I built a dedicated variable LV PSU that tops out at 135VDC for use with a BC-342 and 314. Do you think this could work for a ‘348? I want to give those old parts a break. I found the 342 to run cool with only minor drift at LV between 90-120V. 

Jim Falls K6FWT 

On Aug 8, 2022, at 11:59, Don Sanders <[email protected]> wrote:


I found small transformers at Home Depot used for control voltage on the furnace, I believe. 24 volts at about 2 amps and $12.00. I used two to make a PS for my BC455. Should be good for other filament used also.
Dr. Don W4BWS

God Bless All




On Mon, Aug 8, 2022 at 1:53 PM <[email protected]> wrote:

I only own eight BC-348 receivers and two BC-342's, but in my opinion you'd be better off building a separate external power supply.

 

One BC-348 I bought worked right out of the shipping box and examination revealed that a previous owner had followed the Surplus Conversion article exactly, using a 300V B+ transformer with separate 6V and 5V filaments windings, a 5Y3 and a classic capacitor and choke filter.  Even without replacing the 5Y3 with solid state rectifiers this still left the B+ much too high.  The BC-348 used 220VDC from the dynamotor and will run happily with a lot less and with less stress.  I added power resistors in both the AC line and the B+ line to get the voltage down to about 200 VDC and rebuilt the mounting plate for the internal power supply into something less likely to produce a disaster.  They had used the original dynamotor mounting plate for the power supply and I replaced that with an AL plate so I could create a dynamotor pack some day; hope you are as lucky.  Unfortunately they had used the original front panel ON-OFF switch for the AC line and I did not like that much, installing a inline switch on the new power cord. 

 

Good luck!


Wayne

WB5WSV         

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