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 Post subject: Electra Bearcat III
PostPosted: Nov Sat 28, 2009 2:50 pm 
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Location: Great Salt Lake Valley
I'm not sure if this is the correct place to post this? :shock: Feel free to move. :D Does anyone know how to align the RF modules on these radios? I know the manual "WARNS" against this, but I have a few that were worked on by others that are repairable if I could align them properly. I have the equipment and have sucessfully aligned 70's Kenwood Tuners. Any help would be greatly appreciated. I'm hopeing to find an ex-Electra factory Technician somewhere on the internet.

Thanks.

pmeltech

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 Post subject:
PostPosted: Dec Fri 04, 2009 6:15 pm 
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Have you checked out the Sams information on this? I haven't studied it so I don't know how indepth it goes. As common as those were, sure seems like somebody would know.


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 Post subject:
PostPosted: Dec Fri 04, 2009 8:27 pm 
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Location: Great Salt Lake Valley
Yes,
I have the Sams .. it's in SD-2, but sad to say it is just the original Manufacturer's information reprinted in the Sams manual. I even have a copy of "Scanner - Monitor Servicing Guide" by Middleton and it does acknowledge "Electronically Tuned" receivers, but it also states almost verbatum the warning line in Bearcat's manual. I also spoke to the new owner of the Electra trademark, but he was not able to help either. So it looks like if I don't find someone who actually worked at the factory on these, the alignment procedure may be lost.
Thanks for the reply.

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 Post subject:
PostPosted: Dec Fri 25, 2009 6:48 am 
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It uses synthesized oscillator and phased lock loop.

If its like the Bearcat I had many many years ago. :wink:

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 Post subject:
PostPosted: Dec Sun 27, 2009 12:48 am 
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No this is before ETR radios. This is a crystal controlled 8 channel scanner. It did have a "New" feature for the time Automatic Tuning of the RF front end. This is what is giving me fits. It generates a control signal from the local oscillator and automatically tunes the RF via varactors to the frequency being received. I've been able to align a couple of the VHF Low modules empirically, but it sure would be nice to know how they did it at the factory. Thanks for the input.

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 Post subject:
PostPosted: Dec Mon 28, 2009 5:10 am 
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Location: Federalsburg, MD
Around 1990-91 I bought one of these factory reconditioned. I had one that didn't work and turning it in knocked $15 off the price as I recall. Seems like they charged $85. So, they were still doing them at that point. That was handled by the local Bearcat dealer, and I was surprised at the time that he wouldn't tackle my radio himself. I don't think he was too much of a tech. Somebody out there has got to know the ins and outs.


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 Post subject:
PostPosted: Dec Mon 28, 2009 5:39 am 
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The Electra Bearcat III service manual does provide a circuit description of the track tuning and several Figures that shows what the voltages are doing (up, down, constant) when it's scanning through a certain range. It also provides a circuit description for each of the various modules. While not specifically telling you how to align a module, a stable/accurate sweep/marker generator, along with crystals close to the band edges of interest, can probably get the alignment fairly close. Hang a scope probe on TP1 of the main board or the output of the mixer on the modules to monitor the generator signal. The voltage chart page, which also includes a logic chart section, can also be helpful to determine if device voltages are where they should be.

Pete, wa2cwa


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 Post subject:
PostPosted: Dec Thu 31, 2009 5:03 pm 
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Location: Great Salt Lake Valley
Yes, I have two different copies of op/service manuals and know what you are talking about for the descriptions. That was how I tuned the modules "empirically". That was probably a poor choice of words. I used the info gleaned from the manuals and took copious readings from all the good models I had, then tuned for best sensitivity across the band (33-48 Mhz per Electra's statement of factory alignment). This appears to be a good compromise for the lack of official alignment instructions. You would have thought the readings would have been fairly consistent from module to module, but there was a lot of variation. Even with the variations I seemed to be able to adjust each module to it's "sweet" spot. Unfortunately I chose the wrong band to start this project with. There does not appear to be any broadcasts in the state of Utah that can be reliably depended on to broadcast between 30 - 50 Mhz. Even though I used a Motorola S-1329A to align it with it would be nice to test it under real conditions. I will start this process over, but attempt to align the 150-174 Mhz band, since I can receive over the air transmissions here. On another note I was able to track down the individual who bought the rights to Electra. He was a very nice gentleman who would have sold me reprints of the original manuals as well as a very few original replacement parts. Unfortunately he was not able to supply me with additional alignment info. :cry:
If anyone wants to discuss the Electra "Track Tuned" circuit I would love to do so. Any information obtained from such a discussion should be valuable to my efforts. Thanks for the suggestions and if anyone is interested in the data I'm collecting let me know.

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