[Amps] Step Start on a 3KA Amp

[Bob Maser]

Hi Larry,  there are no solenoid relays in the power supply to control the 
duration that the cone heater to be in the circuit.  The switch on the front 
of the amp is manually switched from off to pre-op to CW voltage.  The relay 
you are talking about is a DPDT relay (RY-101)which protects against more 
than 1A being drawn in the secondary.  If more than 1A is detected, the 
relay trips and shuts off the primary.  This is essentially the same circuit 
that is in the 4K-Ultra.  It is adjustable by moving the slider on R-103.

73  Bob
----- Original Message ----- 
From: "Larry Carman" <lncarman at swbell.net>
To: "'Bob Maser'" <bmaser at tampabay.rr.com>
Sent: Monday, September 18, 2006 7:52 AM
Subject: RE: [Amps] Step Start on a 3KA Amp


Bob,
   You may have a relay problem in the HV PS. The cone heater is just for
soft starting the HV supply. You probably have a couple of solenoid relays,
one is the main and the other allows the cone heater to stay in circuit for
only 1/2 second after switching the HV on. There's a time delayed relay that
determines the 1/2 second after which the cone heater is shorted across by
one of the solenoid relays allowing unrestricted primary voltage. If the
cone heater is not shorted out of circuit there is something wrong and your
secondary high voltage will be down by a few hundred volts. Your secondary
voltage should be at full throttle if the soft start works properly. If you
operate the HV PS with the cone heater active it will burn out. I actually
came across another cone heater to add to the three I already had. Let me
know if you need another.
Regards,
Larry N5BIP

-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Bob Maser
Sent: Sunday, September 17, 2006 12:06 PM
To: AMPS
Subject: [Amps] Step Start on a 3KA Amp

Can anyone tell me what good is it to have one of those cone heaters in
series with the primary of the plate transformer?  When the cone heater is
in the circuit, the secondary voltage is 2800VDC and when it is shorted out,

it is 3000VDC.  Hardly seems worth the effort.  The cold resistance of the
cone is ±30 ohms.

Bob  W6TR

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