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| How To Tell When A motor Control Board is Bad https://8mmforumworldwide.com/viewtopic.php?f=8&t=1562 |
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| Author: | Dan Lail [ Fri Apr 11, 2014 2:32 pm ] | ||
| Post subject: | How To Tell When A motor Control Board is Bad | ||
I have an Elmo ST-600. It started running fast and now the motor does not come on. The lamp comes on and the VU meter lights up. All 3 fuses test good. This projector had the original belts(i replaced them) and looks brand new. I don't see any cracks in the boards. I just ordered a D525 transistor. Is that a good start? I can't read a schematic, but I do have an ohm meter. Muhahahahahaha!
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| Author: | Mike Sands [ Fri Apr 11, 2014 6:16 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Do the value of the resistors check out ok with your meter? If they do then I would check the capacitors. An ESR meter is good for that. if the caps look swelled at the sides or top that could be a sign if you don't have an ESR meter. That is how I do it with some success. I think more luck than anything. |
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| Author: | Ken Layton [ Sun Apr 13, 2014 2:02 am ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
The type 2SD525 transistor crosses to an NTE 54 replacement transistor. The "D525" (a.k.a. 2SD525) probably is the transistor that actually drives the motor. |
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| Author: | Steve Klare [ Sun Apr 13, 2014 6:34 am ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
I agree, and that transistor is a pretty decent suspect here. Basically the power transistor acts like a valve: opening and closing to regulate the current allowed to flow through the motor and the whole point of the rest of the circuit is to control the transistor. Since you have one on order, you may as well give replacing it a try. Dan, do you have an ohmeter? There is an easy way to check a transistor using one. You need the "bad" one out of circuit first. I think there is an IC im the picture too. This may be step 2 if the transistor isn't bad and we can find a relacement. |
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| Author: | Ken Layton [ Sun Apr 13, 2014 12:46 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Yeh, it looks like there is an IC also involved. I would replace the 2SD525 transistor first and see what happens. Hopefully, that will fix it. |
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| Author: | Dan Lail [ Sun Apr 13, 2014 9:05 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Ken and Steve, thanks for the pro help. The D525 should be here next week. I'll post after I solder it in. |
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| Author: | Steve Klare [ Sun Apr 13, 2014 10:03 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Sounds Good! Do the new one (and yourself) a favor and mount it to the heatsink before you solder it. Semiconductors just do better when they are kept cooler. |
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| Author: | Dan Lail [ Mon Apr 14, 2014 11:48 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
I replaced the D525 transistor and still no motor. I ![[set5_b/set5_b/smash.gif]](./images/smilies/set5_b/set5_b/smash.gif "smash") am going for the IC next.
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| Author: | Ken Layton [ Tue Apr 15, 2014 12:13 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Your picture did not show any numbers or maker of the IC. Some types of speed control ICs are long obsolete and very hard to find or else maybe unobtainium. Still also would be a good idea to test the four electrolytic capacitors with an ESR meter or simply replace them if you don't have a meter since those caps are dirt cheap. I see a small "transistor" on the board, but I suspect it may not be a transistor at all. I think it could be a +5 volt (or other voltage) regulator. |
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| Author: | Dan Lail [ Tue Apr 15, 2014 10:09 pm ] |
| Post subject: | Re: How To Tell When A motor Control Board is Bad |
Ken, I don't have the IC out yet. Things got busy around here. I can't see the value on yet. |
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