I also have several units if you need them.
Fletch K3JYD
On 7/19/2023 11:12 AM, David Olean wrote:
Screen voltage drops from the 2000 VDC supply through two 100 watt
resistors. I think they are 47K each. Then they feed three zener dodes
in series to get the approx 390 VDC for the regulated screen voltage.
One of tjose big resistors will open up and you lose scren voltage. I
have had many failures like that. You can get away with using just one
47K, but I would advise against it as it serves as a current limiting
device. I think I have some carcass parts here if you need anything.
I have a few modules like the fan and bias etc.
You could also have shorted zeners. I fixed an amp for WA1T and he
blew out all the zeners so we needed to replace them. The power
resistors are the typical failure mode.
Dave K1WHS
On 7/19/2023 10:48 AM, Donald Fox via VHFcontesting wrote:
Good afternoon gents:
We all have our specialties. I'm looking for someone well versed with
the AM-6154/55 series of amplifiers. In my quest for an RF output
increase for my 144/222 stations, I came across a few of them at an
excellent price. Of course, they are in need of some work. So far, it
appears that I am missing screen voltage on 2 of them, hence no
output. I have done some tracing of the screen voltage circuit, but
it's a bit of a challenge since the screen power is stepped down from
the 2kv plate supply.
Feel free to reply here, or offlist @ taurusshoguy@yahoo.com
TIA Don N8ECH
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