Acme B2, Mids and Highs not Happening

Discussion in 'Amps [BG]' started by Count Bassie, Mar 19, 2014.


  1. Count Bassie

    Count Bassie Supporting Member

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    I've gotten this Series-I in a trade, and the mid and high driver are not working.

    I've written Andy and he's gotten back, and we're narrowing it down... in the Series-II manual he sent me it's mentioned that the mid and high attenuators might toast (see linkage below, the middle of pg 4), so I'm only posting here to get some anecdotal/peripheral/additional info or experiences with this. I know the Sreies-II and -III are the popular ones, but they're not essentially different spec-wise from the Series-I...

    file:///C:/Documents%20and%20Settings/IBM%20T41/My%20Documents/Downloads/Series%20II%20Manual%20with%20Cover%20(1).pdf

    I realize I'm not the priority on his list, but he's been certainly reasonable about staying in touch. Here's what I've done so far in case anyone's been here before and has some experience fixing it...

    I've put a multi-meter on the terminals of the mid-driver (didn't un-solder), and as it's connected to the system it reads regularly between 4.5 and 5 ohms. Does this sound right? I'm a tech-spaz, so I might be doing that wrong. I've also found a small hole in the mid driver surround, I might need to replace that... but I don't see how that would prevent it from trying to function.

    The bulb was also broken when I got it, so I replaced it. I though that it sounded pretty good after that, and I lent it to someone to try out. I realize that memory is a thief, so maybe the mid and high never worked at all... maybe my ears are schizophrenic... also when I turn the posts of the attenuator pots at the jack plate, they feel hard to turn and are a little mechanically noisy.

    Anyway the woofers sound very nice... :smug:
     
  2. Jim C

    Jim C Supporting Member

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    My .02
    I don't think you can measure driver resistance accurately when still connected to the cab.
    If the attenuators are suspect, is it ok to use a jumper across them for zero resistance for a low volume test?
    If that made the miss and tweeter happen one could expect these to be the problem.
     
  3. Steve

    Steve

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    andy's attenuators are hard hard to turn and feel a little gritty straight out of the box. There's a blurb about it somewhere on his site.

    The quick. easy way to check is to run a CD through the cab. That'll give you enough high end content to hear well.
     
  4. Count Bassie

    Count Bassie Supporting Member

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    Oh yeah... thanks.

    JimC, I don't know that I want to jump the attenuators... might be a sure way to blow 'em??
     
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  6. Jim Carr

    Jim Carr Dr. Jim Gold Supporting Member

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    If the bulb was broken, the mid/tweet are out of the circuit. Is the new bulb still good? How does it sound? Are the mids happening? I am unclear on this based on your post.
     
  7. BassmanPaul

    BassmanPaul Gold Supporting Member

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    Andy does have a replacement for the lamp that is not actually a lamp. Ask him about it. I can't remember how long I've had my Series I pair but I have only ever blown one lamp. I was using the cab for a kind of ad hoc PA. The mic fed back and the lamp blew.
     
  8. Count Bassie

    Count Bassie Supporting Member

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    Jim, I think the new bulb is good, but yeah I should re-check again. From the guy I lent it to, the bulb did not get the mid and high drivers working again.

    Paul, I've asked but have not specifically heard a response to that. I'm still after it...
     
  9. Count Bassie

    Count Bassie Supporting Member

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    Update... woofers work fine, mids and highs dead. I've removed the mid driver and put the leads from a multi-meter on it, and it registers nothing at all. I have not tested the tweeter, as I have read in the Series-II manual that this will kill the tweeter. I put the leads from the meter on the ends of the wires remaining after removing the mid driver (and the tweeter), and signal registers (ohms).

    Seems I've got a couple bad drivers, but I need to know why. There is reference in the manual to the Series-1 having issues with the crossover, as in toasting, but I know nothing of electronics really. I'm still hoping Andy will get back when he can spare a minute, and maybe I can get this addressed. Seems I'll need new drivers for starters, and possibly a crossover upgrade. I do hope this is worth it!
     
  10. B-string

    B-string Gold Supporting Member

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    There is a possibility of a crossover failing to control the frequencies properly or at all. If the frequency band going to a mid and/or tweeter is not controlled, the lower frequencies will burn them out pretty quick. Wait for Andy, you don't want to install a new mid and tweeter just to have them fry the first time you use them.
     
  11. Count Bassie

    Count Bassie Supporting Member

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    I will sit quietly. Thanks B...
     
  12. unlined4string

    unlined4string Supporting Member

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    I once had an issue with my series II LoB1 where the mid and high drivers had some king of weird distortion thing going on when playing at at higher levels. I replaced the bulb and the problem disappeared. In my case the bulb hadn't completely failed, but it had partially failed to the point where the effect was audible.
     
  13. Count Bassie

    Count Bassie Supporting Member

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    I've sent the mid, tweet and crossover to Andy at Acme, so it'll be back in biz by the end of next week I think. We shall see what to do with this little dynamo then... my kid may even end up with it to amplify her string harp, which sounds like it might be perfect for.
     

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