[Amps] Power output drop

[Carl]

OK on the caps, etc Mike.

One thing you can try is to get the power drop going good and then power 
down, chicken stick the HV and feel everything for heat.

I dont think you mentioned the condition of the 833A's either; I take it 
they are Chinese?

Carl
KM1H



----- Original Message ----- 
From: Mike Waters
To: amps at contesting.com ; Carl
Sent: Wednesday, September 11, 2013 5:14 PM
Subject: Re: Power output drop


Hello Carl,


Thank you, and you are right about the photos! I'm really sorry about that. 
I should delete the old photos before I answer anything else.



The plate choke (From a Gates 1 kW AM BCB transmitter) was like that when I 
got it. Of course, that doesn't mean it's not the problem. I did check it 
for resonances; it has a very slight resonance at about 2.9 MHz (forget the 
details). I am currently only using it on 160.


The coupling capacitors are two ceramic .001/10kV (marked "102M") in 
parallel. I didn't use that dinosaur coupling capacitor in the old photos.



The choke bypass is a .002/6kV disc ceramic. It's all I had.



Anyway, have work to do ri9ght now, but I appreciate all the advice!


73, Mike
www.w0btu.com



On Wed, Sep 11, 2013 at 11:00 AM, <amps-request at contesting.com> wrote:


From: "Carl" <km1h at jeremy.mv.com>
To: <amps at contesting.com>, <mikewate at gmail.com>
Cc:
Date: Wed, 11 Sep 2013 10:05:01 -0400
Subject: Re: [Amps] Power output drop

Tank circuit cap drifting should be mitigated by retuning and going open is 
very uncommon in US made caps.

More likely a coupling cap, plate coke or its bypass.

A .0047 is sufficient as coupling at 160 and should be made of 2-4 decent 
size ceramic caps that can handle the current. WW2 micas are prone to 
leakage and RF heating.

And the plate choke looks like it got rather hot in the center. The 
Ameritron is a good replacement at $20.

There is too much variation in the photos to figure out what caps are used 
and where/when.

Carl
KM1H




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