Recently rebuilt the diode section of the power supply in a 3-hole 813
linear amplifier from a full wave bridge to a bridge center tap. This was
prompted by the fact that I lost the circa 1964 navy choke a while back
and the resultant voltage was a bit too high for the 813 when in a
capacitor input mode. The result is a static 2200VDC and a stable 2000VDC
key down providing a very comfortable 1KW+ of RF into the antenna with no
strain. I'm using 8- 3A (1KV) diodes in each of the two strings. Each
diode is paralleled with a 100K/.01 capacitor combination. The caps are
rated at 1KV. The problem that I find perplexing is that I'm hearing a
ticking when the linear is in the ready mode (HV on the plates) but
listening on the receiver. It disappears when switched to standby (HV
shut off) with only the filaments lighted. It ticks about 108 times a
minute. When listening to a strong signal, it's not evident in the
receiver. The filter capacitor is a new GE 32mFd@ 4500VDC and had been
working OK before the diode configuration change. All the diodes were
checked for front-to-back integrity prior to installation. On the air
audio signals are reported to be resonant and stable with no noise
superimposed on the transmission. Obviously, there is a problem in the
rather straight forward diode circuit, but I'm at a loss to figure out
where else to look. No component is even near its rated specification.
The diodes were not all new and for the most part the majority of them
were reconfigured from the trashed full wave bridge. Can anyone help with
a solution. Thanks & 73's Ron W2CQM New York City
___________________________________________________________________
Get the Internet just the way you want it.
Free software, free e-mail, and free Internet access for a month!
Try Juno Web: http://dl.www.juno.com/dynoget/tagj.
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|