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Author Topic: Commander HF-2500 Service  (Read 7534 times)
K8AXW
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Posts: 3669




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« Reply #15 on: April 26, 2012, 09:09:43 PM »

When an amp is reduced to the basics, an amp is an amp.  It's when an amp contains a lot of solid state BS to prevent it from being destroyed by stupid operators or just making them idiot proof that things get dicey on repairing them.  And this is what I'm talking about.

Now that the industry is slowing gravitating to solid state, things are only going to get worse!   
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W1QJ
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Posts: 1443




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« Reply #16 on: April 27, 2012, 04:58:08 AM »

When an amp is reduced to the basics, an amp is an amp.  It's when an amp contains a lot of solid state BS to prevent it from being destroyed by stupid operators or just making them idiot proof that things get dicey on repairing them.  And this is what I'm talking about.

Now that the industry is slowing gravitating to solid state, things are only going to get worse!   

100% TRUE!!  When the auto industry went to anti-lock brakes and I was not used to drving with them I borrowed my wife's new car and ass ended someone because the car would not stop in time.  If I was in my car I would have had room to spare before I piled into the guy in front of me.  The roadway was a little wet on the right side so the entire antilock system kicked in and I got no positive braking from the other wheels on dry pavement.  Anti-lock brakes are for people who don't know how to drive.  The people who do suffer minor accidents in panic situtations because the lack of braking.  The insurance industry pushed for them because they avoid head on collisions from cars spinning out of control when unknowing drivers don't know how to drive with non antilock braking.  If they are so good
why don't race cars have them?
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N3JBH
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« Reply #17 on: April 27, 2012, 09:40:21 AM »

Brakes Huh Who need's stinkin brakes? that why there is tree's  Grin
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N4ATS
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Posts: 799




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« Reply #18 on: April 27, 2012, 09:45:25 AM »

Ya , if they would stop cutting them down.. Seems now most folks hit a pole....

I would imagine if you do a pole to the Amateur Radio Operator world , only a handfull know how to tune an amp.

"If ya ain't got no swing on FM ,crank it up! "
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KD8MJR
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Posts: 2066




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« Reply #19 on: April 27, 2012, 10:53:11 AM »

When an amp is reduced to the basics, an amp is an amp.  It's when an amp contains a lot of solid state BS to prevent it from being destroyed by stupid operators or just making them idiot proof that things get dicey on repairing them.  And this is what I'm talking about.

Now that the industry is slowing gravitating to solid state, things are only going to get worse!   

Depends on your point of view. I would much rather work on a SS amp because the "follow the voltage rule" typically makes for a quick fix, that's not something I would do with a Tube Amp.  My Tokyo Hy-Power has all the "stupid operator" bells and whistles but the schematics are great; test points are marked and the boards are laid out with service in mind.
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K8AXW
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« Reply #20 on: April 27, 2012, 05:14:39 PM »

MJR:  Everything depends on one's point of view. 
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K6UJ
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Posts: 305




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« Reply #21 on: April 27, 2012, 08:56:45 PM »

I have a Commander HF-2500 in here right now to be looked at.  The person is local and I am sure I can borrow the transformer out of it to troubleshoot the OP's amp.  The window of opportunity is the time it takes to get to looking at it and back to the owner. If the OP would like to remove his transformer it will be easier for him to send the box sens the transformer here for repair.  Once the amp leaves here the opportunity of that will be missed.  At that point it would be better off for him to try to get it to someone local to look at or else shipping the transformer will be costly.  The last 2 Commander amps I fixed were done through a series of emails with the owner and the owners fixed them themselves as I guided them through the tests to make to find the problem.  If the OP has a VOM and a little understanding of amps and how to use a VOM I'd be glad to do an email check on the amp to see if we can turn up the problem.  Often times on this board one will present the symptoms of the problematic amp and someone on here will probably know the problem right off the bat.  With the cost and RISK of shipping amps I always like to try and see if the owner can find the problem with our help.  I haven't seen any mention of the OP's problem(s).  Many times it is a bad tube(s). One of the problems with the Commander amps is that the documentation of changes is practically non existant.  The control board underwent 3 different generations as far as I can tell and it seems all the schematics never match what is there.  Since some parts are not particularly critical many different parts show up in the same places.  A lot of creativity is needed on the part of the tech to weed through this.  Also no "complete" schematics exist on these amps.  They are all seperate schematics of the whole and one must go nuts matching up the connections from one segment schematic to the next segment schematic.  Lots of fun Shocked


You sure got that right !  I just spent a very long time fixing my 2500, and the schematics didn't reflect the way mine is wired, sigh........     Found the problem down under the RF chassis on the power supply board.  Removing the RF chassis to access the power supply board was an absolute nightmare.  When I completed the repair, I cut a rectangular access hole and installed a removable panel so I can access this area in the future, sheesh.

