YJM100 - 'The Ultimate Plexi' thread!

[crossroadsnyc]

Red, have you tried re-biasing the amp? I suspected a problem on mine a week or two ago, and I fixed the issue by just re-biasing. When I turned it on, it was very low volume / sounded kind of scratchy (when i hit the boost it sounded even worse) ... actually, it reminded me very much of a video someone did on youtube trying to identify some kind of issue they were having. Anyway, it just turned out that it needed to be re-biased.

Here's the video that it reminded me of (i have no clue what happened w/this dude as there doesn't seem to be any kind of update on his video) ...

[ame=http://www.youtube.com/watch?v=Qcv5H7WyKGw]Marshall YJM100 Problem - YouTube[/ame]

 

[duncan11]

Red, have you tried re-biasing the amp? I suspected a problem on mine a week or two ago, and I fixed the issue by just re-biasing. When I turned it on, it was very low volume / sounded kind of scratchy (when i hit the boost it sounded even worse) ... actually, it reminded me very much of a video someone did on youtube trying to identify some kind of issue they were having. Anyway, it just turned out that it needed to be re-biased.

Here's the video that it reminded me of (i have no clue what happened w/this dude as there doesn't seem to be any kind of update on his video) ...

Marshall YJM100 Problem - YouTube

Yup Autobias tends to fix a lot of the little anomalies that crop up from time to time. Sometimes, after I let the tubes warm up for a minute (not 4 mins like I used to) when I kick off standby i get nothing. No sound. Turn amp back onto standby, the power off, repeat. Same thing. Only autobias cures it. Happens every once and a while. In fact the last time I moved it from outlets I forgot to autobias right away. Nature of the electric beast is what I say.

Preamp tubes are easy swap, I'd just buy them and do them yourself Red. No special skills required unlike power tubes which on any other amp model need to be biased which I used to hate taking my amps into the shop for. That was one reason why I went to Mesa for a while, fixed bias as long as you used their tubes.

 

[marshallmellowed]

I suspected the preamp tubes at first, but after trying a regular distortion pedal instead of the onboard boast and getting the same problem, I thought it might be the cab. I tried using my JCM1C through the cab and everything sounds fine with the gain on max, even with a pedal on max so I am back to thinking its the tubes again. I'm not sure whether to take it back to the guitar store and get a free service and tubes but have to wait a few weeks without it, or if I should just buy my own preamp tubes.

Sounds like you've ruled out everything but the amp. If it sounds bad only with the boost engaged, that would indicate a problem with the boost circuit or the settings. If it sounds bad even without the boost, that would indicate a problem with the basic signal path, most likely a preamp or PI tube.

 

[Redstone]

I've tried re-biasing it normally as well as a hot bias and a cold bias. No luck I might just go ahead and order some cheap tubes for now, I spent all my money on the EP Booster I'd love to get some decent tubes. I might hold off for a week and see if I can stretch for something better. My JCM1 will keep my mind of not being able to unleash to fury. Maybe I can try ripping the tubes from my JCM1 to test what tube is gone in my YJM, if any. I could always use the JCMs tubes to keep me going until I get some for the YJM.

 

[Holme]

I'm sure I've read something similar to this & it turned out to be a pre amp valve Red!

Hope you get it sorted out mate!

 

[Redstone]

Bad news guys, its not a preamp tube :Ohno: Looks like I've got to take it back to the crappy music store I bought it from and get them to fix it I swear if they damage my YJM, I'll damage their faces. How am I going to survive the next few weeks without it. Well, at least I've got the JCM1 as backup, but its not the same. I might also borrow the JTM45 or JVM210 that the store has had for the last 5 years, just as something to keep me going.

I think I'd better get a 2nd YJM incase something like this happens again Maybe a 1960AX and BX to run both into

 

[dash8311]

That's my video, actually.

The amp is with Jam Industries, the Canadian distributor for Marshall, being fixed as we speak.

 

[Odin69]

Bad news guys, its not a preamp tube...How am I going to survive the next few weeks without it.

I hope it only takes a few weeks for you to get it back? I had to take one of my amps to repair man and it took 3-4 months to get it back because the company didnt have the "so called" special transformers for it. I thought he was pulling my leg so, I called the company direct and they told me the same thing.

