[Amps] Single Band Amplifiers One Power Supply

[N7EME]

I have a 6 meter GS31B amplifier that I am running on a single power 
supply currently. The plan is to run
a GS31B 2 meter amp and a GS31B70cm amp from the same supply. 2Meter amp 
is in design stages now
and the 70cm is waiting for permission from FCC to run more than 50 
watts in Arizona.
For the 6 meter amp I monitor the HV coming into the amp along with a 
blower switch and an enable line
for the amplifiers PTT circuit. If any of these conditions are not 
active, then the PTT is disabled preventing
the G-G amp grid from being RF driven when HV or blower is missing. The 
2 meter and 70cm amps will
have the same circuit.

Jerry - N7EME



On 11/30/2016 10:20 AM, Jim Thomson wrote:
> ##  agreed about mixing triodes and tetrode amps.  But IF its just 2+  GG triode amps, its not really an issue, provided the same tube / B+ is used on all the RF decks.   What I have learned..the hard way, is when using
> HV in one box, and the RF deck in another box, the  B- connections have to be 100%  rock solid.   I once had the B- open  ( forgot to connect it) on back of a 4-1000 amp.   With B+ on, the cathode tries to assume full B+ value.
> The bypass caps at the cold end of the bifilar fil choke started to crack and explode !   Had a similar problem when the black  B- millen connector went open on a 6m  GS35B GG triode amp, all hell broke loose.   That, and make sure
> u have solid bonded chassis ground connections to each RF deck.   I used a combo star ground and also bonded between decks.   Then the plate /grid / B+ metering stays normal.  With paralleled 6A10s between B- and chassis, and fault current  from a B+ arc to anything... just flows from chassis... up through the 6A10 diodes, back to B-...... completing the loop.  50 ohm glitch + also B+ fuse in HV supply do their job.   If B+ fuse opens up, then all  1-6  RF decks will  have their PO drop to zero.   With drive applied, and no B+... the grid current meters will all peg,  so you either require grid over current protection..and /or  a scheme  that kicks all 1-6 amps offline, when B+ is below a certain threshold.
>
> ##  IMO, IF one is going to use 2-6 identical RF decks,  ( or  6 x monoband RF decks), with same tubeS,  its more cost effective to build one big B+ supply vs   2-6 smaller B+ supplies.   I have found that 6A10 diodes can be paralleled
> and the current split is always 50-50..or at worse 48-52.   3 of em will split evenly..as will 4.   I have paralleled the 6A10 diodes on a FWB..and also a FWD.    Also what works is paralleling 2 x identical FWB assys.  Of course any HV filter cap assy has to be able to handle the ripple current.
>
> ##  I looked at the pix on ur supplies.  Your work over the years always impresses me....superb metal work and construction.
>
> Jim   VE7RF
>
>
>
> From: MU 4CX250B
> Sent: Wednesday, November 30, 2016 8:36 AM
> To: Jim Thomson
> Cc: amps at contesting.com
> Subject: Re: [Amps] Single Band Amplifiers One Power Supply
>
> Running multiple RF decks simultaneously from one HV power supply is a bit trickier than it might seem at first, especially if you want individual metering on each RF deck. Grid-driven tetrode amps with grounded cathodes introduce another complication, especially if mixed with triode amps. Also, keeping track of the fault currents from flashovers or internal tube arcs and keeping them from damaging anything can be a challenge. It can be done, but it's just a bit harder than one might think at first. Here is a photo of two HV power supplies I built recently, each designed to operate three RF decks.
> http://www.w8zr.net/homebrew/HV%20Power%20Supplies.html
>
> Details are in a QEX article I wrote a couple of years ago, and I'm happy to send a copy to anybody who wants one.
> 73,
> Jim w8zr
>
> Sent from my iPhone
>
> On Nov 30, 2016, at 7:36 AM, Jim Thomson <jim.thom at telus.net> wrote:
>
>
>    Date: Sat, 22 Oct 2016 19:07:58 +0000
>    From: Bill Turner <dezrat at outlook.com>
>    To: Amps group <amps at contesting.com>
>    Subject: Re: [Amps] Single Band Amplifiers One Power Supply
>    On Wed, 19 Oct 2016 18:47:05 -0500, W7RY wrote:
>
>
>      How would you go about metering them?
>
>
>    REPLY:
>
>    In modern amps. both the B- and B+ are NOT connected to ground, but
>    left floating. The grid current meter is connected from B- to ground.
>    The plate current (actually cathode current) meter is connected in the
>    B- lead BEFORE the grid current meter    , i.e. on the power supply
>    side of the B- lead, not the cathode side.
>
>    Sounds weird, but it works. Check the schematic of any late model
>    grounded grid amplifier and that's how they do it.
>
>    If you want to use a single switched meter for all the amps. simply
>    put a low value resistor on the order of one ohm or so where you would
>    normally put the meter and them simply measure the voltage drop across
>    it. That way you can switch the meter from one amp to another without
>    disturbing current flow. Simple Ohm's law will give you the values.
>
>    73, Bill W6WRT
>
>    ## The plate meter will only read plate current, and not cathode current.  The grid meter
>    will only read grid current.  This assumes u wire the meters like have been shown in every arrl
>    book for years.. for a GG triode.  POS of both plate and grid meter bonded together...then off to the
>    CT of the fil xfmr.   Neg off plate meter to B-.    Neg of grid meter to chassis.
>
>    Jim  VE7RF
>
>    _______________________________________________
>    Amps mailing list
>    Amps at contesting.com
>    http://lists.contesting.com/mailman/listinfo/amps
> _______________________________________________
> Amps mailing list
> Amps at contesting.com
> http://lists.contesting.com/mailman/listinfo/amps