Marshall 5002 Lead 20 Gut Pic !! - Tech Advice -

[manuel-sevilla]

Hi,
I recently bought a Marshall Lead 20, see picture.
I'm good with the solder but my knowledge for components is quite low.



... so I have few questions:

- Gain and Volume Pots (VR1 and VR2) and both imput connectors needs to be replaced for heavy crack and noise issue. I'll go for a pair of PEC pots and switchcraft sockets.

- Do you think replacing the Capacitors entire set make sense for a 20 years old SS amp like that ?

- Do you have any suggestion for a better Op-Amp ?

- Do you have any suggestions for any Components upgrade ?

Thanks in advance
Manuel

[Steve Conner]

Changing the electrolytic capacitors won't do any harm.

The op-amp could be replaced by a TL072 or NE5532, these might give lower noise.

Be careful if changing to Switchcraft jacks, they may need isolating from the front panel to prevent hum.

[Gtr_tech]

The noisy pots can be cleaned....I doubt they need replacing. The jacks likely are due for replacement....those cliff jacks aren't known for longevity.

[Enzo]

I agree, squirt some cleaner in the controls first, probably all you need.

And have you resoldered the existing jacks? Before replacing the jacks, swab them with a Qtip full of Deoxit and resolder the pins to the board

And replacing those jacks? Why not just put in a couple nice NEW Cliff jacks. if you have to replace them again in another 20 years, oh well. Your amp appears to be about 22 years old, they made it this far. Seriously, they work, they will fit right in the hole on the panel and sit right in the holes on the circuit board, no screwing around making things fit, and there won;t be any grounding issues either. COnsider the panel hole is a lot larger than the 3/8" of the Switchcraft.

[manuel-sevilla]

Yep, in the end, I bought a pair of PCB Cliff sockets, a direct replace for the original ones. I've already cleaned the two Pots but both needs to be replaced, no way to be fixed. I bought a pair of PEC pots, double expensive than standard stuff, but I really want to test what you get from two times money not East Made components.

I bought also a socket for the OpAmp so I'll able to try different chips.

I have one more question, I would like to place a switch to take In and Out the EQ section ....



Thanks again.
Manuel

[manuel-sevilla]

Yep, in the end, I bought a pair of PCB Cliff sockets, a direct replace for the original ones. I've already cleaned the two Pots but both needs to be replaced, no way to be fixed. I bought a pair of PEC pots, double expensive than standard stuff, but I really want to test what you get from two times money not East Made components.

I bought also a socket for the OpAmp so I'll able to try different chips.

I have one more question, I would like to place a switch to take In and Out the EQ section ....



Thanks again.
Manuel

[weekendclimber]

I've surfed this site for a while as a guest and signed up today after I saw this old thread. From the schematic, it's not quite legible enough for me to tell what the ohm rating for the pots are. On the board they all just say AIM on them with no ratings. I've emailed Marshall, but after a week I've still not gotten a reply. I was hoping someone might help me out if they know. Thanks

[Billy R aka DynaFreak]

AIM is just Marshall's way of saying it is a 1 megohm audio taper pot. You often see this a 1MA on Fender schematics.

[weekendclimber]

AIM is just Marshall's way of saying it is a 1 megohm audio taper pot. You often see this a 1MA on Fender schematics.

Now that you say that it makes complete sense. Thanks for the clarification.

[LPMojoGL]

Howdy ya'll! I stumbled on this thread looking for a way to add an effects loop to this amp. Basically, I'd like the option of running effects post preamp and tone stack, but before the power amp, much like a Peavey Classic is setup. I'm handy with a soldering iron, but I must admit that I can't tell where to add the send and return to this circuit. Any info would be much appreciated, thanks!!!