K7000 Help

[Chopper79]

Got a K7000 19" chassis, that is completely dead, with no neck glow at all.

128v input ok. I have checked R103 is not open circuit, and tested ok. I've replaced a few caps and resistors,and 4 loose tracks. B+ is 128v on the blue wire end of resistor, and around 165v on the red lead end. I have also just replaced the hot. The voltage at the shutdown diode is 9.7v.

I've checked all over this board, and now stuck. Only thing I cant check is the flyback, which is the original white knob version, but I swear this flyback was working a few months back.

Any other suggestions?

 

[M K L]

B+ is a bit higher than it should for a 19" (123V). Shutdown uses a 12V line from the flyback so it would seem that the flyback is working. Voltage should be 12V at the anode of D10. Check if you have the other secondary voltages: 24V at the cathode of D13/R91 and 6.3Vrms at R213 on the neckboard ("true RMS" meter needed to measure this). No sign of high voltage whatsoever? Try turning the "screen" pot on the flyback and see if a raster appears.
M K L2022-09-27 11:02:02

 

[Chopper79]

I remeasured B+, and 123.5v. 166v on the other side. 11.1v at D10. Chassis completely dead, no neck glow. Turning up the flyback pots do nothing.Chopper792022-09-27 21:05:12

 

[tb2000]

I'd recheck for broken tracks/traces, especially around the parts that got hot like the big ceramic resistors etc. and check that they're not open circuit. I had a K7000 a couple of years or so ago that would just give out at random times or not start up at all. Nearly drove me up the wall, I found an almost invisible break in a track/solder point round one of the big ceramic resistors, which didn't show up on a continuity test unless I moved the components about.

 

[Chopper79]

I'm now done with this chassis.

New 5v Regulator
New Hot
New Flyback
Several new components
All dry joints resoldered
Fuse not blowing.

Still completely dead, no neck glow.

Spent nearly £80 trying to fix this piece of crap! Not spending another penny on it.

I can now see why people are fitting LCD's. I have a 19" crt tv that I will fit, and run a modded scart lead.Chopper792022-10-14 18:07:41

 

[karlcdoe]

The K7000 tube/chassis look pretty good when they are working. I haven't found them as troublesome to keep running as, for example an MTC9000. The worst issue I had was long warm up/bad focus driving me round in circles until someone here suggested changing the neck socket (I scavenged and adapted one off an old tv).

I actually managed to neck a K7000 19" tube by mistake a couple of months back

-a very rare error for me, so don't scrap your tube

Anyhow if it were me I'd completely remove the LOPT/flyback and stick in an old incandescent 60/100 watt light bulb on the inputs that normally drive the LOPT see if it lights up and then start gingerly taking measurements. Frankly I'm at least as wary of the B+ as the HV.

If you look on KLOV there's a thread on the K7000 showing a load of dodgy traces that are common to reflow or bridge with wire, the thread has be rubbished by people cross posting their 'me too' stories and fix logs but half way down page4 the post from 'modessitt' might help

https://forums.arcade-museum.com/threads/common-k7000-issues-common-repairs.134818/page-4