Howdy all. I was given a Cobra 148 that is missing a few parts, such as the famous TR--24 transistor. Can anyone give me a part number for a TR-24 so I can order a replacement?
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Replacing the infamous TR24.
- Thread starter El Kabong
- Start date
You could pull out TR26 and install it at the TR24 position.
This will leave the AM modulation open, but still allow you to set the sideband ALC trimpot VR11 below the distortion point. Without TR24, there is no limiting in SSB modes. Transmitting sideband with no limiter can be quite unhealthy for the final transistor, not to mention the ears of anyone listening on the channel.
AM audio is more forgiving with the limiter disabled. SSB will sound like dirt without it.
Not sure who you go to for "just one" 2SC945.
73
This will leave the AM modulation open, but still allow you to set the sideband ALC trimpot VR11 below the distortion point. Without TR24, there is no limiting in SSB modes. Transmitting sideband with no limiter can be quite unhealthy for the final transistor, not to mention the ears of anyone listening on the channel.
AM audio is more forgiving with the limiter disabled. SSB will sound like dirt without it.
Not sure who you go to for "just one" 2SC945.
73
Thanks guys. I needed that.
One last question. Should there be two open holes near TR24? They are just forward of 24's spot and are not marked with an ID. I suspect they are unused.
One last question. Should there be two open holes near TR24? They are just forward of 24's spot and are not marked with an ID. I suspect they are unused.
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There are a bunch of unused holes in various places on the chassis.
I would make sure that R131 has not been clipped or removed too.
I would make sure that R131 has not been clipped or removed too.
Gotcha. The two holes I am looking at are the other direction from R131. Kinda out in the open too.
Some of those open holes are feed through passages to conduct a signal or voltages from one side of the board to the other. Also used to jump over a traces in the design.
Quite common on two layer circuit boards(Double Sided) Also one of the reasons you will see jumper wires going from one point to another.
Quite common on two layer circuit boards(Double Sided) Also one of the reasons you will see jumper wires going from one point to another.