Casino wrote:

For those of you with radios or amplifiers that have power
transformers with blown primary windings, I would like to offer a
temporary solution to keep your equipment working while you search for
a replacement. Assuming your transformer has 6.3 volt and 5 volt
windings in addition to the high voltage B+ supply, you could
disconnect either the 6.3 volt or 5 volt heater/filament supply and
hook-up the low voltage winding from the radio's power transformer to
an external 6.3 or 5 volt AC source such as a small transformer. You
will also need another transformer of the same low voltage to supply
the filament/heaters. Basically, you are now running your amp or
radio with a low voltage AC source and the original power transformer
(with the blown primary) is now stepping-up the 6.3 or 5 volts to 700
volts CT or whatever the B+ might be. Now you can search for a
replacement transformer for that old radio without missing the lastest
hit music releases. Hope this helps.

This would only work if the primary of the blown tranny has no shorted
turns.

I'd be very careful about this strategy.

Patrick Turner.

Tim Williams wrote:

"Patrick Turner" wrote in message
...
Snip
I'd be very careful about this strategy.

Especially since most amps have more VA invested in the HT winding vs.
heaters; it's a physically smaller winding.

Tim

If you blow a tranny in an old radio, then it'd be best to connect an
external
large transformer with long leads into the appropriate internal connection
points,
to the heaters, and rectifier inputs, until such time as the original can
be rewound,
or the right sized or right VA tranny can be found.
Tim is dead right about using the heater the heater winding as input
to the rest of the set, the VA of this winding might be a lot lower than
what is demanded of the HT winding.
A typical radio might have 6.3v x 3.0A,
The B+ might be +300 x 70 mA, so that's 21VA, but if it was more,
you'd have to watch it. The 5v x 2.5 amp rectifier would also load the
6.3v winding.
But a fuse would be essential, since the buggered tranny would run
hot.....
which wouldn't matter, since it is to be replaced anyway, hopefully with
something
better.
If the input to the radio was at the 6.3v connection, the heaters of the
set
load the external temporary transformer, not the set's tranny.

Patrick Turner.



--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

"Tim Williams" wrote in message
...
"Patrick Turner" wrote in message
...
Snip
I'd be very careful about this strategy.

Especially since most amps have more VA invested in the HT winding vs.
heaters; it's a physically smaller winding.

Tim


To paraphrase you (sort'a), imagine a transformer with 1 A 6V winding, and a
1A 450V winding (hypothetical....). The only *real* trick is to have
serious tonnage of transformers! stupid but proud smile

"Shiva" wrote in message
...
To paraphrase you (sort'a), imagine a transformer with 1 A 6V winding, and
a
1A 450V winding (hypothetical....). The only *real* trick is to have
serious tonnage of transformers! stupid but proud smile

Reminds me, for that Quad 6146 PPP amp I'm going to build some day,
well it'll use a 250V-or-so 2A transformer (feeding a doubler for the
600V 500mA required for full steam), and need 'only' 6.3V 10A (actually
8A IIRC, but close enough). That's a difference of about 10x the VA
Of course, I'll be using a seperate filament transformer so the subject
of this thread isn't applicable.

Tim

--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

On 17 Jul 2003 23:06:54 -0700, (Casino)
wrote:

For those of you with radios or amplifiers that have power
transformers with blown primary windings, I would like to offer a
temporary solution to keep your equipment working while you search for
a replacement. Assuming your transformer has 6.3 volt and 5 volt
windings in addition to the high voltage B+ supply, you could
disconnect either the 6.3 volt or 5 volt heater/filament supply and
hook-up the low voltage winding from the radio's power transformer to
an external 6.3 or 5 volt AC source such as a small transformer. You
will also need another transformer of the same low voltage to supply
the filament/heaters. Basically, you are now running your amp or
radio with a low voltage AC source and the original power transformer
(with the blown primary) is now stepping-up the 6.3 or 5 volts to 700
volts CT or whatever the B+ might be. Now you can search for a
replacement transformer for that old radio without missing the lastest
hit music releases. Hope this helps.

In Most cases I just use one of my Heathkit 1P32 power supplies to
supply up to 400vdc at up to 100ma as well as 6.3vac at up to 4 amps.
That usually lets me check the rest of the radio for other hard to
obtain items, before replacing the Power Transformer.

"Tim Williams" wrote in message
...
"Shiva" wrote in message
...
To paraphrase you (sort'a), imagine a transformer with 1 A 6V winding,
and
a
1A 450V winding (hypothetical....). The only *real* trick is to have
serious tonnage of transformers! stupid but proud smile

Reminds me, for that Quad 6146 PPP amp I'm going to build some day,
well it'll use a 250V-or-so 2A transformer (feeding a doubler for the
600V 500mA required for full steam), and need 'only' 6.3V 10A (actually
8A IIRC, but close enough). That's a difference of about 10x the VA
Of course, I'll be using a seperate filament transformer so the subject
of this thread isn't applicable.

Tim


Care to send me a few bux for a Triad 20A 6.3 CT? It's big. It's gray.
You want it.
-dim ineptly tryin' to raise cash...
--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms

Tim Williams wrote:

"Shiva" wrote in message
...
Care to send me a few bux for a Triad 20A 6.3 CT? It's big. It's gray.
You want it.
-dim ineptly tryin' to raise cash...

Alright, I've got a few pennies on the way, but they may or may not already
have been melted :-p

Tim

Crikey Tim, youse gotta job!!!

Wonders will never cease!

Patrick Turner.



--
In the immortal words of Ned Flanders: "No foot longs!"
Website @ http://webpages.charter.net/dawill/tmoranwms