[MRCA] SCR-284/BC-654 1.8

[mstangelo at comcast.net]

Ray,

I'm impressed woih your rework? How do you remove the solder on the original connection - a solder sucker?

Mike N2MS

> On 02/10/2025 2:40 PM EST Ray Fantini via MRCA <mrca at mailman.qth.net> wrote:
> 
> 
> Been a while between post, the receivers are now complete on the BC-654 project. All questionable capacitors have been replaced including very old leaky electrolytics along with Black Beauties and weird round ceramic 0.01 capacitors that break apart when you touch them! Most of the brown molded mica capacitors were still strong so they got to stay. Oddly some of the tubes tested bad with low emission and that’s something I don’t think I have seen that much on that old WW2 stuff, common on more modern radios like R-390 receivers that were left in operation for years but with the WW2 stuff its uncommon to find that they have high operation hours.
> Frequency conversion is somewhat simple along with all the work being done years before by K4CHE, so added two 27pf capacitors acrost the RF Trimers and did change from Mr. Smith’s directions in one place where he added a 120pf capacitor acrost the Oscillator capacitor that was 68 pf for a total of 188pf I removed the old 68pf unit and replaced it with a 180pf capacitor.
> On the subject or recalibrating the dial drum, Mr. Smith produced little labels and affixed them to the drum. I decided that I would produce a new strip that’s 8.5 long and .75 wide and calibrated it for the new range that’s 3.5 MHz to 5.1 MHz I am including this along with a picture of the layout of the new tuning capacitors. The new tuning strip is not linear, I have noticed at the top end of the tuning range the band spread is not the same as the bottom so I did corrections on the scale so it tracks accordingly. Remember that this scale is assuming that you are using a 180pf capacitor and do not know what the difference would be if two separate capacitors were used.
> Have one of the power supplies working and waiting for parts for the others and will be starting the transmitters next.
> Expect numbering to be along the lines of receiver 1.X, vibrator power supplies 2.X and transmitters 3.X I know that I will be doing video just don’t know if I will do one on each part or just one big one at the end? Open to comments.
> 
> Ray F/KA3EKH