Best way to check an FET is in circuit.  

This is because they have a failure mode in which there can still be enough junction left to make it look right on an ohmmeter, but will fail under load in the circuit.  


KE3WD

"eSperience"?  


si.



LOL



Don't worry, what I have to say makes too much damn sense for hams to want to follow.  There will be plenty of hash all over the bands for years to come no matter what.


KE3WD

>>Regarding ALC overshoot. Have you anything besides gut feeling to back this statement up? <<

Only going on close to 50 years of esperience backed by data taken with oscilloscopes, real time analyzers, test sets, datalogging equipments, frequency analyzers and a few other apparatus.

I've worked at type acceptance labs for commercial stuff, too, as well as just being the "lowly" service tech or station engineer.  


But don't take my word for it, the information is in writing in many places.  ARRL tests and procedures is a good starting place, but don't just take their word as gospel either.  Get a compendium of research data -- and start taking your own measurements also.  


KE3WD

You'd think that more would realize the implications behind taking any meaningful data at all away from such polls...

>>I have done repairs for 35 years<<

Then get on with it, man!  


Having been in the repair bidness myself for many years myself off and on, first real job at it back in the late 60s, but that doesn't count all the time spent in my uncle's TV repair shop from childhood on, this small amount of work is just weekend hobby stuff, to be enjoyed, right?


KE3WD

All the more reason to investigate the exciter circuit and see if you can't implement a simple resistor changeout or the like to allow for a trimpot to simply dial in the exciter output...


KE3WD

Alan is telling you the full skinny on the subject.  

You may not find 811s getting the ICAS rating, they were never considered to be commercial grade transmitting tubes while the venerable 3-500Z was once the low power workhorse of the AM band...

I've found 30-L1's with the original tubes still in them that still had fairly stout output -- there is no need to run the exciter past the 70W mark at all, matter of fact I just leave mine there for both "barefoot" and when I turn the amp on, doesn't make enough difference, those "missing" 30 watts.  Rig lasts longer, too.

Those that refuse to hook up the ALC and use it are also courting shortened tube life, too.  Along with other things that make hamming hard for those upband of them.  The argument that ALC overshoot happens doesn't make much sense either, the amount of overshoot is orders of magnitude below what can happen with no ALC operating.  A little overshoot for a few mS at a pop versus steady state overdrive...


KE3WD

I don't see cold solder joints, what I see are shiny -- never a sign of a "cold" joint, which is almost always dull and nonreflective, that bubbling look around the joints appears to be solder flux that was not cleaned off from a hand soldering assembly job.  You can clean that off with a shot of flux remover spray if you like, not likely to be causing a problem though.  

The disconnected choke, which I can't really see from the picture, may be your lucky day.  Put things back to right, don't guess, if there is no schematic make Ameritron send you one.  Lucky day, because if no other components got damaged, it may just bring the thing right back up and operating.  

In all my years of troubleshooting, it is typically only ONE thing that stops the show.  Unless something catastrophic like lightning was the cause.  Many novice troubleshooters need to realize that "one thing" concept so they don't overlook it when they see it.  Whatever you find that is not right, make it right first and then fire things up and check for function and operation -- it can often be all that needs to be done.  

Luck,

KE3WD

You might also take a look at the schematic for the RF source and see if you can't simply change the amount of current to the final transistor by way of a single current dropping resistor changeout, assuming a bipolar transistor output.  

This would be more efficient in terms of power use.  


But the T pad will do the trick too, if power is not an issue for your intended use.  If battery powered, consider the above.  



KE3WD

>>12. There is NO loss or change in the receiver! Signals stay the same whether or not in operate or standby.<<

>>"I believe another relay is responsible for T/R"<<


Shouldn't be a relay involved when the QSK kit is installed, the T/R switching relay is what the solid state PIN diodes replace.

Receiver working in either state of amp means the QSK board is not switching now.  It is very likely stuck in the amp bypass mode.  Since it is all solid state this must be due to a circuit fault of some kind, not a simple stuck mechanical relay or anything you could return to working order with a mechanical push somewhere, unless the fault was caused possibly by a bad connection.  It is, after all, Ameritron, and the bad connection situation has been seen before, solder joint never soldered comes to mind.  That will work right up until the point where carbonization or the like becomes too high of a resistance for the circuit path to function anymore, so you might take a look at all connections too and from the QSK board to see if they look properly soldered, screwed, or whatever, and tight.  

Have you tried the basic CW test as described in the Ameritron QSK-5 manual?

http://www.ameritron.com/man/pdf/QSK-5PC.pdf

The QSK line from rig to amp is critical IIRC, there is a timing issue here.  Check the line carefully for fault, disconnect, etc. first.  Check the rig to see if the QSK line is still active and if it is timing correctly, QSK line MUST become active before RF output at rig.  This will require an oscilloscope, preferably a dual trace triggered job, freeze function would be desirable to take a single snapshot, but not necessary by viewing a dash string, one trace on the QSK line, the other on the RF out of rig across dummy load.  Trigger off of the leading edge of the rig's QSK line.  

From the QSK-5 manual:

"RLY:
CAUTION!! This jack must always be directly connected to the transceivers QSK output line.

NEVER attempt to operate the amplifier without this jack properly connected.

Do not connect any devices between this jack and the transceiver.

This jack provides the connection from the Key 2 terminal (D) of the circuit board. This jack has 5 volts open circuit and supplies a maximum of 1 mA of current.

This jack must be pulled low (below 2 volts) at least 1 mS before RF is applied to the amplifier.

The jack must not be returned to an open circuit
condition before RF is removed from the amplifier.

Failure to comply with these restrictions will damage the amplifier or the QSK board.

The QSK board will inhibit the receive signals for one mS after this jack returns to an open or "high" condition."


If the above is seeming to be a bit much to you, call Ameritron Customer Service.  

But you do need to know if the fault originated with the rig or the amp here, could be either if this is the problem and sounds like it surely is.  



KE3WD

You don't really need the original bulb for the intended purpose, though.  

Know the rule of thumb:  

The coil is for the low side of the band and the cap is for the high side.  

Back and forth between the same two points at low and high (use a signal generator) should allow tweaking that in in no time, sans calibration from manual.  What you are looking for is linearity across the dial.  


KE3WD

>>and will increase as the audio gain is increase (volume). <<

Get the skat and take a look at what's been done there, could just be a hack job since the receiver appears to be working okay.  

http://6mt.com/swan.htm

http://6mt.com/6tech.htm

http://www.mods.dk/manual.php?brand=swan

A "freak" ?


Damn, I thought this was a matter of physics.  


There's something freaky there, alright...


KE3WD

To add to that, make sure that all involved switches and their contacts are clean, lubed and in good working order before attempting cal.