k7000 Running, need help with a horizontal issue now (Updated)

[NightWolfx03]

So the K7000 I have been working on now gets picture and powers up, however it shuts down after a few moments, I think my B+ is running a bit high since I put in the new voltage regulator, is there a way to adjust it ?  I think it's running about 155 ~ 160 when it should be 123V. When I try to read it with my meter to chassis ground the monitor shuts down as well.


Help ?

[lilshawn]

best place to check the B+ voltage is right as it comes out of the regulator... positive to pin 4 and ground to pin 3.

sounds like maybe an issue with the high voltage hold down circuit.

check or better yet, replace C36 if not done already.

check the caps in the feedback circuit c55 c56

[NightWolfx03]

c36 has been replaced, originally it exploded. C36 C37 and c 38 were all shorted, so those 3 were replaced and the HOT along with the regulator. It runs and warms up for about 45 seconds then shuts down.

[NightWolfx03]

Actually, lemme ask, can anyone find me a replacement for C36 from digikey, mouser, jameco etc ?


I ponder, the one I used was from happ and physically, it's tiny compared the how big the old one was.

[boardjunkie]

Modern electrolytics are normally smaller than ones that are 20-30 years old.

[SirPeale]

Modern electrolytics are normally smaller than ones that are 20-30 years old.

Good info - except C36 isn't an electrolytic.  It's a mylar cap.  They should be roughly the same size as the original.

[boardjunkie]

I didn't pull up the schemo....just assumed it was a lytic.

[NightWolfx03]

C55 and C56 are electrolytic though correct ?

[NightWolfx03]

Bump and Nix that last question.

So far I have replaced:

voltage regulator IC (STR30130) ( originally shorted out)

HOT ( D1398 ) (originally blown)

C36 ( though there are 2 capacitors here, originally it had 2, the normal C36 having it's legs cut on one side and another cap in that place) (C36 originally had exploded)

C37 (Originally found dead shorted )

C38 (Originally found dead shorted )

C57 (Originally dried out)

C56 (Originally dried out)

C55 replaced as well just for good measure.


After doing all this, I still get high voltage for only about half a second, is there something I am missing here ? I've checked alot of the diodes and have not found anything shorted out.

I'm hoping to get this working in house instead of having to send it to shaffer or betson and get charged an arm and a leg. But its starting to feel alittle hopeless.

[NightWolfx03]

Actually not soo hopeless, I replaced the STR30130 and the HOT with other spares I ordered and it powered up, though my horizontal size is a bit small and I got a wobble on the screen.

Measuring B+ I am seeing between 104vdc and 112vdc, I notice it's fluctuating, and I am wondering what is causing that.

Isolation Transformer is supplying the monitor with a stable 125 VAC.

I noticed 2 things, the horizontal hold pot doesn't respond much, and horizontal wobble / size shifts are related the the brightness and amount of stuff being shown on the screen, so I am guessing something is still out of spec somewhere.

I'm guessing is that my wobble is coming from the B+ voltage fluctuating, but what would be causing that ?

Also to note, the time I see the wobble the most is when the screen changes, going to black and then refilling the whole screen with an image, looks kinda like if you were to poke jello at the edges.

Any more input would be appreciated.

~Night

[buffett]

i would do a full cap out including the filter cap.

a faulty filter cap will give you the wobbles in your pic.

after that i would re-flow the entire power section and the neck board.

Peace
Buffett