Gain drop

[Richie_B]

Hey guys I'm hoping you can pass on some advice. When playing through gain channels on the MP1 its ok for a few min then it drops off and the signal becomes weak, clean. I pulled the tubes out and put in some groove tubes i had around and it still happens. Clean channels are ok but i will be checking it all out over the next few days.

[MarshallJMP]

Is this a V1 or V2 mp-1? (topswitch or not)

Could also be the input jack.

[Harley Hexxe]

   Hi Richie,

      It may be possible that the tubes you swapped out in the unit are not in prime shape either. Without a tube tester, it would be difficult to know for certain.
    One way to test out that theory that it is the tubes would be to play through the MP-1 until the level drops as you describe, then switch to a solid state program and see if the level is still low, or is it full strength?  If your tube programmed patches are all low volume, but your SS patches are full volume, then it's definitely the tubes getting too weak.

        Harley 8)

[Richie_B]

Hey guys, Ok first its the version with no switch on top. Regarding the tubes, it's possible. I'll get back to you on it and will check the patches.

[MarshallJMP]

So it's a V2,what input do you use,front or rear?

[Harley Hexxe]

So it's a V2,what input do you use,front or rear?

    That shouldn't matter. Plugging into the rear input will disable the front input. The only thing plugging into the different inputs will tell you is if there may be a dirty or faulty input jack.

[MarshallJMP]

Plugging in the rear jack doesn't disable the frontjack,the signal still goes thrue the front jack switch.Sometimes this switch can get dirty and give a bad contact.
Now this problem only happends if you use the rear jack.

[Harley Hexxe]

I stand corrected.

    I thought I had read in the old Forum that it worked that way.

[MarshallJMP]

Well the front jack always works even if you plug in something in the rear jack.The front jack has how should I say, priority (?) ,over the rear jack.

[Richie_B]

I usually plug in via the front. I replied earlier on my phone on my way to work, tram full of people. I knock off earlier tomorrow so as soon as I get in, I'll start trying things out. Once this is resolved I think I want to start doing all the basic mods if I can then eventually go for the 3tm. Start small and go from there. Cheers for the support

[rnolan]

Hey Richie, there's 2 tube shops in Melbourne I found the other day, (http://tubeaudio.com.au/ I just bought 6 Mullard long plates from these guys) & (http://thevalvestore.com.au), both had about the same price for tubes, shipping costs were a little different.  When you say clean patches are ok do you mean the SS voice ? or clean tubes voice ?  Also worth giving the input jacks a clean with decent contact cleaner put the jack in and out and give it a spin while you clean it (or in between sprays).  It's sounding like it's either a jack or tube problem.

[Richie_B]

Cheers mate I'll give that a go and check out those stores. Any recommendations on the contact cleaner? Also as much as I want to do whatever mods I need to do myself, I may need to find a tech if I get a bit lost.

[MarshallJMP]

Check this topic if it's the input jack.

http://adadepot.com/index.php?topic=794.msg6372#msg6372

[Richie_B]

So... it does look like it's the jack, will try giving it a clean tomorrow. Today it only dropped down in volume twice. Turned the jack on the guitar lead and no more problem, so that's something. There was another issue that Ive always planned on looking into and that's the chorus, it's never worked. The sound really breaks up on patches where the chorus is active, if it's off then no problem. Is there a way to fix it or should I just let it go. Next on the shopping list will be new tubes, any recommendations on combinations would be very welcome.

[MarshallJMP]

About the chorus,what do you mean by "the sound breaks up" ?

Also check out trimpot T4 which is the bias pot for the BBD,it should be set at around 11 o'clock.