ADA Depot - A Forum To Support Users of ADA Amplification Gear

Please login or register.

Login with username, password and session length
Advanced search  

News:

Let us never forget our beloved founder - RIP Jurrie, we all miss you very much

Pages: [1]   Go Down

Author Topic: Only high gain voicings working  (Read 331 times)

0 Members and 1 Guest are viewing this topic.

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Only high gain voicings working
« on: Time Format »

Dug out my old MP2 and only the high gain voicings work; all of the clean and vintage voicings there is no sound passing through. Also seems a bit noisier than I remember. Tried swapping out the tubes to no avail. Any ideas where the problem may be?
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4636
    • marshalljmpmodshop.net
Re: Only high gain voicings working
« Reply #1 on: Time Format »

Do you feel that the high gain is really high gain, or do you feel there is gain loss?
Logged

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Re: Only high gain voicings working
« Reply #2 on: Time Format »

They still seem like proper high gain voices, though perhaps the Input control needs to be juiced a bit more than before. It's been some years since I last used it so I can't recall if this was always the case.
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Re: Only high gain voicings working
« Reply #3 on: Time Format »

I've done a bit of troubleshooting and confirmed the signal makes it as far as pin 2 of U302 (input of 2nd tube stage) in the clean voicings, but there is no signal at pin 7 of U300 (input of 3rd tube stage). The plate voltage at pin 1 of U302 also measures 190V for clean voicings and drops to 155V for high gain voicings, while the other three plates maintain voltages around 130-134V for all voicings. Cathode voltage at pin 3 of U302 is 21.3V for clean and 21.8V for high gain; grid voltage at pin 2 is 17.5V for clean, 20.7V high gain.
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Re: Only high gain voicings working
« Reply #4 on: Time Format »

So it turns out it was a bad Q311, which luckily is a super common 2N3904 I had a replacement for. Now time to clean all the jacks, pots and switches  ;D
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4636
    • marshalljmpmodshop.net
Re: Only high gain voicings working
« Reply #5 on: Time Format »

Was just going to say that  ;D, had a similar problem many years ago but with the medium gain voicings and there it was Q310 that was bad.
Logged

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Re: Only high gain voicings working
« Reply #6 on: Time Format »

I'm guessing heat stress from being mounted so close to the tubes. There are a lot of components that seem to run pretty hot even with the top and bottom removed. I can only imagine how hot it gets in a rack with other gear.
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4636
    • marshalljmpmodshop.net
Re: Only high gain voicings working
« Reply #7 on: Time Format »

MP-2's get very very hot, I use fans in my rack to keep it cool. But you could be right it's heat related although it's not a common problem with MP-2's. You are the second one that had this problem as far as I know.
Logged

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5664
Re: Only high gain voicings working
« Reply #8 on: Time Format »

Interesting.  I built a 4 RU rack recently with one of my MP-2s (it was a US version but I swapped the power tranny with another I have that has some other issues).  It was all good, loaded programs from main live MP-2 the racked it up.  Worked fine for a bit then suddenly no distorted (vintage 5 voice) sounds worked, only clean (crystal 1 voice) worked so I had to swap it out for my studio MP-2  :facepalm: .  I haven't tried higher gain voices so maybe I have the same issue  :dunno: .  I'll do some more testing but if it's the same issue, nice to know there is a fix.  Worse now is that my studio MP-2 (now in the 4 RU rack) drops a channel then comes good intermittently.  And at the gig I played last night my main live MP-2 was also doping a channel, then coming good.  Very frustrating, particularly at a gig.
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

Thor

  • Newbie
  • *
  • Offline Offline
  • Posts: 9
Re: Only high gain voicings working
« Reply #9 on: Time Format »

Interesting.  I built a 4 RU rack recently with one of my MP-2s (it was a US version but I swapped the power tranny with another I have that has some other issues).  It was all good, loaded programs from main live MP-2 the racked it up.  Worked fine for a bit then suddenly no distorted (vintage 5 voice) sounds worked, only clean (crystal 1 voice) worked so I had to swap it out for my studio MP-2  :facepalm: .  I haven't tried higher gain voices so maybe I have the same issue  :dunno: .  I'll do some more testing but if it's the same issue, nice to know there is a fix.  Worse now is that my studio MP-2 (now in the 4 RU rack) drops a channel then comes good intermittently.  And at the gig I played last night my main live MP-2 was also doping a channel, then coming good.  Very frustrating, particularly at a gig.

The MP-2 has always been too temperamental for live use for my liking. I've had a number of issues with mine over the years that I would just never trust it for gigging. The MP1 on the other hand the only issue I ever had was the battery dying (thankfully not right before a gig).
Logged
ADA MP-1 (Mod3.666)->Peavey Classic 50/50->Marshall 1960A 4x12" (G12T-75)
Line 6 Pod HD500X (MIDI controller)

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5664
Re: Only high gain voicings working
« Reply #10 on: Time Format »

Hey Thor, I bought my first MP-2 new many years ago and it's been rock solid for many many gigs (over 26 years) up until now.  And also before that I had a MP-1 also bought new which was rock solid for 20 plus years gigging.  Up until now it's only been the 2nd hand MP-2s I've bought that have developed issues.  I've never used fans in my rack (although I've thought about), I have my live MP-2 mounted at the top of the rack so it has space above it and I try to maximise the gap between it and my Quadverb for better air flow.  MP-2s do get very hot, way hotter than MP-1s so some fans would be useful.
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5664
Re: Only high gain voicings working
« Reply #11 on: Time Format »

Split this as we were getting into a rack fan discussion, a bit off topic. MP2s get Very Hot - Rack fans http://http://adadepot.com/index.php?topic=2785.0
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5664
Re: Only high gain voicings working
« Reply #12 on: Time Format »

Well good news, spent Friday night going through my MP-2s and their rigs and they all seem to be working fine now. In my live rack (channel drop) issue turned out to be gummy faders in my AM802 mixer (all the right panned channels and the right master).  I have MP-2 main outs ch 1&2, cab sim outs 3&4. I didn't expect all the right panned channels to be bad so I thought it was MP-2 issue.  Cleaned the faders with isopropyl alcohol and is now all good  :whoohoo!: .  MP-2 that had lost distorted patches is now in my studio rig, but is now working fine so maybe a heat related issue around U611  :dunno: . And MP-2 in the new 4RU rack (again I thought was dropping a channel) is also behaving properly.
Logged
Studio Rig: Stuff; Live Rig: More Stuff; Guitars: A few
Pages: [1]   Go Up