Matsushita 14" repair log

LongJohns

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Thought I would post this since there doesn't seem to be a lot of info on here with regards to the 14" monitor (there is for the 19").

This monitor is found in my Monaco GP and suffered from vertical collapse, first only partially and then full shortly after. A cap was done earlier in the year, so this was covered.

Thank to dyno for the link to the circuit diagram, here is his post from another thread I started asking if anyone had a copy of it.

Just finished working on my matsushita 14" in my monaco gp that had vertical collapse. Thought it was the vertical output transistor but that didn't solve the problem, turns out there was a switch on the monitor that I moved by luck and the vertical collapse was fixed. Here is a link to the manual and schematics http://www.arcade-museum.com/manual...nd Printing Matsushita 14in Color Raster .pdf You could try to change the vertical output transistor


First thing I checked was DC power: B+, +12vdc and +24vdc. Those all seemed fine.

The next obvious solution was to replace IC451 (AN5512) vertical output IC. This didn't solve anything so the next step was to break out the old oscilloscope and check some waveforms. Refer to the diagram for signals.

Before I went any further I verified that the yoke was reading ok and I didn't have an open winding - that was ok.

Using the scope I checked pin 6 of the yoke connector and there was no signal, which was expected as there was no vertical deflection. IC401 (AN5430) deflection signal processor was checked. First pin 13, ok and then pin 14, also ok; these provided a signal for the vertical oscillator.

Pin 11 was also checked and it's signal was ok as well.

That left pin 8, the output signal. Was getting a waveform similar to pin 13 not as shown in the diagram. IC401 was then replaced once I finally found a source for 1 (seemed to be tough to find, would appreciate it if someone knows of another source as the one I found only had 1 left and may be a good idea for me to have a spare ;) ) and all is good and back to a full picture.

Hopefully this will help someone else out in the future.

Cheers,
 
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Good information...thanks. I bought an IC401 locally in the Dayton Ohio area at an electronics surplus store. They found a cross reference on it. If I remember, I will get it added to the post. Unfortunately, this IC did not correct my collapse. I do not have an o-scope and am only going with a DMM. I hopefully will be able to get back to the monitor this month. Not enough time these days!
 
Good information...thanks. I bought an IC401 locally in the Dayton Ohio area at an electronics surplus store. They found a cross reference on it. If I remember, I will get it added to the post. Unfortunately, this IC did not correct my collapse. I do not have an o-scope and am only going with a DMM. I hopefully will be able to get back to the monitor this month. Not enough time these days!

Did you check/replace IC451 - that one would be more obvious as it is the vertical output (hence why I replaced it first). Since it didn't fix the problem I figured I best dust off the scope and figure out where to go from there.

There is a switch in there as well, make sure it is in the correct position (and is working).
 
Thanks for the advise. I did not change out the other IC. I will. Can you tell me where the switch is that you had to flip? This would be a less expensive fix than to order and buy a new IC. Thank you!
 
Thanks for the advise. I did not change out the other IC. I will. Can you tell me where the switch is that you had to flip? This would be a less expensive fix than to order and buy a new IC. Thank you!

The switch is along the edge of the board where all the other controls are (at the front of the monitor) - it looks more like a pot than a typical switch (tab at the top of the circle moves left or right flips the switch).
 
Anyone have a flowchart or decent place to start on these damn things? I have one that is totally dead now… Fuses are fine and so is the AC in.
 
Anyone have a flowchart or decent place to start on these damn things? I have one that is totally dead now… Fuses are fine and so is the AC in.

Do you have any voltage on the board like +12v (measure on the emitter of Q802 or pin A15, pin A14 is GND). If no power here - something in the power supply section. Any voltage on the + side of C807 (and ground)? Do you have 115v at F2 (fuse) or emitter of Q801?
 
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