YJM100 - 'The Ultimate Plexi' thread!

[usablefiber]

well my phone pics aren’t uploading cause they are too large apparently which is par for the course with this amp.

Also for some reason I’ve always had problems with my YJM and burning through tubes. Maybe it’s cause of the attenuator but tubes blow fast and it always seems to have problems.

If you can get your hands on a jcm 800 with MV or a 1987x and attenuator it’s probably a better option than the yjm. Also even with the power scaling it doesn’t totally solve the volume problem of the plexi as for it to actually sound good it’s still gotta be pretty loud. if you scale it all the way it loses a lot of the oomph as you’d expect, it is helpful though in a live band setting to be able to dial it down a bit to be much more manageable but it’s not the end all be all on that front.

It’s a great amp sure but don’t feel like you are missing out on the end all be all of marshall’s if you can’t get your hands on one for a manageable price. The other options like a jcm 800 or a reissue plexi with attenuator as mentioned sound just as great in their own right.

 

[usablefiber]

it’s not so much the added weight but the added bulk with that weight that makes it a pain to lug around. the handle on top is pretty much useless as it’s really hard to carry it one handed perpendicular. idk it’s always annoyed me a bit. but again if you have roadies or the space and strength to deal then yeah

 

[marshallmellowed]

Yes, both big and heavy, would be a terrible amp to gig (move...). A cool design, but I preferred the tone of an attenuated 1959 RI, as well as the smaller size. Didn't care for the YJM on-board boost, but the gate worked pretty well.

 

[marshallmellowed]

The YJM100 weighs 52 pounds. Heavier than some other amps? Yes. Heavy overall? Nope.

Reminds me of a song from when I was young, "I don't want her, you can have her, she's too fat for me...". Yes, it was a very in-sensitive song.

 

[crossroadsnyc]

Reminds me of a song from when I was young, "I don't want her, you can have her, she's too fat for me...". Yes, it was a very in-sensitive song.

 

[marshallmellowed]

Mmm, steak. Told my wife we needed to have steak one night this week. She can have some too, but I'll need to weigh her first.

 

[vintmodJCM]

It's a design flaw obviously not a failure of a faulty component so I think it's save to say that all amps are affected sooner or later.
If I'd solely depend on that one amp I'd do the update ASAP.

I've had my 2011 YJM100 for 11 years now. I have always had it plugged directly into a Furman Power Conditioner that regulates the AC voltage and protects from low/high voltage especially spikes and drops. This must have protected my noise gate board and the vulnerable IC5. I have never experienced any problem with this incredible amp. I did lose a NOS fat bottle 6CA7 once for which the amp detected and automatically switched to 50w and identified the bad tube.

One important note about the controversial attenuator: it is a fantastic system imho! It does not alter tone, which VariACs, Hot Plates and others do. The result of any attenuation is subjective to the ear of the player. The YJM's attenuator is smart and integrated with the amp in order to protect the electronics from starving of power while the power section is "starved". Speaker compression is the primary issue. Reducing the power scaling to say, 12w output (noon), allows the YJM100w to become a YJM12w and safely play through a single 20w Greenback in an iso recording cab. Amazing!

 

[crossroadsnyc]

I've had my 2011 YJM100 for 11 years now. I have always had it plugged directly into a Furman Power Conditioner that regulates the AC voltage and protects from low/high voltage especially spikes and drops. This must have protected my noise gate board and the vulnerable IC5. I have never experienced any problem with this incredible amp. I did lose a NOS fat bottle 6CA7 once for which the amp detected and automatically switched to 50w and identified the bad tube.

One important note about the controversial attenuator: it is a fantastic system imho! It does not alter tone, which VariACs, Hot Plates and others do. The result of any attenuation is subjective to the ear of the player. The YJM's attenuator is smart and integrated with the amp in order to protect the electronics from starving of power while the power section is "starved". Speaker compression is the primary issue. Reducing the power scaling to say, 12w output (noon), allows the YJM100w to become a YJM12w and safely play through a single 20w Greenback in an iso recording cab. Amazing!

I haven't had any issues with mine either ... then again, I haven't hit the front end of mine with a boost with the internal boost already engaged, so maybe that has something to do with it? Though, I'll admit that I've been very tempted to see not only how it'd sound, but also whether or not the amp will be able to take it. I'd have a serious case of sad if something happened and I had to send it off for repair. Then again, the onboard boost gives me all the juice I need, so I'm not sure if I'll take the chance (but I still kinda want to). Hmmm, I think it's time to fire it up!

 

[Holme]

Mine is still 100% stock since I recieved it new direct from Marshall - same valves everything - still works 100% as it should!

 

[indeedido]

Mine is still 100% stock since I recieved it new direct from Marshall - same valves everything - still works 100% as it should!

Same here! Still making the best doughnuts!

