Listing of bad valve batch numbers anyehere?

[N_Cook]

2007 made Marshall 2266. Someone had been in there before and changed ECC83
V3 and V4
which function and tested fine. Impossible valve crackle
V1 and V2 are probably originals , at least 07 dates agree
V2 had a tested CH/R of 700K
marked VLVE 0066 and grey shields dated 02/07
V1 marginally acceptable (part of the valve sound) noise intrusion
VLVE 0067 and shiney shields, dated 04/07
with a tested CHR of 15M.
Now both measure 25M or better, driving heaters to 13V for a couple of
seconds and placed in my emergency- use pile of similar questionables
Is this just random failures or are there know bad batches listed
somewhere.?

From an amp retailer insider source BlackStar amps have been hit by complete
batches of amps with bad valves, did they take the same valve supplier they
were used to at Marshall?
In valve production is a routine final stage , over-driving the heaters to
push back the oxide coatings of the heaters , if they happen to be marginal
clearance.
I know this fudge , like for the 700K one above is only temporary in that it
will return after a few hundred hours of normal use, without vibration/abuse

 

[Phil Allison]

"Nutcase Kook"

From an amp retailer insider source BlackStar amps have been hit by
complete
batches of amps with bad valves,

** LOL.

Would that be the ECC81s they use for OUTPUT valves in their mini amps ?

No kidding, the two halves operate in class A push-pull ( 300VDC supply) and
deliver about 0.5 W into an 8 ohm speaker.

But not for long ................

did they take the same valve supplier they were used to at Marshall?

** The "supplier " is not too relevant.

AFAIK China only has one factory making audio valves.


.... Phil