[Yaesu] FL-2100B, Help Troubleshoot...

Fri May 18 13:13:49 EDT 2012

The problem resolved itself.....  I kid you not!

I was on the net on 80m just a few ago and warmed the amp up, decided to try 
10m into the dummy load one more time to get accurate readings on what its 
doing.  10m worked, about 375w output and the SWR is now high on the input 
but it works.  Odd...

So I shut down, disconnected, discharged, and checked again.  Now there is 
no continuity on the output side.  Hmmm... A wiggle here and a wiggle there 
and the meter stops beeping, bump it again, now its beeping.  Well I be 
darned.  The tap where its wrapped around the 10m position on the tank coil 
seems intermittent, wasn't when it was cold... Ah hah!!  As the amp heated 
up and the copper strap warmed up it must have expanded enough to cause an 
intermittent contact.

Will go eat dinner, let it cool down, and come back to it and check again. 
I will desolder it, clean the coil and the strap and solder it back on to be 
sure now.  The others are fine but maybe I will reflow them as well.  I 
never touched the tank coil end of the taps.  Oh well, a little solder, a 
little adjustment to the input of the 15/10m coils and maybe a new Mica or 
two on the tuned input and everything should be perfect once again.

73,

Scott KBØNLY

-----Original Message----- 
From: Martin Sole
Sent: Friday, May 18, 2012 11:47 AM
To: 'KBØNLY' ; 'Yaesu Reflector'
Subject: RE: [Yaesu] FL-2100B, Help Troubleshoot...

I'd still say it's in the output circuit, and the fact that you replaced the 
switch might well be the key. The tank aint resonating since there ain no 
dip! Check the 10m coil tap and measure for continuity when it gets switched 
in. Most likely you are trying to get power out through a tank that's either 
resonant near 15 or else the whole coil is in circuit, not sure how they 
switch that.

Cheers
Martin, HS0ZED

-----Original Message-----
From: yaesu-bounces at mailman.qth.net [mailto:yaesu-bounces at mailman.qth.net] 
On Behalf Of KBØNLY
Sent: 18 May 2012 23:40
To: Yaesu Reflector
Subject: [Yaesu] FL-2100B, Help Troubleshoot...

Hey all!  I got a question here on the Amp I have been working on, I have 
worked on a few of these but this one is acting odd.

Here is the story... The amp had a burned band switch, I helped Multi Tech 
Industries design a new one, it will be on the market soon in case anyone 
needs one, and I got the switch installed.  New tubes.. A couple new 
capacitors, the 1000pf cap on the plate end of the RF Choke was broken by 
the previous owner removing the blown bandswitch.  And one cap on the T/R 
relay, a bypass cap, was broken as well, looks like someone just caught it 
on the bench and cracked it while trying to work on the amp.

Tossed in a new set of tubes, let it warm up a bit, checked the bias, 
adjusted.  Tried 80m, perfecto... 600w output with 50w drive and the tubes 
are looking good, voltages and current looking good, no problems.  Drop to 
40m, same thing 600w and no problems.  Drop to 20m, again no problem and 
600w output.  Drop to 15m, about 400w output and a very hard to find dip on 
the plate, but otherwise the current is where it should be and it looks ok, 
I think on 15m I actually just have a bit of an input SWR problem and the 
coil for that band has been adjusted its not in the stock location so I will 
have to put the analyzer on it and tweak it.

Now comes the problem...  10m is dead.  According to my radio the input SWR 
is below 2:1 as its not backing off, the current on the amp comes up but the 
plate capacitor has no apparent dip, meter never moves, tuning capacitor 
doesn’t seem to make any difference either, there is ZERO output on 10m.  I 
mean dead dead dead.  So the only thing I can think, since the output 
bandswitch is brand new is that I have a problem in the input section of the 
amp.  I checked the input bandswitch for continuity in the 10m position and 
its fine, I inspected it with a flashlight and a small dental mirror, no 
contact problems there.  The coil for 10m looks ok, and the tuning slug 
doesn’t appear to have been moved.

So, could the cap on the 10m input, 1000pf, be bad causing this?  If so why 
wouldn’t my radio be complaining about a high input SWR?  And why would the 
plate current come up when drive is applied but no output?  Very very 
odd....

73,

Scott KBØNLY

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