[Boatanchors] Re: Hii FI amp as speech amp

[rbethman]

Folks,

Biggest failure mode for modulation that is a "known" issue for BC-610s 
is the Mod deck input transformer, T7.

That's why I keep a couple spares on the shelf.

To apply AF directly to the Mod deck WITHOUT the BC-614, WB2FCN, (James 
Walker), does this with an old Rat Shack stereo/mono amplifier.

Suggest you contact him directly.  He's good in QRZ.

Bob - N0DGN

Roger Basford wrote:
>
> ----- 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
>
>
>
>

-- 
Bob - NØDGN