K7000 Medium Res Blues

[FrizzleFried]

Alright,  so I get what was supposed to be a working K7000 medium res chassis in the mail.  I plug it in to my tube,  fire it up...I get an initial "zap" sound then static...it seems the HV starts to fire then goes in to shut down mode.  So I remove D10 per the instructions of the seller and try again,  sure enough,  it fires up...

I am told the voltage regulator is likely shot...he sends me 2 more voltage regulators.  I install one today and I get the exact same thing.  This time,  per his instructions,  I pull the chassis and fire it up.  I can hear it working...it sounds like static coming from the anode wire...that tells me that HV is working and the regulator isn't shot,  right?

Well,  I put it back on the tube...same thing.  I get an initial "quick static zap" sound then crackle static as the HV shuts down.

I tested D10 and it measures 1 one way and .701 the other (told that is OK)....

....I also ran the monitor from a different power source just in case and got the same result as described above.

I am at my wits end here... Any suggestions?

[sarge]

I've never really worked on a k7000 medium res monitor but if it is like a standard res C57 causes symptoms similar to what you are describing.

[grantspain]

so the chassis works with the tube out of the frame?or am i misreading this

[FrizzleFried]

The chassis appears to work with the chassis removed from the frame/tube.  As soon as I install it in the tube,  HV shuts down.

[FrizzleFried]

I've never really worked on a k7000 medium res monitor but if it is like a standard res C57 causes symptoms similar to what you are describing.

The chassis was completely re-capped...

[qrz]

also check  c56  22uF /160v

a quick unpowered regulator check is to measure the pass resistor .  it should not read much less than 180 ohms.
 will read low if the str30123 is shorted.   ( 123vdc  +/-  a bit when working )
a faulty c23 ( 47uF/25v )  can cause h start problems as can c10 (1uF/50v)
and c20,21 should be checked (10uF/25v)


qrz

[qrz]

The chassis appears to work with the chassis removed from the frame/tube.  As soon as I install it in the tube,  HV shuts down.

just to be clear, does the above statement mean an unterminated anode lead , disconnected yoke and crt pcb ?   

i hope NOT   

no yoke connection affects the normal duty cycle of the h out xistor . (also affects regulated voltage)
can change the pulsewidth and cause the xistor to short
a loose anode lead .......   umm..., 30kv looking for ground .  BZZZZZZZZZAPPPPPPTT !!!
the neck board is not an issue as long as the focus lead has not been removed ( 6kv -12kv)


be safe !!!

qrz

[grantspain]

i think we are all getting confuzzled here,
i just want to be clear-frizzle,when you fire up the chassis out of the frame do you mean just unbolted and repositioned away from the frame  with all the wires connected or do you mean with the wires disconnected

[FrizzleFried]

Bah...sending it back to the guy who rebuilt it.  I meant completely removed sitting on the bench but with 120v  plugged in (per the guys instructions)...

...it "chatters" (ie static sound from the anode wire - ie a boatload of voltage snapin' around over there (which was FAR away from my hand or anything metal btw) when removed from the cabinet/frame/tube.... plug it in and it goes in to HV shutdown.  The guy says there is a chance my tube is shorted.

Fun.

[Kevin Mullins]

The guy says there is a chance my tube is shorted.

Then I would think you could leave the neckboard unplugged from the tube, turn it on and get HV chatter without it going into shutdown. (anode attached to the tube)

And the tube can be checked for shorts.
Either with a meter or better yet a tester/rejuvinator.

[FrizzleFried]

Welp,  I sent the chassis back to the guy...I'll keep you updated.

[grantspain]

is the original chassis exactly the same?

[SirPeale]

I tested D10 and it measures 1 one way and .701 the other (told that is OK)....

Was that tested out of circuit?  It should measure 0 one way and .400ish  to .700ish the other way out of circuit.