Heater to cathode short repair(ed)!

[menace]

So I have a WG K7191 that has been working just fine for the last few months.  I unhooked it all and removed it from the cab so that I could wrestle it up the stairs.  When i hooked it all back up--this is what i get.  

There is no change in the picture other than i can briefly see the bootlogo as it starts but thats it.  I'm running a trident t64 through a jpac (which has both leds lit, so i don't think thats the problem)  It look like its in need of a really good de-gaussing but the monitor is facing the same direction as it was previously.  

I have checked all the connections but am kind of stumped why this pink fog is all i get.  i have started up a couple of times over the last few hours to see if the built in coil would do it but i haven't seen a change yet.  Any thoughts are welcome.

Oh yeah R103 is hot to the touch after being on for a minute or so--is this normal?

[Ken Layton]

R103 is rated at 7 watts so it should be hot. I bet the crt socket on the neckboard is going bad ($8 to buy from Wells-Gardner). Could also be the flyback going bad (hairline cracks in it). Flyback is only $24 from Zanen Electronics. This chassis is well known for bad solder joints so eyeball it good.

[menace]

turns out its the tube that's no good--it must have been when i took it out to move the cab--maybe i shook something loose (although i was very gentle with it when i set it down on its face)  So I guess is there any hope for it--other than a pricey rejuv job?  How about a good vigorous shake    seriously--anyone know a good way to bring it back from the brink?

Oh, and i know all this cause i swapped the chassis onto another tube at it looked spiffy!

[Ken Layton]

Randy Fromm has some tips for bad tubes on his Super Secret Technical Page. If you have a rejuvenator, I'd zap the tube. If you don't have a rejuvenator you could take the monitor to a tv repair shop and see if they'll zap it. Usually around $50 is the charge for doing it.

[menace]

Ok o I have read randy fromm's how to on how to potentially fix this and would like to give it a try.  Firstly though, I would like to confirm my parts so i don't remove anything (or short anything) that might be valuable.  I have attached a pic of the trace of the neckboard.  If someone could have a look and let me know if this is labelled correctly I can give it a go.  

Also what does G1, KG,G2,KR,KB Mean?  I assume the G,R and B mean green blue red, but what about the K?  Does this mean cathode?

[MonitorGuru]

K is the abbreviation for Cathode.

G1 = Control Grid 1 (Brightness)
KG = Green Cathode (Gun)
G2 = Screen Grid 2 (Cutoff)
KR = Red Cathode
KB = Blue Cathode
G3 = Focus Grid 3 (Concentration)
H = Heater [May be numbered, usually not]

Here is a good site explaining CRT basics: http://www.geocities.com/SiliconValley/2072/bit71.txt

You don't see the G3 (focus) pin as it's the isolated pin in the socket away from all the others with the big wire attached to it from the flyback (second in size only to the Anode wire). The focus grid takes the most power next to the anode and must be isolated from the other pins to prevent arcing and has it's own wire supplying it

[Ken Layton]

To do the Randy Fromm trick you only need the two "H" heater pins to have the foil traces cut.

[menace]

Update:  I did a continuity test on it and it looks like I have a short between G1 and H.  I haven't read anything that explains how to fix this.  Is it the same procedure, i.e. put a long in it?

with regards to his instructions I'm clear up to the point where he says "unsolder and remove the wire that connects the ungrounded side of the CRT heater to the flyback transformer"  I have no wire connecting the ungrounded CRT heater to the flyback--or not one that is immediately obvious.  the only one that would fit that bill is pin 5 of the blue and white wiring harness that goes to the mainboard--is that it?

thanks for any and all help ken/MG!

[JoeB]

Sorry I can't help you (considering I got the exact same monitor as you) but I must say.. in the last 9 months you've learned more than a TV repair guy does in a few years!  

Good to know someone like you in town..  in case anything happens to mine.    

