It would be nice if you could pdf all the variants that you have and
upload them to BAMA.
http://bama.edebris.com/manuals/
73, Alek.
On 7/04/2013 9:33 PM, K1TTT wrote:
Ok, now I'm making some progress... thanks for some of the tips in here.
Yesterday I traced out the circuits for the rf deck, hv power supply, and
meter board, and was able to connect up the whole loop from B+ to B-, and it
obviously didn't match the schematic that came with that amp... mainly the
schematic showed a 8.2v 50w zener doing the biasing during tx and a grid
leak resistor during rx that were switched by a relay... well, that relay
existed but the terminals that should have switched the bias weren't hooked
up. So today I was going to trace out the control and bias board which is
up against the side frame of the inner case and partially blocked from view.
So last night I dismounted it and got it so I could expose the whole thing
so I could take pictures of the top and bottom to make tracing it out
easier. This morning after another hint, and in looking at the board I
found a label on it "QSK-1"... I don't have QSK in this amp and the old
schematic had no reference to that. BUT, the circuit started looking
familiar, and since I have several generations of those amps (8 of them in
total from s/n 427 to s/n 765) I flipped through a couple of the newer books
where I remembered seeing schematics for QSK boards and other variations.
It appears that Pat started using newer boards but shipped some of the older
amps without updating the schematics. So by s/n 427, bought in 1993, he had
changed the control board in non-qsk amps to use the qsk bias and control
board that is documented in later manuals. I have found one of the 400
series ones where he stuck in an updated schematic for the control board,
but not all of them have that.... and that schematic isn't the same as the
one I have, nor the same as is documented in a 700 series book. So this is
progress... I went from having one bad schematic yesterday, to at least 4
different schematics this morning, one of which looks like the right one...
and also comes with a board layout diagram that looks correct.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
-----Original Message-----
From: K1TTT [mailto:K1TTT@ARRL.NET]
Sent: Saturday, April 06, 2013 14:05
To: 'amps@contesting.com'
Subject: RE: [Amps] commander hf-2500 schematic
What would you expect the voltage to be from Cathode to Ground when keyed
and when idle on this thing??
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net
-----Original Message-----
From: K1TTT [mailto:K1TTT@ARRL.NET]
Sent: Wednesday, April 03, 2013 23:43
To: amps@contesting.com
Subject: [Amps] commander hf-2500 schematic
Has anyone actually traced out the real schematic from an older commander
hf-2500, around s/n 435??? The one in the book is not complete (parts list
missing stuff) nor correct. there appears to be lots of extra stuff on the
control board, probably for stuff not used in this amp like qsk or grid
current protection. I can't find the rx cutoff grid leak resistor nor the tx
bias zener and the relay contacts that should switch switch them don't seem
to be connected. And the connections of the plate current shunt and meter
look backwards.
When the amp died the transformer shorted primary to secondary causing a
quite bright arc through the 1.5a B- fuse. I have had the transformer
rewound but now when I power it up it doesn't make full power and in rx the
idle plate current is about 400ma, so I am assuming the bias to the cathodes
is messed up. So far I have found that a 200ohm 10w resistor that is in
series with a 1n54?? diode on the power supply board going from B- to ground
is open, but the diode seems ok. I am assuming that this is the replacement
for the grid leak that should cut off the tubes in rx. but then there are
some other things on the control board that may also be generating a bias
voltage that I haven't identified yet. Anyone puzzled one of these out???
David Robbins K1TTT
e-mail:<mailto:k1ttt@arrl.net> mailto:k1ttt@arrl.net
web:<http://wiki.k1ttt.net/> http://wiki.k1ttt.net AR-Cluster node:
145.69MHz or<telnet://k1ttt.net/> telnet://k1ttt.net
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