Rich Measures writes:
>
> Did the 8877 design team use improper grid-grounding that resulted in
> the "oscillation condition" they observed that caused gold to
> evaporate from the grid of the DUT?
The discussions we had related to bad design in general and not to
any specific test fixtures they may have designed. I would, however,
expected them to have designed the first test fixtures using a belt
and suspenders approach and then later evaluated reduced cost designs
for stability/sensitivity ... that is, after all, how much real world
development is done.
In any case, and this is my last comment, I have read your "Foote
letter."
1) You are 'leading the witness.' He specifically refers to your letter
(21 Jan 1986 which is not reproduced) suspecting parasitics.
2) The tubes in question are 8875 not 8877 - there is a big difference.
Don't confuse the two.
3) Foote only confirms that the grids were overheated. "An oscillation
condition" (note: he does not say "parasitic oscillation") is but one
possible cause of grid overheating. Severe overdrive is also a known
pathway for grid overheating - particularly of the fragile grids in
the 8873/8874/8875.
73,
... Joe, K4IK
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|