Amplifone vector monitor - vertical collapse

jehuie

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My Star Wars monitor suddenly only has graphics along a straight horizontal line going through the middle. I haven't even opened it up yet. I will start by looking for cold solder joints and such.

But failing that....does anyone have any troubleshooting tips for this for once I get in there? I searched the threads on here but didn't see much that was helpful so far.

Thanks!
 
check bottle cap transistors(2N3716's and 2N3792's) on the heat sink, Check deflection transistors(MPSU57's and MPSU07's)I would start there. This is on the deflection board.
 
Check the XOUT and YOUT test points on the game board first, to make sure it didn't lose one axis. It may or may not be a monitor problem, so you want to confirm that first.

You should see between -1V and +1V DC for both X and Y, and roughly between 2V and 4V AC on both X and Y. (They will fluctuate as the game cycles through attract mode.) But if the Y AC is zero, it's a game board issue.

If it isn't the game board, start by visually inspecting the deflection board. Look for any cracked solder joints, or burned or damaged components. If there are any, just post them here, and I'll look at the schematics and try to triangulate what might have blown, to try to narrow it down.

If there are no visibly burned parts, test the 2N3716's and 2N3792's, as Robotronguy said. You can try testing them in-circuit, without removing them. Use the DMM's diode test, not a continuity test (google if needed). However if any are bad, they're more often a symptom of something else being wrong, and not the issue itself, so you'll want to test all of the other transistors for whichever axis it is, before replacing the bottlecap.

Also, there are two diodes, close to the large heatsink that the bottlecaps are on, which often short. Check those as well.
 
You should see between -1V and +1V DC for both X and Y, and roughly between 2V and 4V AC on both X and Y. (They will fluctuate as the game cycles through attract mode.) But if the Y AC is zero, it's a game board issue.

Ok I'm testing between the GND1 test point and X-Out (and Y-Out). With the meter set to DC I do indeed get the fluctuations on each of them as you indicated.

However, when I measure between those points with the meter set to AC I'm not getting a reading. Or more specifically, my meter reads 1 volt AC as soon as I touch it to GND1 and stays there when I touch either X-Out or Y-Out.

Perhaps I am not understanding what you are asking me to do?
 
Ok I'm testing between the GND1 test point and X-Out (and Y-Out). With the meter set to DC I do indeed get the fluctuations on each of them as you indicated.

However, when I measure between those points with the meter set to AC I'm not getting a reading. Or more specifically, my meter reads 1 volt AC as soon as I touch it to GND1 and stays there when I touch either X-Out or Y-Out.

Perhaps I am not understanding what you are asking me to do?



Something isn't right. I'd say sanity check your meter first. Is it an autoranging meter? Different meters behave differently, so just make sure it's in auto mode, or you have it on the right range setting, if it's a manual-ranging meter.

Make sure your meter's leads are ok as well. Put the meter into continuity test mode (so it beeps when you touch the leads together), and touch the leads together, and wiggle the leads around, to make sure you don't have a break in one of them.

Also, find some other AC source, to make sure your meter is working right. You can try measuring the 36V AC on the AR. (Put the leads across the two 36V test points to get 36V, or measure from either one to ground, which should measure 18V AC).
 
Ha. Right after I posted that I realized I had my meter on the wrong range. It looks fine on both X and Y for the AC as well.

I was hoping I'd get back in time to edit my post before anyone saw it! :)
 
Ok I'm finally finding time to look at this. I went ahead and pulled the transistors that seemed flaky to test them out of circuit. Using the diode test on my meter, one of them reads shorted no matter which way I test it (I tried all combinations and in each direction) and the other reads open no matter which way I test it.

So I should test the small transistors next to them on the heat-sink now? Can they be tested in-circuit or do I need to pull them first?

Also, I noticed this burned area on the board but the components don't look fried so I'm guessing it's from a previous issue.

I didn't see any cold solder on the back as far as I can tell.

37623458315_d487db0d34_b.jpg
 
Yes, test all of the transistors on the deflection board (and the other two smaller ones on the heatsink).

A blown bottlecap on a vector monitor is almost always a symptom of something else being wrong, not the root cause. People think they've found the issue, pop in another bottlecap, and poof, there goes another 3 bucks. You always want to check all of the smaller transistors when you find a bad bottlecap.

You can typically test them in-circuit, and don't need to remove them. Occasionally you may get a situation (with the wrong transistor blown the wrong way, in the wrong location) where you can get false readings (usually a transistor measuring ok when it really isn't), but these cases are the rare exception, not the norm.

In your case one or more are probably shorted, which are typically pretty straightforward to find.
 
Also, clean off that old thermal grease with Goof Off and some Q-tips, and replace the mica insulators with some new silicone pads, which don't use any grease. Much nicer to work with.
 
