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| Repairing a Kortek/Sharp Image KTM-F Arcade Monitor (STRS5741 VR Pinout) |
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| WolfgangFox:
Hey all, I am repairing an arcade monitor and I need to know the pinout of the voltage regulator on the chassis/board. It is an STRS5741 VR, and the only datasheet I can find is a schematic of it ("https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQcu4Ov7xwGrYZMCPpDMIVgtzjFFZOGxl-hAA&s") ("https://datasheet4u.com/pdfhtml/0558/609592/page-000001.png") (Hard to find a high quality pic of the datasheet) I'm trying to troubleshoot a no b+ voltage issue, and having this pinout would be incredibly helpful. It looks like either pin 1, pin 9, or pin 2 would be the output (not sure what voltage that would be) and either one of the other pins is another voltage output? If someone could help me answer this question of the pinout, I'd appreciate it. :) I do have a schematic of the monitor board/chassis showing the connections to the VR if that would help. Edit: I found this also, on a mexican site? ("https://www.carrod.mx/cdn/shop/products/2_93bdfdba-703c-4abe-8243-1f43d4d43353_1024x1024.png?v=1658775512") |
| bostonman:
If you just need the pin out, then just measure the pins to other points on the board. If the schematic you sent is correct, then the emitter is ground, so you know one pin. From there you can figure out which one is the collector by measuring the other two pins in diode mode; or measure the pins to other components in the circuit. |
| WolfgangFox:
Yes, I thought of that, but I was trying to get the voltage references (or am I looking at this wrong?) So, I did find the chassis ground pin (2), but I get voltages on pin 1, and 9 I think it is, so which is input, output, and the other pins may have a different voltage reference on it? I only see a 12v reference on the schematic, and the B+ which I'm trying to troubleshoot should be around ~130v. Here is the schematic snippet from the monitor itself and the voltage regulator use on the schematic: The B+ measuring point is the cathode of D605, and I get ZERO volts there, so the VR could be a fault, but I don't even know how to fully test it to ensure it's putting out the proper voltages? When I measure at the C606 filter cap, I do get around 160ish but just wanted to make sure the VR was doing it's job. |
| bostonman:
I read that wrong. The "Mexican" schematic shows you circled a transistor, so I thought you were looking at a three-pin device and trying to figure out the base, collector, and emitter. Now I understand, the regulator is six or more pins. Without the datasheet, you can only "shotgun" and trace. We didn't have schematics for most monitors when I worked in the field, so that's how we did it. As for tracing, I had to figure out a multi-layer board with blind vias, so I would measure, draw, measure, draw, etc... and that's how I figured out pin outputs for a particular section of the PCB. |
| WolfgangFox:
Yeah, that is definitely what I am faced with here. The mexican site does have the transistor "section" circled. I am used to having the voltage in on a certain pin, voltage out, on a certain pin. Etc. There is even conflicting information on what the voltage regulator should be outputting (I'm thinking, once again, around 133ish volts). Any ideas from anyone? |
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