Gene Marcus wrote:
I am repairing my B&W 51SB-B Single Sideband Generator and need the
following audio transformer:

Primary 20,000 ohms single plate 10MA DC
Secondary 500 ohms
B&W part # T-826


Hi,

Looking at the 51SB schematic, is the T-201 input transformer
for the antivox circuit the same as one you need?
If so, move that transformer over and use any generic
20,000 Ohm to 600 Ohm transformer for the antivox input.
(You don't need precisely 500 Ohms in the antivox circuit).
The antivox input circuit has no d.c. current at all
in the high Z winding, so any small transformer
will work there.

73,
Ed Knobloch

Edward Knobloch wrote:

Gene Marcus wrote:

I am repairing my B&W 51SB-B Single Sideband Generator and need the
following audio transformer:

Primary 20,000 ohms single plate 10MA DC
Secondary 500 ohms
B&W part # T-826


Hi,

Looking at the 51SB schematic, is the T-201 input transformer
for the antivox circuit the same as one you need?
If so, move that transformer over and use any generic
20,000 Ohm to 600 Ohm transformer for the antivox input.
(You don't need precisely 500 Ohms in the antivox circuit).
The antivox input circuit has no d.c. current at all
in the high Z winding, so any small transformer
will work there.

73,
Ed Knobloch

Thanks for the tip Ed, but I have used T-201 to replace T-204 in the
past. T-202 is bad. When all is said and done, I will probably have to
use the two good original transformers as a matched pair in the output
circuit (T-202 and T-203) to maintain balance.

I don't know why the audio transformers seem to be the weak link in
this rig. The B+ is correct and I'm measuring 4 ma through the
high Z winding, well below the rated 10 ma.

73,

Gene

Gene Marcus wrote:
I am repairing my B&W 51SB-B Single Sideband Generator and need the
following audio transformer:

Primary 20,000 ohms single plate 10MA DC
Secondary 500 ohms
B&W part # T-826


Hi,

Looking at the 51SB schematic, is the T-201 input transformer
for the antivox circuit the same as one you need?
If so, move that transformer over and use any generic
20,000 Ohm to 600 Ohm transformer for the antivox input.
snip
Ed Knobloch

Gene Marcus wrote:
Thanks for the tip Ed, but I have used T-201 to replace T-204 in the
past. T-202 is bad. When all is said and done, I will probably have to
use the two good original transformers as a matched pair in the output
circuit (T-202 and T-203) to maintain balance.

I don't know why the audio transformers seem to be the weak link in
this rig. The B+ is correct and I'm measuring 4 ma through the
high Z winding, well below the rated 10 ma.

Hi,

Gene, you might consider picking up a Heath SB-10 sideband adapter.
It is a near clone of the B&W 51SB, and should provide the transformers
that you need inexpensively.

73,
Ed Knobloch

Gene Marcus wrote:
Thanks for the tip Ed, but I have used T-201 to replace T-204 in the
past. T-202 is bad. When all is said and done, I will probably have to
use the two good original transformers as a matched pair in the output
circuit (T-202 and T-203) to maintain balance.

Sowter 9915. Freaking expensive but it's what you want.
http://homepages.tcp.co.uk/~sowter/a...FORMERS_5.html

I am really, really surprised Hammond doesn't still make one.

I don't know why the audio transformers seem to be the weak link in
this rig. The B+ is correct and I'm measuring 4 ma through the
high Z winding, well below the rated 10 ma.

Probably because they got the cheapest possible transformers from a low
bidder, since they were commodity items. And they have a huge number of
turns of tiny wire in the primary, so it doesn't take much to damage one.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:



Sowter 9915. Freaking expensive but it's what you want.
http://homepages.tcp.co.uk/~sowter/a...FORMERS_5.html


Wow, your not kidding. I think this project will be on hold until I can
either find a replacement or a junk donor rig at a hamfest.

Thanks for all the info Scott.

Gene

Gene Marcus wrote:

Wow, your not kidding. I think this project will be on hold until I can
either find a replacement or a junk donor rig at a hamfest.

Whenever you go to hamfests, ALWAYS go through transformer boxes. Anything
you see for a couple bucks, buy it. Sooner or later you'll need them all.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."