Post by cadillaccharlie on Jul 20, 2021 14:19:01 GMT -5
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 34.1 MHZ crystal to chassis ground from the grid of the 12AT7 tube. The other schematic shows no 34.1 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 34.1 mhz crystal from the switch to the white wire hooked directly to pin 2 of the 12AT7 tube. Was the 34.1 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 !
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.
"One accurate measurement is worth a thousand expert opinions" -- Admiral Grace Hopper