--- In ham_amplifiers@..., Jan Erik Holm <sm2ekm@...>
wrote:
Jim,
Grid drive I suppose? In GG I would guess with 200W drive
maybe 5-6 kW, or?
### 9-12 kw out with 200w of drive. ..easy. [7900 v no load]
I?m planing to replace my 2x4-1000A?s with a YC-156, I think
it?s a ideal tube. As soon as I can get hold of a good one
at a decent price, would be a quick swap. However it will
be GG.
The 4-1000A is a pain in the rear end and I?m getting to old
to struggle with them.
#### The trbl with 4-1000's is trying to find good one's
these days. I had single 4-1000's and pairs of em... between
1976- late 80's.
### The YC-156 in GG has a huge amount of gain. 100 w and low
plate v... like 4 kv will do 4 kw out. My buddy had a 4-
1000 amp... he converted to a pair of 8877's.... then later on...
replaced the 2 x 8877's with a single YC-156.... best thing he
ever did.
### They all used a removeable aluminum plate for the tube...
so the plate could be removed... and replaced with another
plate / diff tube/socket combo. Of course all the LC
ratio's on the pi-net had to be changed.
### I'm told the YC-156 has an input Z of 25 ohms.... so base
any tuned inputs around that... and use paralled RG-58 u coax to
make the 25 ohm cable from output of tuned input... to socket.
### also beware.... the YC-156 has 36 pf of anode to grid
C........ which will INCREASE to 50 pf.... when the YC-156 is
bolted to the chassis !!!
### The 3000A7 does the same thing.... anode to grid C is 24
pf.... and rises to 33 pf when plugged into the grid ring.
### The 6000A7 is 24.5 pf anode to grid.... and rises to 36 pf
when plugged in.
### To get these big tubes to work on 20-10m.... you gotta
add .6 uh between plate block cap and tube.... OR just tap
into the 1st .6 uh of main tank coil.... with the vac tune
cap.... amounts to the same thing.
### This will DROP ther plate load Z WAY down.... so the PI
net is designed around this lower value.
### I use GM3SEK's excellent pi pi-L spreadsheet. It factor's
in this L between tube anode and the pi net. Any stray L
between the anode and the input of the PI net will make a HUGE
difference in transformed plate load Z on the higher bands. [I
also use his spread sheet for the pi tuned input calcs]
### also if u have any kind of Z bump bewteen vac load cap and
the vac T/R relay...... you will have a mini PI-L on the high
bands.. esp 10m..... which will put the vac load cap at a sky
high Voltage. 11m ops have used just wire, strap between vac
load cap.. and the vac T/R relay.... and smoked 5 kv rated vac
load caps !!
### I deep sixed 10/12 m from the last bunch of linears I have
built. Also, if you do, beware of trying to re-use the 10m
tank coil tap... on 12M. The Q will sky rocket... and the
circulating currents will cook everything.
Later.... Jim VE7RF
73 Jim SM2EKM
-----------------
pentalab wrote:
### These YC-156's [and YC-172's] are a huge bang for
the
buck. 200 w drive = 10kw + out. No socket required.
$400.00
### after messing about with multiple tube linears in
the
Later.... Jim VE7RF
