Re: Repairing Farmerik's SRF-29


sdwillingham
 

Thanks for the photos, Gary.

The SRF-29 looks like a 3-Volt system. I wonder if it might have greater dynamic range than that one-battery wonder, the SRF-59?

-Scott-

--- In ultralightdx@..., D1028Gary@... wrote:

Hello All,

When Farmerik (Richard Hayden) of Union, CT mentioned on the Ultralightdx
list that he found an old SRF-29 that needed serious help, it was an easy
decision to offer him a free repair and alignment job, in order to get a
chance to see this relatively rare analog model for the first time. In 2008 and
2009 I had performed about 65 free alignments on the SRF-59, SRF-39 (both
variants), and SRF-49, but had never run across an SRF-29, believed to be
the original member of the Sony family of CXA1129N-IC based analog radios.
Because of the intense interest of the SRF-59 and SRF-39FP in our
Ultralightdx group in early 2008, I knew that any SRF-29 photos would be of interest
to many of us.

The fairly rare SRF-29 turned out to be quite different than expected,
having not only a larger, rectangular loopstick (than the SRF-59 and other
models), but a different tuner component, volume control, and top-cabinet
tuning dial. Although the general circuitry appeared identical, the components
were almost always different, and could not be exchanged with the newer
models. But the big surprise was the master IC hidden under the SRF-29's
circuit board-- the SRF-29 is apparently not a CXA1129N model after all, but has
an IC labeled (apparently ) as CXA1238M, made in Thailand. This apparently
accounts for the slight AM image reception issue that Richard and I both
noticed, which never occurs in CXA1129N-based radios.

Richard's SRF-29 had a volume control stuck at the maximum level, which
was repaired with a spray of contact cleaner (which was fortunate, since the
spare volume controls from other models won't fit). The AM alignment
proceeded routinely, although the squarish loopstick design has the smaller
(alignment) coil backwards from the design of the CXA1129N units. In Richard's
SRF-29, AM alignment did provide a significant gain in low-band sensitivity.
The tuning dial also has a completely different gearing system to allow
the upper-cabinet location, and is actually covered by the same plastic piece
having the belt clip..

For those interested, I've uploaded a 4-photo album of Richard's SRF-29 to
our Ultralightdx photo section, showing the circuit board, master IC chip,
alignment procedure, etc. For anyone having an SRF-59, SRF-39FP or other
Sony analog Ultralight model, the SRF-29 photos should be quite interesting,
and are posted at
_http://groups.yahoo.com/group/ultralightdx/photos/album/712405260/pic/list?mode=tn&order=ordinal&start=1&dir=asc_
(http://groups.yahoo.com/group/ultralightdx/photos/album/712405260/pic/list?mode=tn&order=o
rdinal&start=1&dir=asc) . Thanks again to Richard for the chance to work
on the rare SRF-29, and hopefully it will provide great DXing service for
years to come.

73, Gary DeBock (in Puyallup, WA, USA)

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