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marshall 5210 problem

Started by stargroves, January 13, 2012, 01:37:49 PM

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stargroves

hello everyone..so glad i found this forum..very informative..i have a marshall 50 watt ss..the 5210..it has been an awesome amp thru the years..i recently got the new haze 40 which i like..but for recording the 5210 is king..about a year ago the amp volume(sound i should say) kept cutting out..i thought it was the speaker not being connected good..but i tried 2 other speakers and they would not work either..finally there is not a any sound at all..my repairman had it at his shop for a year and didnt even touch it which made me angry..so i picked it up and brought it home..i think he may have replaced the input jack but it still doesnt work...i am able to plug into the effects loop and get a faint sound out of speaker but that is all..it powers up and looks clean inside..but no sound when i plug into input jack..it also had some rumbling that sounded like a storm..which seems to common with this model..but i can live with that..sorry post so long..anybody with any ideas would be great..this amp is the last really good marshall ss..it was made in england..i have a mg50fx and it doesnt even come close..thanks guys

Loudthud

Seems like there is a power amp problem. Do you get any sound with the reverb turned up when you give the pan a thump? Have you tried running the Effects loop out to another amp? That will tell you if the preamp is working.

stargroves

No...but im gonna try giving that a shot..i guess if i get a faint sound out of effects loop..my power amp should be ok..could be my pre amp..thanks i will try it

FRANKJC

Not sure if you fixed your problem or not....I am new here and stumbled across your post. I have a 5212, and mine does strange things unless I connect a cord between the send and return on the effects loop.

joecool85

Quote from: FRANKJC on June 14, 2012, 03:28:34 PM
Not sure if you fixed your problem or not....I am new here and stumbled across your post. I have a 5212, and mine does strange things unless I connect a cord between the send and return on the effects loop.

This means there is something wrong with your jacks.  Probably they are just dirty, but they could be worn out.
Life is what you make it.
Still rockin' the Dean Markley K-20X
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FRANKJC

Quote from: joecool85 on June 14, 2012, 03:47:19 PM
Quote from: FRANKJC on June 14, 2012, 03:28:34 PM
Not sure if you fixed your problem or not....I am new here and stumbled across your post. I have a 5212, and mine does strange things unless I connect a cord between the send and return on the effects loop.

This means there is something wrong with your jacks.  Probably they are just dirty, but they could be worn out.
Probably, but now worth taking apart right now. I use it all the time with no problem.

marshalldog

I have a pair of 5210s, one for main amp the other is drives my talkbox (spare too if needed).  I added speaker jacks to the back of each of them - one for talkbox send and so I can optionally drive a Genz-Benz G-Flex George Lynch 2x12" cab (at 4 ohms).

I've had minor problems over the years (yes I bought one of these new in 1982) - they are very road amps but you must protect the knobs on these.  I have had to re-solder joints on the inputs and sends and some of the pots...bad solder joints, which have caused pops, hums and intermittent input signal.  Seems the knobs/jacks flex and the board does not so the damage is at those component interfaces.  I find them by carefully wiggling and prodding things with the head out of the casing and it on and playing (BE CAREFUL).  I have also had to blast inside the back of the pots with cleaner/lubricant.

I also found the jacks on the reverb tank leads are prone to being damaged and this can induce a nasty hum.  Cut the ends and resolder.  I like these amps live - the MG30DFX, MG50DFX don't have the same tone capability.

I do have a nasty pop in one of mine when I turn it off...likely a bad capacitor somewhere.  Anyone know?

Pooch

J M Fahey

Turn off pop is normal, but you may add some cap or RC snubber across the switch contacts; check what Commercial Amps do and post it here for revision.

Roly

A "snubber" is an RC circuit connected across switch or relay contacts to prevent arcing.

Neither the resistor nor capacitor value is very critical, but it is important that in the case of a mains switch the capacitor is a mains-rated X2 type.  Generally a suitable cap can be found in a dead computer power supply.  They are normally yellow and rectangular and have a large number of type acceptance symbols marked on the side, but the critical marking is "X2".  Because this is mains switching it is also important that the pair and their leads be well insulated with heat shrink tubing or similar (but NOT electrical sticky tape).

If the amplifier uses double pole mains switching, i.e. both Active and Neutral are switched, then two identical snubbers are required, one for each contact pair.

If you have any doubts about your ability to do mains-connected wiring then please take the job to your local amp tech.
If you say theory and practice don't agree you haven't applied enough theory.

Ross

I am new to this forum so bear with me (late, I know).

I fixed my 5210 amplifier years ago when it had the same popping/rumbling sounds (I needed to get into the schematic and use a meter to do it, so this is not for non-electronic types out there). It turned out that the problem was one of the coupling capacitors - a tantalum type that is polarized - between two stages of the amplifier. It was installed correctly but experiencing a reversed bias across it (either a design flaw or the circuitry bias points drifted over time, I do not know which caused it but the prevalence of this sympton points to a design flaw by Marshall). These components can tolerate *small* reverse bias for some time but eventually will fail like we have all seen. The fix was to replace it with a bi-polar capacitor of approximately the same value (the value is not terribly critical here, a larger one will permit more low frequencies through and a smaller one will start to reduce the bass response if too small).

I did this mod to mine, and the amplifier has been free of these pops and rumbles for almost 10 years now.

J M Fahey