Ok the small transistors on the heat sink I'm getting strange readings. Testing them in curcuit:

Q4- PNP
B to E: Short
B to C: Short
E to B: Short
C to B: Short
C to E: Short

Q5- NPN
B to E: Drop
B to C: Short
E to B: Short
C to B: Short
C to E: Drop

Q15- NPN
B to E: Open
B to C: Short
E to B: Drop
C to B: Short
C to E: Open

Q14- PNP
B to E: Drop
B to C: Short
E to B: Open
C to B: Short
C to E: Drop

Now based on my (extremely limited) understanding....this indicates that all four of them are bad doesn't it?
 
Interesting. Do you have a good source for these?

Also, I just stumbled upon this related interesting discussion on the merits of both: http://www.diyaudio.com/forums/pass-labs/37262-mica-goop.html


Interesting thread (though I didn't read all 33 pages, lol. But I actually might.) I've been interested to know the actual thermal resistance measurement differences between silpad + mica (and there are a few different options for silpad as well), but I switched over to silpads years ago, and haven't looked back.

Atari used them on all of the AR-I's and AR-II's, and those things get pretty toasty. But the real benefit is that after 35 years, the mica on the monitors are all dried out, but the silpads on the AR's are still fine (I don't even replace them when I change the 2N3055's).

I don't get the arguments in that thread about things puncturing the silpads, as they are reinforced with fiberglass, and are pretty hard to tear. You'd have to have an extremely rough component with some kind of burr (which you then didn't remove, so you installed it poorly IMO), in order to have an issue. I've used hundreds of them on many monitors, and never had one puncture.

Anyway, I get mine here:

https://www.digikey.com/product-detail/en/SP400-0.007-00-05/BER203-ND/529920


GPE also has these (which I've used as well), which are 0.002" thicker, but I can't tell the difference:

https://www.greatplainselectronics.com/proddetail.asp?prod=SP400-0.009-00-03


They look and work great, and turn out like this:

http://forums.arcade-museum.com/showthread.php?t=404635


(I'll reply to the other transistor short comment separately, BTW.)



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Ok the small transistors on the heat sink I'm getting strange readings. Testing them in curcuit:

Q4- PNP
B to E: Short
B to C: Short
E to B: Short
C to B: Short
C to E: Short

...

Now based on my (extremely limited) understanding....this indicates that all four of them are bad doesn't it?



Not necessarily, as other nearby components being bad can cause the transistor measurements to look bad. But finding shorts like that in-circuit tells you something is wrong, and to look further.

When you find ones that have shorts, you generally want to remove and verify them, as they may test differently out of circuit. The one that is completely shorted is likely surely bad, but the others may not all be.

However, one additional thing to check first is the two diodes that are right up closest to the heatsink (CR11 in the pic in my post above, and its match on the left side of the board). Test to see if those are shorted, and I'll bet one or both of them are. If so, replace those first, then re-measure and repost the same data above for the transistors (before removing them), and see if any of them change.

EDIT: You'll also note that in the pic above, CR11 appears to be missing, but it's actually mounted on the underside of the board. I have a theory that these diodes tend to fail prematurely on these boards, and I wonder if it's because they're too close to the heatsink, and the heat shortens their lifespan. So when rebuilding, I always mount them on the underside of the board, to shield them a little more from the heat.
 
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However, one additional thing to check first is the two diodes that are right up closest to the heatsink (CR11 in the pic in my post above, and its match on the left side of the board). Test to see if those are shorted, and I'll bet one or both of them are. If so, replace those first, then re-measure and repost the same data above for the transistors (before removing them), and see if any of them change.

You are correct. CR11 is fine but the other one, CR2 is shorted. I don't have a spare so I will need to go find some schematics and figure out what it is and order one.

Do you know if there is a "shotgunning kit" available for these that comes with most of the often-replaced parts?
 
You are correct. CR11 is fine but the other one, CR2 is shorted. I don't have a spare so I will need to go find some schematics and figure out what it is and order one.

Do you know if there is a "shotgunning kit" available for these that comes with most of the often-replaced parts?

most don't recommend shotgunning parts that are good, but if you need individual parts i stock darn near every component so you can replace just what is bad.
 
most don't recommend shotgunning parts that are good, but if you need individual parts i stock darn near every component so you can replace just what is bad.

Good to know! Are you familiar enough with the monitor to know which parts should be upgraded? I know there are a lot of sources of recommended upgrades. For instance, the diode I need to replace is a IN914 it looks like. But since they seem to burn up a lot....is there something else that should go in there?
 
Bad example. Reading through teh Amplifone FAQ it looks like those stay the same size.

By the way, I forgot to mention the F1 was blown as well. Not sure if that helps diagnose things or not.
 
The diodes I mentioned are just 1N400x's. Just get a bunch of 1N4007's, as they are all 1A diodes, but the 1N007's are the highest voltage rated (1000V), so you can use them for any lower-numbered diode (as x can be 1 through 7, where 1 is 50V, and 7 is 1000V).

As mentioned, you can't shotgun these boards (and you shouldn't shotgun anything really), as the ways they fail are not all the same, depending on which parts fail. You need to figure out what parts are bad, and determine what went wrong.

Just follow what I'm telling you, be patient, and we will get you working again.
 
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