Marshall 30th Anniversary Series thread (6100 / 6101)

[Reer]

Yours is already swapped for 16Ohm.
Stock it looks like on this photo:

 

[Mike_LA]

Yours is already swapped for 16Ohm.
Stock it looks like on this photo:

No, both of mine are completely stock.
Can you point to one more case of what you have found?

 

[Reer]

Perhaps the USA ones came with 8 / 16 Ohm switching stock and the European ones with 4 / 8 Ohm.
When I do a google picture search of 6101 gut shots, I only found photos with wiring like mine.

 

[Mike_LA]

Perhaps the USA ones came with 8 / 16 Ohm switching stock and the European ones with 4 / 8 Ohm.
When I do a google picture search of 6101 gut shots, I only found photos with wiring like mine.

Ok, well then you have to check your amp before making the change.
Are you referencing Euro 220V models?
That may be where the difference occurs.
Both of my US 110V models were factory wired for 4/8 ohms and I switched both sets to 8/16.

 

[MarshallLaws]

Hey friends! Wanted to share the results of some troubleshooting w/ my 6100LM. I've been having some issues with *massive* squealing when playing with high gain, especially if I use, say, a boosted fuzz pedal into the lead channel (just for laughs, and when debugging this issue.) It also happened when I did things like push the lead channel with a boost and then turn up the channel volume a bit: things seemed to form a feedback loop, maybe through a ground loop of some form, going back through all my pedals into the front of the amp and out through the FX send back to my pedalboard (I connect things w/ the "four cable method".) When I ran just the boosted fuzz, the squeal happened on all three channels of the amp.

Anyways, I hit the effects loop level switch on the back of the amp (to switch it to -10 dB instead of +4 dB, instrument instead of rack level) and the squealing is now gone, replaced with the hissing white-noise I would expect from very-high-gain operation! I suspect there still is a ground loop somewhere in my rig but I can now crank gain all I want and not have to worry about a horrible high-pitched ear-destroying banshee wail.

I had a squealing issue with one of my 6100 heads. It was a simple fix, but not so simple to troubleshoot. The fix was to re-cable some wires where a "tech" had cut the zip ties, failed to retie the wires, and left them dangling. They were cross talking and causing an internal feedback loop that would become very pronounced as the volume increased.

 

[Mike_LA]

Yours is already swapped for 16Ohm.
Stock it looks like on this photo:

Ok, so I was totally wrong.
6101 Impedance switch
Found the same thing on one today.
Got to check each amp.





6100 schematic

 

[Reer]

After all this years, has someone found a reliable solution to shield the output transformer against the power transformer hum on the combos?
I think the problem is more due to the open side of the transformers, where the terminals are exposed and also that the end caps aren’t earthed due to silicone washers.

 

[Mike_LA]

After all this years, has someone found a reliable solution to shield the output transformer against the power transformer hum on the combos?

Hmmm, my 6101 is dead quiet.
My other 6101 had a humm until I redressed the cables inside and changed preamp tubes.
Both pretty quiet now.

 

[Reer]

Redressing the cables is a good hint. I see the most cables towards the OT are in proximity to the PT. If I guide them other routes perhaps it will solve the hum.
The PT on my combo is already physically humming very loud, but I don’t get speaker hum on standby like some owners reported. But on play it hums even when no guitar cable is attached, on the other hand this hum is only half as loud as a single coil guitar.

 

[Reer]

I think I discovered another questionable design choice on the 6101 and it is kinda related to hum problems.
The input jack is grounded to chassis via a tag on the pot mounting plate. But there is also a star ground with hum blocking network on the psu pcb which also grounds to chassis. The input jack grounding is bypassing the hum blocking network, rendering it useless and eventually forming a ground loop.
On the schematics there is also no chassis ground at the input jack, so why were they producing it like this?
(Nut removed on the photo)

 

[Mike_LA]

I think I discovered another questionable design choice on the 6101 and it is kinda related to hum problems.
The input jack is grounded to chassis via a tag on the pot mounting plate.

Hummm, I will look at mine when I get home later this week.

 

[Reer]

I just tried it with and without the chassis ground tag at the input jack - did not make a difference in hum.
I guess I have to settle now with that remaining bit of hum; just put the combo a bit farther away so it isn’t noticeable in the first place.
The problem with mine seems that the PT is already physically loud and vibrating, so that’s the limiting factor in all my measures.
In comparison, the PT in my Orange Rocker 30 is so quiet, if there were no pilot light you wouldn’t notice that it’s on (standby).

 

[tallcoolone]

Looking at a local 6100LM head—what would you guys say a good price would be? Are all the LM models 5881 tubes?

Thanks!

 

[rtcook]

Hard to say. Price depends on condition and functionality. The early 6100 LM models could have EL34's from the factory. Or, someone may have done a conversion.

 

[tallcoolone]

Hard to say. Price depends on condition and functionality. The early 6100 LM models could have EL34's from the factory. Or, someone may have done a conversion.

Few small scuffs but excellent condition, everything works, no footswitch. Waiting to hear what the power tubes are.

 

[rtcook]

These amps are prone to MIDI issues. Make sure that works and switches channels. Is it quiet? Alot hum from old capacitors. Tube preference is up to you. I really don't know what a good price is for one. I probably paid more than I should for mine, but is was pretty much NOS in the box.

 

[tallcoolone]

I feel like my amp guy is on retainer already lol. I have read the MIDI issue is a relatively easy fix and yeah 26yr old caps can dry out. I guess that's why I want to get a decent price if I buy one b/c that will prob not be the final bill.

As I'm judging by this thread, lots of people think highly of this Marshall. That means I need to own one at least once!

 

[rtcook]

Great amps. Love mine. Worth the investment in my opinion. Has the Marshall tones i need.

 

[Mike_LA]

These amps are prone to MIDI issues.

Maybe, but just in case I bought a set of spares from Pete.
Best investment outside of having him recap it, No worries now

 

[rtcook]

I have spares myself. Never have needed them, but doesn't hurt to have them.