Re: Repairing Farmerik's SRF-29

Gary DeBock

Hi Scott,
Thanks for your comments.
Without actually using test equipment, dynamic range seems about the same as the SRF-59. The AM sensitivity (when aligned) also seems equivalent,  but the AM image reception issue (reception of a strong 1450 local on 540 kHx, complete with whistles) is something that the CXA1129N IC chip (in the SRF-59)never allowed.
The superlative CXA1129N IC chip in the SRF-59 was the subject of great fascination in our Ultralightdx group in the beginning days, Scott, and gave us the impetus to get started as a niche group. The combination of great DXing performance at a rock-bottom price made the SRF-59 wildly popular in late 2007 and early 2008.
After a crash course to learn the Adobe Photoshop software (for issuing the Award Certificates), I've also had the chance to take up your suggestion to experiment with PL-380 7.5" loopstick coils of varying inductances (300 uh center-wound, 400 uh center-wound and 500 uh, in addition to the original 550 uh model, all pictured below). The tests (both with a signal generator and using live signals) certainly showed the versatility of the Si4734 chip in providing great performance over the entire range of inductances, and I plan to report the full details shortly.
73 and Good DX,  Gary 
In a message dated 3/19/2010 6:36:33 P.M. Pacific Daylight Time, sdwillingham@... writes:


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?


--- In, 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
> _
> (
> 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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