Bob
K6UJ
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K6UJ
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Posts: 305




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« Reply #22 on: April 27, 2012, 09:10:36 PM »

My last post sounded pretty negative about the Commander amps.  Yes, the schematics are a problem and access to the power supply board on the 2500's are a bear, but I actually like the amps.  The construction is very good, big wide spaced tank circuit caps, the plate leads from the tubes are 1/2"  silver plated strap,the bandswitches are huge, everything is nice and heavy duty.  I have two Commander HF-2500 amps and an Alpha 76CA converted to two 3CPX80A7's.  The Alpha is the legendary "brick on the key" model and is a real workhorse but overall I would have to say the Commanders are superior in their construction.  (sorry old Alpha :-) 

Bob
K6UJ
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W1QJ
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Posts: 1443




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« Reply #23 on: April 28, 2012, 03:42:09 AM »

My last post sounded pretty negative about the Commander amps.  Yes, the schematics are a problem and access to the power supply board on the 2500's are a bear, but I actually like the amps.  The construction is very good, big wide spaced tank circuit caps, the plate leads from the tubes are 1/2"  silver plated strap,the bandswitches are huge, everything is nice and heavy duty.  I have two Commander HF-2500 amps and an Alpha 76CA converted to two 3CPX80A7's.  The Alpha is the legendary "brick on the key" model and is a real workhorse but overall I would have to say the Commanders are superior in their construction.  (sorry old Alpha :-) 

Bob
K6UJ
Bob, if you take a real close look at the 2500 or any amp by Commander in the HF region, Pat took a very different approach to his tank circuit, an approach you don't see many other amp mfger's take, if any!!  Almost every other amp that covers 160 meters uses switched in padding for the load and tune caps which requires another switch wafer on the bandswitch as well as heavy duty capacitors to pad the load and tune.  Most amps need this on 80 meters also.  This is because most PI networks designed by most companies convert the plate impedance to the antenna impedance of 50 ohms.  This method requires the tremendous amounts of load and tune "C" on the lower bands.  Pat did something different, he takes the plate load impedance and his PI net converts it to 200 ohms.  Then passes it through a 4 to 1 transformer to bring it down to 50 ohms.  This eliminates all the extra switching and padding needed on those bands.  When I first saw this I was amazed and brought it to the attention of this group.  I don't recall much action on it except for Tom offering his opinion on that method.  As usual he did back up his answer, but I never did any testing on my own on that design and it's pros and cons.  All I know is that it works but because no other mfger used that technique, it makes me wonder why since it does take away alot of complications.  To my knowledge the 4 to 1 transformer in those amps do not seem to be a subject of problem.  Have you noticed that design Bob?
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KD8MJR
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Posts: 2066




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« Reply #24 on: April 28, 2012, 08:56:59 PM »

MJR:  Everything depends on one's point of view. 

My point of view is that I feel a lot more comfortable working with the Low voltage in a SS amp and I absolutely fear the HV in Tube Amps.  Unfortunately I was one of those EE's that got no training in Tube based circuitry, I really wish I had some experience since that lack of experience makes me very hesitant to do any work on them.
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WA4DRM
Member

Posts: 3




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« Reply #25 on: May 01, 2012, 03:50:38 PM »

Lots of great comments to my post.  Thanks.
I have taken the cover off of the HF-2500 and have determined the smoke smell probably comes from one or both of the Caydom TA2425 Solid State Relays.  So most likely the noise I heard when I keyed the amp was those relays.  My schematics indicate they are attached directly to the input windings of the high voltage transformer.
I don't have any direct experience with solid state relays but I'm assuming that they could fail with or without something else being faulty.  I did see some plate current and some rf output for the couple of seconds I was keying but I did not take the time to look at the plate voltage before I shut it down and unplugged due to the noise and smell.  During the time I was keyed I was driving the amp with 20 watts or less and the tune and load controls were set in their respective pre-tune-up postions for 160 Meters and connected to a 50 ohm dummy load.  The amp is used at least once a week for the three years or so that I have owned it, mostly on 160M but the day before the failure I was in a pileup on 20M and used it there to make the contact.
Again, thanks for all the comments.
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WA4DRM
Member

Posts: 3




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« Reply #26 on: May 14, 2012, 11:27:35 AM »

After talking to Pat Stein on the phone about my Commander HF-2500 I ordered two solid state relays from Newark-element 14.  I replaced them yesterday and the amp is now back on line.  Pat insisted that rf in the shack was the cause.  I find that hard to believe as my antennas are over 300 feet away from the shack and I have had no other evidence.  Larry Malone (W4LJM) tells me that in his business he has replaced many solid state relays that had failed on their own.  At this point I tend to agree.
Again, thanks for all the comments.

Eddie, WA4DRM
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