[Amps] Amp Supply LK-500ZBx 3-500z tube & cooling question
kb8nty at wowway.com
Tue Jul 8 15:09:20 EDT 2014
Asking for more help please.
My early Amp Supply LK-500ZB model has the letter X at the end, reading
LK-500ZBx, The x is also included at the end of the three digit serial
Does anyone have any idea as to what the "X" suffix in my model number may
I have read up on some past history of the Amp Supply line and am aware of
the changes within the same models and at times not documented.
Possibly as a long shot someone who may have been associated with the
company may have any insight to what the "x" in the LK-500ZB model may refer
In my researching of the LK-500ZB pictures found on line I see changes on
the raised sub-chassis that the two 3-500z tubes mount on. Some have a
series of holes along the top exterior side (closest to cabinet), some
sub-chassis are open on that end. In my early model there are no holes at
all on the sub-chassis, and the sub-chassis is complete, in other words the
end of the raised sub-chassis on the exterior side is all one piece down to
the bottom of amp chassis (closed, not open) like in other versions I have
Upon reading of the overheating of the tube pins I guess Amp Supply had made
changes along the way by drilling holes on the top of the sub-chassis and
leaving the side open, all for better cooling ventilation.
My fan is mounted low in that a 1/4" or so is placed to blow down below the
sub-chassis, but I guess in this earlier version, they didn't leave the
other end open and had no ventilation holes to help the air exit.
I hate to do so but when I replace my power supply board upgrade, I am going
to carefully take the 500z tubes out and drill out some holes into the
sub-chassis to allow for the air from fan to flow through and exit.
I have also obtained a new ebmpapst 4600z fan, thinking I may secure it to
the outside, side of the amp along with a speed control (as this fan really
spins fast) to help exhaust the air flow.
Speaking of the tubes....just by chance I had the top off and turned the
lights off in shack to get a thrill of seeing the 500z tubes glow...Sadly in
one tube upon key down I observed a slight purple haze up near the top of
tube right at the anode location. I mean slight...I would say 1/4 to 1/2
inch at most. This presented itself upon key down.
Upon my reading I have read of leaks, and sometimes gas from unused tubes. I
cannot say if the tubes were or were not used much as I only recently
obtained the amp.
My question; I am asking for advise from the groups knowledge as to what's
Is my tube going to blow-up?
If so is there a chance if it does will it affect or take out any other
Will it cause my other tube to blow?
If I am to replace, can I still use it until it gets worse or should it be
If I have to replace can I just replace that tube or should I be required to
purchase both say as in a matched set?
These are Eimac's with date code of 8438
Again this purple haze is only slight, only seen in the dark, is small in
size 1/4 to 1/2" at most and is located right at the top of the tube.
Power output don't seem to be affected at this time as I can obtain close
to1400 watts at best with amp.
Prior to replacing the P/S board upgrade I am going to snap photos and post.
Sorry for all the questions. Trying to learn here and appreciate your valued
Kind Regards...Ross KB8NTY
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