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January 27, 2020, 08:34:26 AM

Author Topic: How to short the PT primary?  (Read 266 times)

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Offline Deke609

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How to short the PT primary?
« on: September 25, 2019, 03:45:33 PM »
I've been playing around with snubbering today. The snubbering device instructions call for every winding that is not being tested to be shorted. In the attached photo I have attempted to short everything but the HV secondary. Have I shorted the primary correctly: tying terminal 1 to terminal 6?

many thanks, Derek
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Paul Birkeland

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Re: How to short the PT primary?
« Reply #1 on: September 25, 2019, 06:32:07 PM »
What are the rest of the instructions?
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: How to short the PT primary?
« Reply #2 on: September 25, 2019, 07:09:46 PM »
I think the essence of it is: the pcb "rings" the transformer with a sub-20V AC signal, while putting a CRC snubber across the winding under test (2 parallel nodes - a C and an RC). The first C is 0.01uF, and the RC is a 0.15uF in series with a 1K trimmer resistor.  You use two scope probes: one to trigger on the falling edge of the ringer signal, and the second on the winding to look at the ringing. You adjust the scope to see the oscillations, and then dial the trimmer to snubber same.  Then you pop out the trimmer and measure the resistance, and that plus the two C values gives you your snubber.

The much longer and detailed (and accurate) version is attached.

It seemed to work fine on the BeePre, but I was having problems getting it dialed in on the Kaiju - so I suspected I was shorting the PT incorrectly. But I now think that at least part of the problem is the trimmer that came with the parts kit - the BOM calls for a Murata or a Bourns 3296W (about $2 each), but my kit came with a "Bochen". It's gone all screwy on me. It's supposed to be 25 turn, but with less than a quarter turn the measured resistance can shoot from say 10R to 2000R and then drop to below 1R. I looked up "Bochen 3296W" and found it for sale from a major Chinese online retailer @ 100 pieces for $12! As best as I can tell, no US/Canada retailer sells them. I am going to pick a Bourns tomorrow morning from a local electronics store.

But I'd still like to know if I'm shorting the primary correctly.

cheers and many thanks, Derek

Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Raymond P.

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Re: How to short the PT primary?
« Reply #3 on: September 25, 2019, 07:26:47 PM »
From the Kaiju schematics (and instructions), it looks like the primary has two separate windings. To short each, terminals 1 & 3 should be connected and terminals 4 & 6 should be connected.
Raymond P.

Offline Deke609

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Re: How to short the PT primary?
« Reply #4 on: September 25, 2019, 07:33:10 PM »
Thanks Raymond. That's what I was wondering about. That makes sense, but I think I then need to ties the two windings together by adding what you suggest to what I already have.
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: How to short the PT primary?
« Reply #5 on: September 26, 2019, 02:53:46 AM »
Raymond: a second thank you. With the benefit of some sleep I see that I need to connect the two primary windings in parallel - and then my existing connection of terminals 1 and 6 should do the trick. For some reason when I looked at the schematic last night I thought it reflected the internal wiring of the PT itself, but looking at the manual it is clear that the windings must be connected externally. I think your suggestion of shorting 1-3 and 4-6 would definitely work, but just to be extra careful I want to connect them exactly as they configured in the amp -just in case the parallel connection has some influence on secondary ringing (I have no idea whether it does - I'm just erring on the side of caution).

cheers and thanks, Derek
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Paul Birkeland

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Re: How to short the PT primary?
« Reply #6 on: September 26, 2019, 04:42:23 AM »
1 and 3 should be connected and 4 and 6 should be connected. That will short both primary windings.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Deke609

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Re: How to short the PT primary?
« Reply #7 on: September 26, 2019, 05:10:08 AM »
Many thanks both. Got my legit "Bourns" trimmers and am back in business!
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4

Offline Deke609

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Re: How to short the PT primary?
« Reply #8 on: September 26, 2019, 07:38:10 AM »
Some pics and scope traces from this morning's snubber testing of the Kaiju HV.

Much fun - and good way for me to get familiar with the basics of the scope.

cheers, Derek
Derek
______

Roon Intel NUC ->  Yggdrasil DAC -> BeePre (w/ BeeQuiet and EML 300B)  -> Kaiju (w/ DCFil and EML 300B) or Stereomour II (2A3 [EML Mesh] and 45 Conversion [EML 45B])  -> Audeze LCD4