Repairing Farmerik's SRF-29


Gary DeBock
 

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 . 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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