The schamatic of this PV amp out there is for 2000, this 1994 version
quite different. All the CC caps are small mustard colour epoxy covered
small cylinders. Labelled with likes of 473 or 104 presumably for 47nF
or 100nF but what about marks of 424 and 419?. Or are these the
week/year date marks and the 3letter codes such as KNO and RSC are the
value markings?
2 of these are physically broken, the wire ends broken at the solder
slab. One labeled 473 measures 57nF and one marked 424 measures near
enough 100nF. Vibration failure , inside Bandit 112 combo,preamp section
with no stress telltales anywhere ?

N_Cook wrote:

The schamatic of this PV amp out there is for 2000, this 1994 version
quite different. All the CC caps are small mustard colour epoxy covered
small cylinders. Labelled with likes of 473 or 104 presumably for 47nF
or 100nF

** Sounds like AVX Spinguard ceramics.

Some of them are made with a high K ceramic (5ZU ) that has a horrible negative tempco and lousy tolerances.

Marshall used them in some versions of the Valvestate series - the negative tempco was so bad that you could hear the amp lose bass as it warmed up. Hit the PCB with some hot air and the effect was staggering.

Such caps are only good for supply bypass and ought never be found in any tone control or even stage coupling circuit.

Wrong markings probably indicates slack manufacture.

They appear to be no longer made.

My advice is to replace the lot.



.... Phil

On 14/12/2014 08:24, N_Cook wrote:
The schamatic of this PV amp out there is for 2000, this 1994 version
quite different. All the CC caps are small mustard colour epoxy covered
small cylinders. Labelled with likes of 473 or 104 presumably for 47nF
or 100nF but what about marks of 424 and 419?. Or are these the
week/year date marks and the 3letter codes such as KNO and RSC are the
value markings?
2 of these are physically broken, the wire ends broken at the solder
slab. One labeled 473 measures 57nF and one marked 424 measures near
enough 100nF. Vibration failure , inside Bandit 112 combo,preamp section
with no stress telltales anywhere ?

Looking properly under x30 mag
The 2 broken ones are marked
R5I
473

and

KDQ
424