Hello all,
After a week of distraction - repairing an SBE SB-34 - I turned my attention back to the TR7. Time for an alignment. I had set up a proper bench, with a 5-foot shelf for test equipment. I had also
installed an LED tape under the shelf, so the entire bench is bathed in light.
To prepare, I printed out the alignment procedure. I have found two scans of the Service Manual on the net; one is complete but low quality - all the pictures in black & white ( no shades of gray ). The other one is grey-scale with usable pictures; but it is missing the first page of the alignment procedure. So I printed out the first page from one, and the rest of the pages from another.
I also took a picture of the rear circuit boards with the shield panel removed. Printed it on the color laser, and wrote the designators of all the adjustable stuff on the printout. When I opened the radio, I noted a lot of flux on the parent board; A half hour of quality time with Q-tips and IPA made it much nicer.
Getting started, the 10V was 10.35; I set it to 10.00 with my most trustworthy DMM - an almost
new Fluke 87V. That committed me to doing the complete alignment, but I was planning to do that anyway.
My new ( to me ) HP 5385A frequency counter performed admirably for setting the oscillators. Ran into a little problem with the 8.05MHz oscillator; the adjustment cap didn't
have enough range. There's a cap in parallel with it, and the manual advises that you can change that one. 10 caps and 2000 years later, it was dead nuts on. First, I was adjusting it the wrong way - it's subtractive mixing, duhhh. Then with out realizing it, I moved the PBT control in the
heat of battle, and kept adjusting...
One problem was that I didn't have the right size tuning tool for the small adjustable inductors. I used to have every tuning tool known to man, but that was years ago, and they seem to have gradually dribbled away. Back in my misspent youth, I worked in an instrument shop
for a few years, doing repair & calibration.... lots of peaking & tweaking back then!
I discovered that I can tune those cores with one of those screwdrivers with a plastic body & a metal tip; the ones that have an exposed metal tip at one end, and a recessed one at the other end. Two sets of tuning tools on order; one from GC Electronics, and the other one from China Inc.
Luckily, I had replaced all the power supply pots with 10-turn units. Wow, the adjustments are
pretty twitchy. No idea how one could do it with the original 3/4-turn units.
Now at the VCO calibration. The manual advises that you don't have to do it if the unlocked VCO is "about 17MHz" on 20M, and "about 32Mhz" on 15M. Well, those numbers are 18.12MHz and 33.62MHz. So I guess I should probably do it. Need to get into that area anyway to clean connectors.
In addition to the alignment, I have in hand a new 2.7kHz filter from Noble Radio. Going to install that as the default SSB filter and move the stock 2.3 to another slot.
- Jerry, KF6VB
