How to "trim" in the radio???

[Christopher A.]

I was told that there is a way to synch the original radio with the antenna, which was referred to as "t******* in" the radio.

My radio has not worked well, sometimes not at all, since i had it rebuilt. Initially i was told by the rebuilder that it was not working because i was using a reproduction speaker with components that varied from the originals, so i bought an expensive correct reproduction speaker, same problem. I can get a very light signal on two stations, but nothing else. If the antenna is up, the signal gets worse.
-The coaxial cable appears to be fine with no breaks, but it is the original.
-I've tried 3 different speakers

Anyway, i was told there is a screw on the side of the radio that will allow me to adjust the "trim". I do not see an adjustment screw, so i thought i would ask here if anybody is familiar with the trim adjustment.

I guess if that is not an option, then i will try a new coaxial cable next.

[Wayne W.]

Re: How to "trim" in the radio???

The trimmer on radios was usualy under the tuning knob or near the antenna cable connection on old radios. I dont know if yours has one or not, but you tuned to a weak station near the 1100 end of the dial and tuned it for best reception.

[Robert G.]

Re: How to "trim" in the radio???

One way to trim the radio is to get an SWR (standing wave ratio) meter from Radio Shack. Before you do that, with the radio on touch the antenna. If the reception gets louder I would suspect it is a problem with the germanium amplifier transistors that usually go bad. In addition, the correct speakers should be 10 ohm and many if not all of the replacements are 8 ohm. That's about all I know about the radios.

[Edward J.]

Re: How to "trim" in the radio???

I was told that there is a way to synch the original radio with the antenna, which was referred to as "t******* in" the radio.

My radio has not worked well, sometimes not at all, since i had it rebuilt. Initially i was told by the rebuilder that it was not working because i was using a reproduction speaker with components that varied from the originals, so i bought an expensive correct reproduction speaker, same problem. I can get a very light signal on two stations, but nothing else. If the antenna is up, the signal gets worse.
-The coaxial cable appears to be fine with no breaks, but it is the original.
-I've tried 3 different speakers

Anyway, i was told there is a screw on the side of the radio that will allow me to adjust the "trim". I do not see an adjustment screw, so i thought i would ask here if anybody is familiar with the trim adjustment.

I guess if that is not an option, then i will try a new coaxial cable next.

Chris, the antenna trimmer is for fine tuning your radio on weak AM stations in the 1400 range. generally the FM signals don't have much problems,

I would do a test with a aftermarket complete antenna w/cable assy.( there not much money).just plug in to the back of radio, if it works you know you have a cable problem.

[Paul J.]

Re: How to "trim" in the radio???

Chris, you did'nt say which year C2. In general, you must set the SWRs on CB radios, but automotive AM/FM radios are less picky. Fixed mast antennas like on 67s are set at 38"? in length because that gets the SWRs close enough for FM reception. For AM reception it's not as critical, and the telescopic antennas on 63/64s can work fine at 18".

Turn your trim screw until you get the strongest signal. That's about all you'll get. If you still can't hear the station, try Ed's suggestion. If you have a 63/64, play with the antenna length. If none of this works, then you have connection problem possibly at the antenna connection inside the radio, or a short in the coaxial cable connection at the radio. You could also have a problem with the radio, or a problem with the antenna, but check out this connection first.

Paul

[Bob H.]

Re: How to "trim" in the radio???

Chris

Go with Ed's suggestion. You have eliminated the speaker as an issue so it has to be the radio or antenna at this point. Unless you live in the middle of nowhere, you should easily receive several FM stations that require no tuning. I assume you have plenty of volume even if off a station.

Am can be fine tuned with the trim screw but usually not required. It should be located behind the tuning knob. you will see it when removed. I believe it should be tuned on a high in range station.

I would not be surprised if it is the final power transistors. Hopefully, you used one of our known rebuilders that will take care of you. If not, be prepared to hear that you blew out the transistors using the wrong speaker.

Let us know how it goes.

Bob

[Christopher A.]

Re: How to "trim" in the radio???

Thanks for the info. This is for a 1966 model, so i am still not sure if it has an adjustment knob to trim the signal or not. I have not found one yet, but the radio is still installed and i am attempting to find it while crammed under the dash.

Update: I just found that the coaxial cable is bent at a 90 degree angle in the rear near the antenna and it is wrapped in tape. It feels like the cable is busted under the tape. I'm not sure how i missed that, but apparently i did. Well, either that or i wrapped it and simply do not remember, which is highly possible.

The signal goes away all together when i disconnect the coax cable, but comes back in very faintly when connected. I need to drop the muffler to investigate further. I'll report back with my findings.

[Wayne M.]

Re: How to "trim" in the radio???

.... This is for a 1966 model, so i am still not sure if it has an adjustment knob to trim the signal or not. I have not found one yet, but the radio is still installed and i am attempting to find it while crammed under the dash......

Here it is, in the small trapezoidal opening to the upper left of the station tuning knob. Once you remove the knob, the dummy bezel, the nut, and then the bezel with the lettering on it, you'll have access to this screw via the slotted arc in the dash; not necessary to remove the radio. All '65-7 model '986281' radios will have this trim screw.

[Christopher A.]

Re: How to "trim" in the radio???

Thanks Wayne, I really appreciate it!!!

[Gerard F.]

Re: How to "trim" in the radio???

Update: I just found that the coaxial cable is bent at a 90 degree angle in the rear near the antenna and it is wrapped in tape. It feels like the cable is busted under the tape. I'm not sure how i missed that, but apparently i did. Well, either that or i wrapped it and simply do not remember, which is highly possible.

Christopher,

Looks like you found the problem with a broken cable. To confirm that is the problem, just buy a cheap generic antenna and try it on FM. If you get good FM reception on other radios in your house or garage, you should get FM reception on your 66 radio. The trimmer screw works only on AM, and nearby AM stations may be a problem.

Since you had different speakers on it, it could be the transistor blown, or some other part. I had a similar problem with my 67 radio and an incorrect speaker (without the little transformer on it). The radio would work OK for a while but low in volume. Then it would heat up and then just go out. After cooling a while it would again work but pretty crappy.

I wound up changing the main transistor, the tone volume control, and got the correct 10 ohm speaker with the little transformer on it. It now works like brand new.

I have a technician's manual for the 65-67 radio with wiring diagrams, parts list and test procedures. It is about 12 pages and 2.2 meg as a pdf file. If you PM me with your direct email address, I'll send it to you.

Don't waste your time with the trimmer adjustment for AM until you eliminate the cable problem and get FM reception.

[Doug L.]

Re: How to "trim" in the radio???

Even if the cable is the problem the radio may need to be "trimmed". I can't speak about the '66 radio but the JG for '63-'64 contains a procedure. I would think the procedure would be the same for just about any radio. The '64 JG, U69, sheet 2.00 says:
1. extend the antenna mast to 31 inches +/- 1"
2. Set Volume control knob to maximum volume
3. Tune radio to signal at or near 1350 kc on AM scale
4. Adjust antenna trimmer screw until maximum, (+/- 2 degrees screw rotation) volume is received. Turn radio off.

As I recall when I had my radio restored by Jerry Rudbeck he gave me instructions on tuning it. Jerry's contact information can be found in the member's list.
Doug

[Gerald C.]

Re: How to "trim" in the radio???

I've "trimmed" my 63 am/fm radio where I get a strong am station. But when I switch to fm, all I get is static. All the components are new and correct. Jerry Rudbeck did the radio years ago, but I trust that's not the issue.

Thoughts?