[Amps] 8877 Plate Voltage

[Jim W7RY]

I don’t use a suppressor. But I do use the Eimac socket and good shielding. 
My 8877 is perfectly stable at 4100V.


See:    http://s900.photobucket.com/albums/ac206/w7ry/8877%20Amplifier/

73
Jim W7RY


-----Original Message----- 
From: Jim Thomson
Sent: Sunday, July 01, 2012 6:01 AM
To: amps at contesting.com
Subject: [Amps] 8877 Plate Voltage

Date: Sat, 30 Jun 2012 16:33:23 -0500
From: Charles Bibb <zedkay at telepak.net>
Subject: [Amps] 8877 Plate Voltage

Starting a new project.

I'm collecting parts for a new HB 8877 amp. One really nice part
that I've recently acquired is a massive transformer for the HV
supply. This transformer came out of a commercial FM transmitter
that ran an 8877 at 1 kw continuous duty.

While that power supply used a choke-input filter in the HV supply, I
want to run the higher voltage obtained by a cap.-input filter. With
a cap.-input filter, however, the HV supply will be a tad over
4150VDC, using the "best" primary taps available. Can wire for
higher, but not any lower.

My question(s) is/are: How critical is Eimac's "absolute maximum
ratings" as far as plate voltage is concerned. I know that under
load, with acceptably regulation, the plate voltage will be about
where I want it at 3800V. Is the slightly-too-high potential on the
anode under no-load a problem? Or, should I just not worry about it
and "let 'er rip, tator chip".

Anyone have experience here?

73,
Charles – K5ZK

##  The B+  can be sky high on RX.  On TX... sucking normal idle current.. 
it will drop a bit.
The actual voltage on the tube..when driven, will be almost double the the 
key down B+  voltage.
The AC  RF voltage on the pi net will back feed..via the plate block 
caps..back onto the anode. ( when driven)
That’s  why the 8877  will hi pot test  to well over 8 kv....it has to.

##  Expect  2.5 kw  pep out  with your loaded B+.    And use a 
suppressor...and a glitch R in the B+ lead.

Jim   VE7RF


_______________________________________________
Amps mailing list
Amps at contesting.com
http://lists.contesting.com/mailman/listinfo/amps