[Milsurplus] BC-348-Q restoration

[William Props]

I just went through an N model this past weekend which should be close or
maybe even the same as your Q.

Everything was pretty straightforward except the crystal filter had drifted
up to almost 919 khz. After aligning the IF to that frequency, it still
didn't work worth a crap. More like an attenuator than anything. I
disassembled the crystal, and found the quartz had stuck to the side of
it's holder. It's hard to explain without pictures, but a slight poke broke
it free. I reassembled the holder and reflowed the wax with a quick pass of
the propane torch. After that the crystal peaked on 914.8 khz and worked
quite well.

That might be something to try if the crystal filter isn't very effective

Chris
W4SVA

On Mon, Jun 15, 2020, 2:33 PM Dennis Monticelli <dennis.monticelli at gmail.com>
wrote:

> Just answered one of my own questions.  The manual states that at the 1 yr
> maintenance interval, the tuning gears should be lubricated.  So they
> didn't intend to run them dry.
>
> Dennis AE6C
>
> On Mon, Jun 15, 2020 at 8:00 AM Dennis Monticelli <
> dennis.monticelli at gmail.com> wrote:
>
>> Hi guys,
>>
>> I am beginning my first BC-348 restoration. Luckily the Q model is the
>> simpler of the two basic types. It appears to have decent caps, not
>> micamol. Not badly hacked either.
>>
>> First order of business has been to remove unwanted mods. That means all
>> other than the AC supply, which fortunately was well executed.  A 1uF
>> bypass cap on the cathode of the 2nd IF has been added.  The stock 0.1uF
>> bypass is still there.  Was this a published mod to change AVC action?
>>
>> Regarding the tuning gearing.  It was stiff and I found dried grease.
>> Was any grease used on stock units?  I note the use of brass on steel gear
>> design choices which I recall is naturally lubricating.  What do you
>> recommend regarding cleaning and possible lube of the gears?  I am using
>> WD-40 on Q-tips to clean off the old lube.
>>
>> Any other restoration hints would be appreciated.
>>
>> Dennis AE6C
>>
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