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The Monitor FAQ
menace:
info on the zenith K7000A chassis as provided by Ken Layton:
Around 1990 or so Wells-Gardner was getting so many orders from game manufacturers that they were falling behind in production. The k7000 was their most popular model at the time for arcade video games. So they subcontracted with Zenith Electronics for Zenith to build the k7000 MAIN circuit board and NECK board (but not the remote adjustment board). This became known as the "K7000A" chassis. It did not have the usual "P447" or "P538" numbers silk screened on the circuit board like the genuine Wells-Gardners did. Instead the main board is silk screened 204-2205-07 and the neckboard is silk screened 204-2203-02.
The easiest way to identify this version is that there are TWO PINK wires going to the suction cup whereas the standard Wells-Gardner k7000 has ONE RED wire going to the suction cup. It is unfortunate that Zenith chose to partly redesign the circuit board from Wells-Gardner's design in order to use a proprietary Zenith made flyback. This particular flyback (Zenith numbers 95-4149 and A-15945) is no longer available anywhere thus making this chassis unrepairable should the flyback fail (a common problem). The flyback for standard Wells made k7000 (the 0528 flyback available from many suppliers) will not physically nor electrically work to repair the Zenith made chassis.
So if you have a k7000A chassis and the flyback is bad, then you're only hope to repair the monitor would be to either get a working regular k7000 Wells-made chassis (direct plug 'n play swap) or order an 8liners.com universal replacement chassis.
BTW, the k7000A uses the same cap kits as the regular Wells-Gardner K7000 monitors. Zenith kept the same component designations (and values) on the pc boards at least.
Oh, and to further confuse people, Wells used (mostly) Zenith picture tubes in both versions.
GalaxyForce:
My monitor was just recapped and now it doesnt work (wont turn on) , any ideas? :-X
MonitorGuru:
Did you do the recapping or did a "professional" do it?
Without more details, here are my thoughts...some may be blatently obvious, but may not to some.
- Did you reconnect the power correctly? (Test if there is 120 volts where the power comes into the chassis)
- Did you blow the fuse?
- Did you remember to reattach the ground wire that surrounds the outside of the tube and plugs into a pin on the neckboard?
- Did you reattach the anode cap correctly?
- Is there an orange glow in the neck but just no picture?
- Is there a high pitched whine when you have your ear close to the chassis? (not all people can hear this if you have damaged high-end (15.75KHz +) hearing.)
- Did you reattach the yoke wires correctly?
- Did you reattach the video input signal correctly?
- Did you double check every capacitor is installed correctly for polarity?
Start with that list and see where it leads you.
menace:
so you have your randy fromm's flow chart but aren't sure what to do with this new fangled digital multi-meter...
On a digital multimeter you should have AC volts, DC volts, Resistance (in ohms), milliamps, and Amps--some have special diode reading function and some also have npn ,pn, transistor readings.
For a (typical) arcade monitor, AC volts comes in off of the isolation transformer 110-120 (sometimes 100 if its nintendo or something). It is then converted to DC volts on the board. Therefore any measurements on the board should be done in DC unless you have some weird type, and more than likley you should ask about it first anyways before believing everything you read on the web :D.
The DC volt range can go anywhere from 5V up to 250V (or higher) so it helps if you know what voltage you should be reading before you do it (i.e. refer to your flow chart) To get your reading attach the black electrode to the frame or the ground of the chassis and use the red to probe for measurments (and don't be dumb about this--you are working with live electronics).
To test components, you should always remove them from the board unless your device specifically allows you to leave them in. An example of this would be an ESR meter to measure caps. But for all resistors, diodes, transistors the part needs to be removed so that the circuit its in doesn't confuse your readings.
For transistors, you can A. get a known good one to compare it with, B. Measure it based off the flow chart (typically the HOT is an easy one to find out if its bad or not) . For integrated circuits, you pretty much have to replace it since so few people would have the equipment to test these. For capacitors all you can really do with a multimeter is see if its open or closed. Like i said earlier, if you have an ESR meter you can actually test this but again its not your average piece of equipment.
Navmaxlp:
Just a quick thing about transistors, diodes and the testing of them. These things are basically switches. They use junctions that require a voltage to turn them on. Most Diodes and trasistors use a silicon based substance for the junction which take a small voltage to conduct.
Now what is my point? It is this...if you use a digital multimeter to test these things, the PN junction will forward bias from the multimeter's output. In other words, do a resistance check on the diode or transistor. For a diode, with the positive lead on the Anode and the negative lead on the cathode, you should read a short and with the leads flipped around, you should read open.
Transistors work the same way but are a little more complicated in that they are two junction switches. Junction one is emitter to base, and junction two is base to collector. You can perform the checks in the same manner as the diodes but as there are different types, I cant say where to put the leads.
Just know that when testing a junction, try it both ways. If it's a good junction it will be a short one way and an open the other way. Hope that helps someone and that it wasn't too confusing. Let me know if you need more info.
Oh and by the way, Menace has a good point about removing components from the circuit. I can't tell you how many times I've gotten cocky and left them in only to be proven wrong.