[MRCA] BC-654 Project 1.4

[B. Smith]

Lots of info:
Z

http://k4che.com/SCR-284/SCR-284%20Part%205/SCR-284%20Part%205.htm

On 1/23/2025 1:13 PM, J Mcvey via MRCA wrote:
> I used schottkey rectifiers for the low Vf  to replace the selenium 
> rectifier in the filament  circuit.
> A couple of tenths of a volt is  a lot when we are talking about 1.5 
> volts!
> The original selenium was shot, measuring about 10 ohms both ways.
>
> On Thursday, January 23, 2025 at 11:02:54 AM EST, Ray Fantini via MRCA 
> <mrca at mailman.qth.net> wrote:
>
>
> Thanks everyone for the help with the VBP-1, informed the sets owner 
> and it should be on the way. Will work with the one working VS-3 that 
> I have for now. Built a cable that has an eight-pin connector on one 
> end and lug terminals on the other for running the receiver on the 
> bench and working on getting everything sorted on the receiver before 
> attempting to change the coverage. Attached are a couple pictures of 
> before and after, all the electrolytic and big black capacitors were 
> bad. Did pull several mica capacitors in the converter and IF stages 
> and replace but examination of the micas showed that they were all 
> solid so not going to mess with the others. Also discovered a couple 
> of the 1N5 tubes were week and replaced them, whoever designed the 
> tube shields should be taken out and shot. Wanted to remove the 
> shields to clean the tubes but that’s a choir. Got sensitivity up 
> about where it should be and have plenty of audio when driving six 
> hundred Ohm headphones but no so much when trying to drive an eight 
> Ohm speaker but that’s expected. Biggest issue now is I noticed that 
> the AVC action is not all it needs to be on strong signals. May have 
> an issue with the decoupling capacitors on the AVC bus, little leakage 
> on those makes a big difference.
>
> The next item after the receiver is finished will be the power supply, 
> already started with the vibrator replacement and will also have to 
> visit the Dry Disc Rectifier issues. The receiver power pack will 
> benefit from several new solid-state devices that will all be covered 
> under part two.
>
> Ray F/KA3EKH
>
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