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P a g e
Warning!
You can blow up a power amp with considerable drama by inserting a
KT150 power tube incorrectly.
This happens when you break the plastic key and do not insert the pins with the proper
orientation into the socket.
Notice there are 8 pins in the socket, but only 7 pins in the tube with pin 6 missing, so
it’s easy to get it wrong. Intuitively you think the open pin matches the key, but it
doesn't. The key orientates at 6 o’clock, but the missing pin 6 orientates at 10 o’clock.
Tip:
The logo on the metal collar and the alignment key on the tube faces forward.
For your safety, all Zesto Audio power amps ship with a copper plug inserted in the pin
6 socket to avoid any accidents. The good news is your power amp can be repaired at
the factory or authorized service technician. The bad news is any repairs caused by
tubes installed incorrectly are
not covered under warranty.
Changing Tubes
Turn the power OFF, then wait for both the amber and green LEDs to go OFF.
For the best performance, this amp needs to warm up for 30 minutes.
If your amp is already warmed up, you only need 15 minutes for the new output tubes
to warm up.
Tubes are fragile when hot, so handle carefully with a cotton towel and place them to
cool down on a cotton towel, not a hard surface and not your carpet.
Warning!
Hot tubes will melt Micro cloths and most synthetic fabrics.
Replacing tubes
If one output tube goes bad like V1, it is recommended to replace it with a matched pair for
both V1 & V2 or both V3 & V4.
