[Hammarlund] Question/Help on SP-600 fuses

[Al Parker]

Hi Bill,
    I don't know the direct answer to your question, but -- there is almost 
no difference between the various SP-600 models that would affect current 
draw.  Some (many) had the FCU, xtal freq. ctrl, which added a tube, but 
other than that there was no difference that I can think of off the top of 
my head, in no. of tubes, etc.  I don't think there's an extra tube in 
the -JX-17 diverstiy models.  Andy Moorer can probably tell us immediately. 
So, maybe the 1.6a fuses tended to blow on turn-on, just a guess, and they 
changed to 3a.  I hadn't noticed the difference in the schematics, which 
ones do you find it on?
    That said, you shouldn't be blowing fuses if things are OK in your rcvr, 
no matter what value you have..
    Things to consider:
1.  What tap is the pri. of the pwr xfmr set to?  If it's still on the 117v 
tap, move it to the 130 immediately.  That'll reduce load on the pwr xfmr. 
Most of us have line voltages of 125+-, almost 20% higher than the old 115 
that was normal when these BA's were designed, over 50 yrs ago.  Would you 
drive a 50 yr old car 20% faster (all the time) than you would have when it 
was new?
2.  How's the electrolytic filter cap, C-161, the 3-section can mounted 
hoizontally under the filter chokes?  If it's original, or vntage, it should 
probably be replaced, re-stuffed, etc., however you prefer.  If it's leaky 
it'll load down the pwr xfmr.
3.  Does it still have the BBOD's ini it?  (or are you lucky enuf to have 
one with s/n later than 17,xxx with factory installed disc deramics.)  Leaky 
BBOD's, about 55+- of them, are mostly bypass caps in the LV & HV lines, and 
will cause additional draw on the pwr xfmr.  They can also cause dropping 
resistors to get hot & change value, thus dropping performance.
    All these things can cause the line draw to be higher than normal, and 
should be considered anytime you get into an SP-600.  There are probably 
other things that don't come directly to mind right now.  YOur recvr might 
seem to be working OK with any of these things still unattended to, but they 
all can reduce performance.
    If it still blows the fuse when the HV rectifier is out, you've probably 
got a bigger problem than noted above.  The power xfmrs rarely go bad, but 
it does happen.
73,
Al, W8UT
New Bern, NC
www.boatanchors.org
www.hammarlund.info

"there is nothing -absolutely nothing- half as much worth doing as simply 
messing about in boats."
   Ratty, to Mole




----- Original Message ----- 
From: "Bill" <kirklandb at sympatico.ca>
To: <hammarlund at mailman.qth.net>
Sent: Saturday, November 15, 2008 12:36 PM
Subject: [Hammarlund] Question/Help on SP-600 fuses


>
> Depending on the serial number the power line fuse for a sp-600 is 1.6 A
> or 3A.
> Why the difference ?
>
> Now for the hard question: The sp600 I am currently working on
> periodically
> blows the 3A power line fuses at turn on. Once on the rig seems to run
> fine.
> Any suggestions for cause/trouble shooting ?
>
> I'll pull the HV rectifier and see what happens.
> If necessary check out the resistances again.
>
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