[Hallicrafters] SR-2000 HIGH VOLTAGE TICK AND MORE

[jeremy-ca]

If a 20-25 Ohm 25W wirewound resistor is placed in the HV lead it will limit 
fault current to a safe value and allow higher value caps to be used. A 200 
Ohm 2W in the screen lead will help also if not already included.

National read the same RCA spec sheet for the 8122.

Ive rebuilt many NCL-2000 PS using 220mF caps in place of the 80mF. It 
stiffens up the regulation which helps improve IMD.  BTW, Eimac does not 
have the capacity caveat in their spec sheet. I dont know if Burle has 
rewritten the RCA one but their tubes do perform a bit different in the 
NCL-2000; higher bias settings and more output.

Carl
KM1H
National Radio 1963-69
Member of NCL-2000 Design Team
(Also many Hallicrafters in my collection)


----- Original Message ----- 
From: "Jim Liles" <james.liles at comcast.net>
To: <hallicrafters at mailman.qth.net>
Sent: Monday, November 05, 2007 11:40 PM
Subject: [Hallicrafters] SR-2000 HIGH VOLTAGE TICK AND MORE


A while back we started chasing an intermittent high voltage tick in the 
SR-2000 that occurs at about 1/2 second in low power mode and about every 
1/4 second when high power is enabled.  The culprit was the plate/screen 
plug that connects to the SR-2000.  Disassembled and cleaned it and voila it 
is history.  Tried it on another with the same result.  Another issue with 
the P-2000 is the tendency to replace the high voltage capacitors with much 
higher values of capacity --- more is better.  Not so.  The manual calls for 
90uf capacitors which are difficult to find but 100's or 50/50's are common 
and can be used.  Anything higher can cause damage to the tubes if a 
flashover should occur.  The 8122 specs call for no more than 10uf in the 
plate filter for that reason.  Lastly, if you are restoring a P-2000 check 
that the overload relay trips out at 120 to 140ma isolated or 850 to 980ma 
with the 4 ohm resistor across it --- might save tubes one day.  We have 
found a few with open coils that simply couldn't trip, fall back goes to the 
main fuses which is usually to late.

Don't let em smoke!
Kindest regards Jim K9AXN


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