[Boatanchors] BC-1004, Bringing up BA Slowly via Variac

[Al Klase]

Hi Phil,

A couple of random comments on your project:

A 5Z3 is a 4-pin 5U4.  the filter caps in most of the 
Super-Pro power supplies are paper/oil units.  I've never 
seen a bad one.

I don't much beleive in "brining it up slow on a variac." 
In this case I'd probably just watch the rectifier plates 
for a couple minutes after I turned the set on.  If they 
grow at all, you've got a short.  Turn it off.  There really 
aren't any old electrolytic you're hopin to reform.

Of course you don't have a 5Z3 any more.  Put a millimeter 
in series with the HV lead.  I'd expect to see something 
like 150mA.  (That's a SWAG.)

For my money, I'd cut out the diodes and put a 5Z3 back in 
or rewire for a 5U4.  I can't swear you're going to damage 
the 6F6's, but they're going to see B+, possibly higher than 
design value, a long time before they have bias.

73,
Al


Al Klase - N3FRQ
skywaves at webex.net
Flemington, NJ 08822
Web Page:  http://www.webex.net/~skywaves/home.htm


Philip Atchley wrote:

> ...Anyway, I haven't been into the power supply at all.  The owner of the 
> radio had already brought it up and tested it.  HOWEVER, I am still 
> bringin' 'er up slowly.
> 
> The owner said that he ALSO replaced the 5Z3 with silicon units. I'm not 
> sure why, if he were going to go to the trouble, he didn't replace BOTH 
> tubes with silicon rectifiers.  On the same subject.  The schematic I 
> downloaded doesn't show a 5Z3, it shows a 5U4 and 5Y3 tubes,
> 
> I realize that the remaining tube rectifier won't start conducting till 
> it's filaments reach a certain temperature.
> 
> A couple quick questions.
> 
> 1.  At about what point (percentage of rated line Voltage) can I expect 
> this to begin to occur?
> 
> 2.  Do I need to worry about the filament of the tube being
> stripped" by having Voltage (al-be-it below normal) on the plates while 
> the filament is still too cool to "squirt electrons"?