 

[AllenCollinsExplorer]

Just played my YJM again, since I hadn't had the chance the last two days! It sounds soooooooooooooooooooo incredible! Jammed to a couple of songs and did some improvising and boy, the tones in there are awesome! I think I've noticed that over 100 times by now but I still can't get over how good it sounds!

 

[Redstone]

One thing that makes me think twice is that the boost sounds funny, but the same thing happens when a regular boost pedal. I would have thought that would be because of the tubes. Its strange.

 

[marshallmellowed]

One thing that makes me think twice is that the boost sounds funny, but the same thing happens when a regular boost pedal. I would have thought that would be because of the tubes. Its strange.

Which preamp tubes have you tried changing? Did you also swap out the PI tube (next to the power tubes)? Also, does the amp sound bad even without the boost, gate or reverb engaged?

 

[Redstone]

I first swapped out V1 and V4 for the tubes from my JCM1 and then swapped V2 and V3 with the tubes from my JCM. There is no preamp tube beside the power tubes, just the 4 next to them. I think V4 is the phase inverter tube, hence me switching V1 and V4 since V1 has something to do with the gain (I think). Is there any chance of it being a power tube?

 

[crossroadsnyc]

That's my video, actually.

The amp is with Jam Industries, the Canadian distributor for Marshall, being fixed as we speak.

Did they tell you what was wrong w/it?

 

[dash8311]

Not yet. They replaced the noise gate but that didn't fix it, so now I'm quite nervous... $$ ...no warrantee!

 

[BlackSG91]

Check out this 10 year old phenom! She's getting a pretty good tone through her YJM.

[ame=http://www.youtube.com/watch?v=bXVKi0IHXOI]Yngwie J. Malmsteen Spellbound[/ame]

 

[marshallmellowed]

I first swapped out V1 and V4 for the tubes from my JCM1 and then swapped V2 and V3 with the tubes from my JCM. There is no preamp tube beside the power tubes, just the 4 next to them. I think V4 is the phase inverter tube, hence me switching V1 and V4 since V1 has something to do with the gain (I think). Is there any chance of it being a power tube?

I suppose it's possible, but I would think one of your fault LED's would be on if that were the case. You didn't mention if the amp sounds bad even without the boost, gate or reverb engaged.

 

[Redstone]

I suppose it's possible, but I would think one of your fault LED's would be on if that were the case. You didn't mention if the amp sounds bad even without the boost, gate or reverb engaged.

I forgot about the Indicator lights, none of them are on anyway, so that rules that out. The amp sounds fine without the boost. Reverb sounds fine too. I haven't tried the gate since I basically never use it. I'll do a little more testing tomorrow and see what happens. I'm reluctant to sent it off to get fixed since its not really a major problem for me since I rarely use the boost, but I'd rather have it fixed than broken.

 

[Redstone]

This shape-

It was an absolute bag of crap!

Oh Holme, my rich uncle just bought 2, not 1, 2 of those Escorts As if his 7 Mercedes-Benz's weren't enough, the moron goes any buys 2 XR3s to "reconnect with his childhood". Just one of those Mercedes is worth more than my dads house I'll never understand how such and idiot got so rich. If I had as much money as him, I'd buy something cool like 10 YJMs and 20 cabs or something similar. Free gear for everyone!

 

[Holme]

Oh Holme, my rich uncle just bought 2, not 1, 2 of those Escorts As if his 7 Mercedes-Benz's weren't enough, the moron goes any buys 2 XR3s to "reconnect with his childhood". Just one of those Mercedes is worth more than my dads house I'll never understand how such and idiot got so rich. If I had as much money as him, I'd buy something cool like 10 YJMs and 20 cabs or something similar. Free gear for everyone!

I had a mate buy the RS Turbo version!
It was quick!
When it was working!
Not very reliable cars at all from my experience-still by the sounds of it I don't think your Uncle is going to be stuck for a ride if one breaks down!

 

[db3266]

I forgot about the Indicator lights, none of them are on anyway, so that rules that out. The amp sounds fine without the boost. Reverb sounds fine too. I haven't tried the gate since I basically never use it. I'll do a little more testing tomorrow and see what happens. I'm reluctant to sent it off to get fixed since its not really a major problem for me since I rarely use the boost, but I'd rather have it fixed than broken.

And you want to make sure you have it fixed whilst withint he warranty period.

Pedals in front of the amp sound so much better than the internal boost