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GE Model 7-2990A

Posted: Thu May 25, 2023 12:41 pm
by Blubby
This radio is the first SW radio I ever bought that had a digital display. I bought it new in the 80's. I found SW performance good but
very fiddly for SSB. FM and AM BCB were outstanding! I have searched in vain for something small that equals it's AM performance.
But what I wanted to share here is that as these radios age the plastic gear on the brass main tuning knob cracks. This causes a big bump as you tune and eventually will fall off completely. A 64 pitch 18 teeth RC electric motor gear is the correct gear to replace it and is hard anodized aluminum...fastened with a 1.5mm set screw. The gear is too long so it has to be shortened. I used the set screw to fasten mine
to a drill and end milled it by hand to fit. Then I chucked up the tuning shaft and milled it down to accept the new gear. With a drill press you could also drill a bigger hole in the gear too. A deep flat was then hand filed into the shaft and the set screw was shortened very slightly so it did not protrude into the teeth of the gear. I removed the end play in the shaft while I was there and now it feels better than new!!!
I bought the gear from Yeah racing on Amazon. Yeah Racing part number MG-64018.

I bought a Sangean PR-D15 radio and was really excited by its AM performance and compared it to the GE. The GE is better...and mine is original so 40 years old and need caps and an alignment too most likely. It does have low hours though...

Thomas posted a video with one and a super radio 2, a cc crane and a 2200 panasonic. Until I went to repair mine I had never researched it and I was horrified by the prices they command used. I also found a write up saying that it was built by Panasonic for GE and is an "improved"
RF-2600. It only has a 4.75 inch ferrite bar and it still beat the Sangean with a 200mm twin coil antenna. I remain unimpressed with small modern portables on AM but the Sangean is actually excellent and unlike the GE tunes to 1710kc!!!

The GE is big. Heavy too. But still my best AM portable.

Re: GE Model 7-2990A

Posted: Thu May 25, 2023 10:38 pm
by Icon
So if I go to a hobby shop and ask for a 64 pitch 18 teeth gear, along with measurements, they can hook me up with one? And all I need do is shorten it to the same length as the original, and do some shaft work. might be a little more than what I can do.. but sometimes we have no choice.
Mine is cracked, but has all the teeth, and I am thinking it won't hold together long.

Re: GE Model 7-2990A

Posted: Fri May 26, 2023 12:36 am
by Blubby
Yes. You can search online and get it that way too. I paid 8 bucks and bought 2 of them in case I ruined one. Mine came via amazon so I probably overpaid. If you use a small screwdriver you can spread the old gear apart and it will slide up the shaft easily. Underneath it the shaft
is knurled so the gear can grip it. I just used a hand drill and a file along with some stones to turn the shaft down because I don't have a drill press. Shortening the gear is easy but you have to be steady and take your time. I am an old Master typewriter repairman and actually apprenticed into the field. I have fabricated many parts before so YMMV. When turning the shaft down I was really tempted to rush...but I didn't and it came out perfect using the drill as a handheld lathe. If you are steady you can do it. If not, a machinist can do it easily.
The c clip on the end of the shaft is tiny...and japanese. Be careful when taking it off. Once the gear is removed the shaft and tuning knob will fall right out the front of the radio. My tuning knob was on tight. There is a coil spring wound around the plastic of the knob to apply pressure on the shaft. I had to remove it to free the shaft. When I was done machining I had to carefully degrease the shaft where it goes in the knob and then reinstall the spring. Once I was done the knob was secure but now can be pulled straight off and also pushed straight on.
The only torque limiter in the radio gear train is the knob slipping on the shaft...don't glue it. If you do and someone cranks hard at the cap movement limit it will probably destroy the planetary gears. Remember...they are all nylon. OLD nylon.
Another thing. Before you unmesh any of the gears use a sharpie to mark where the gears mesh to each other. I didn't and had to retime the slide dial. The center gear is the capacitor shaft gear. Mark it across the gear teeth in the same axis as the shaft. It is a 2 piece gear that is
spring loaded. If it slips you will have excessive backlash. The sharpie marks allow you to re tension it to exactly the same position as when you took it apart.
I hope this helps.