DX-35 Xmfr?

[Kenneth G. Gordon]

On 3 Dec 2006 at 12:47, Stephen Tetorka wrote:

> Hi all:
> 
> Got a DX-35 w/o the power xmfr.

Not an uncommon problem. My original DX-35, in 1956, ate two power 
transformers within 2 years after I built it. The DX-35's power 
transformers were DESIGNED to be running "red-lined" even at key-up. 
At this late date after they were first sold, there are very few of those 
original power transformers that are any good. 

DX-40s, which had a somewhat more robust power transformer, are 
now starting to lose theirs.

What I did with my original DX-35 is to mount a heavy-duty power 
transformer from a console TV set of the period, and wired it up with SS 
diodes in that "Economy Power Supply" mode.

I also got rid of that really stupid series-ed DC feed for the oscillator 
and buffer and went to a straight parallel DC feed system as is 
commonly used in nearly every other rig in existence.

After I did that, I used that DX-35 for the next 10 years, even for RTTY, 
and never lost another power transformer.

> Anyone have one?

They are getting more rare by the day.

> Anyone know the xmfr specs so I can try to find a substitute?

The power transformer had a single center-tapped high voltage winding 
of 1500 VAC at about 100 mA, or 750 VAC either side of the center-tap. 
It also had a 5.0 VAC at 3.0 amp winding to power the 5U4GB rectifier, 
one 6.3 VAC at 1.0 amp for the buffer filament, and one 6.3 VAC at 
about 3 amp winding to provide filament power to the oscillator, 
modulator, and final amp tubes. The oscillator and buffer tubes are 
12BY7s. 

The oscillator gets its plate voltage from the cathode of the buffer, so 
the buffer filament could have neither side grounded, and had to be fed 
from a separate filament winding since it was at 300 VDC or so above 
ground.

I really liked my DX-35 back in 1956, and I like those I have now, but 
that power supply setup was/is completely dumb, IMHO.

Ken Gordon W7EKB

-----------------------------------------------------------
Products bought, sold or traded here is the responsibility of the
parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

-----------------------------------------------------------
This list is a public service of the City of Tempe, Arizona
-----------------------------------------------------------

Subscription control - http://www.tempe.gov/lists/control.asp?list=HEATH
To post - HEATH at LISTSERV.TEMPE.GOV
Archives - http://listserv.tempe.gov/archives/HEATH.html