[Boatanchors] Re: Hii FI amp as speech amp

[Roger Basford]

----- Original Message ----- > Date: Sun, 2 Nov 2008 17:41:22 -0700
> From: "Barrie Smith" <barrie at centric.net>
> Subject: [Boatanchors] Hii FI amp as speech amp
> To: "Boatanchors Mail List" <boatanchors at mailman.qth.net>
> Message-ID: <3C81856F98044D2ABA475689A3F343DA at barrylww3pb8pz>
> Content-Type: text/plain; charset="iso-8859-1"
>
> I know it's possible to use a Hi Fi amplifier to drive the modulation in 
> the BC-610, but Googling for half a day has not yielded results.
>
> Any information on that subject greatly appreciated.
>
> 73, Barrie, W7ALW

Hi Barrie,

I had a similar problem earlier in the year with my BC-614-E and BC-610-E.

To eliminate the transmitter modulator, I injected an audio signal from a 
Marconi signal generator straight into the octal socket on the TX back. The 
sig gen I used had a 600 Ohm balanced output and can give up to 20 volts 
p-p, not an uncommon spec in older sig gens. The '610 came up OK with plenty 
of mod. The problem turned out to be the output transformer in the BC-614-E; 
the primary winding, which is centre-tapped, had gone open on both legs. I 
did have a (used) spare transformer but checking that out showed a similar 
fault. I asked around for anyone who had a transformer but the only offer I 
got turned out to be a transformer with the same fault, leading me to 
suspect this is a weak point in the '614. I eventually located a similar 
spec, but physically different, RCA transformer on ebay in the audiophile 
area and that works fine, with just a little metal work to the '614 chassis 
to make the RCA fit.

I did look at the possibility of using a modern commercial pre-amp/amplifier 
but wanted to stick with the '614 if possible. I also felt there might be an 
issue with RF getting into a modern amp.

Hope this helps,

Roger Basford, G3VKM - Norfolk, England




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