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The ones that were originally well made are now so old they have
strange faults most techs have never seen before - while the ones
made more recently have designed in faults never seen before by anyone.
A few examples.
1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
when hot - output valve bias goes crazy and even the phase splitter
stage goes way out of DC balance in normal operation because of leakage
from anode tracks to grid tracks. There is simply no fix for this
problem.
Care to give me a model for that behaviour ?
** Yep - the JCM2000: TSL100 combo series.
Easy to find many stories about the same problem on usenet and web
forums.
Yes, Marshal TSL 100. Sigh. I have had two of these with faulty
PCB's. They do indeed leak, and destroy the output tubes, as the bias
goes totally crazy.
I spent hours on the first one trying to establish what the fuck was going
on, as it made no sense whatsoever.
Eventually I phoned Marshall. They know about this problem and are unable
to fix it. You need to replace the PCB with an upgraded design.
"Gareth Magennis"
The ones that were originally well made are now so old they have
strange faults most techs have never seen before - while the ones
made more recently have designed in faults never seen before by
anyone.
A few examples.
1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
when hot - output valve bias goes crazy and even the phase splitter
stage goes way out of DC balance in normal operation because of
leakage
from anode tracks to grid tracks. There is simply no fix for this
problem.
Care to give me a model for that behaviour ?
** Yep - the JCM2000: TSL100 combo series.
Easy to find many stories about the same problem on usenet and web
forums.
Yes, Marshal TSL 100. Sigh. I have had two of these with faulty
PCB's. They do indeed leak, and destroy the output tubes, as the bias
goes totally crazy.
I spent hours on the first one trying to establish what the fuck was
going
on, as it made no sense whatsoever.
Eventually I phoned Marshall. They know about this problem and are
unable
to fix it. You need to replace the PCB with an upgraded design.
** Hope the are willing to supply that for free ??
Whole PCBs going leaky is hardly an example of "normal wear and tear".
.... Phil
Tube sockets and PCBs have always been a problem."Phil Allison" <phil_a@tpg.com.au> wrote in message
Whole PCBs going leaky is hardly an example of "normal wear and tear".
Er, no they are not.
The ones that were originally well made are now so old they have
strange
faults most techs have never seen before - while the ones made more
recently have designed in faults never seen before by anyone.
A few examples.
1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY
when hot - output valve bias goes crazy and even the phase splitter
stage goes way out of DC balance in normal operation because of
leakage
from anode tracks to grid tracks. There is simply no fix for this
problem.
Care to give me a model for that behaviour ?
** Yep - the JCM2000: TSL100 combo series.
Easy to find many stories about the same problem on usenet and web
forums.
Yes, Marshal TSL 100. Sigh. I have had two of these with faulty
PCB's. They do indeed leak, and destroy the output tubes, as the bias
goes totally crazy.
I spent hours on the first one trying to establish what the fuck was going
on, as it made no sense whatsoever.
Eventually I phoned Marshall. They know about this problem and are unable
to fix it. You need to replace the PCB with an upgraded design.
Gareth.