Sudden Sanyo EZ 20 monitor issue in my DK cab

[ckong]

A few minutes ago I was enjoying a nice game of DK when suddenly out of nowhere and in the middle of gameplay the screen went black with a very small very bright vertical line in the center of the monitor!!!   

I was shocked, and in the second or so that took me to turn off the cab I still could hear the gameplay sounds. I waited a few minutes, and turned the cab on again. I could hear the game startup normally, but the monitor came on black with the same vertically centered bright line. Shutted it down immediately again.

I did not investigate yet what could be wrong, but what could be wrong? 

[level42]

You lost the vertical deflection.

Anything from a simple contact problem to a bad pot to a transistor problem.

Check you connectors first. Also check the service switch (although you probably didn't move it during a game)..

http://forums.arcade-museum.com/showthread.php?t=93743

[ckong]

Service switch is OK. But thanks for the link, it did guide me to a flow chart in which my problem and solution (hopefully) is dispalyed.

[ckong]

I found some documents (flowchart and EZ20 trouble shooting guide) which will help me to solve the monitor problem.

First thing which I have to do is to check and maybe replace TR402 and TR403 and according to the EZ20 trouble shooting guide maybe also TR401 and D401 and D403. I am electrical/technical a pretty noob, so I have a few questions about these parts:
- where stands D for? (diode?)
- where are all these parts located on the chassis (a picture would be nice)?
- how are these parts technical described (parts name and perhaps number), so that I ask the right parts in an electronics shop?
- does anyone know a good online electronics shop, preferably in the Netherlands because of shipping costs?

[level42]

TR are transistors, D is indeed diode.
C=capacitor, R=resistor,W=wire bridge and there are more of course.

Download the 20EZ manual for a parts lay-out: http://arcarc.xmission.com/PDF_Monitors/

www.rsonline.nl if you have a chamber of commerce number. No shipping costs and FAST ! They may not have all the parts because of course we need old parts. Also, expect to have to order more than 1, it's a company that normally delivers to businesses so in large(r) quantities.

But first of all you need a multi-meter to first check those components....

[ElPancho]

Hope you get this sorted Erik. Maybe start hunting after some old tv's aswell .....

Good luck, if I can be of any help lmk.

[level42]

Maybe start hunting after some old tv's aswell .....

I've been using old TV's in the past, but I'm not 100% happy with them. The old one's often don't have all the controls you need. This way, you can't adjust the screen optimally for the game.
If you go with a TV, use a very modern CRT one (like the one's Bruno uses). These have a digital setup menu that allow all settings, be sure that you have the service code for that TV before you buy it !

Also, this problem on the 20EZ should be very fixable and it's one of the best monitors around IMHO.

[ckong]

Hope you get this sorted Erik. Maybe start hunting after some old tv's aswell .....

Good luck, if I can be of any help lmk.

It's all in the game Onno. At least I had a few nice days with gameplay. And as Level42 said, it shouldn't be too hard a problem to fix it, but I first will have to practice on my soldering skills. And try to use a multimeter properly, but fortunately there are some good tuts on the www.

I just got the monitor and chassis out of the cab and now I am trying to locate the transistors, but I can't find them .... yet on this small board.  Probably because of the time of the night, eh, morning I mean.

Edit: found them, they were a bit hidden. Next step is to check the transistors. Do I have to desolder them first?

[ckong]

According technical documentation I need to replace two transistors on the 20 EZV chassis, TR402 (part number 2SC2073R) and TR403 (part number 2SA940R) to solve the vertical collapse problem.

I did a search on Ebay for these parts, and found the part numbers, but without the 'R'. Are these the same?

http://shop.ebay.com/i.html?_nkw=2sc2073&_sacat=0&_trksid=p3286.m270.l1313&_odkw=2sc2551&_osacat=0

http://shop.ebay.com/i.html?_nkw=2sa940&_sacat=0&_trksid=p3286.m270.l1313&_odkw=2sc2073&_osacat=0

[petieken]

From what I remember from electronics class at school, the suffix letters had something to do with different gain numbers (hFE). In circuits this doesn't really matter in 99% of the cases, because a decent transistor circuit is servo controlled.

