

There's a lot to die before the HOT, if the CRT is bad.

Regards. H.

tem00 wrote in news: snipped-for-privacy@57g2000hsv.googlegroups.com:

Just thinking does the H.O.T. run unusally warm ?

If not, I read that there was some problems with the sealing of the anode connector on some projection sets that would arc, but this should be a very audible snap!

If it is a bad tube it would not be much of a snap.

R!