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May 17, 2022, 08:20:50 PM

Author Topic: CAS voltage not the same  (Read 4544 times)

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Offline Paul Birkeland

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Re: CAS voltage not the same
« Reply #30 on: December 28, 2020, 07:22:00 AM »
The next step would be to play your 100Hz tone into the amp through both channels.  Measure the AC voltage between 5 and 10 on each transformer, then also measure the AC voltage at the speaker binding posts.
Paul "PB" Birkeland

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Offline bqc

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Re: CAS voltage not the same
« Reply #31 on: December 28, 2020, 08:09:27 AM »
question on measuring at the speaker terminal, do I need to have speaker or dummy load or should it be left open?

Offline Paul Birkeland

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Re: CAS voltage not the same
« Reply #32 on: December 28, 2020, 08:17:44 AM »
I would leave it open.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline bqc

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Re: CAS voltage not the same
« Reply #33 on: December 28, 2020, 08:38:16 AM »
So with the source at full volume, the AC voltage across 5 and 10 of left transformer is 52V  and right transformer is 122 V
AC voltage across speaker terminal left 2 V, right 8 V
BTW I also measure the inductance of the 16 ohm secondary (which is what I am using)  Left transformer 0.2 mH  ,  right trans  37mH

Offline Paul Joppa

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Re: CAS voltage not the same
« Reply #34 on: December 28, 2020, 09:17:27 AM »
The photos show a wire connected to transformer terminal 6, and none connected to transformer terminal 8. This is not consistent with the 16 ohm wiring. I can't see the rest of the secondary wiring well enough to say more, but the voltage and inductance data suggest a short across a portion of the secondary.
Paul Joppa

Offline bqc

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Re: CAS voltage not the same
« Reply #35 on: December 28, 2020, 09:31:32 AM »
Sorry, the pictures were old and were taken when I had it wired for 8 ohm, I will retake pictures

Offline bqc

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Re: CAS voltage not the same
« Reply #36 on: December 28, 2020, 09:40:54 AM »
The photos show a wire connected to transformer terminal 6, and none connected to transformer terminal 8. This is not consistent with the 16 ohm wiring. I can't see the rest of the secondary wiring well enough to say more, but the voltage and inductance data suggest a short across a portion of the secondary.

Offline Paul Birkeland

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Re: CAS voltage not the same
« Reply #37 on: December 28, 2020, 10:22:59 AM »
One of your short red output transformer jumpers looks to be touching the chassis.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline bqc

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Re: CAS voltage not the same
« Reply #38 on: December 28, 2020, 10:39:54 AM »
Do you mean the jumper between 1 and 2 of the transformer ? I lifted the amp and look  at it from the side and see that there is a 1/2 gap between the jumpers and the chasis so they are not touching.

Offline bqc

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Re: CAS voltage not the same
« Reply #39 on: December 28, 2020, 11:57:43 AM »
So what to check next  to find out why there is a short in the secondary

Offline Paul Birkeland

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Re: CAS voltage not the same
« Reply #40 on: December 28, 2020, 01:28:41 PM »
Take all of the jumpers and leads off the transformer you believe is bad, but leave the wires on 5 and 10, then recheck the AC voltage across 5 and 10.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline bqc

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Re: CAS voltage not the same
« Reply #41 on: December 28, 2020, 03:50:21 PM »
with all leads and jumpers removed except at 5 and 10 on the left transformer, with input at full volume, the AC voltage across 5 and 10 on the left transformer is 55V while the AC voltage across 5 and 10 on the right transformer is 120 V

Offline bqc

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Re: CAS voltage not the same
« Reply #42 on: December 28, 2020, 06:24:01 PM »
So can we conclude that there is a short inside the transformer on the secondary winding? If so what are my options? Is the transformer still under warranty ? if not how much would it cost to get a stock replacement transformer and how can I order it?

Offline Paul Birkeland

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Re: CAS voltage not the same
« Reply #43 on: December 29, 2020, 04:56:16 AM »
Now lift the wire off terminal 10 on the output transformer, then measure the AC voltage between this wire and terminal 5 on the output transformer.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline bqc

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Re: CAS voltage not the same
« Reply #44 on: December 29, 2020, 07:12:59 AM »
with wire on left transformer terminal 10 lifted, AC between wire and terminal 5 on left transformer is 140V, a jump from 55V to 140V, while the AC voltage between 5 and 10 on the right transformer remains at 120V