Sound plays but no picture appears on screen?

[raventy]

Hey guys, I have a soul calibur arcade machine which I got from someone which "works" like as in sound plays and you can "play" the game.. but no picture appears on the screen. When opening the machine up I found a note inside saying "Int. Loss of Pic. Tap on board, pic come back. goes out after about 10 min. Tap on board again, pic come back for about 10 min then goes out." which is dated 5-19-99 so it seems like this machine had this problem once before. The machine worked fine up until it was moved recently when this problem seemed to have come back. Anyone got any ideas?

[Ken Layton]

Well, without knowing the specific make and model of your monitor I can only give generalizations:

Check for bad solder joints

Check for bad connectors

Check for bad fuses

[raventy]

well I pulled the board out of its current machine and tested it in another so I can verify that the board DOES work. The fuses I found were on the bottom of the cab by the ISO transformer which tested out to be working. (any other fuses I should know about to check?) Its interesting.. it seems as if the monitor just isnt getting power.. like their is absolutly no sound or reaction from it as a normal monitor with power would get. The monitor is a philips MO8X 25"(i belive) montor

[MonitorGuru]

The Philips label was probably on the glass tube itself (who makes tubes, not monitors, as far as I know).  Check for other labels on the electronics board (chassis) surrounding the tube.

There should always be a fuse or two on the chassis right after the power cable goes into it (should be easy to spot). Check this out next.  

If it was intermittent, it probably was a cracked neck board or chassis and unfixed it may have blown the main transistor, flyback and/or fuse on the monitor.  Or it is just in it's non working mode now and a good whack would make it come back on temporarily (or a change in temperature or humidity)

[raventy]

alright I looked on the chasis and heres what I found written on it:

Wells Gardner
Model #: 25K7197
120V 60hz 100 w Max

Also I looked around but couldnt seem to find any fuse on the chasis anywhere

[Ken Layton]

Aha! Now we're getting somewhere. There is a fuse on the 7197 in a fuse clip at the farthest away from you (close to the picture tube glass). It's hidden partially behind a black block-shaped capacitor. Fuse should be a 2 amp slo-blo.

This chassis is well known for bad solder joints especially at resistor R89 (particularlly troublesome!) the flyback, and horizontal output transistor Q11 (mounted on a large aluminum bracket). You need to order a capkit for a "K7000" series Wells monitor from either Bob Roberts or Zanen Electronics.

Your monitor is described very well at www.jstookey.com/arcade/WG_25k7191/

The 25K7191, 7193, 7194, and 7197 are the same chassis just mounted differently. Early versions had all the controls on the main monitor board. Later versions had some of the controls moved to a "remote adjustment" board connected by a short umbilical cable.

[raventy]

Thanks for the replies! Im going to order a cap kit and give it a try! thanks again!

[raventy]

hhmm well A new cap kit has been done to the monitor and the soldier joints have been checked and redone if thought needed yet still no picture appears on the screen. I would also like to note that like 5 of the caps replaced in the cap kit were found leaking all over themselves. Anyone got any ideas?

[Ken Layton]

After doing a capkit it's common to need to readjust the brightness & contrast controls and sometimes the "Screen" control on the flyback.


Next thing to do is break out the old high voltage probe and measure the high voltage. It should be in the range of 19,000 to 25,000 volts. If it's less than 19,000 volts the flyback is shot. If it's more than 25,000 volts or the voltage is swinging wildly then the  "B+ regulator" IC is bad.

[raventy]

When measuring the high volatage do you mean the 2 wires that provide the monitor chasis with power and such?