[menace]

Thanks--its amazing what you can learn when you have some really great resources that answer even the tough questions (K.L., M.G. to name a few)  Also a complete lack of respect for my own welfare never hurts

On topic--I have desoldered the CRT socket but didn't get around to doing much else tonight--maybe tomorrow night.  I'll post back with results on my experiment to fix a screen to heater short.

[MonitorGuru]

You're welcome Menace.  BTW--even though I've never tried to zap a HK short (I've just swapped in a replacement tube) I'm curious why you desoldered the CRT socket??

Couldn't you have just removed the neck board and attached the zapper to the 2 affected pins on the tube directly?

Or are you doing a different type of zap?


And remember, I'm not a Guru.. I just played one until Ken arrived here, who is the real Guru!!!

[Ken Layton]

Suggested reading is also Randy Fromm's "Shooting the Tube 129" on his technical page just above "putting a Long on it".

If I have occasion to do Randy's neckboard trick for heater to cathode shorts, I always unsolder the whole CRT socket assembly in order to bend up the two "heater" pins to connect the new wires to.

Naturally, if a person has access to a picture tube restorer/analyzer (a.k.a. rejuvenator) you can usually blast those shorts right out of the with the simple turning of a knob and pushing a switch.

[menace]

Yeah i decided to go the "put a long in it" route since even the famous randy fromm said he only has a 25% success rate on the heater to cathode short--and he knows what he's doing!  This process sounded much safer from a CRT perspective since i'm not inducing any shorts, just by-passing one.  My plan was to drill out the heater traces on the neckboard and then follow randy's idea step by step  

Of course if i can actually find someone who can rejuvenate for less than 100$ around here, i will consider that route...

[Ken Layton]

Hey Menace:

If you have a lot of games it may be worth it to buy your own rejuvenator. Even a used one from ebay will work. I have a B & K 467 with a full complement of socket adapters and it gets used all the time.

[fredster]

Ken,

I saw a rejuvenator at an auction in Knoxville, it went for over $300.  How much are the worth on or off ebay?  What catagory do you look under?

[JoeB]

menace,

I had a local TV repair guy rejouve my TV for free!  (he was in to repair my parents projection TV).

Just call around.. some do house calls for 50$CDN at the most!

[Ken Layton]

fredster:

A good used rejuvenator shouldn't sell for more than $300 on or off ebay. One without the socket adapters should sell for alot less since you'd have to buy the adapters new at $50 a pop from the manufacturer.

Currently on ebay search under: Business & Industrial -> Test Equipment -> Television Test Equipment.

I wouldn't buy any B&K model previous to the 467 since the earlier models had different adapters that are very hard to find nowadays. In my opinion, the 467 is their finest model and is still supported. Any of the B&K models 467, 470, 480, and 490A are good used units and work great on arcade monitors. Be sure it comes with socket adapters 23 (the most often used adapter!), 30, and 31 at a minimum.

[menace]

Update:  drilled out the heater traces and made wire and plugs with precisely 2 1/2 turns around the flyback ferrite core --see pics below.  Result--heater does not function.  I can here electricity sizzling in the anode cup, so I think th flyback is working and thus, generating a volatge in the secondary winding but it doesn't glow.  Any tips from here?

[menace]

my stupendous winding job--no crossed wires around flyback  

[menace]

Doh, looks like I had a bad connection and guess what--she works! well almost...I had another chassis i got off ebay and it looks like IC3 has died, but it is a very nice horizontal line, as far as horizontal lines are concerned    i wish i had a local source for all these bizarro chips... ah well--I'm just happy that the "long method" works!  thanks randy fromm wherever you are!

[JoeB]

WOW!

Are you ready to make your own chasis from scratch now??  You almost replaced every single part on that one!

[menace]

Actually its my third one--I've just been replacing parts here and there on all three--new Ic4 on #1, new IC 2,3 on #2 and now IC2,3 on #3--I'm beginning to see a pattern here....So each board has been relatively cheap to fix--but i guess if you read all my posts it looks like I spent alot of time on this model eh?