[ARC5] 1625 question

[jeepp]

The old PH linear, etc. amp used 4 1625s at about a kv.  I recall that one had to use certain physical variants of the tube such that one could drill onto the side of the tube base and tie pins together to change the tube to either a triode or tetrode?  807s could not be so modified, however.  But, 1625s are cheap....still.Jeep K3HVG


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-------- Original message --------
From: Brian Clarke <brianclarke01 at optusnet.com.au> 
Date: 2/5/18  20:50  (GMT-05:00) 
To: "'Ron.K3PID'" <ron.k3pid at sbcglobal.net>, ARC5 at mailman.qth.net 
Subject: Re: [ARC5] 1625 question 

It depends on how you measure ‘on the plate’. You need to pay attention to the Voltage excursion when there is an RF component and when there is modulation. If you apply 1000 V to the plate supply, ie, on the cold side of the tank circuit, and then drive the 1625 / 807 to clipping, the plate Voltage will be twice that applied to the plate circuit. 73 de Brian, VK2GCE From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Ron.K3PID
Sent: Tuesday, 6 February 2018 12:07 PM
To: ARC5 at mailman.qth.net
Subject: [ARC5] 1625 question I am reading some old surplus manuals and find that they like to use the 1625/807 as a power amplifier ( typical ARC-5 parallel style ) and suggest that one could run up to 1000 volts on the plate. Every listing I can find shows a absolute maximum plate voltage for the 1625 of 750 volts. Yes, the operating plate voltage will depend upon class of service and therefor duty cycle but isn’t absolute maximum absolute maximum? Now I can remember pushing the stated maximums a bit and I even have a friend who admits running a tube in a coffee can full of water to get a few more watts out of it.  But none of it was “published” that I know of. What am I missing?  Ron K3PID  
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