 

[vintmodJCM]

I haven't had any issues with mine either ... then again, I haven't hit the front end of mine with a boost with the internal boost already engaged, so maybe that has something to do with it? Though, I'll admit that I've been very tempted to see not only how it'd sound, but also whether or not the amp will be able to take it. I'd have a serious case of sad if something happened and I had to send it off for repair. Then again, the onboard boost gives me all the juice I need, so I'm not sure if I'll take the chance (but I still kinda want to). Hmmm, I think it's time to fire it up!

The YJM100 was my gigging rig for a few years before covid and I ran a pedal board in the front and a delay in the loop. I used a Tube Screamer with an EQ boost for Boston songs, and a ProCo Rat plus EQ and the YJM internal boost for late 80s hair metal like Mr. Big, Living Color, Extreme, Winger, White Lion etc. and I had no issues. It was completely reliable and I didn't even bring tubes with me anymore. I even played a couple gigs with a full stack dimed (with no attenuator) and an EQ + Phase 90 + Echoplex pedal in the front with the booster on mild for Dave-era Van Halen and it was LOUD & totally sick! What a blast that was Maybe i've been lucky. I still play & record with her and she's never quit on me.

 

[IPlayFender]

Jaysus, its been too long since I've poked my head in here. My poor beloved YJM100 has suffered an injury. Long story short, I bought an attenuator to try out (Rivera Rock Crusher as Thomann had one in stock and offer 30 days money back). What a job it makes of the YJM! I've always found the YJM to be a bit clean sounding when its all the way down on 0.1 watts. Its not a true Plexi sound. When you set it to 100 watts and use an attenuator to bring down the volume, it sounds much more aggressive. I love it even more! (still probably going to return the Rivera and buy an Aracom). One funny thing I've noticed with all my amps is that the Presence and Treble have much less impact on sound when using an attenuator.

Anyway thats not the point, the point is my poor auld YJM is having a wobble. It seems to be intermittent and also seems to temporarily repair itself after its powered off. The issue just seems to happen at random. The V1 tube light lights up and the amp sounds a bit "off". It seems to happen even when I'm playing in 50W mode. The only pedal used is my SVDS replica with the dials on about 12 o clock. As I said, powering it off and back on sorts it out temporarily. I tried switching the 1st tube with the 4th tube and still the first tube fault light always lights up when this happens. I'll keep investigating when I have some time.

Here is an up to date family photo.

Hello , I’m a new member and have a YJM100 as well and I’m having the exact same issue you have or had ! My tech is currently troubleshooting it . Did you get it fixed and if so what was the fix ?? Thanks and really appreciate it ! - Anthony

 

[crossroadsnyc]

Hello , I’m a new member and have a YJM100 as well and I’m having the exact same issue you have or had ! My tech is currently troubleshooting it . Did you get it fixed and if so what was the fix ?? Thanks and really appreciate it ! - Anthony

What exactly is happening? Not that I’ll know the answer, but I’m just curious. I read the quote you quoted, but was having a difficult time following exactly.

 

[marshallmellowed]

Hello , I’m a new member and have a YJM100 as well and I’m having the exact same issue you have or had ! My tech is currently troubleshooting it . Did you get it fixed and if so what was the fix ?? Thanks and really appreciate it ! - Anthony

If you're saying you used your YJM with an attenuator, and then had issues with it, I might be able to help. I once used my YJM with an attenuator to do an A//B comparison to my 1059 SLP. The YJM does not work weill with attenuators (IMO), as there are components in the YJM which will get very hot, hot enough to melt the solder used in the YJM. The components I'm referring to are in the EPA circuit, and I had one fall completely off the PCB when using my YJM with an attenuator. Luckily, it was an easy repair, only requiring the component to be soldered back into place (close call). After that experience, I've stuck with the simpler 1959 SLP design, which I think sounds better anyway.

 

[Solid State]

One important note about the controversial attenuator: it is a fantastic system imho! It does not alter tone, which VariACs, Hot Plates and others do. The result of any attenuation is subjective to the ear of the player. The YJM's attenuator is smart and integrated with the amp in order to protect the electronics from starving of power while the power section is "starved". Speaker compression is the primary issue. Reducing the power scaling to say, 12w output (noon), allows the YJM100w to become a YJM12w and safely play through a single 20w Greenback in an iso recording cab. Amazing!

People were so negative about all of the onboard features, I had written off the amp as a power switchable 1959 with premium transformers and built-ins you don't need. When I finally heard just how good that attenuator works, I was kind of mind-blown that it's not a standard feature on their 100 watt line. A guy I befriended through Youtube and Facebook sent me a clip of it at its lowest setting and it was down as low as I can take any MasterVolume amp.

 

[crossroadsnyc]

People were so negative about all of the onboard features, I had written off the amp as a power switchable 1959 with premium transformers and built-ins you don't need. When I finally heard just how good that attenuator works, I was kind of mind-blown that it's not a standard feature on their 100 watt line. A guy I befriended through Youtube and Facebook sent me a clip of it at its lowest setting and it was down as low as I can take any MasterVolume amp.

