This revised procedure is
based on the Ten-Tec method and has been clarified with extra details and a
labeled image. Reference https://www.tentec.com/?p=1169
When the knob is rotated
clockwise, the dial string is wound on the PTO drive shaft to pull the pointer
toward the right side of scale. When the knob is turned counter-clockwise,
elastic cord takes up string slack and pulls the pointer toward the left side
of scale.
Procedure
1. Remove the front panel,
as per manual.
2. Turn the PTO knob fully
CCW to the low end of band. Turn the Mechanical Zero knob to midrange.
3. Make a very small loop
and tie a secure knot in the Dacron string. Leave a 1 /2 inch tag to allow for
knot slippage. Place the small loop around the pin on the PTO shaft.
4. Run the string CCW only
once around the PTO shaft. NOTE: If the pin is on top of the shaft, the string
will only need to go part way around the shaft. If the pin is on the bottom of
the shaft, run string 1 full turn around the shaft.
5. Run the string down &
under the plastic pin on the Mechanical Zero adjust knob. Then continue to the
right under pulley #l up the right side and up around pulley #2. Then go across
the top around pulley #3. The dial pointer should be placed on the string just
touching pulley #3.
6. After passing pulley #3,
go down and around pulley #4. Tie the Dacron string to the elastic cord at
about l inch from pulley #5. Tie this knot securely and you may need to put a
dab of two-part epoxy glue on the knot, to keep it from slipping.
7. Run the elastic cord over
and around Pulley #5 and then back across the panel around Pulley #6.
8. Stretch the elastic cord
about 1 inch & tie it to the solder lug, located on the screw immediately
to the left of the PTO shaft.
9. Turn the PTO shaft completely
through its range, while noting that the dial painter doesn’t bind or turn out.
If the pointer stands out from the panel, flip the pointer up & over one or
more full turns as necessary. This will prevent it from catching on front panel
when it is installed.
Foot Notes
1. The following materials
are needed for dial string mechanism repairs; 26 inches of Dacron string and 12
inches (relaxed) of elastic dial cord.
2. Ten-Tec insulated the
front panel printed circuit board with tape. By age failure, the tape may be
detaching to possibly hang-up the dial string/pointer mechanism. To solve this
problem, remove the old tape and replace it with a double layered piece of 1.5
inch width clear packing tape. Trim around the shaft cutout to fit and run it
fully across the panel, but don’t overlap the visible dial scale.
3. Don’t try to force the
graduated dial onto the PTO shaft or you’ll probably break something. Instead,
utilize a 24 inch piece of dental floss as a tool. Bend the floss into a
U-Shape and hook it over the tip of the friction clip behind the dial. Pull the
string to open the clip and then safely press the dial back in place.
4. After reassembly, the
dial string/pointer mechanism may tend to hang up. Details follow for adding
about 1\8 inch spacers to solve this problem. Obtain four hex nuts that have
slightly larger holes than the mounting screws. If necessary, run a drill
through the nuts to cut out the threads.
Temporarily install the
mounting screws through the nut spacers into the four panel mounting posts. Mix
two-part epoxy and glue the spacer nuts to the posts. After hardening, remove
the screws and note that the spacers remain in place.
5. If the Mechanical Zero
knob tends to bind on one side, widen that side of the aluminum trim slot, by
about 1/8 inch with a hacksaw and file.
6. Original lubricant that
Ten-Tec installed in the PTO assembly usually hardens over time. Consequently
the dial mechanism becomes frozen and the PTO can’t change frequency. During a
dial restringing operation, it is recommended to remove old lubricant and
replace it with fresh grease. Utilize cotton swabs and alcohol to clean old
lubricant from the PTO main bearing housing and associated spring assembly.
Re-Lubricate the PTO assembly, as follows.
Ten-Tec engineers designed
the PTO to use open gear grease because it is tacky and stays in place
when the main tuning knob is rotated. But if thinner consistency grease is
substituted, it tends to run out over time. Consequently, premature wear to the
bearing race and/or inner drive shaft will result. (In a pinch as an untried
idea, consider utilizing marine wheel bearing grease because it's tacky and
functions well in open boat trailer wheel bearings.)
7. If storing the 243 VFO
for a time, leave the dial tuned to the low end of band. This action relaxes
the elastic cord, which should give it a longer life span.
