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What am I doing wrong ??

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benjamaniac

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Nov 11, 2009, 2:06:47 AM11/11/09
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I'm all out of ideas on this one. Recapped an RCA 128 and before I put
the signal generator to it, I thought I'd just listen to it to see how
it sounded. The tuning is WAY off. 770 comes in on about 980, 1050
comes in on 1250 and to top it off, from about 700 on
down...nothing...except at about 600, I'm picking up the local airport
locator beacon that transmits on 318. I've been through the
realignment steps (per the Riders schematics) several times now and it
seems to align just fine, except that nothing changes, the tuning is
still the same as before. What am I doing wrong here ??? Any ideas
would be appreciated.
thanks,
Ben

Brenda Ann

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Nov 11, 2009, 2:33:33 AM11/11/09
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"benjamaniac" <benja...@yahoo.com> wrote in message
news:84420738-f677-446a...@f18g2000prf.googlegroups.com...

Normally, I would say that your LO is a couple hundred KHz off frequency.


Bill M

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Nov 11, 2009, 6:04:29 AM11/11/09
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benjamaniac wrote:

> I've been through the
> realignment steps (per the Riders schematics) several times now and it
> seems to align just fine, except that nothing changes, the tuning is
> still the same as before. What am I doing wrong here ??? Any ideas
> would be appreciated.
> thanks,
> Ben

Its possible that you are aligning with the generator output level set
too high and you wind up peaking on one of its harmonics.

For a test do this. Place a second radio next to the 128. Set its dial
to about 1200 and then tune the 128 back and forth until you hear the
local oscillator. That should occur with the 128's tuning dial around
740. If its anything drastically different than this then indeed the LO
is not aligned correctly.


Scott W. Harvey

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Nov 14, 2009, 12:33:26 AM11/14/09
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Sounds like the LO is aligned 455Khz higher than the receiving frequency
when it should be 455Khz lower (or 455 Khz lower when it should be 455
Khz higher). This will result in a set that appears to align OK, but
will behave with much weirdness as you tune across the band.

-Scott

Ken G.

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Nov 15, 2009, 2:00:00 PM11/15/09
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Did it work before you ''recapped '' it . To much work done at one time
can cause wiring mistakes . oops .

benjamaniac

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Nov 15, 2009, 10:34:58 PM11/15/09
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On Nov 15, 12:00 pm, goodg...@webtv.net (Ken G.) wrote:
> Did it work before you ''recapped '' it . To much work done at one time
> can cause wiring mistakes . oops .

When I started on this one, the filter caps were so far gone
that all I could get was so garbled it sounded like it was under
water. But in answer to your question, I would have to say that yes,
it did work...kinda. I'm still hammering away on this one, but I sure
appreciate all the pointers you guys have given me.
Ben

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