25k7191 voltages *UPDATE* Hula no more!

[Grauwulf]

I've been working on repairing a WG 25K7191 monitor and I'm still having a small problem. The monitor is doing a slight 'hula' so as per the troubleshooting chart on Randy Fromm's site I checked the B+ voltage at the ceramic resistor on the side frame. Now if I'm reading this right I got measurements of 155-157v DC on one side of the resistor and 105 on the other. The low side voltage dropped off to the mid 80v range after about 30 seconds or so and stayed fairly conatant ranging between roughly 85-90v. The monitor also has a blossoming problem when there's flashes on screen, or the screen switches. So the way I'm reading this is the higher voltage side of the resistor is the input to the voltage regulator and the low side is the output, and since I don't have the +130v at the output side I likely have a voltage regulator problem.

Can someone confirm this for me?

[Ken Layton]

That large white ceramic resistor is R301 and yes one side (with the red wire) is the input side. It should measure anywhere over 145 volts. The other side (blue wire) is the output side of the regulator. It should read +123 or +130 volts depending on what # the regulator is that's installed. The last 3 digits of the regulator's part number is it's output voltage (123 or 130). It could read plus or minus a volt or two depending on the quality of your voltmeter. If the output voltage is not within those specs then the regulator is shot and needs to be replaced.

[Grauwulf]

Thanks Ken, looks like I'm off to the parts store after work tonight.

[menace]

I posted ohm readings from a new voltage regulator in the FAQ--you could also compare your regulator values to those and see where you come out.  Note ken's message following the values (I forgot to add that tidbit of info in my original post)

[Ken Layton]

For reference here are the NTE replacement numbers for the various regulators that Wells-Gardner uses on the k7000 series:

STR3123 = NTE 15021

STR30123 = NTE 1776

STR30130 = NTE 1777

[Grauwulf]

Well I picked up a new voltage regulator tonight, but I got the wrong one. I got the right voltage, wrong style regulator though. *grrrrr* I guess I should have checked to make sure I had the right part number, I got a STR30130 and I actually need a STR3130. So I get to go back to the parts store tomorrow after work. I have the pinouts for both and I know I could make the STR30130 work, but I just want the right one.

[Ken Layton]

This chassis has some jumper wires you have to move (and resolder) to use a different style regulator. The jumpers are on the schematic. I find it easier to just replace with like for like.

[Grauwulf]

Thats exactly my mentality as well. I'm not messing around with this any more than I have to. I've already had to repair someone else's shoddy repair work on this chassis in addition to changing some incorrect parts. So I'm not in the mood to try and substitute parts unless I have no choice! So we'll do it all over again tonight and hopefully have a fully working monitor!

[Grauwulf]

Well I have the right voltage regulator now and I have no more hula and bossoming problem! Yay! So this concludes the saga of my first monitor repair! So now I'm on the hunt for a second 25k7191 chassis for my spare tube so I can have a second complete monitor. Thanks to everyone who has offered information and advice for all my questions. Thanks also go out to Bob Roberts and Randy Fromm, if it wasn't for all the information on their sites I probably wouldn't have attempted to do these repairs myself.

[Ken Layton]

This is great news! Glad it's working. And don't forget the information at www.jstookey.com/arcade/WG_25k7191/



This is one of the best chassis Wells-Gardner ever made. Why they discontinued it is beyond me.

[JoeB]

I second that Ken!  with a bid of TLC, the chasis should last forever!

[Grauwulf]

Thanks Ken, I don't think I actually had that link yet. I also just got a 19" k7000 monitor in a cab I picked up at an auction yesterday.