U2000 repair - single click

[Woobie]

So working on repairing a 27" U2000 I have. Just feels like it's been problem after problem with it but I think its most of way there just stuck at the end

So a this point it will start up, single click then nothing. No HV, no neck glow, no video

I have taken a look at the start up circuit

R760, R765 both test properly
Replace Z702 and Z705 as they seemed out of spec (not totally bad but reverse breakdown voltages seemed off for both and was grasping at straws a bit)

Monitor appears to have been recapped

Changed flyback, MOSFET, U101, 701, b+ adjustment pot, and HOT

Set b+ to 117v. Also tried to change back to original flyback (since I heard the new ones potentially jack up the b+ and cause shutdown)

So turn on power, hear a single click, b+ appears stable, and on pin 10 of U701 I get 8.5V

So I am wondering if there is something that might be causing it to go into HV shutdown on the startup and then it never tries again? When the HOT was blowing it would click fast / repeatedly. Just not sure where to start looking now, my thoughts are either its something in the startup circuit (q708?) or just the HV shutdown is unhappy for some reason..

Any help/advice is appreciated

 

[Woobie]

So few of the resistors look cooked (R727, R728, R111). From trying to test resistance on R728 it seems to jump all over (from as low as like 100ish ohm up to the proper 1K). So guessing that one might be cooked which is causing the voltage to jump all over the place on Q704 which makes it "click" once and go into shutdown.

Going to replace those resistors that look burned up and see if that does it..

 

[behrmr]

What HOT are you using? If it's a C3688 then toss them and use and FJL6920.

If you haven't already you should do the light bulb test. Unsolder the leg of R100 that is common to TP202. If R100 is not present, unsolder the leg of jumper that is in its place that is common to TP202. Connect the unsoldered leg to one contact on the light bulb and the other contact of the bulb to a ground in the power supply (the large heat sink works). If the bulb lights and stays on the power supply is working and your issue is in the horizontal deflection section. If the bulb does not light you have a power supply problem.

 

[Woobie]

What HOT are you using? If it's a C3688 then toss them and use and FJL6920.

If you haven't already you should do the light bulb test. Unsolder the leg of R100 that is common to TP202. If R100 is not present, unsolder the leg of jumper that is in its place that is common to TP202. Connect the unsoldered leg to one contact on the light bulb and the other contact of the bulb to a ground in the power supply (the large heat sink works). If the bulb lights and stays on the power supply is working and your issue is in the horizontal deflection section. If the bulb does not light you have a power supply problem.

Yep did that first thing. When my hot blew I immediately swapped it out for a FJL6920 then did light bulb test to confirm PSU section

Like I said been chasing ghosts a bit on it ha.

When I first did that PSU section seemed bad (would start to power, click, off and cycle like that), turning up B+ stopped it but if b+ was too low would happen again. So I changed out MOSFET and U101. Issue persisted then realized when someone changed the filter cap they never soldered it properly . One leg was loose, resoldered that one and it fixed the PSU section (power then would turn on / be solid / could turn b+ all the way down and bulb would just dim)

Will change out the cooked resistors maybe tomorrow and report back. I'm honestly guessing the one that was cooked / resistance was all over is part of the problem (if not the problem itself) as it's the one feeding b+ to the horizontal section near the HOT (so if the resistor is suddenly dropping to short / near short....)

 

[Woobie]

So no joy still. Just single click and nothing

 

[Woobie]

Ok so further testing

T701 primary windings seem to be shorted (measuring r728 to r727 shows like 2 ohms)

Going to pull transformer out of circuit and test again to confirm that has a short

If it does ..anyone know what the replacement part is ?

Ok so from checking a spare k7000 I have the horizontal transformer primary windings test about the same (uses the same transformer)

 

[Woobie]

Alright. So further testing and progress

T701 was apparently installed backwards...checked my other u2000 and noticed that it was backwards, pulled it / turned it around/reconnected it and now vertical collapse (at least I get raster). Checked and around 25v at tp205 so guessing the vertical IC got toasted at some point as well. So will swap that and hopefully we are good to go

 

[M K L]

You also need 12V on pin 20 of U701.

 

[Woobie]

Ok so, progress, D301 was loose / not connected. I pushed it in and resoldered it to give a good connection. I now have picture

Buuuut now I am stuck with being unable to sync. Both horizontal and vertical sync are problematic. I can get "close" but it either rolls one way or the other

I changed out both Q601 and Q700 but no luck. Also checked and D700 seemed fine as well

 

[Woobie]

Alright so got it figure out. I looked at the other u2000 I had kicking around and it turns out the cap that goes from I believe its d805 to the collector of q601 was not installed right

When I looked at my other board it is to the collector. On this board it was to the emitter....

Replaced cap and put it to the collector and everything now works as expected