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Marshall MG30DFX (fixing of)

Postby ef37a » Fri Apr 22, 2011 6:59 am

Son lugged one of these home in the early hours of Wed am.

Reported fault: Sound fades but can be reinstated by a big "clang" on the geetar.

I checked for drys around the TDA2050 power op chip but the problem turned out to be a poor contact thru' the headphone jack earth path. This carries the 0V speaker return current and thus effects speaker kill for headphone operation. This is it seems a very common failing of the design.

A re-tension and clean has it working fine but son will convey the message that if wonga is available(unlikely!) dad will fit a new jack, otherewise he can have it back pro bono..THIS time!

Dave.
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Re: Marshall MG30DFX (fixing of)

Postby Dave B » Fri Apr 22, 2011 11:07 am

I realise that it's probably a problem for you to do, but if it were me, I'd tell him to bin it and buy a decent amp. The MG series is just nasty sounding IMHO. I had a small one as a 'general knock about at low levels at home' amp and it was _awful_ - and that was with real guitars and guitarists as well as my mad fumblings. Someone has since borrowed it and tbh, I can't be bothered to remember who!
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Re: Marshall MG30DFX (fixing of)

Postby ef37a » Fri Apr 22, 2011 11:16 am

Dave B wrote:I realise that it's probably a problem for you to do, but if it were me, I'd tell him to bin it and buy a decent amp. The MG series is just nasty sounding IMHO. I had a small one as a 'general knock about at low levels at home' amp and it was _awful_ - and that was with real guitars and guitarists as well as my mad fumblings. Someone has since borrowed it and tbh, I can't be bothered to remember who!

Heh!Heh! My son (who is a fussy B as a rule) quite likes the sound and he is a dyed in the wool valve man!

Actually I might offer him silly money for it (shan't get paid to repair it you see, jazz musicians!) then gut it and build a nice 6V6 15W jobbie in it. The "custom" 10" isn't up to much but I could splash out on a 10" Greenback, even a Gold!

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Re: Marshall MG30DFX (fixing of)

Postby Dave B » Fri Apr 22, 2011 5:47 pm

Dave,

I didn't know I _was_ a dyed in the wool valve man until I came across that!

Oooh - build a decent amp inside .... that would be cool. It would also be the sort of thing that would wind today's yoof up - "How come your amp sounds better than mine?" ... "Well ..... "

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Re: Marshall MG30DFX (fixing of)

Postby Folderol » Fri Apr 22, 2011 6:30 pm

ef37a wrote:
Actually I might offer him silly money for it (shan't get paid to repair it you see, jazz musicians!) then gut it and build a nice 6V6 15W jobbie in it. The "custom" 10" isn't up to much but I could splash out on a 10" Greenback, even a Gold!

Dave.

Go for it!

Then have a camera ready for the look on his face when he hears the 'serviced' amp - just don't tell him or his mates exactly what you did
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Re: Marshall MG30DFX (fixing of)

Postby 4TrackMadman » Tue Apr 26, 2011 3:48 pm

Great idea, might as well gut that nasty amp out and put something decent in its stead.
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Re: Marshall MG30DFX (fixing of)

Postby ef37a » Wed Apr 27, 2011 1:14 pm

4TrackMadman wrote:Great idea, might as well gut that nasty amp out and put something decent in its stead.

Gooorn now anyway.
I finished up linking out the H/P earth path and sent it back with the message that I could fit an new socket but that would cost "something". Stoney so far!

On the brighter front. just paid 99.99 for a very clean Squier Tele. Son loves the sound and playabilty over his Mex Strat.

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Re: Marshall MG30DFX (fixing of)

Postby sszdl » Thu Apr 28, 2011 11:32 am

ef37a wrote:
I checked for drys around the TDA2050 power op chip but the problem turned out to be a poor contact thru' the headphone jack earth path. This carries the 0V speaker return current and thus effects speaker kill for headphone operation. This is it seems a very common failing of the design.

Hmm... My father-in-law offloaded a broken one of these (maybe a different one in the MG series) and I never found the problem either.

I'll try this tonight!
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Re: Marshall MG30DFX (fixing of)

Postby ef37a » Thu Apr 28, 2011 12:22 pm

sszdl wrote:
ef37a wrote:
I checked for drys around the TDA2050 power op chip but the problem turned out to be a poor contact thru' the headphone jack earth path. This carries the 0V speaker return current and thus effects speaker kill for headphone operation. This is it seems a very common failing of the design.

Hmm... My father-in-law offloaded a broken one of these (maybe a different one in the MG series) and I never found the problem either.

I'll try this tonight!

If it does turn out to be the H/P socket the best plan if you want to keep the speaker kill facility is to run the earth link out to a switch on the back of the chassis, a wee 2A jobbie should be fine.

I did not mention such a mod' since folding stuff was never in evidence!

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Re: Marshall MG30DFX (fixing of)

Postby Folderol » Thu Apr 28, 2011 6:33 pm

ef37a wrote:
On the brighter front. just paid 99.99 for a very clean Squier Tele. Son loves the sound and playabilty over his Mex Strat.

Dave.
Pictures... or it never happened
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Re: Marshall MG30DFX (fixing of)

Postby _ Six _ » Wed May 04, 2011 10:01 pm

I borrowed an MG amp for a gig when I was in the [ ****** ] once and wished I'd canceled it instead.

Awful. God Awful even
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Re: Marshall MG30DFX (fixing of)

Postby ef37a » Thu May 05, 2011 7:43 am

_ Six _ wrote:I borrowed an MG amp for a gig when I was in the [ ****** ] once and wished I'd canceled it instead.

Awful. God Awful even

Well all gone now!

I am BTW looking for a tatty,cheap, 1x12 combo cab. I have built a 60W (clips at 73W!) valve amp and want to build it into a cab with a Century Neo speaker to make a compact, kickass, fairly lightweight amp. (with the Tele this thing produces so much treble you could shave with it!).

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