[ARC5] BC-348-R Update

[Dennis Monticelli]

FYI.  An old powered computer speaker works as a signal tracer.  Put a 100K
resistor in series with its medium Z input for audio tracing.  Add a diode
for IF detection.

Dennis AE6C

On Thu, Aug 18, 2022 at 1:10 AM Robert Downs via ARC5 <arc5 at mailman.qth.net>
wrote:

> Jim, you might want to check the B- bias line running from the B-
> dynamotor brush holder through to the grid of the audio output tube.  It
> should be only a few volts below ground.
>
> Robert Downs
>
> -----Original Message-----
> From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net]
> On Behalf Of JAMES FALLS
> Sent: Thursday, August 18, 2022 02:14
> To: milsurplus; ARC5
> Subject: [ARC5] BC-348-R Update
>
> Still dead.
>
> I replaced all the leaky can caps, the burnt resistor and suspect 240pF
> cap in the 2nd IF can. No leakage at the tie point detected per Dave’s
> recommendation, but it’s still silent.
>
> Dynamotor sounds happier/quieter, and I get a faint “tick” when I switch
> the BFO on or off, so at least the audio is working. DIal lights are OK.
>
> Ran it with the BC-375 in SPOT mode like I’d do to zero on a station.
> Didn’t hear a thing, and the 375 was putting out its usual 50W.
>
> I’m going to pull it from the cabinet again, recheck all the tubes,
> install the relay jumper,  go thru the resistance tables, hotwire it so I
> can measure voltages and see what turns up. Start working back from the AF
> stage. Wish I’d already restored that old Signal Tracer. Fake it with my
> Eico or LM-13.
>
> At least no hot smell or crackling when I pulled the chassis after running
> a couple minutes or so. Just warm MFP.
>
> More later. Think I’ll let it sit a few days. Let my brain cool down.
>
> Jim Falls K6FWT
>
>
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