Power Supply V-Adjust is not responding.

[RHeTTRoNiCS]

Good day mate...now have new problem regarding my astec power supply. Should have 12Vdc output but I measured only 8Vdc. Then I tried to adjust the v-adjust trimmer but it doesn't seem to work. The trimmer resistance is changing from 0 to 5K ohms using ohm meter but voltage output is not changing....Really appreciates any help...thanks.

 

[FvM]

Possible reasons:
- output overload (did you try withjout load)
- power supply defective
- meter defective

 

[RHeTTRoNiCS]

Yes...tried already with no load...also confirmed dmm (fluke) is ok. Yes most likely power supply is faulty...so am planning to troubleshoot myself...have good knowledge in electronics but less experience in troubleshooting power supply...thus really need any inputs....thanks.

 

[RHeTTRoNiCS]

Stumped :sad:

 

[betwixt]

Astec make hundreds of different power supplies, many of custom designed for specific applications. Without knowing more about yours it's difficult to help.

The first thing to establish is whether the output is DC or you are actually seeing a varying output. A DVM is not suitable for checking that, you either need an oscilloscope or if one isn't available, a 'dirty' check is to wire a capacitor (say 47uF but not critical) in series with a loudspeaker and connect it across the output. If you just hear a loud 'pop' as the capacitor charges it indicates the output is clean and you have a stabilization fault, if you hear a hum, it indicates a problem in the rectifiers or reservoir capacitors. Please note this is not a conclusive test, for example if you have an SMPS and one of the output capcitors has gone o/c it may still produce hum but at a frequency too high to hear.

Brian.

 

[RHeTTRoNiCS]

Hello Betwixt....thanks for the sharing your idea...this astec power supply model is MP6-2Q-1E-4LL-4NN-00. Basically it consist of 1 mainframe and 5 modules. Each module has different Vdc output. But I do have problem with 12Vdc 2ch module. The problem is the upper channel (ch1) is ok, I mean I can read 12Vdc. But the bottom channel (ch2) will read only 8Vdc output. Try to trimmer v-adjust for both channels but only ch1 is working. Can you please recommend any possible root cause so I can proactively replace it and test...Please see attached file for the photo of module...Thanks a lot.

View attachment astec module.doc

 

[betwixt]

I can't find a schematic for it, either under the Astec brand name or Emerson who also seem to market it. Without a schematic it would be very difficult to repair.

All I can suggest is that it looks like both modules are fed from a single SMPS circuit so that must be OK if the other channel is working. You need to work out what kind of regulator it is before going further. For that you must look for clues within that regulator module, for example, look at IC types and whether there are many inductors. Typically a switching regulator will have more inductors than a linear one but there isn't any definitive number that tells you one way or the other. Perhaps the easiest starting point would be to take a note of all the IC numbers within the module you can see and post them here. Also, if it has an internal heat sink, note the numbers on parts bolted to it. I'm afraid we are working blind but getting some idea of what we are dealing with would be useful.

Brian.