Marshall 5210 Solid State (Combo)

[jateater]

Recently I was given a early 80's Marshall 5210.  Plugged my guitar and started playing.  I really enjoyed the sound of the amp.  After about 10 minutes, the amp started cracking and making popping noises.  Then the amp went quite.  I was not getting any sound what so ever.  I can turn the amp off and let it set about 20 minutes.  Turn it back on and I get about another 10 minutes of playing time before it does it again.  I am not sure if this is a common issue with the model of amp.  I am looking for some suggestions on what it may be.  As well as if there is any thing I can do to test it.

It was a free amp, but if I can get it working, that would be so great!

Thanks in advance for any suggestions you may have.

[Roly]

Plug a known good lead into Effects Send and Return.

Does this cure the problem?

5210, 50W 1x12" combo

The 5210 was introduced in 1981 and it was discontinued in 1991. This combo is the transistorised version of the 4210 combo. This amp had a reverb and an effects loop. At first it was fitted with a 12" McKenzie 4? 70W speaker. It had a dark red chassis. Later on Marshall switched to a 12" Celestion G12M-70 T3575 4? speaker.

Attach;
Amp schematic, Issue 5 (Marshall, 1986).
Amp schematic, Issue 3 (Marshall, 1988).

[jateater]

Amazing, that did fix the issue above.  I know the amp is older and going to have some noises.  But there are a couple noises I wonder if they can be fixed.

1.  When the amp is on, but the guitar's volume is turned off, you can hear noises coming from the amp.  Almost sounds like the amp is breathing.

2.  When you adjust some of the levels (volume, reverb, etc) the amp makes a popping noise.  Only happens when you turn the knobs.

I really appreciate the help received so far.  Even if there no easy fix, just knowing what the issue may be, puts me ahead of the game on getting it repaired.

[Enzo]

Noisy controls means they are dirty.  Spray control cleaner into them and turn them back and forth a few times to spread it around.  The standard of the industry for control cleaner is Deoxit D5.

[g1]

  Also spray some cleaner into the FX return jack, then plug a cord in and out of it a few times to work the cleaner in.  There is a switch in the return jack that closes when you are NOT using the FX loop.  If the switch gets dirty/oxidized, the amp will cut in and out.  Plugging a cord between the send and return bypassed the return jacks internal switch, temporarily solving the problem.
  If you are lucky, cleaning the pots will solve the "breathing" noise, otherwise it may be a noisy semiconductor (transistor or IC).  In this case, finding which semiconductor is the noisy one can sometimes be difficult.

[Roly]

Amazing, that did fix the issue above.

:dbtu:

The impossible we can do right away - miracles take a little longer.   

[jateater]

This site is amazing!  Your input and suggestions is very much appreciated and I thank you for taking the time to respond.

I will get some cleaner and try that on the controls and FX return jack.

Last night while I was working with the amp.  The volume level would going up and down.  But I could wiggle the input cable around in the jack and get it back to a full volume.  It did seem like once I found a good spot, the noises went away and the amp sounded great.  As long as I did not move the input cable. 

Could a loose input jack be causing the breathing noises?

One last thing.  I do still have the original footswitch, but no longer have the cable.  When I turn the amp on, the amp is already in boost channel.  Last night I took a foot switch from my Fender amp.  Plugged it in the Marshall.  When I clicked the button, the boost light would go off.  But I would not get any sound from the clean channel.   I am not sure if the fender footswitch was not actually putting the amp in to the clean channel, or maybe just turning off the boost channel.

Could it be possible that by not using the original footswitch, the clean channel was not activated?
Is there a way to manually put the amp in to clean mode?

I am very excited about using this amp.  Thanks for everyone's help so far

[Roly]

Last night while I was working with the amp.  The volume level would going up and down.  But I could wiggle the input cable around in the jack and get it back to a full volume.  It did seem like once I found a good spot, the noises went away and the amp sounded great.  As long as I did not move the input cable.

Could a loose input jack be causing the breathing noises?

This is also fairly classic since the advent of sockets mounted directly on printed circuits, which I'll bet this is.

It could just be more dirt, but there is a common fault caused by the combination of sockets mounted directly on PCB's, and people tripping over guitar leads.  This results in a fractured solder joint where the socked is soldered in, or some times a cracked/torn PCB track.  If a good clean doesn't fix it then you will need to get the PCB to where you can clearly see the solder/copper side (which may be a major chore), then wiggle the socket body and see if  there is any movement to be seen on the copper side, either within a solder joint, or perhaps a whole joint.  If so make good as required.  I often back up such repairs with a small loop of wire from the socket to wherever so that the socket can move a bit without breaking the connections.  Not perfect, but then mounting sockets on PCB has turned out to be a cheap but wrong idea.


Looking at the circuit it seems that the footswitch is two switches between tip and ground and ring and ground on a TRS plug.  If this is what your substitute footswitch does (and this is pretty common) then we have another jack that has switch contacts and (if the others are dirty) most likely also needs a good clean.  The remarks about the input socket also apply to this footswitch socket.

HTH