Pete,

Sounds like all of your efforts are paying off! Lots of work,
but it had to be done.

The original DM-28 dynamotor put out +220 VDC for the plates.
Sounds to me like it's OK to exceed 200 VDC. Running the set
about 70 Volts low on plate voltage could account for the low
sensitivity.

I have an all-original BC-348-R that I picked up at a recent
hamfest. It's complete and in nice shape, but it's missing
the dynamotor. I need to locate one because once I have the
set restored and working, it's going aboard our Museum's B-17
Flying Fortress (which means it has to run on 28 VDC). Any
leads will be appreciated. I'm also in need of a BC-348-R
manual. Apparently the "R" model is different from all of
the previous models, although I don't have a clue how.

73,
Dean K5DH

In article ,
says...

Hello, folks.

I couple of weeks back, I posted here about an old BC-348Q I had started
work on. So far, I have:

a) replaced the tubes (found one open filament and some weak tubes)
b) rewired the filaments (including errors introduced by a past owner)
c) recapped the set
d) found several bad resistors, leading me to re-resistor the set
e) repaired the BFO
f) replaced mouse-eaten wires
g) dismanted the "dead" filter crystal, soaked/cleaned it in alcohol,
and reassembled it
h) replaced intermittent BFO and Filter switches
g) aligned the set, as per the service manual. (alignment was way
off...apparently somebody went around "adjusting" slugs and caps
helter-skelter.)

Nifty set, and it seems to work fairly well now, from one end of its
span to the other. I do have a few observations and questions I wonder
if you'd comment on.

1) I notice some apparent variation in sensitivity from band to band. Is
this normal, or am I looking at the possibility of leaky caps inside of
the RF compartments? (If the latter, I may just let this be for now. I
don't relish the idea of trying to get those rf boxes out of the set!)

2) Tracking is a little bit off as far as dial calibration, despite
repeated attempts at alignment. I wouldn't expect digital frequency
display accuracy, but is this typical of this set?

3) The crystal filter works, but the insertion loss is significant. Am I
still looking at a crystal that is not quite up to snuff? Should I try
having a new crystal ground and install that instead? Or, is this
normal? ---Side note: Why is the crystal element so darned thick? I have
32khz realtime clock crystals in the junkbox that are slivers compared
to this 915khz filter crystal....and that filter crystal has got to be
an 1/8 thick!)

4) I have been running the set from bench supplies, and would now like
to build a power supply module to fit where the dynamotor used to go. I
have been running the set with 150 volts on the B+. Somewhere I read
that I should not exceed 200 volts. What is the appropriate plate supply
for this radio?

Thanks for the help.

Pete
AC7ZL

email is
hpf (atsign) gainbroadband (dot) com