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Dynaco 400 outputs crossed

184.75.211.146

Posted on December 31, 2020 at 16:36:27
jeffl@yorku.ca
Audiophile

Posts: 4
Location: ON
Joined: December 31, 2020
Hi, When I put a sine wave from a sig. gen. in the right input, it comes out the right output (and only the right output).
When I put the sine wave in the left input, it comes out the left and the right outputs .It is not distorted and the left volume control controls
both outputs.
I have built and installed upgraded pc 28 boards.
I found that IC3 was very hot so I removed it.
Later ,I found that cap. 125 (200mfd., 3v )was totally missing!!
This amp was a kit put together by someone else.
Any help would be appreciated.
Thanks, Jeff

 

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Is it possible......................, posted on December 31, 2020 at 18:07:08
Kal Rubinson
Reviewer

Posts: 11825
Location: New York
Joined: June 5, 2002



..............that it has been internally set for mono operation?

 

RE: Is it possible......................, posted on December 31, 2020 at 19:19:24
jeffl@yorku.ca
Audiophile

Posts: 4
Location: ON
Joined: December 31, 2020
It had been working as a stereo amp. I haven't knowingly changed anything.
I have a feeling maybe there is an IC gone bad-- if it was a wiring problem
it would work both ways- the input to the right would give you two outputs as the left currently does.
(Believe me I've been at this a while...........)
Thanks for the reply,
Jeff

 

Maybe a dumb question..., posted on January 1, 2021 at 09:02:29
mlsstl
Audiophile

Posts: 523
Location: Midwest
Joined: September 1, 2015
...but have you run down the original assembly/owners manual? If not, check the link below to get a PDF version.

 

RE: Maybe a dumb question..., posted on January 1, 2021 at 10:00:02
jeffl@yorku.ca
Audiophile

Posts: 4
Location: ON
Joined: December 31, 2020
I already have the original manual.

 

RE: Maybe a dumb question..., posted on January 1, 2021 at 11:18:27
mlsstl
Audiophile

Posts: 523
Location: Midwest
Joined: September 1, 2015
From your original post, it sounds like the person who originally constructed the amp made an error or two. I used to build, rebuild and repair a lot of Dynaco tube gear and one of the most frustrating things was to run down someone else's less-than-obvious mistake. Sometimes you have to go through the manual page-by-page from the beginning to figure out what went wrong where. Good luck!

 

RE: Maybe a dumb question..., posted on January 1, 2021 at 12:01:36
jeffl@yorku.ca
Audiophile

Posts: 4
Location: ON
Joined: December 31, 2020
I should have mentioned that the amp was working fine until I put the
upgrade pc 28 boards in . The problems started after that.

 

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