ADA Depot Too - 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: Microtube 100 Blowing fuses  (Read 89 times)

0 Members and 1 Guest are viewing this topic.

kissfan113

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Microtube 100 Blowing fuses
« on: Time Format »

I just picked up a MT100 with a bad channel, Channel B immediately blows the fuse anyone have an idea where to start to cure this issue up, channel A works great.
Logged

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4587
    • marshalljmpmodshop.net
Re: Microtube 100 Blowing fuses
« Reply #1 on: Time Format »

Most likely cause is a blown power mosfet(s). For channel B these are Q106 and Q107 part numbers IRF9538 and IRF538. Sometimes you also have a defective driver transistor.
Logged

kissfan113

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Microtube 100 Blowing fuses
« Reply #2 on: Time Format »

What is the location of the driver transistor on the schematic?
Thanks
Kevin
Logged

kissfan113

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Microtube 100 Blowing fuses
« Reply #3 on: Time Format »

Also, what could have caused the original chips to blow? I don’t want to replace parts and have them directly fail again.
Logged

David Drake

  • Newbie
  • *
  • Offline Offline
  • Posts: 32
Re: Microtube 100 Blowing fuses
« Reply #4 on: Time Format »

Hey I'll point ya in the right direction maybe? I'm not one of the brains 'round here. But I just got thrugh reading this the other day as my Micro Tube 100 had twice suffering from this reoccurring illness.

Quote from: MarshallJMP
I think I know why the B channel gets blown when it's in bridge mode. Problem is that the output of the B side is connected to the sleeve of the speaker jack. Most of these jacks are metal so if something is touching the jack that is grounded it can blow up the B channel. So best is to isolate the metal part of the jack.

Quote from: Harley Hexxe
Does this also apply to the MT-100?

Quote from: MarshallJMP
Yes it does.
Complete thread is here @ http://adadepot.com/index.php?topic=2587.
Logged

rnolan

  • Administrator
  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 5600
Re: Microtube 100 Blowing fuses
« Reply #5 on: Time Format »

Hey Dave, well spotted  :thumb-up: . I think allot of MT100 users ran their units in bridge mode.
Logged
Studio Rig: MP2/MB1 > Eurorack UB2442FX-Pro > TC M-One XL > Behringer Truths (with Truth Sub) / QUAD ESL 63s
Live Rig: MP2/MB1 > Alesis Quadverb > Alesis Midiverb 4 > Yamaha AM802 > B200s/Carvin TS100/DCM200L > ADA Split Stacks/Mesa P112s

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4587
    • marshalljmpmodshop.net
Re: Microtube 100 Blowing fuses
« Reply #6 on: Time Format »

Bridging can cause the problem like David said. 90% of the time it's the B channel.

The safest way to test it is using an external power supply and put a current limit on it of around 100mA this way you can't blow up the mosfets if something is wrong.
That's the way ADA did it too.
Logged

kissfan113

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Microtube 100 Blowing fuses
« Reply #7 on: Time Format »

Thank you for that document MarshallJMP, I always appreciate the original tech literature for the gear I have it helps a huge amount when it comes to maintenance and service
Logged

MarshallJMP

  • Superhero Member
  • ******
  • Offline Offline
  • Posts: 4587
    • marshalljmpmodshop.net
Re: Microtube 100 Blowing fuses
« Reply #8 on: Time Format »

No problem, just let me know if you need help.
Logged
Pages: [1]   Go Up