Yep, it’s a fantastic system. The only drawback is that you lose a little breakup when fully attenuated, but kicking it in the pants with a little boost works just great. I’d choose the EPA over any attenuator out there. Your post is a good one, as it highlights the need to be discerning when taking advice from people online (including my own advice!).

As for mine, I’ve had it since they were released, and it’s never given me a problem. I‘ve used it regularly over the years (it’s been my primary amp since day 1), and believe it or not, the amp still has the original tubes. It’s been literally flawless. I’ve read countless threads/posts during this time regarding other supposedly “more reliable” amps having problems, so it just goes to show any amp can experience issues. If something ever happened, I’d just have it fixed (like any other amp), and keep enjoying it! Over the decade+ that it’s been around, only a minority of YJM owners have experienced issues, and all of those issues have been exactly the same, with an easy fix (that seems pretty reliable to me all things considered).

 

[IPlayFender]

If you're saying you used your YJM with an attenuator, and then had issues with it, I might be able to help. I once used my YJM with an attenuator to do an A//B comparison to my 1059 SLP. The YJM does not work weill with attenuators (IMO), as there are components in the YJM which will get very hot, hot enough to melt the solder used in the YJM. The components I'm referring to are in the EPA circuit, and I had one fall completely off the PCB when using my YJM with an attenuator. Luckily, it was an easy repair, only requiring the component to be soldered back into place (close call). After that experience, I've stuck with the simpler 1959 SLP design, which I think sounds better anyway.

What exactly is happening? Not that I’ll know the answer, but I’m just curious. I read the quote you quoted, but was having a difficult time following exactly.

Ok. First off I have owned this amp the same year it came out and have used it extensively in studio and gigs and not one issue till now. In the last 5 months Ive been recording playing this amp to 11 but using both power scaling and an aracom attenuator ( slightly) . So all of a sudden while playing, big drop in volume and everything just got saggy . The v1 and v3 lights were on . So I have a bunch of healthy EL34’s as spares so I replaced the two and re biased ( using self bias feature). Same problem , then I said I will swap all of them with know good tubes pulled from My 100w JCM800. Rebiased , then it display v1 only being bad. After swapping and rebiasing several tubes I had no luck and brought to my tech . here’s what he discovered attached a fried transistor like component which is in route now . He also mentioned something about this heat sick not providing the amount of voltage see attached

 

[marshallmellowed]

Ok. First off I have owned this amp the same year it came out and have used it extensively in studio and gigs and not one issue till now. In the last 5 months Ive been recording playing this amp to 11 but using both power scaling and an aracom attenuator ( slightly) . So all of a sudden while playing, big drop in volume and everything just got saggy . The v1 and v3 lights were on . So I have a bunch of healthy EL34’s as spares so I replaced the two and re biased ( using self bias feature). Same problem , then I said I will swap all of them with know good tubes pulled from My 100w JCM800. Rebiased , then it display v1 only being bad. After swapping and rebiasing several tubes I had no luck and brought to my tech . here’s what he discovered attached a fried transistor like component which is in route now . He also mentioned something about this heat sick not providing the amount of voltage see attached

Yes, that's the component I was referring to. It's on the top side of the main PCB, therefore inverted when the chassis is installed. In my case, while using an attenuator with the amp, EPA turned to max volume, the component and heat sink got so hot, it melted the solder and the entire assembly, (heat sink and transistor) fell to the bottom of the headbox and the volume went to zero. in your case, it sounds like the component just overheated and failed. A design flaw (IMO), as the heat sink is not of sufficient size to dissipate the heat at max volume. Bottom line, IMO, the amp should be usable, either utilizing the on-board EPA, or using an external attenuator, whichever the user prefers, and without frying components.

 

[crossroadsnyc]

Ok. First off I have owned this amp the same year it came out and have used it extensively in studio and gigs and not one issue till now. In the last 5 months Ive been recording playing this amp to 11 but using both power scaling and an aracom attenuator ( slightly) . So all of a sudden while playing, big drop in volume and everything just got saggy . The v1 and v3 lights were on . So I have a bunch of healthy EL34’s as spares so I replaced the two and re biased ( using self bias feature). Same problem , then I said I will swap all of them with know good tubes pulled from My 100w JCM800. Rebiased , then it display v1 only being bad. After swapping and rebiasing several tubes I had no luck and brought to my tech . here’s what he discovered attached a fried transistor like component which is in route now . He also mentioned something about this heat sick not providing the amount of voltage see attached

Oh, ok, so you were using the EPA and the outboard attenuator at the same time? I guess I could see how that’d cause some additional stress that the amp probably wasn’t designed for. Given you had such good luck with it prior to doing so, I’d probably just return to using it as you were. Still, happy to hear it’s an easy fix!

 

[IPlayFender]

it’s not fixed yet . Pending part arrival . I’ve pushed old non master old Marshall’s I own (Ed) with the same attenuator and worst case scenario was new output tube replacement. Of course there is no digital brain in those !