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Thread: Peavey Bandit 112

  1. #1
    Supporting Member bsco's Avatar
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    Peavey Bandit 112

    I had started a thread on this before but couldn't find it.....anyway, this amp uses a quad switch..actually two of them....NJU211.....I had ordered a DG211D but it isn't compatible....anyway, the one on the power amp board is actually part of the pre-amp ckt...and that is where the problem seems to be....Pin 11 has 15V on it.....it should be zero...I have it installed in a socket...so I should be able to remove the chip, and going by the schematic, use jumper wires to wire up the switching configuration to get the amp to produce sound... I can scope the signal all the way up to pin 2 but nothing on Pin 3 and pin 3 feeds one of the jacks at the rear of the chassis....and I believe pin 7 does the same thing......there are no signals coming out.....the chip does have the proper voltages at pins 4, 12 and 13......and I also noticed that the op-amps, U2 and U3 have DC voltage at pin 7....over 1 volt actually.....pin 1 on these chips checks fine.....so it looks like I have multiple issues?? I will do some more testing and post the schematic later this evening as it is over to the shop.....
    Cheers

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    Last edited by bsco; 03-27-2020 at 05:24 PM.

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    Supporting Member Jazz P Bass's Avatar
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    It sounds like you have the 'Red Stripe' Bandit 112.
    The parts list shows DG211 for the switch ic.
    https://datasheets.maximintegrated.c...201A-DG211.pdf
    I have no idea what a UJN211 is.

    " I can scope the signal all the way up to pin 2 but nothing on Pin 3"
    Is Pin #1 going Lo?
    Pin #1 must go Lo to turn on pin 2/3 connection.

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  3. #3
    Don't forget the joker g1's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    I have no idea what a UJN211 is.
    Not UJN but NJU
    Attached Files Attached Files

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    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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    Supporting Member bsco's Avatar
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    Quote Originally Posted by g1 View Post
    Not UJN but NJU
    You are right g1.....I had posted the wrong part number.....I jumped pin 2 to pin 3 and everything worked....so either the chip is bad, or something is preventing it from activating..I do have some DG211's, but they don't seem to want to work....I will re-check them after the weekend and post back......stay safe everybody...
    cheers

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    Lifetime Member Enzo's Avatar
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    So monitor its control pins and see if they toggle when you channel switch.

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    Education is what you're left with after you have forgotten what you have learned.

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    Supporting Member bsco's Avatar
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    Quote Originally Posted by Enzo View Post
    So monitor its control pins and see if they toggle when you channel switch.
    will do....You are up early..it is 6 AM here and I am ahead of you by 1.5 hrs...

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    Lifetime Member Enzo's Avatar
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    I am old, I have no schedule. I might sleep all afternoon. Tomorrow might be opposite.

    1.5 hours? So you are in that Labrador zone?

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    Supporting Member bsco's Avatar
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    Quote Originally Posted by Enzo View Post
    I am old, I have no schedule. I might sleep all afternoon. Tomorrow might be opposite.

    1.5 hours? So you are in that Labrador zone?
    No. I am on the edge of St. John's, NL actually...Labrador is an hour ahead of you...I am 1.5 hours....

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    Last edited by bsco; 03-28-2020 at 03:49 PM.

  9. #9
    Supporting Member Jazz P Bass's Avatar
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    Red Stripe schematic: Red Stripe Schematic Parts.pdf

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  10. #10
    Supporting Member bsco's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    Red Stripe schematic: Red Stripe Schematic Parts.pdf
    I'm not sure if the one I have is the red stripe model...I will have to check on Monday....
    Cheers

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  11. #11
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    just got a MIC recent Bandit,service manual is the one from 2007,same problem,channel chip is stuck in clean mode

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  12. #12
    Supporting Member bsco's Avatar
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    Quote Originally Posted by alexradium View Post
    just got a MIC recent Bandit,service manual is the one from 2007,same problem,channel chip is stuck in clean mode
    My problem is not quite the same...I am getting 15V out of the chip and it is sending that voltage to the send./return jacks......I also have 1.2 volts on pin 7 of all three op.chips...(4560's)....I do have a couple of DG211's here which I am going to try again when I get over to the shop......should be later today or tomorrow for sure........let me know if you solve your issue...
    Cheers

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    just got it sorted out right now,it was a broken path from the s3 switch to the chip, pins 9 and 16,too many vias,replaced with a straight wire directly.

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