Quote:
Originally Posted by Myles B. Astor
Be really careful with the "A" version. The output cap that blocks DC failed fairly regularly and could, if you have a DC coupled amp (for instance Krell) produce that hated kaboom! You might want to find if the caps were changed and if not or any question, contact ARC. This problem was fixed in the "B" version 
Sent from my iPad using A.Aficionado |
Thanks for the heads up.
arcdb doesn't have a B schematic, but comparing the A to the C and later versions, the only difference I see is the addition of clamping diodes from grid to cathode on the cathode followers, I assume to limit the havoc that would be caused by V2 or V5 failing open. Edit: I just found a reference to start up conditions in the SP-6. If V6 starts conducting before V5, there is excess voltage on the output coupling cap. The same applies to V3 and V2.
This has been updated on my unit.
