Browning Eagle R27/S23 31.400 MHZ Crystal Question

[cadillaccharlie]

Hi Again All !



A friend gifted me a Browning Eagle R27/S23 which I recapped and replaced the rectifier diodes because someone hooked one up wrong. I started to get fantastic receive on it but it came in and out at times with squeals and then finally went away all together after I tried spotting a fixed frequency from the transmitter spot button in fixed mode. I also noticed that the dial lights would not go out as they should in the fixed mode. I found the function rotary switch to be the culprit as the ceramic wafer was cracked in half. I tried an epoxy repair to no avail. I have a new function switch on order. My concern is this, one schematic for the R 27 shows a 31.4 MHZ crystal to chassis ground from the grid of the 12AT7 tube. The other schematic shows no 31.4 mhz crystal in the circuit but just a wire from the grid of the 12AT7 to the function switch and then to chassis ground in the fixed position of the switch. My switch had a 31.720 mhz crystal in series with a 31.4 mhz crystal from the switch to the white wire hooked directly to pin 2 of the 12AT7 tube. Was the 31.4 MHZ a later mod to the circuit of the R 27 ? I'm just stumped as to why one schematic shows the crystal and the other does not. Then I see the 31.720 added in series with the 34.1 crystal which really through me for a loop ! lol As always, even the smallest of help is appreciated !



Dave

[2600]

For starters it's 31.4 MHz, not 34.1. That crystal selects a tuneable band from channel 1 to either channel 23 or channel 27, depending on which tuning dial the radio has. The 31.72 crystal tunes from channel 28 to channel 60. For a tuning dial that only goes up to channel 23, you'll skip channels 26 and 27. Years ago, we could buy a stock crystal for 31.70 MHz. This was used for that tuning dial, and began at channel 26. The 31.72 crystal begins at channel 28. This matches a tuning dial that goes up to 27.275 at the top.

That model simply soldered the 31.4 crystal alongside the socket of V3. A long wire from that tube to the front-panel switch is how the late Mark 3 was set up for more than one tuneable band.

The 31.72 crystal isn't in series with the other. It should have one side grounded, same as the other crystal does.

The other "hot" side of each crystal is connected to V3 through the band selector switch and that long wire. This mod is a retrofit to a R27. Don't remember seeing one built with a crystal mounted to the band selector switch.

73

[cadillaccharlie]

Thank you so much for sharing your knowledge to help others ! Sorry about the typo on the 31.4 crystal. My mind was in sleep mode before bed when I posted this post lol. Attached are jpgs of the to circuit schematics with one showing the crystal wired as you stated and the other showing no crystal but what appears to be a choke to the grid or the 12AT7 tube. I also included a jpg of how the function switch was wired with the 2 crystals when I first looked at the receiver. This radio was definitely altered as after I recapped it  Used a 200 watt light bulb as a current limiter to power her up and it burned full brightness and one of the new caps got hot instantly. This is when I found one diode open and the other connected wrong directly from the transformer to ground. I want to have this baby as an "As Built" so asking for your expertise,  which circuit should I go by ?  I really appreciate your help !


Dave

Attachments:

[2600]

Both schematics show the 31.4 crystal connected directly to pin 2 of V4. The first one is from a Howard Sams-published "CB" service data book. The second one has Browning Labs' ID info at the lower-right corner.

The tuneable oscillator controlled by the main tuning knob uses the other half of V4. This has a selector that substitutes a screwdriver-adjust capacitor they called "LOK-SET" for the one with the knob and dial. It's meant to provide a fixed receive channel not affected by the main tuning dial.

Later models used multiple crystals to add band coverage. This one only provides a fixed channel using the single 31.4 crystal soldered to the tube socket.

Your radio has been modified for two tuneable bands, one from each crystal. Not gonna agree exactly with any factory-stock schematic. Both the Howard Sams diagram and the factory schemo agree about how the factory wired V4.

73

[cadillaccharlie]

Thanks for all your help.  Got the switch hooked up and the 31.4 MHZ crystal placed at pin 2 of the 12AT7 to ground all I could get was The Super Bowl at channel 23 with a low to mediocre  signal. I had all the tubes test good and I purchased a new 34.1 MHZ Crystal & 2 Nuvistor 6DS4's which I could not test with my tube tester. For the heck of it I tried another 12AT7 tube that I had laying around and "Bingo" all channels started coming in like a runaway freight train ! Now I just need to do some more TLC on the receiver & transmitter. I get a strong spot signal carrier from the transmitter but it is not modulated with a tone. Now I am making good progress   Thank you again for your help and expertise! My troubleshooting skills are coming back to me after a hiatus from my antique radio collecting days   " Eli The Ice Man" is back  lol



Dave,
KB9EGD