Hi John,
On Sun, 15 Feb 2015 12:12:22 +1100, John Bennett wrote:
Problem 1. Tuning: Each division movement of the main dial moves the digital
display 1,8kHz up or down and the same on TX /RX. The Digital Display counter
has been checked against a laboratory standard and is perfectly accurate.
Why does this happen? This fault makes the rig useless.
That's a new one on me. I assume you mean the 1KHz markings on skirt of the
tuning knob are not tracking with the display. To be honest I rarely ever use
those. I know us old-timers like analog dials, but I've comp tp depend on that
nice digital display way too much. It is possible that your clutch bushing is
slipping. Remove the knob and skirt and you will see a likely hard and
deteriorated piece of rubber hose over the shaft. The job of the hose is to
allow the skirt to slip enough for you to manually calibrate it to the
fiducial but stay put when turning the knob. This can be replaced with a piece
of automotive hose cut to the same length. When you put the knob back on apply
slight inward (towards the radio) pressure as you tighten the set screw. If
that's not it then the PTO probably has an internal issue. There are PTO gurus
lurking here.
Problem 2. There is an instability problem in the bands above 14MHz. The
display goes crazy and does not lock. Higher bands useless. Why?
The high VCO is unlocking. Most likely either dirty/oxodised pins in the Molex
connectors for the plugin circuit boards or a fault on the DC-DC converter
power supply in the front right corner of the radio. Check to make sure the top
half of the transformer E-core has not fallen off. Replace the large
electrolytic capacitor on that board. Regardless, just do it. Use a decent
quality 105C part. Be prepared to check the +!0V and re-do the fixed passband
adjustments afrer you have handled the power supply board.
Problem 3. There is no or erratic keying on CW. Why?
Again, Molex connectors. Often just re-seating the plug-in circuit boards will
solve odd problems with 7-Line gear. If you have some DeOxit it wouldn't hurt
to treat them. DO NOT SPRAY. You just need a little bit on the pins.
This aged ham, licenced 1950, needs a fellow Ham with comprehensive knowledge
of the wonderful Drake TR7.
Clues, ideas, thoughts or threads I can follow greatly appreciated.
There is a wealth of information online in the message archive of this group.
Let your fingers fly.
73
-Jim
NU0C
--
Theres something out of place lets go and poke it with a stick. The
Doctor, Amys Choice
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