Here is part of a good thread on the rec.audio.tubes list:
Andre Jute wrote:
>
> On May 28, 4:20 am, Jon Yaeger wrote:
> > My recent post about the phasing of OPTs came up because I'm configuring
> > a
> > tube amp based around the iron from a Sansui 1000A, -- the OPTs are
> > reputedly made by
: Re: [AMRadio] push pull output XFMRs and neg feedback
>Have you tried swapping the transformers to make sure it isn't something else?
73,
Darrell, WA5VGO
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Hi John,
Just in case you are interested, I have a pair of original Altec PP
outputs and matching power trans from the 1569A amp. Ran PPP EL-34'S
for 100w into 4-8-16-70V.
I'd like to sell all 4 pieces as a set, $300 plus shipping.
73 Dennis W7TFO
--
2nd Parentheses 2:13
"And the slow of
...@mailman.qth.net]
On Behalf Of John Coleman
Sent: Thursday, May 21, 2009 9:18 AM
To: Discussion of AM Radio in the Amateur Service
Subject: Re: [AMRadio] push pull output XFMRs and neg feedback
Jim:
Open Loop:
A square wave input at about 1000 HZ results in a square wave at the
grids of the
Jim:
Open Loop:
A square wave input at about 1000 HZ results in a square wave at the
grids of the KT88s. Both channels appear equal in amplitude at the grids of
the KT88s. But the output of the 8 ohms tap to the speakers is not a square
wave but is sort of a pointed sine wave.
Message: 4
Date: Mon, 18 May 2009 19:16:10 -0400
From: John Coleman
Subject: Re: [AMRadio] push pull output XFMRs and neg feedback
To: Discussion of AM Radio in the Amateur Service
Jim
I had a chance to add the 3300 ohm resistor and the .001uf capacitor to
the circuit at the grid of
>
> Message: 3
> Date: Mon, 18 May 2009 10:42:01 -0400
> From: John Coleman
> Subject: Re: [AMRadio] push pull output XFMRs and neg feedback
>
>
> Thanks Jim
>I'll give that a try before switching the XFMRs out. I guess what
> your saying is that
nd 16
ohm secondary -- rating 40 watts
John Coleman, WA5BXO
-Original Message-
From: amradio-boun...@mailman.qth.net [mailto:amradio-boun...@mailman.qth.net]
On Behalf Of Jim Candela
Sent: Friday, May 15, 2009 11:06 PM
To: amradio@mailman.qth.net
Subject: Re: [AMRadio] push pull output XFM
Thanks Jim
I'll give that a try before switching the XFMRs out. I guess what your
saying is that the slight tolerance differences of components and layouts me be
enough to cause this and that the XFMR wires are color coded different doesn't
mean they or all wrong. In his schematic the
John,
I had similar issues with a stereo 6L6 amp I built many years ago. The
oscillation would come and go, and it eventually killed the tweeters on my old
Utah 12" 3 ways. The following article describes the problem well in a similar
amplifier:
http://www.pmillett.com/file_downloads/chic
No Darrell, I haven't swapped the XFMRs yet.
That is part of the testing that will take place but it is all on hold for a
few days because of Boy Scout events this week end. I'll keep you guys
informed as to what is found.
Come see us sometime Darrell.
Bret,
Yep I'm sure it is a phase problem a
2009 6:21 PM
Subject: [AMRadio] push pull output XFMRs and neg feedback
>
> This is maybe a little off subject here but I ran across an interesting
> thing. It may be of interest for someone building higher quality speech
> amplifiers of modulators for AM.
>
> While constructing
>Have you tried swapping the transformers to make sure it isn't something else?
73,
Darrell, WA5VGO
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pull output XFMRs and neg feedback
It sounds like you may have a shorted turn in one of them, NOS
notwithstanding. It has happened to me, and it forms a tuned circuit
resulting in a phase shift as it is an LC network now.
73 de W7TFO
It sounds like you may have a shorted turn in one of them, NOS
notwithstanding. It has happened to me, and it forms a tuned circuit
resulting in a phase shift as it is an LC network now.
73 de W7TFO
On Thu, May 14, 2009 at 3:21 PM, John Coleman wrote:
>
> This is maybe a little off subject here
This is maybe a little off subject here but I ran across an interesting thing.
It may be of interest for someone building higher quality speech amplifiers of
modulators for AM.
While constructing two identical amplifier circuits with inverse feed back for
a stereo operation, I discovered that
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