[Hammarlund] 180A Concerns & Problems(Long)

[Kim Herron]

>Hi Gang,




> >
> > I just found this group....Great!!  I just bought a decent
> > 180A (SN68xx) for $150.
> >
> > My observation are these.........I have the late model
> > orignal manual and addendum.
> >
> > 1. ALL the tubes run very very hot, I removed the tube
> > shields and tuning cap covers
> > as per addendum.

       Yes, get rid of the covers on the tuning capacitors, but leave the 
tube shields in place.
You will have IF shielding problems if you don't and you'll be chasing 
around a bunch of intermod
troubles you can't fix.  It's a pain.

 > My house AC is at 121VAC, the 180's 250VDC is at 275VDC, and
> > the 275VDC is
> > 300VDC.  Should I run the 180A with a variac at 110VAC??
> > Will the 180A fail?

           The only really good way to see where you are is to put a good 
voltmeter
across the B+ supply and see where the voltage is.  I have two receivers 
(170A and 180A).
They work just fine at regular line voltage (126 VAC, as measured with a 
Fluke 87 series 3).
If you feel you still have problem, change out the filter caps (just pitch 
them, they are old and dried out),
and then go back and see where you are.  Leaky filter caps are the biggest 
problem in these receivers.
You draw all kinds of extra power supply current which translates into 
extra heat.  The A series receivers were
designed with the higher input voltages and the dropping resistors in the 
power supply take care of the voltage
drop needed.  remember too that the usual temperature of the tube envelope 
is around 250 degrees, centigrade.
That's the design spec.  Another point.  the receiver was designed to work 
at 117 VAC +/- 10 percent.  If you add
117 and 11.7 you get 128.7 VAC.  So unless you're running higher than that, 
you've no need to worry about
overvoltage at the wall.  Plug the thing in and use it, after you replace 
the caps


Thanks!!

Kim Herron
1-616-677-3706