Can't help with the Thunderbolt II info, but thanks for posting this question.  I looked for an Avenger for many years, but never ran across one.  I downloaded the manual from mods.dk and found the Thunderbolt II photo and info - very interesting.  The Avenger manual reminds me of a Heathkit manual from the same period - full of explanations on how the circuits function and troubleshooting info (it was assumed that you were going to try and fix it yourself!).  I was a bit surprised on the Avenger to see that they really didn't accommodate CW operation very well - no narrow filter option and the CW offset was apparently fixed at 1 KHz.  I believe some of the Collins S-Line gear used a similar CW offset, making transceive operation on CW somewhat cumbersome.  Anyway, best of luck in locating a Thunderbolt II.  That and the Avenger would indeed be a one-of-a-kind station.

73, Floyd - K8AC

Just about every microphone and microphone connector wiring ever used in the world of amateur radio is found here: http://homepage.ntlworld.com/rg4wpw/date.html

73, K8AC

I think you mean the speed is 38.4 kbps.  You can reduce the Refresh Rate on the Display tab of NaP3, but I find anything below 12 or so to be unacceptable.  I'd also look at the rig polling rates on the Setup tab.  And, reduce the speed to 4800 bps.

You might want to try the LP-Pan group on Yahoo.  You're sure to find someone there who's using an FT-2000.

73, K8AC

Damon - not enough info to understand what the problem is.  Are you getting a trace on NaP3 showing signals?  Apparently you're having problems with the CAT control, but is that the only problem?  You can achieve shared access to a com port by using free software like VSPE.  That allows multiple applications to talk to the port at the same time and it works better than other software port sharing offerings I've tried.  Do you have the com port parameters in NaP3 set properly to talk to the FT-2000? Check speed and number of stop bits in particular.  I've found that the number of stop bits being wrong can sometimes lead to intermittent operation with a Yaesu rig.

Depending on the vintage of the Pro III, there were two different PA boards used.  So, if you have the diagram for the wrong board, that's why you can't find the pot.  I ran into the same problem a few years back.  In what mode do you see the reduced power output?  If you haven't done this already, measure the output in CW mode with the key closed.  I had one Pro III that showed lower output in SSB mode (80 watts max) when fresh from the factory, but full power in CW and RTTY.  I sent it to Icom on the west coast and they returned it a few weeks later saying they could find no problem.  I put it back on the bench in the same test setup and mysteriously the output was now 100 watts as it should have been in the first place.  My testing was done with an accurately calibrated audio signal generator and precision wattmeter.  I suspect that there was something misadjusted from the factory and the service guys just ran through the PA adjustment and all was well.  I'm pretty sure that the Pro III service manual was eventually updated with the correct diagrams for the MOSFET PA boards that came later.

Good points, but in all the instances I've run into, I've been able to work around them.  I haven't yet run into a situation where the multi-turn wouldn't fit in the available space, but I can see where that could be a problem in very high density SMD boards.  Some of the little pots are hard to see, let alone adjust.  Other than the high density stuff, I've always been able to find a variation of package that allowed me to maintain the existing adjustment holes without problem.  Regarding the "time is of the essence" situation: agreed that can be a real problem.  I usually measure the tap position of the trimmer I'm removing and then set the multi-turn replacement to nearly the same value.  So, the time to final adjustment probably isn't any longer than struggling to find the sweet spot on the single turn trimmer. 

Maybe the quality trimmers you mentioned don't exhibit the difficulty of setting to a precise position?  That's been my number one gripe with the trimmers I usually run into.

Often, the mechanical noise you hear from the Astrons is coming from the thin sheet metal cabinet.  When you're hearing the hum, put your hand on the cabinet top and press down lightly.  If the noise is substantially changed or reduced, the problem is that the steel cabinet is being affected by stray flux from the transformer.  One way to fix this is to damp the cabinet - something you'd normally do from the inside, but there's no room in the Astron to do that and the cabinet top can't be simply pulled straight up anyway.  The way it slides would prevent using damping material inside.  You could apply damping foam (adhesive backed) to the top of the cabinet on the outside and that would help a bit.  The foam can be obtained from a number of companies on the web who deal with quieting down noisy PCs. 

Another approach might be to take the steel cabinet top to a sheetmetal shop and have them bend an aluminum top for you.  I've had more noise problems with Astrons from this source than from loose transformer laminations or bolts.

Why is it important that you use single turn trimmers?  I long ago switched to 10 turn trimmers for most applications in my radio and audio gear.  Compared to single turn trimmers, they're just about immune to value changes caused by vibration.  Bournes is a good brand, but I've very good success with the Chinese copies available on eBay.  They're available in a variety of control and lead configurations so just about any of the single turn trimmers can be replaced by a 10 turn trimmer.

