SB-1000 Problem

[Randy Kaeding]

Ron:

I think I remember what the inside of that amp looks like. I had the pleasure of doing the manual for it. In fact. As you probably know, its a kit version of an Ameritron amp. We didn't like the circuit boards used in their product, so I completely redid them myself.

The amp has a relay in the primary AC wiring (takes the high current load off the front panel switch). That's probably the relay you hear.

The Standby/Operate switch should not cause the amplifier's T/R relay to close (which it is doing according to your plate current indication). All the Standby/Operate switch does is apply 14 volts to one side of the T/R relay coil, so that it can close when the other side of the T/R relay coil is grounded (via the Relay jack). It seems to me, the ONLY thing it can possibly be is a short to ground between one side of the T/R relay coil and the rear panel Relay jack. According to the schematic, there is a .01 uF cap between this line and ground (I think it's mounted right on the jack). Is it shorted? You can disconnect one lead and see if that cures the problem.

Now the fuse blowing problem is a different story. Let me think about that one.

Hope this helps some.

Randy, K8TMK
"One of the Hams (still) at Heathkit."


-----Original Message-----
From: Heathkit Owners and Collectors List
[mailto:HEATH at LISTSERV.TEMPE.GOV]On Behalf Of Rinkie & Ron Pollack
Sent: Monday, November 28, 2005 1:28 PM
To: HEATH at LISTSERV.TEMPE.GOV
Subject: [HEATH-TEMPE] SB-1000 Problem


First, thanks to all who replied to my question of keying this amp directly
or through a relay.  The consensus is that I should use a relay, but I
finally found in the circuit description that the coil is 12 volts, so I'd
probably be ok.

But first, I have to get the beast working!  I got it several months ago,
and it hasn't been used for about a year.  When I power up, with the switch
on standby, I get the 3100 volts specified in the manual.  When I go to
"operate," with nothing plugged in the back relay socket, I hear a relay
close, plate current reads about 100 mils, and the fuse blows after a few
seconds.   Since the high voltage can stay on without the fuse blowing, I
think the filter caps are ok. From the diagram, it doesn't seem that the
relay should close with the relay line open.  I'm not experienced with amps,
so any suggestions would be welcome!

Thanks!

Ron K2RP

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