Was given a Marshall MG 50DFX but no volume

[bignaughtydog]

TR1 should be a 2N7000 FET.
It is used in the footswitch circuit.
The parallel circuit Enzo was describing is in the Standby Voltage (ie: mute) circuit for the power amp IC. TR2 (2SC2120).
The SB voltage is slowly ramped up to the SB pin of the output IC.
What are you trying to fix?
A footswitch problem or a "no sound" problem?

Yeah its a no sound problem.I try to use it but their is no volume, i turn it up but with no result.But in doing this, the sound could kick in at any moment and presents itself at the volume i originally required,(i.e. loud since i have turned it up).Not very good with electronics so any help would be great.

[g1]

Is the circuit board marked with the names of the components? Find where the board says TR1, what is the number on the part? Now find where the board says TR2, what is the number on that part?
Did the amp work before, or has anyone else worked on it?
You said you are worried about it cutting back in at high volumes, does the sound cut in and out or is it always quiet?

[Enzo]

If three parts are in parallel, then if one shorts, the others will appear to be shorted because they are wired together.

Parts are put in parallel because the different parts do different things, but they all need to do their things to the same point in the circuit.

Think of a soft drink vending machine. Into the cup we must send water from one source, syrup from another source, and ice cubes from a third source. Very different things, but all wind up at the same point. In the mute circuit, the transistor normally controls whether it is on or off, the zener prevents the voltage from going higher than a certain value, and the cap smooths out any little variations and a little timing.

The bottom line however is this: if there is several volts across that transistor/zener/cap, then it is not the problem.

[guytar]

Any Idea Where to Get the Cord for the MG50DFX? Got the amp used from a bandmate, found this forum, but cord never returned to me from a local repair shop, which is now closed.

[mort]

As far as I know it should use a fairly typical power supply cable that would fit a computer tower. I bought one the other day from a local electronics surplus store for ~$5. Just make sure it's not a really thin chincy one.

[Enzo]

Standard generic detachable power cord.

[Steve Conner]

It's an "IEC" power cord. (and as Enzo says it is the standard detachable power cord for modern equipment) Any electronics or computer store should have them.

In the UK we call them "kettle leads" for some reason.

[Jazz P Bass]

I like "Jug Plug".
Australia.
Wiki Link: IEC 60320 - Wikipedia, the free encyclopedia

C15/C16 coupler


Some electric kettles and similar hot household appliances like home stills use a supply cord with a C15 connector, and a matching C16 inlet on the appliance; their temperature rating is 120 °C rather than the 70 °C of the similar C13/C14 combination. The official designation in Europe for the C15/C16 coupler is a 'hot condition' coupler.

These are similar in form to the C13/C14 coupler, except with a ridge opposite the earth in the C16 inlet (preventing a C13 fitting), and a corresponding valley in the C15 connector (which doesn't prevent it fitting a C14 inlet). For example, an electric kettle cord can be used to power a computer, but an unmodified computer cord cannot be used to power a kettle.

Many people are not aware of the subtle differences between the C13/C14 and C15/C16 couplers, and so all are loosely referred to as kettle plug and kettle lead (in the UK) and jug plug (in Australia)[citation needed] when referring to these mains cords.

In Sweden and some other countries the C15/C16 coupler has replaced and made obsolete the formerly common appliance plug in most applications. In the United Kingdom it has also replaced a once-common large, round plug which had two round pins for power and a larger round pin for earth. These were common on kettles, particularly those from Russell Hobbs and were also used on home-brewing machines and large film projectors.

[guytar]

Thanks / will do.