[Milsurplus] BC-474

[Al Klase]

Meir and the Group,

I built a 12-volt supply based on a DM-64A dynomoter a couple of years 
ago.  I replaced the 6V6's in the TX with 12A6's.  This has all proved 
very handy.  It draws about 3 amps on receive with the TX heaters hot, 
and 5 amps on transmit.  That way a 17 AH 12-volt gelcell will run it 
for quite a while.  You can see the schematic here:  
http://ar88.net/skywaves/SCR-288_Power.pdf

73,
Al

On 3/29/2010 10:22 PM, Meir WF2U wrote:
> This discussion gives me the push I needed to cobble together a suitable
> power supply for my RCA MI-8751. It's been staring at me from a shelf long
> enough to want to start using it...
>
> 73, Meir WF2U
> Landrum, SC
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Al Klase
> Sent: Monday, March 29, 2010 8:16 PM
> To: milsurplus at mailman.qth.net
> Subject: [Milsurplus] BC-474
>
> Mike and the Group,
>
> Now you did it!  I just dragged out the RCA MI-8751/SCR-288.  That's the
> original version of the BC-474.  I managed to break the group on 75 AM,
> and got a reasonable report from K1AAM in Maine.  Not bad for an almost
> 70-year-old QRP radio working into a doublet draped front to back over
> the townhouse.
>
> Regards,
> Al
>
> On 3/29/2010 7:29 PM, Mike Feher wrote:
>    
>> Dave -
>>
>> No, I did not, but, I am well aware of what you are talking about. I have
>> never used mine on CW, just AM. I built a power supply that fits, tightly,
>> into the battery compartment, so, all I have to do is plug it in. I had to
>> use DC on the filaments and totally isolate it from the rest of the
>> circuitry as I recall due to an excessive hum otherwise. I really like
>>      
> those
>    
>> crude early sets, and the 474 sure fits into that category. 73 - Mike
>>
>> Mike B. Feher, N4FS
>> 89 Arnold Blvd.
>> Howell, NJ, 07731
>> 732-886-5960
>>
>>
>>
>>
>> -----Original Message-----
>> From: milsurplus-bounces at mailman.qth.net
>> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of David Stinson
>> Sent: Monday, March 29, 2010 7:20 PM
>> To: 'milsurplus'
>> Subject: [Milsurplus] BC-474 and TBY
>>
>>
>> ----- Original Message -----
>> From: "Mike Feher"<n4fs at eozinc.com>
>>
>>
>>      
>>> More recently, using my BC-474 I worked up and down the east
>>> coast without problems and it was fun....
>>>
>>>        
>> I had a blast with mine awhile back as well,
>> even making several contacts on AM.
>> Did you disconnect that B+ filter electrolytic
>> that is before the TR switch contact, C-13?  Before I found that,
>> the discharge arc as I switched to TX was eating-up
>> the switch contact.  It is an obvious design flaw,
>> and I can't understand how the rig could have functioned
>> for very long without destroying the switch contact.
>> I just disconnected the cap and no more problem.
>>
>>      
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/