looking for a channel selector

[cameronfby]

Hey there,

Looking for some advice on locating a new channel selector switch for a Cobra 139xlr.

The switch is a Pulser sr-157.

thanks

 

[nomadradio]

Not so different from seeking a new door handle for a 45 year-old car. It's a dealer part, but the dealer no longer stocks it.

That selector was used in a half-dozen brands that hired Uniden to make their 1978 SSB CB radios. A used one is probably your only hope. Biggest aggravation with that one is the flat cable that connects the channel selector/display board to the main circuit board. Fragile and annoying to repair.

Didn't turn one up on fleabay.

73

 

[DelR]

I need a LSB/AM/USB switch for my Cobra 139xlr, Know anything about that one??

 

[9C1Driver]

Barkett Electronics

stores.goldeneagleradios.com

This used to be a go to place for old parts. Not sure what stock is left since covid ruined everything.

 

[DelR]

Barkett Electronics

stores.goldeneagleradios.com

This used to be a go to place for old parts. Not sure what stock is left since covid ruined everything.

Nice site, but no luck on my part. Thanks for the link...

 

[nomadradio]

The XLR series radios date to 1978. Not so different from needing a part for a 1978 car. The dealer won't be any help.

Make sure you replace C179. It shorts and damages the relay. Might also clobber the circuit in the mode switch that feeds the final and driver stages.

We found a fleabay dealer in Taiwan that has similar rotary switches. The numbering of the pins will probably be different. I'll fetch the info from work and check back in tomorrow.

73

 

[nomadradio]

The switch we would use is made by Alps. A single deck has four circuits. The 139XLR schemo shows at least 5 sections in the mode selector.

Here's a fleabay link to the 8-pole version Has two decks of four circuits each.

https://www.ebay.com/itm/1441452140...pid=5336136228&customid=&toolid=10001&mkevt=1

That one has a 20 mm long shaft. The same switch with a longer 25mm shaft has the same part number. Go figure.

https://www.ebay.com/itm/1338427251...pid=5336136228&customid=&toolid=10001&mkevt=1

Pretty sure the first number with the short shaft is what your radio needs.

Tricky part comes when the numbers on the lugs won't match from the old selector to the new one.

The Alps pin numbers are below. Best of luck.

73

 

[DelR]

The switch we would use is made by Alps. A single deck has four circuits. The 139XLR schemo shows at least 5 sections in the mode selector.

Here's a fleabay link to the 8-pole version Has two decks of four circuits each.

https://www.ebay.com/itm/1441452140...pid=5336136228&customid=&toolid=10001&mkevt=1

That one has a 20 mm long shaft. The same switch with a longer 25mm shaft has the same part number. Go figure.

https://www.ebay.com/itm/1338427251...pid=5336136228&customid=&toolid=10001&mkevt=1

Pretty sure the first number with the short shaft is what your radio needs.

Tricky part comes when the numbers on the lugs won't match from the old selector to the new one.

The Alps pin numbers are below. Best of luck.

73

Thanks, I will give it a shot...

 

[cameronfby]

I appreciate all the input,

I was wondering if anyone would know if it's possible to use an Arduino to simultaneously control the oled display and inputs for the pll, that being the UPD858. I would replace the band switch with a rotary encoder.

Thanks.

 

[TM86]

I appreciate all the input,

I was wondering if anyone would know if it's possible to use an Arduino to simultaneously control the oled display and inputs for the pll, that being the UPD858. I would replace the band switch with a rotary encoder.

Thanks.

Yes. Depending on the Arduino board chosen you may need to go through an IO expander.

I had a thread here where I attempted to control the PLL and the original LED display that I never could get working right. Which is somewhat confusing as it was the second radio I had done it with and the first one is still working.

 

[nomadradio]

Simplest way to expand parallel bits like the 858 needs is a serial-to-parallel shift register. Serial in, parallel out gets abbreviated to "SIPO" sometimes. We used a 74HC165 to control a MC145106 PLL in a design from the 90s. Only needs two output pins from the controller. One for data, one for the clock. Has eight outputs. The state of the data-input pin gets shifted one bit down when the clock pin shifts from high to low. In an older design we got ten bits from a '165 by shifting the most-significant bit first. The next-to-last bit was the data-input pin. It only matters during the high-to-low transition of the clock pin and we fed that out as the ninth bit. The tenth bit is the chip's clock input pin. Since it only does anything during that high-to-low transition that output from the controller gets set high at the end of the shifting sequence. And if the least-significant bit "LSB" is is low, it just gets left alone, since the previous bits being shifted out of the controller leave it in the low state after shifting the next-to-last bit.

Whew!

The ten-bit routine was for the original Browning Mark 4 PLL. Dropped that like a rock when we saw how few of the PLL sections would stay fixed. Only needed nine bits to control a MC145106.

You may or may not wish to directly control all 10 input pins on the 858, but this trick will do it.

There are fancier port-expander chips with more parallel output bits, but the 74HC165 is cheap.

73

 

[Chris Millas]

Will this work?