68 RR Radio Trim Adjustment
- Thread starter Ed Martin
- Start date
Yes it can be accessed. If the antenna is extendable pull it to its longest length. Find a weak station and tune it for best reception.
Ed Martin
Well-Known Member
Thanks pnora. That's a big help! I'll try it out.
Antenna Trimming
All radios are trimmed at the factory and should
require no further trimmer adjustment. However,
whenever a radio is being installed after repair, or if
verification of trimmer adjustment is desired, proceed
as follows:
(1) Extend antenna to 40 inches.
(2) Manually tune radio to a weak signal between
1400 and 1600 K.C. (3) Increase radio volume and set tone control to
maximum treble.
(4) The trimmer screw is located at the rear lower
right hand corner of the radio and can be reached by
inserting a screwdriver into the trimmer
All radios are trimmed at the factory and should
require no further trimmer adjustment. However,
whenever a radio is being installed after repair, or if
verification of trimmer adjustment is desired, proceed
as follows:
(1) Extend antenna to 40 inches.
(2) Manually tune radio to a weak signal between
1400 and 1600 K.C. (3) Increase radio volume and set tone control to
maximum treble.
(4) The trimmer screw is located at the rear lower
right hand corner of the radio and can be reached by
inserting a screwdriver into the trimmer
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I thought this was about the dash bezel 
Ed Martin
Well-Known Member
I wonder why plastic or ceramic?
I have always used steel screwdrivers. Never heard of needing plastic or ceramic in these applications. I have been tuning these since 1968. I am sure there could be some non automotive applications that needed them used. For your 1968 just tune it as I suggested.
A capacitor is two plates across a dielectric. The trimmer screw itself is connected to one plate of the trimmer capacitor. A metal screwdriver unbalances the capacitance. Also, the trimmer is connected to the RF amplifier and a metal screwdriver, especially a long one is defeating the goal of balancing the input tuned circuits as you are connecting another antenna with your long screwdriver.
I used to have a bunch of cheap ceramic screwdriver I bought in Hong Kong in the early 1990s that I would give away with every radio I serviced, but my supply has diminished over the years.
I used to have a bunch of cheap ceramic screwdriver I bought in Hong Kong in the early 1990s that I would give away with every radio I serviced, but my supply has diminished over the years.
I understand what you are saying however in all my years trimming an antenna I have not had any difficulty or problems doing it with a short steel screwdriver. I have never seen a FSM even reference using a plastic or ceramic screwdriver. Back in the days of AM only radios in the dealership we most likely set 50 percent of them. Most people in our area wanted the AM station in the 500 kc range which had the Detroit Tigers broadcasts.
Ed Martin
Well-Known Member
I tried to adjust the trim with the antenna up all the way and tuned to the best station (which was prwetty bad) around 1400. I adjusted it about a half turn clockwise and the station got better (but still not very good), but coulds not turn it beyon that amount. It seem the screw will ony turn about one full turn total. Does that sound right? I had just fixed my antenna cable by splicing a new connection at the radio because the signal wire had got broken there years ago and this was the first to try it out. I wonder if that is part of the problem as it is a little longer than original by few inches. I though I read the cable length has some affect on tuning the trim. Thanks for your help.
Do you think. Get a new antenna.
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