Dragon's Lair Fans - Arcade Lifestyle
General Chat => Technical Area => Topic started by: ckong on December 11, 2009, 11:53:22 PM
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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!!! :shock:
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? ???
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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
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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.
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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?
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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....
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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.
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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.
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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?
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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
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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.
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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.
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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).
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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.
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Thanks Petieken. So I will have to exchange TR401 and TR402 for working ones, I suppose.
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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.
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some time ago there was a threat about soldering and desoldering here
https://www.dragonslairfans.com/smfor/index.php?topic=922.0 (https://www.dragonslairfans.com/smfor/index.php?topic=922.0) maybe this helps you
the metal plate is indeed for cooling purposes , sometimes there is white paste between them, thats thermal grease
it helps to conduct the heat to the heatsink (metal plate)
its the same as the paste between the processor and the heatsink in your pc, so very good available at any pc store if you need it
through the years the paste will be dried out is my experience, and for the cost of new its recomendable to add this paste
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I did have another look at the location of the faulty transistor(s), and there is no way that I will go and try to exchange them. Too much stuff has to be removed in order to be able to replace TR402. Besides, I checked a few other transistors and got a few strange readings at them also. Could also be faulty transistors.
Decision (also based on my past experience with soldering and repair attempts): I will have this one repaired by someone else or get a replacement chassis.
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some time ago there was a threat about soldering and desoldering here
https://www.dragonslairfans.com/smfor/index.php?topic=922.0 (https://www.dragonslairfans.com/smfor/index.php?topic=922.0)
its the same as the paste between the processor and the heatsink in your pc, so very good available at any pc store if you need it
through the years the paste will be dried out is my experience, and for the cost of new its recomendable to add this paste
Actually, it's much better to get this paste at the electronics store, or even better yet, from dealextreme.com
The "regular" thermal conduct paste is fine for transistors and processors. All those kind of "arctic" paste and stuff are simply hyped up stuff because of the PC overclocking and case-modding scene. The difference in practice often is only a couple of degrees celsius between a 13 Euro paste and a 2 euro paste. Esp. for our goal, this is nuts.
Even worse: some of those Arctic pastes contain metal parts and you don't want to have electrical conductive paste in most cases !
But you are right Etienne, after 25-30 years the stuff will have dried out completely. Replacing it is very advisable. I've done it f.i. on my Amplifone deflection board, and I could FEEL the difference in heat staying at the heat-sink.
Clay Cowgill (from the multi-kits) has recently done some more scientific testing with heat measurement devices, and the results were spectacular to say the least. The (old) transistors will be working much happier after a new layer of paste.
B.t.w. Ckong, wise decision. Are you sure it's not simply a connector problem on the monitor chassis, or a bad soldering ?
My experience in electronics is that the vast majority of problems are simply contact problems.
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B.t.w. Ckong, wise decision. Are you sure it's not simply a connector problem on the monitor chassis, or a bad soldering ?
My experience in electronics is that the vast majority of problems are simply contact problems.
I am certain that at least one transistor is faulty. I also checked the soldering, but didn't see bad soldering. I already got one offer for another chassis and a tip to contact Graig von giz10p, which I did. Perhaps I will get another chassis ánd repair the one I have. A spare one is always usefull.
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Actually, it's much better to get this paste at the electronics store, or even better yet, from dealextreme.com
The "regular" thermal conduct paste is fine for transistors and processors. All those kind of "arctic" paste and stuff are simply hyped up stuff because of the PC overclocking and case-modding scene. The difference in practice often is only a couple of degrees celsius between a 13 Euro paste and a 2 euro paste. Esp. for our goal, this is nuts.
thats true, did not think of that in the first place, it was the first thing that popped up in my head as a "easy supplier"
Even worse: some of those Arctic pastes contain metal parts and you don't want to have electrical conductive paste in most cases !
I knew i forget to write it ;) , many time there is a insulator plate between the heatsink and the transistor, and like andre say's that part is not there for nothing ;D especially when there are more transistors mounted on the same heatsink
(http://www.kpsec.freeuk.com/photos/rapid/heatsink.jpg)
heatsink
(http://www.kpsec.freeuk.com/photos/rapid/insulkit.jpg)
Insulator plate
(http://www.kpsec.freeuk.com/photos/rapid/heatpast.jpg)
Thermal grease
The site i ripped the pics contains some info (http://www.kpsec.freeuk.com/components/heatsink.htm) about the heatsinks if your interested
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I got my replacement chassis yesterday from the US. Mounted it today, and whoopiedoo, it's working 100%. ;D ;D
Finally I can play my DK game again, just before the new year.
I will send the faulty chassis to Graig from Giz10p in a few weeks. He is very good with monitor chassis and I am sure that he can repair mine so that I will have a spare one. In fact, at the moment he is repairing an exact same chassis with the exact same problem for someone else. I will wait and see how that turns out before I will send mine.
Happy New Year
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Nice to hear that the best game in "arcadeland" is working again :D
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Nice, the year started well for you ....
:spaceace:
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.................whoopiedoo, it's working 100%......................... ;D ;D
Glad that's sorted !