[Milsurplus] BC-348-Q restoration

[Mark K3MSB]

None in particular;  the usual rules of old carbon composition resistors
apply.

There is a 0.05 uF 400V cap in the Oscillator Module to be aware of.   I
had the opportunity to complete disassemble a 348Q last year (it was a true
mouse house -- gross pictures available upon request)  and I was able to
test that capacitor for current draw:

100V:   8 uA
200   36 uA
300    70 uA
400  125 uA

The "good" news (note quotation marks)  is that the voltage it has to
handle is below 200V.  Replace or not to replace?  Good question.  When I
removed all the modules on the mouse-piss junker unit I found it wasn't as
daunting as I thought it would be.    I have detailed photos of the steps
involved if interested.

73 Mark K3MSB

On Mon, Jun 15, 2020 at 11:50 AM Dennis Monticelli <
dennis.monticelli at gmail.com> wrote:

> Mark,
>
> Good point regarding 24-2.  Should not trust any cap that could take out
> iron.
>
> As for the filament resistors, this set was rewired for 6.3V and I think I
> will leave it that way.  Any other resistors to watch out for?
>
> Dennis AE6C
>
> On Mon, Jun 15, 2020 at 8:35 AM Mark K3MSB <mark.k3msb at gmail.com> wrote:
>
>> Hi Dennis
>>
>> Check the audio plate bypass cap (24-2) so you dont take out the audio
>> transformer primary if it's bad.
>>
>> Check both filament dropping resistors (85, 85).  Mine were way off.
>>
>> 73 Mark K3MSB
>>
>> On Mon, Jun 15, 2020, 11:01 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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>>
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