Spares And Accessories - Marshall Amplification 30th Anniversary 6912 Handbook

The following list outlines some of the most obvious problems and causes.
PROBLEM/SYMPTOM/CURE
Valves And Pilot Light On, But No Sound.
1. Check valve fuse fail lights to see if HT fuses are blown. If they are, replace them with the same value
fuse. If they blow again replace all the power valves if possible.
2. Check standby switch.
3. Check that the series/parallel switch and power amp mute switch are both out, unless their operation is
intended.
Constantly Blows HT Fuses.
Check the output valves; If they need replacement use matched sets and replace all power valves if possible.
Have a service centre check the bias on the output valves. If it's too low the amp will not clean up. If it's
too high it will stay too clean no matter how loudly you play.
High Pitched Whistle At Hi Gain Settings
Most likely this is a microphonic pre-amp valve. Replace if necessary.
Rattling Noise From Head Or Chassis
99% of the time this is caused by the spring output valve retainers jangling against the valve. Gently bend
the spring holders out a fraction.
No Sound, Lights, Hum, Etc.
1. Check mains fuse, but never with the amp plugged in.
2. Make sure the amp is plugged in.
Quick Hint
Someday, probably at a most inconvenient time, you will blow a fuse or your valves will go. This is no
reflection on any amp, valves have a definite lifespan. Always make sure you have replacements, just like
you carry spare strings, or you could be left stranded. Always thoroughly check speaker leads to ensure
that (A) they are properly connected and (B) they are fully working. Also, use good quality guitar leads
and check them regularly.

Spares And Accessories

Superb engineering is a part of Marshall tradition and your amplifier is built to withstand the abuse of a
working musicians heaviest demands. However it is worth remembering that at it's heart, your amplifier is
full of electrical components and glass bottles. If you think of it as an extension to your guitar and treat it
accordingly, then long life and small service bills should be the norm. Using only Marshall valves as
replacements will give you optimum performance from your amplifier and will remove the need for any re-
biasing by a technician.
In the event of component damage Marshall agents worldwide maintain a stock of spares and accessories
capable of refurbishing your road-worn beast!
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