dead WG 25K5515 (medium res) in my 720°

[modessitt]

The last two 5515's I fixed had high B+ and did not need new flybacks.

But - it won't hurt to replace it if you want (unless you're Leinhit)...

 

[arcadecup]

You would need a tool that can read frequency..
you want str380.
service manual here
http://arcarc.xmission.com/PDF_Monitors/WG K5515_Manual.pdf

Thanks for the tips, how would i go about check the 25khz drive to the hot? Or what supplies it?

Its also in shutdown with such a high B+, would that stop the pulse?

 

[gwarble]

My 19" K4915 is an STR380. IIRC, on the K4915, the STR380 is used for 19" (123v B+) and the STR381 for 25" (130V B+). Check your B+ test point and use the correct VR for your unit.

Thanks, 25k5515 manual says str380 and ic501 pin 2 @ 123vdc

Mine is high at 155, monitor was working but could be VR failure... know which it should be?

 

[gwarble]

The last two 5515's I fixed had high B+ and did not need new flybacks.

But - it won't hurt to replace it if you want (unless you're Leinhit)...

Thanks... i'd rather not unless i can test it as the fault

 

[modessitt]

Thanks... i'd rather not unless i can test it as the fault

If you have a ring tester (as I do) you can test it to see if it's bad...

 

[gwarble]

nope... unfortunately i don't

i'm still not clear as to if the flyback was failing, would it cause the high B+?

well i'll start with the cap kit, str380, and VR and see what i get...
thanks again everyone for all the help
- gwarble

 

[SuperSprint]

Thanks, 25k5515 manual says str380 and ic501 pin 2 @ 123vdc

Mine is high at 155, monitor was working but could be VR failure... know which it should be?

Not sure I understand the question as STR380 is the VR. I'd pull the HOT and test the B+ "naked"

 

[gwarble]

well if the str380 is supposed to put B+ at 123vdc, and there is an str381 in there, would that pull B+ to 130 (if everything else was fine)

I'm basically trying to find out the root cause of my B+ being too high, which i assume is why its in shutdown and i don't get neck glow...

So if i pull the HOT and measure a B+ difference, does that tell me the HOT is causing the high B+? i'll do that tonight

thanks!
- gwarble

 

[SuperSprint]

well if the str380 is supposed to put B+ at 123vdc, and there is an str381 in there, would that pull B+ to 130 (if everything else was fine)

Yes. The 381 is designed to output 130V.

I'm basically trying to find out the root cause of my B+ being too high, which i assume is why its in shutdown and i don't get neck glow...

Unless you have test equipment for the individual components, in that chassis I recommend replacing VR, HOT, and fly as a set. Each can (and does) kill the other when it shorts our, so replacing one at a time can put you in a circular fail loop.

So if i pull the HOT and measure a B+ difference, does that tell me the HOT is causing the high B+? i'll do that tonight

With it running high, probably not. The HOT tends to fail shorted and cook the VR (B+ may be fused in the K5515, it's not in the K4915). Even with the HOT removed, there are lots of other sections that feed off B+ that can't be isolated.. But the HOT is easily removed and when shorted grounds the B+. Taking it out of circuit eliminates that potential short in the circuit. Also, a shorted HOT likes to eat the VR when it goes. Removing the HOT eliminates one possibility when you are replacing/testing the B+'. With a high B+.my money's on the VR.

For an absolute test or VR, you could find the B+ trace that feeds the rest of the chassis (usually at a TP) and cut it. That is a bit extreme, but would tell you if the VR and rest of the DC power supply is good.

Oh, and in case no one told you, do not measure the HOT with the circuit live. It's switching 1500V and will bite you.

 

[gwarble]

Oh, and in case no one told you, do not measure the HOT with the circuit live. It's switching 1500V and will bite you.

thanks, you mean for short? the HOT tests ok in the circuit (with monitor off, no short between HOT case and chassis)... with the monitor on i did check VDC on the case of the HOT as 155 (meaning no pulse, so i guess i got lucky

 

[SuperSprint]

thanks, you mean for short? the HOT tests ok in the circuit (with monitor off, no short between HOT case and chassis)

Do you have a replacement? If so, do a pin to pin diode check and compare.

with the monitor on i did check VDC on the case of the HOT as 155 (meaning no pulse, so i guess i got lucky

Yep. That's why the manual says "DO NOT METER"

 

[gwarble]

Yep. That's why the manual says "DO NOT METER"

good to know

 

[modessitt]

Replace the $5 VR and the $5 caps first, and go over it for cold solder. if that doesn't help, then you can do a $33 flyback if you wish...

 

[gwarble]

Precisely...

 

[SuperSprint]

Modessitt is the man, and his help was invaluable in getting the K4915 I've been mentioning done. So with great hesitation, I must disagree. I replaced the VR and HOT 2x before replacing the shorted fly that was eating them. If you're going to replace all the caps, HOT, VR, etc. go ahead and finish the job with a new fly. If you don't, you may be doing this all over again...

 

[gwarble]

Good point, but like everything its just risk and time management... 2 $5 parts that are easy to swap is a worthy risk in case the flyback is fine...

 

[SuperSprint]

Good point, but like everything its just risk and time management... 2 $5 parts that are easy to swap is a worthy risk in case the flyback is fine...

Yes, but you're not factoring in the risk of continuing to use a 30yr old flyback. When that sucker goes, it may take out a lot more than the HOT. When my matsushita fly went, it choose death by fire and pretty much toasted the chassis.

Personally, I vote for fixing it right once (for $43) instead of gambling $10 against $53. Hell, the fly takes about 5 minutes one you have the chassis out.

Anyway, that's my $0.02, and you already have Modessit's advice which is money in the bank.

 

[modessitt]

Modessitt is the man, and his help was invaluable in getting the K4915 I've been mentioning done. So with great hesitation, I must disagree. I replaced the VR and HOT 2x before replacing the shorted fly that was eating them. If you're going to replace all the caps, HOT, VR, etc. go ahead and finish the job with a new fly. If you don't, you may be doing this all over again...

The difference with his is that he doesn't have a shorted VR or HOT like you did, so there is no evidence that the flyback is causing any problems. The wrong VR might...

 

[gwarble]

got it running... exactly the reason to try the VR before the flyback...

if i had known the VR and HOT weren't soldered in, i could have done it without even pulling the chassis (though i did also change C507... was too lazy to do the full cap kit but i will when i get the str380 VR in...)

FYI... swapping them didn't immediately fix it... but i made some tweaks and got it to stay on for a few seconds before high voltage shutdown...

the h width coil was backed way out of the plastic... i didn't know how it was supposed to be, but when bob roberts suggested the str381 may have been swapped in in the past because the width wasn't big enough (thus using the 130vdc VR to enlarge it)... then when the monitor was rebuilt that part was probably swapped with the same str381, but the width coil was backed way out to compensate for it... so i backed it out even more, fixed the other knobs i had tweaked trying to bring it to life, and got it to stay on...


convergence is off, but i'll worry about that after the full rebuild and correct B+

thanks again everyone for all your help

- gwarble