[Amps] AM-6154 questions

[pmills7 at houston.rr.com]

You obviously offended the boatanchor gods by putting a Soviet made
tube in a US military amplifier  :-)

good luck, 73, Phil
W5BVB


----- Original Message ----- 
From: "Web Williams" <kr4wm at earthlink.net>
To: <amps at contesting.com>
Sent: Sunday, September 12, 2004 12:58 PM
Subject: [Amps] AM-6154 questions


>I thought I'd come in here begging for an answer, since I have not
> been able to turn up anything on the internet about an AM-6154
> VHF amplifier that I have.
>
> It's been working fine with an 8930 for about three years, but
> seeing all the improvements being raved about, I felt compelled
> to try a Svetlana 4CX-400. The tube swap was uneventful, as
> well as the tuneup with the new tube. Everything looked just
> fine! I was advised by the tube seller to "keep it down" for the
> first 24 hours or so, and he provided me with a procecure for
> tube burn-in. I had no way to do it the way he described, but
> he said alternately that I could leave the amp turned on for 24
> hours, and if there were any problems with the tube being gassy,
> or having a bad seal, it would likely show up.
>
> After checking for output (I did want to see if it was going to work)
> I tuned up at about 150 watts for a couple of watts in, and everything
> looked great! I assumed (hope I was correct) that this minimal power
> level would not really stress anything. I then left the amp turned on for
> 24 hours to burn in.
>
> The next morning, I went to my shack, and checked everything, and it
> seemed just fine. Same 150 watts output (I had not tried to go for max
> smoke yet- I have an ARR preamp in line that is only rated for 160 watts
> pass-through). I heard a station on, and called him. My wattmeter is
> situated where I cannot see it when I am speaking into the microphone.
> After several unsuccessful calls, I looked over at the meter, and it was
> dead on zero when I was transmitting!
>
> I made an assumption that I blew the new tube, so I quickly put the
> 8930 back in. Still no output (after retuning to proper positions on all
> dials).
>
> Both fuses on the front check good with my DVM. Plate voltage goes
> to mid-scale (not sure how this unit was set up, I didn't do it, and don't
> know who did). Screen voltage is 40 (about 3/4 scale) and grid voltage
> goes to 50 (not pegging the meter, but almost). Heater voltage puts the
> meter at 28. Still no output!
>
> I let the amp sit for about a week, went back to it, and still no output.
> Three weeks of sitting there without me even touching any controls
> I went back to it, and it's fine! Other than turning it on and checking 
> the
> voltages by spinning the test switch through the various test positions, 
> it
> seems perfectly OK! (Didn't put the 4CX400 back in it.)
>
> Does anyone have any ideas as to what to check? I'm totally lost!!!
>
> Thanks, -Web Williams in Myrtle Beach, SC
>
>
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>