Re: Sony SRF-M37V/W alignment


Gary DeBock
 

Hello Richard and Kevin,
 
     Because of a timing quirk, the SRF-M37V is one of the very few Ultralights that I haven't yet aligned.  It was part of the "Round One" Shootout posted on dxer.ca in late December, before I routinely started to align Ultralight radios prior to shootout competitions.  I know that local Puyallup, WA resident (and filter guru) Guy Atkins has done an alignment on an SRF-M37V, using instructions that I provided for a "quick and dirty" alignment on any AM portable without a service manual.  Perhaps he will read this, and share his experience. 
 
     For the benefit of those brave souls eager to align their Ultralight radio without a service manual, the "quick and dirty" alignment instructions are given below.  Proceed at your own risk, and be advised that some Ultralights (like the SRF-59) have a nasty reputation for inducing extreme regret in careless tinkerers.
 
1)  Remove the back cover to allow access to the loopstick.  Remove all wax binding the coil (or movable coil, if there are more than one) to the ferrite bar.  Ensure that the coil may be slid .25" either way, on the ferrite bar. NOTE:  The ICF-2010 and ICF-SW7600GR loopsticks cannot be aligned for sensitivity.
 
2)  If batteries are disconnected by the removal of the back panel, run jumpers and turn on the radio.  Tune in a WEAK station on the lower end of the dial (anything from 570- 630 kHz will do).  Slide the loopstick coil to peak the weak signal, and temporarily secure it with tape on the ferrite bar. NOTE:  This step will usually provide a major improvement in Ultralight radio sensitivity, and is quite easy to accomplish.
 
3)   Tune the radio to a WEAK station anywhere from 1360-1440 kHz.  On an analog radio, locate the 1400 kHz alignment trimmer (almost always located on the main tuning capacitor component) by attempting to peak the weak signal on the various trimmers, always after carefully noting the original position of the trimmers and returning to these exact positions, should the attempt prove unsuccessful.  The correct trimmer will peak the weak signal, but not shift the frequency to allow reception of adjacent stations.
    On a digital radio (assuming it is not the DT-200V, DT-200VX, DT-400W, DT-210V, DT-220V, E100, or C.Crane SWP for which we already have a procedure), the hobbyist will need to locate the correct 1400 kHz trimmer capacitor on the RF circuit board, usually adjacent to other trimmer capacitors for different bands.  Using the trial and error method described above for analog units, attempt to peak the weak signal by adjusting various trimmers, always after carefully noting the original position of the trimmers, and returning to these original positions if the peaking attempt is not successful.  The correct trimmer will peak the weak signal, but not shift the frequency to allow reception of adjacent stations.  NOTE:  AM IF transformers will behave exactly like 1400 kHz trimming capacitors, in peaking the weak signal. This is favorable to accomplish, since improvements in AM IF transformer peaking will increase the AM sensitivity.  For this reason, any component with an appearance like an IF transformer should have adjustment attempted, as described above.  The cumulative affect of multiple IF transformer adjustments can provide astonishing sensitivity improvements in some vintage radios like the TR-6400, 6R-33, etc.
 
4)   Return to the loopstick and attempt further peaking of the movable coil on the low-band (570- 630 kHz) weak signal by shifting the coil along the loopstick. If no further sensitivity improvement is noted, secure the coil in this position with wax, tape or a spot of woodworking glue. If a major improvement is noted, repeat Step 3, then repeat this step and secure the coil on the loopstick.
 
5)  Reassemble the radio, and enjoy the full sensitivity that the engineers designed for your particular model.
 
                             73,  Gary DeBock    
 
     
    




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