[ARC5] Vibrator Power Supplies

[Roy Morgan]

On Dec 7, 2012, at 8:50 PM, Geoff wrote:...
> A lot of the old gear transformers are already starting saturation  
> at 123 and are toast at 130. The use of bucking transformers to get  
> down to 110-113 is very popular and the heat reduction is dramatic.

Geoff,

Thanks for your experience in the power supplies.  I often suggest  
bucking transformers and sometimes note that you can run the primary  
of it from either the line, or the reduced, bucked, output voltage.  I  
had not realized that an older transformer from the junque boxe might  
not do well running on the higher voltage line.

Experiment request to the group:

Find a recent Radio Shack small filament transformer  Run it at modern  
line voltage and load it with a resistive load at or very near the  
rating of the thing.  Look at the load voltage with a scope and see  
how hot it gets in free air after an hour of running.  I've read that  
they operate well into saturation with squared off voltage peaks, and  
get quite hot.  This implies that the designers cut the iron used  
below a happy amount,  and are counting on modern materials and  
insulation to keep it running at least past the warrantee period. (IS  
there a warrantee?  Maybe not.)

A search at http://www.radioshack.com
returns NO hits for "filament transformer" but does list some  
candidates for "transformer".
They don't believe in filaments any more!
The 12 volt offerings are:

  Model: 273-1352  |  Catalog #: 273-1352

12.6V CT 1.2A Standard Center Tap Transformer with leadsPrice:$10.49

Model: 273-1511  |  Catalog #: 273-1511

12.6V CT 3.0A Chassis-Mount Transformer with Leads

  Model: 273-1365  |  Catalog #: 273-1365

RadioShack® 12V CT 450mA Std Chassis-Mount Xformer w/ LeadsPrice:$7.49


Model: 273-1385  |  Catalog #: 273-1385

12.6V 300mA PCB-Mount Miniature TransformerPrice:$4.99



By the way this item:

RadioShack® Audio Output Transformer
Model: EI-19  | Catalog #: 273-1380

Claims 1000 ohms primary, 8 ohms secondary and 300 to 10 khz  
response.  Might do for command set use.  Price is $2.99  No power  
level given.

Roy

Roy Morgan
k1lky at earthlink.net
K1LKY Since 1958 - Keep 'em Glowing!