A good friend of mine gave me this 138. I’ve always wanted one but never could find one. I’d like some input on how the channel selector works because I’ve never used one. Radio does not turn on as it’s been sitting for years. It was built in Japan with serial number 50709688. I’m guessing early 70s. But I’d like to get some infor on the 138 because I want to have it restored if it’s possible and also get some info on the MATTCO 777 channel selector. Thanks you
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Cobra 138 with MATTCO 777 Channel selector.
- Thread starter Texaspete359_2
- Start date
The matco 777 is nothing more than a crystal switch another words it's probably connected to channel 123 and 4 I don't know for sure but probably and then the positions on the matco switch have a crystal probably to gain the 40 channels and maybe even higher. Each position will give 4 more channels on each position. Usually one of the positions returns it to 1 thru 4 if that is where it was installed.
Ok I appreciate it. Do you know what final these radios used? I haven’t had a chance to open it up and check it out.
The 138 used a C1307 final. In stock form, it was good for 4W AM and 12W SSB output. These did NOT tune very hot, so on AM, you could get 7-8W of swing and maybe 14-15W PEP output on SSB when tuned.
~Cheers~
~Cheers~
How hard is it to find one of those finals? And if they can’t be found what would u recommend for a final?
Seems to me that's the radio with the suicidal relay.
We learned to watch the radio's current draw in sideband transmit. The ALC should never bet set for more than 3 Amps current draw on sideband transmit. "Opening up" the ALC for more power would overheat the relay contacts. The plastic that supports them would soften, and the contact points would sag together until both transmit and receive sides would energize at the same time.
Caused a short to ground on the main power bus in the circuit board.
Not sure where you would find that exact relay these days.
Or if.
73
We learned to watch the radio's current draw in sideband transmit. The ALC should never bet set for more than 3 Amps current draw on sideband transmit. "Opening up" the ALC for more power would overheat the relay contacts. The plastic that supports them would soften, and the contact points would sag together until both transmit and receive sides would energize at the same time.
Caused a short to ground on the main power bus in the circuit board.
Not sure where you would find that exact relay these days.
Or if.
73
Nope, it's a 4-pole, same size/shape as Potter and Brumfield R10.
But with the order of the center row of four common pins different.
Adapting the american-style relay is a challenge. No overhead clearance to allow a socket. A clumsy patch-and-jumper task. And not a good bet for a radio used mobile, once that's been done to it.
Seems to me Barkett had some NOS relays like that a while back. But he didn't advertise them as such.
Same problem you encounter replacing the 6-pole version of this type relay in a Yaesu FT-101. The center row of common pins gets each of three pairs reversed to use the relays you can still buy.
73
But with the order of the center row of four common pins different.
Adapting the american-style relay is a challenge. No overhead clearance to allow a socket. A clumsy patch-and-jumper task. And not a good bet for a radio used mobile, once that's been done to it.
Seems to me Barkett had some NOS relays like that a while back. But he didn't advertise them as such.
Same problem you encounter replacing the 6-pole version of this type relay in a Yaesu FT-101. The center row of common pins gets each of three pairs reversed to use the relays you can still buy.
73
Would it Be better to do away with the channel selector and just run it on 23 channels? I won’t have many channels but also I do mostly am but I would like to talk sideband. But if the channel selector is junk then I don’t really need it. I just really started getting into the old school radios. Yes exit I still love my crappy exports but I’m starting to try to turn away from them.
Ok. I’m not going to run any box with it or anything I wanna just restore it and use it the way it’s supposed To be used. I have an old royse 1-602A mobile that’s been restored and I Usenet it often talking local. I’m just trying to get a collection going. Thank u for the info.