[Amps] commander hf-2500 schematic

Sun Apr 7 22:26:57 EDT 2013

I'll second that motion, hihi    
It would be super to have more schematics for these amps.  !!
If you do publish the schematics, please advise us on this reflector.
It is a shame they weren't revised with each change but it is what it is...............

Bob
K6UJ

On Apr 7, 2013, at 7:12 PM, Alek Petkovic wrote:

> 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 at arrl.net
>> web: http://wiki.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>> 
>> 
>> -----Original Message-----
>> From: K1TTT [mailto:K1TTT at ARRL.NET]
>> Sent: Saturday, April 06, 2013 14:05
>> To: 'amps at 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 at arrl.net
>> web: http://wiki.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>> 
>> 
>> -----Original Message-----
>> From: K1TTT [mailto:K1TTT at ARRL.NET]
>> Sent: Wednesday, April 03, 2013 23:43
>> To: amps at 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 at arrl.net>  mailto:k1ttt at 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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>>   
> 
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