The next poor soul trying to fix a U2000 Help!

[carmambo]

I have a U2000 P717 chassis that is just ticking and does not seem to be exciting the flyback. With the help of this website I have been able to find there is no B+ at tp202. The power supply seems to be at issue. I found that when I scope point 13 on the schematic I seem to only have the bottom half of the square wave. My question is I am scoping these points to chassis ground is that correct? Could that be why I show 0 volts for B+? I am now trying Sarge's trick of lifting the w159 jumper and wiring a 40watt light bulb to ground to try and eliminate the the supply as the problem.  Does anyone else have any suggestions?

Craig

P.S. there was a great thread going between CastleSteve and Rob that was reaching the fixed point then all stopped. Does anyone know if they found resolution or did they finally power up there U2000's and get beamed into another dimension?

p.s.s. I wired in the 40 watt light and it did not light.. not sure where to go next?

[Ken Layton]

Call the parts department at Wells-Gardner and order this "service kit":

# S04E0000-000F Power Supply update/repair, U-2000 & U-5000 (around $25 I think)

Might as well get the other kit this model needs too:

# S05F0000-000F Vertical Sweep upgrade, U-2000 & U-5000 ($15)

[sarge]

If it did not light then your power supply is not operating correctly.  Have you changed C117?  It is a commomn failure on this chassis.  That's where I would start.

[Ken Layton]

I think C117 is a 10 uf @ 50 volt high temperature capacitor.

[qrz]

if it is ticking , the smps IS attempting to operate.....

so, make sure the h out xistor ( q704)  is not shorted.
since it likely is , also change c716 (1uF/200v) as a devaluation here WILL affect the waveform feeding the output xistor and may cause premature failure.
after verifying the HOT , check c115,c107 ,
c117 is the "startup" filter cap for the PWM drive ic . if this cap was severly devalued/high ESR, the supply wouldn't attempt to start .....
also note that an slight resistance increase in r108 ( .33/2W) may cause regulation problems....


qrz

[sarge]

C117 is 22uF @ 100V.  The supply will indeed exhibit clicking noise if this capacitor has failed.  The HOT is not likely shorted due to the fact that the supply was isolated and still failed to power up (putting a dummy load on the power supply by placing the light bulb on the output of the supply).

[carmambo]

Wow! great directions found q704 is shorted! hope this is the only problem, can anyone tell me a good location to source this. Mouser says it is obsolete (2sc3686) they cross reference one but I am concerned if the base is biased properly.  Starburst coin has one for $12.00 (whoof).  Can anyone also tell me if it is OK to power the circuit with q704 removed to check if I got my B+ back?

Thany you again for all your help!

Craig

[SirPeale]

That part crosses to an NTE2324.

[qrz]

for original devices , u might give mcm electronics a try 
800 543 4330   www.mcmelectronics.com          $6.59
or union electronics 
 800 648 6657   www.unionel.com                     $2.55-$3.95

ecg/sk/nte are usually more expensive than the originals .
AND in some instances , simply RELABELED ORIGINALS   


qrz

[Kevin Mullins]

That part crosses to an NTE2324.

Which Mouser does list: NTE 2324 $9.10

[SirPeale]

Hm...I found an original.

http://www.bdent.com/search/part.jsp?partnum=2SC3686

Yes, I've ordered from them before.  They're great.

[carmambo]

Thanks for all your help guys! A new Q704 got things going again but I have spent a week trying to set up the picture. I have good color but the picture is washed out and dim. I can't seem to get any contrast (or too much contrast) and or the same with brightness. Both the contrast and brightness pots function to the lenght of there travels but can't do enough.  On the neck board, all three bias pots work work and so does R623  (green drive pot) but R621 (red drive pot) does nothing at all. This is how the monitor acted before I put the Cap Kit in. so after all the work I seem to be at "square one".  Can anyone shed some light (no pun intended) on how to brighten up this display?

Craig

[SirPeale]

Check R811.  It may have gone open.

[Ken Layton]

Resistor R811 is a 100k 1/2 watt resistor located near the connector on the main board that goes to the remote adjustment board.

[castlesteve]

yup.  ive also used a 75k ohm there and it works fine. Glad you got it up and running.  I havent logged on in a while.