The R suffix is probably from a long time ago when there was a cheaper and more expensive variation, but nowadays this transistor is probably made in only one variation (the better one) because it's probably cheaper now to manufacture only one type.

[petieken]

Okay, I looked it up and the suffix it is indeed the hFE range. Generally, higher letter = higher gain.

I would try these. Their power specs are the same, so it can't really do any harm.

[ckong]

Need some technical advice. I discharged the minitor today and pulled out the monitor chassis. The I did some measuring with a multimeter on the following transistors, with the following readings:

TR402 (part nr. 2SC2073R, NPN):
B-C connected with the probes, reading =1, connected with the probes switched, reading =.584
B-E connected with the probes, reading = .615, connected with the probes switched, reading =.594

I would say that B-E is shorted, and that this transistor is bad. Am I correct?

TR403 (part nr. 2SA940R, PNP):
B-C connected with the probes, reading = .556, connected with the probes switched, reading =1
B-E connected with the probes, reading = .615, connected with the probes switched, reading =1

I would say that this transistor is OK. Am I correct?

These transistors are both mounted on a ‘metal’ plate. Why is that?

TR401 (part nr. 2SC2551, NPN):
B-C connected with the probes, reading = 1, connected with the probes switched, reading = .555
B-E connected with the probes, reading = .007, connected with the probes switched, reading =.007

This transistor is of another type than TR402 and TR403. First because it is not mounted on a ‘metal’ plate, but the readings are also strange. A normal resistance reading, if not Infinite, should be somewhere around .600, but this transistor reads on the B-E connection only .007 (both ways) I didn’t expect the low value on the B-E connection. Can I assume this transistor is bad also, like TR402?

What is the easiest way to replace TR402. I can’t hardly reach it, because TR403 is in it’s way. Do I have to remove TR403 first? By cutting the legs and then desolder it? (never done that before).

[petieken]

Need some technical advice. I discharged the minitor today and pulled out the monitor chassis. The I did some measuring with a multimeter on the following transistors, with the following readings:

TR402 (part nr. 2SC2073R, NPN):
B-C connected with the probes, reading =1, connected with the probes switched, reading =.584
B-E connected with the probes, reading = .615, connected with the probes switched, reading =.594

I would say that B-E is shorted, and that this transistor is bad. Am I correct?

TR403 (part nr. 2SA940R, PNP):
B-C connected with the probes, reading = .556, connected with the probes switched, reading =1
B-E connected with the probes, reading = .615, connected with the probes switched, reading =1

I would say that this transistor is OK. Am I correct?

correct, transistors are like diodes so the current can only flow in one way.

These transistors are both mounted on a ‘metal’ plate. Why is that?

cooling, these are power transistors, and they need cooling if there is a high current flow.

TR401 (part nr. 2SC2551, NPN):
B-C connected with the probes, reading = 1, connected with the probes switched, reading = .555
B-E connected with the probes, reading = .007, connected with the probes switched, reading =.007

This transistor is of another type than TR402 and TR403. First because it is not mounted on a ‘metal’ plate, but the readings are also strange. A normal resistance reading, if not Infinite, should be somewhere around .600, but this transistor reads on the B-E connection only .007 (both ways) I didn’t expect the low value on the B-E connection. Can I assume this transistor is bad also, like TR402?

You should do a diode test, not a resistance reading. But either way a resistance test is also done using DC voltage and should thus also give a reading in one direction and infinite in the other. So a transistor should always give an infinite reading in one direction. Both ways non-infinite reading = broken. Both ways infinite reading = also broken.

[ckong]

Thanks Petieken. So I will have to exchange TR401 and TR402 for working ones, I suppose.

[petieken]

I just remembered something, did you desolder the transistors?
I checked the schematics and I noticed a diode across BE from T402, so your BE reading would be normal if you tested in-circuit... To check transistors properly you have to desolder them and do a diode test (or transistor test if your DMM has that function). T401 though is probably faulty, even when tested in circuit.
There is a good chance T402 & T403 are still ok, but to be sure you'll have to desolder them and test them.