Hi Ralph.  I'd advise you to join the Drake Yahoo group where there are many folks who can help with C line questions.  That will be a good source of info to help you with determining whether something is working as it's supposed to, or if there is a real problem.  There are 3-4 people who can service the C line for you, but I wouldn't expect to be able to get any face-to-face teaching time with them.  But, you'll get plenty of detailed help on the Yahoo group from some of those same people.  One of the guys there even has a set of CDs with lots of information relating to troubleshooting.

73, Floyd - K8AC

There's virtually no FCC enforcement of any of the regulations relating to CB or amateur operation today.  While you may occasionally read about some company or individual being fined, only the most flagrant repeat violators  are ever nailed, and it appears to take months or years to even bring those cases to a solution.  If you do a quick search on eBay for "CB amplifier", you'll see hundreds of the amplifiers listed.  They have NEVER been legal and are still sold openly with no regulation whatever.  This has been going on for so long on eBay, that it's clear they just don't care (they claim they are not responsible) and neither does the FCC.  

If I were you, I'd answer any public inquiry during a speaking engagement with the comment that in any endeavor, there is an element which ignores the rules and somehow escapes the notice of the government.  It's illegal to steal property from people as well, but every day Internet scammers (and some non-Internet scammers) steal millions from unsuspecting members of our society.  That goes on in plain sight and no one does anything about that either.  

73, Floyd - K8AC

Hi Dave.  When operating SSB, where there is no carrier, the current draw at any point depends upon the volume of the voice at any point in time.  The meter movement has some inertia and isn't fast enough to follow the voice peaks, so  what you'll observe on the ammeter is an average value and will depend on your voice characteristics, the meter characteristics, etc.  So, even if you were set to run 100W output (remember, that's a PEAK value of power), you'd rarely see the ammeter jump up to the peak value, which might be 22 amps in your case.  The way to see what the current draw peak should be at 100W output would be to switch the rig to CW mode and close the key. 

I'm not familiar with that particular Icom rig, but if it's like almost all other transceivers, the wattmeter is NOT a peak reading meter and so will show you an average value just as the ammeter on the supply does.  Many external wattmeters have a "peak reading" mode where they will actually display a value close to the peak output and the meter circuit will be well damped and the needle will hover around the peak value without jumping around a lot. 

Can't say what might have been happening when you noticed the power output way down on PSK.  In PSK mode, assuming that the transceiver was adjusted for, say, 50 watts output in CW or tune mode, the actual output will depend on the audio drive reaching the mic or aux input of the transceiver.  So, if the line level from the soundcard was reduced or if the mic gain on the transceiver was reduced, the output would also be reduced.  You should be able to reduce the output to zero or nearly so by turning the audio all the way down.

73, Floyd - K8AC

There's an easy way, but it depends upon the transceiver you're using.  Some transceivers have a receive antenna loop - on the rear panel there would be a jack for receive out and one for receive in.  The two would normally be jumpered together.  With that type of setup, you could build or obtain an HF splitter (Clifton Laboratories has a low price kit) and feed the receive out line to the splitter input.  The splitter output #1 would go to the transceiver receive input and the splitter output #2 would go to the SDR antenna input.  This would drop the receive signal by 3 dB in each receiver, but that's really of no consequence.  That's what transceivers with two receivers do anyway.  With this arrangement, you don't have to worry about protecting the SDR on transmit.

73, Floyd - K8AC

I've been using Casper for years to back up our systems.  I use a separate backup drive in an external housing for each PC and Casper backs up only that data that's changed since the last backup, so the backups are fairly fast.  In the event of failure of a hard drive, a destructive virus, etc., I simply swap in the backup drive for the damaged drive and boot from that.  If you use an external drive with an eSATA interface, you can boot from the external drive without having to do a physical swap and so you can get back online quickly. Every now and then, after a backup I do a physical swap of the backup and boot drives to make sure the backup really runs as it should. 

I use a pair of 23" monitors.  One is mounted on an arm above my Orion 2 and the bottom of the display is just about 1/2 inch above the top of the transceiver.  A panadaptor window (NaP3 and LP-Pan) occupies the bottom of the screen on the left (about 4" high, 15" wide) and so is very close to the transceiver allowing me to see both without moving my head.  The remainder of that screen contains the windows of the DXLab suite.  The main screen, which sits behind my keyboard, is used for everyday computer work and for my WinWarbler window when operating RTTY. 

73, Floyd - K8AC