HH Scott 222C TR12-3-1 Transformer Replacement Info Needed
 

HH Scott 222C TR12-3-1 Transformer Replacement Info Needed

The power transformer in my 222C Amplifier is shorted, and I need the
voltages, (HV Secondary, etc) in order to locate a replacement.

The transformer is marked TR12-3-1,

The tube complement in my 222c is:
one 5ar4
two 6GH8
four 12ax7
four 7189

Any info is appreciated.

Many thanks in advance for your assistance,

Dan

The power transformer in my 222C Amplifier is shorted, and I need the
voltages, (HV Secondary, etc) in order to locate a replacement.
The transformer is marked TR12-3-1,
The tube complement in my 222c is:
one 5ar4, two 6GH8, four 12ax7, four 7189
Any info is appreciated.

Dan,
You'll need a five volt winding for the rectifier tube filament (unless
you use a pair of diodes to sub for the tube) and a six volt winding for all
the other tube filaments. Those windings will be pretty hefty to carry that
much current, perhaps 1.5A for the rectifier and 4 or 5 amps for the other
tubes (wild guesses). Look at the thickness of the wires on the old tranny.
If you can scrounge up a receiving tube manual, you can calculate the totals.
To get a rough estimate of the total B+, look at the voltage rating of
the filter caps on the rectifier tube. There is normally about 10% "headroom"
so the caps never see anything at or over their rated voltage even if the AC
line goes high. Keep in mind that if you substitute diodes for the rectifier
tube, the B+ will not be loaded until the other tube filaments warm up, so
the B+ will go immediately to the peak value when the unit is powered up.
Also, there is some voltage drop when using a tube as a rectifier, so subbing
diodes with the original transformer (if you find an exact replacement) may
exceed the cap voltage rating.
Multiply the transformers rated secondary voltage times 1.414 to get the
peak value. For example, for a secondary rated at 260 volts, you multiply
that by 1.414 to get the maximum voltage the input filter has to handle. That
comes to about 367 volts DC (unloaded). With some overhead so the filter is
never pushed beyond it's voltage rating, it would likely be rated at 400
volts. If the filters in your amp have a different voltage rating, you can
recalculate to get an approximate value for the transformer voltage rating.

Ray
--

My return addy is spamblocked. To reply, remove the zeroes.

in article , Ray at wrote on
11/17/04 10:46 PM:

The power transformer in my 222C Amplifier is shorted, and I need the
voltages, (HV Secondary, etc) in order to locate a replacement.
The transformer is marked TR12-3-1,
The tube complement in my 222c is:
one 5ar4, two 6GH8, four 12ax7, four 7189
Any info is appreciated.



I think that the OEM transformer provides the following voltages:

720 VAC center tapped
50 VAC bias winding
5 VAC for the rectifier
6.3 VAC for the filaments

The B+ of the amplifier is 410 VDC
The DC bias voltage is 58

The amp uses a silicon bridge for the bias rectifier, so you could get by
with a 40-42 VAC winding if you switch to silicon (recommended)

Use of a SS sub for the 5AR4 (e.g. Weber Copper Cap) will obviate the need
for the 5VAC tap.

Power consumption on the original amp was 170 watts and the maximum sine
wave power for each channel was 20 watts.

These voltages are pretty common - I imagine you'd have a harder time trying
to find one that physically fit.

For example, I have a tranny in my junk box that delivers 786 VAC CT
(unloaded) and 56V bias with 6.3 volts available (at least 8A) but no 5
VAC.

Hammond's 373BX is rated as follows:

187 VA TOTAL POWER
350-0-350 SECONDARY @ 175 MA
5V @ 3A
6.3V @ 5A
50V BIAS WINDING


Problem solved?

Jon

(Marc) wrote in message . com...
HH Scott 222C TR12-3-1 Transformer Replacement Info Needed

The power transformer in my 222C Amplifier is shorted, and I need the
voltages, (HV Secondary, etc) in order to locate a replacement.

The transformer is marked TR12-3-1,

The tube complement in my 222c is:
one 5ar4
two 6GH8
four 12ax7
four 7189

Any info is appreciated.

Many thanks in advance for your assistance,

Dan


Dan,

The 222-C power transformer has the following characteristics:

Primary: 117 VAC

Secondary:

360-0-360 VAC @ 150 mA

50 VAC @ 150 mA

6.3 VAC @ 5A

5.0 VAC @ 2.0A

www.heyboertransformer.com can rewind this transformer for $90. I've
used them several times, and they deliver a great product, new long
PVC leads as well.

When I had mine rewound, I asked for a 200 mA HT winding, and a 3.0A
5V winding for the rectifier to allow for use of 5U4 tube.

Above are the stock specifications.

Best of regards,

Ryan

www.hotglassaudio.com

(Hot Glass Audio) wrote in message om...
(Marc) wrote in message . com...
HH Scott 222C TR12-3-1 Transformer Replacement Info Needed

The power transformer in my 222C Amplifier is shorted, and I need the
voltages, (HV Secondary, etc) in order to locate a replacement.

The transformer is marked TR12-3-1,

The tube complement in my 222c is:
one 5ar4
two 6GH8
four 12ax7
four 7189

Any info is appreciated.

Many thanks in advance for your assistance,

Dan


Dan,

The 222-C power transformer has the following characteristics:

Primary: 117 VAC

Secondary:

360-0-360 VAC @ 150 mA

50 VAC @ 150 mA

6.3 VAC @ 5A

5.0 VAC @ 2.0A

www.heyboertransformer.com can rewind this transformer for $90. I've
used them several times, and they deliver a great product, new long
PVC leads as well.

Thanks for the info.

But did you mean: www.heyboertransformers.com ???

Thanks



When I had mine rewound, I asked for a 200 mA HT winding, and a 3.0A
5V winding for the rectifier to allow for use of 5U4 tube.

Above are the stock specifications.

Best of regards,

Ryan

www.hotglassaudio.com

Yes, Dan. It is indeed www.heyboertransformers.com. Great company to
deal with. Call and ask for Alden.

Best regards,

Ryan