[Collins] 30L1 problem

[Dr. Gerald N. Johnson]

On Sat, 2008-03-29 at 06:46 -0500, Rodger wrote:
> Cal,
> 
> If you only have 900 VDC then something is going on in the power supply 
> section or with the metering circuit itself.  Any chance you have it 
> wired for 240 and are running it on 120?  There is a mistake in the 
> wiring change from 120 to 240 volt operation in the original version of 
> the manual, it is corrected in later versions.Can you confirm the 
> internal meter reading with another voltmeter?    If the input voltage 
> is wired correctly and you truly only have around 900 VDC HV then either 
> your transformer has an issue causing low voltage (not very likely) or 
> there is something going on with your new rectifier board.
> 
> If the HV is present and correct, what is your idling current for the 
> 811A's (tripped to transmit but no drive)?
> 
> 73, Rodger WQ9E

I go along with the 120 volts applied to a 240 volt connection. That
would also run the tube filaments very cool and they'd act like they
were dead.

Looking at a downloaded schematic, I'm not pleased at what I see. When
wired for 120 volts (jumpers 1-2 and 4-5, black to 5, white to 1, green
to 3) it gets the right voltages to the transformer primaries but puts
the fuses and switches in the neutral side.

I'd much rather see black to 1 and white to 5 to put the fuses and
switches in the hot side, then when the switches are open most of the
primary wiring (all beyond the switches) is a ground potential. The
factory way its all hot at 120 volts causing service bench shock hazard.
Otherwise only go in with the power cord removed from its outlet. The
way the internal wiring is arranged, I don't see an easy safe 240 volt
connection with both fuses and switches in the hot lines.

The schematic's 240 volt connection hooks black to 5,  green to 3, white
to 2. Then jumps 4 to 3 to 1.

Today since it has a 120 volt load (the fan) it properly should use a
four wire 240 volt power cord. Jump 4 to 1. Connect black to 5, white to
4, green to 3, red to 2. Doesn't solve the fuse and switch location
problem, but puts neutral current to the power system neutral, not the
safety ground, and so reduces the shock hazard if the neutral wire
should open.
> 
> C E wrote:
> > All:
> > I recently upgraded my RE 30L1 with that single board
> > retrofit kit.  I have never tested or applied power to
> > the amplifier before until I installed the kit.  I am
> > having some problems.
> >
> > 1) The voltage seems a bit low (about 900 VDC on the
> > meter). From what I gather, the voltage measured
> > should be around 1600 VDC.
> >
> > 2) Power output is abnormally low (around 10 W) with a
> > drive of about 35W.
> >
> > I'm fairly sure that the hv rectifier and cap board is
> > fine.  Can gassy/bad 811a tubes cause this? Thanks.

Be  sure of the connections. Its not obvious to me that the output of
this full wave voltage double would be other than zero if one diode
string was open. I'd check the transformer secondary voltages. The
filament are marked as 6.3 volts AC. The bias winding is probably about
90 volts and the high voltage is about 650 volts. If these are half, its
sure wired for 240 with 120 volts applied.
> >
> > Cal, N6KYR
> >
> >
> > 
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer