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KLM376A1-PS delivering undervoltage at test points

KLM376A1-PS delivering undervoltage at test points

2014-03-03 by tim p

In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers

Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by Bob Grieb

Hi,

  Please measure the secondary voltage of the transformer as it feeds into the diode bridge, (maybe from each fuse to ground?  And also the DC voltage across C13 and C14, the 4700 and 2200 uF caps.   Also, please measure the AC voltage across those caps, in case there is a large amount of ripple.  If we have all of those numbers we can probably tell what's going on.    If one of the transformer secondary fuses is blown, you will still get voltage, just not as much.

    Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Monday, March 3, 2014 6:52 PM
Subject: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers



Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by Chromatest J. Pantsmaker

The transformer might be under-sized... so it can't provide enough current, so the voltage is dropping.  Does the transformer get hot?


On Mon, Mar 3, 2014 at 3:52 PM, tim p <target9@hotmail.com> wrote:


In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers




RE: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by tim p

Am using an original Korg Uk 240v txr. Does not get hot.
From: Chromatest J. Pantsmaker
Sent: ‎04/‎03/‎2014 05:18
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

 

The transformer might be under-sized... so it can't provide enough current, so the voltage is dropping.  Does the transformer get hot?


On Mon, Mar 3, 2014 at 3:52 PM, tim p <target9@hotmail.com> wrote:


In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers




RE: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by tim p

Will do that this evening UK time, Bob. Thanks for the pointers.
From: Bob Grieb
Sent: ‎04/‎03/‎2014 02:06
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

 

Hi,

  Please measure the secondary voltage of the transformer as it feeds into the diode bridge, (maybe from each fuse to ground?  And also the DC voltage across C13 and C14, the 4700 and 2200 uF caps.   Also, please measure the AC voltage across those caps, in case there is a large amount of ripple.  If we have all of those numbers we can probably tell what's going on.    If one of the transformer secondary fuses is blown, you will still get voltage, just not as much.

    Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Monday, March 3, 2014 6:52 PM
Subject: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers



Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by Bob Grieb

Here are my numbers for comparison:

Secondary of power transformer:   41.2 VAC

Across 4700 uF cap:    22.7 VDC, 188 mV AC (RMS)

Across 2200 uF cap:    24.6 VDC, 215 mV AC (RMS)

     Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Tuesday, March 4, 2014 9:14 AM
Subject: RE: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
Will do that this evening UK time, Bob. Thanks for the pointers.
From: Bob Grieb
Sent: ‎04/‎03/‎2014 02:06
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
Hi,

  Please measure the secondary voltage of the transformer as it feeds into the diode bridge, (maybe from each fuse to ground?  And also the DC voltage across C13 and C14, the 4700 and 2200 uF caps.   Also, please measure the AC voltage across those caps, in case there is a large amount of ripple.  If we have all of those numbers we can probably tell what's going on.    If one of the transformer secondary fuses is blown, you will still get voltage, just not as much.

    Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Monday, March 3, 2014 6:52 PM
Subject: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers





RE: [PolySix] KLM376A1-PS delivering undervoltage at test points

2014-03-04 by tim p

You're a gentleman and a legend! Thanks Bob.
From: Bob Grieb
Sent: ‎04/‎03/‎2014 16:12
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

 

Here are my numbers for comparison:

Secondary of power transformer:   41.2 VAC

Across 4700 uF cap:    22.7 VDC, 188 mV AC (RMS)

Across 2200 uF cap:    24.6 VDC, 215 mV AC (RMS)

     Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Tuesday, March 4, 2014 9:14 AM
Subject: RE: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
Will do that this evening UK time, Bob. Thanks for the pointers.
From: Bob Grieb
Sent: ‎04/‎03/‎2014 02:06
To: PolySix@yahoogroups.com
Subject: Re: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
Hi,

  Please measure the secondary voltage of the transformer as it feeds into the diode bridge, (maybe from each fuse to ground?  And also the DC voltage across C13 and C14, the 4700 and 2200 uF caps.   Also, please measure the AC voltage across those caps, in case there is a large amount of ripple.  If we have all of those numbers we can probably tell what's going on.    If one of the transformer secondary fuses is blown, you will still get voltage, just not as much.

    Bob


From: tim p <target9@hotmail.com>
To: "PolySix@yahoogroups.com" <PolySix@yahoogroups.com>
Sent: Monday, March 3, 2014 6:52 PM
Subject: [PolySix] KLM376A1-PS delivering undervoltage at test points

 
In my ongoing P6 power supply saga, have got UK transformer hooked up ok but test points are reading

+5 = 3.6
+15 = 10.8
-15 = -10.7

Is this likely a problem with the transformer or more likely the voltage regulating components on the 376 board? Rectifiers shot?

Have tried adjusting trimpots but that does not make result in a noticeable voltage difference on the test points.

Have tested the two main Caps and they are within tolerance.

Any help or ideas appreciated.

Cheers