crate bt220

Discussion in 'Amps [BG]' started by NOTa-bassplayer, Jul 16, 2009.


  1. NOTa-bassplayer

    NOTa-bassplayer

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    AS my user name states I am not a bass player but a drummer. At a gig recently our bass players amp (crate bt220) just quit. No output at all. Tried running direct to the board, nothing. Pulled the head from the cabinet to check the obvious. Fuse good, got power to the transformer, power from the transformer, check for resistance on all the switches, all good. No scorched components. I have the block diagram but am looking for the service manual and/or schematic so I can dig a little deeper. Or if anyone out there has had the same issue a little advice.

    Nabp
     
  2. DogBone

    DogBone

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    I have a BT220 combo I bought for parts, so I'll try to help if I can.

    Crate and SLM used to be *great* for emailing schematics, but not sure how they are now under Loud management. It would be worthwhile to shoot them an email or call.

    So are you saying the amp powers up, but there is no sound? Or did it just die completely?

    If the amp powers up but no sound, here are some things to try....

    Try plugging the bass into the effects RETURN jack (on back of amp). When you do this you are simply bypassing the preamp and eq circuit and plugging straight into the power amp section. If the bass plays through the speaker, there is a problem somewhere in the preamp section.

    If this doesn't work, plug the bass back into the *normal* input and try using headphones plugged into the headphone jack on front. If you hear the bass through headphones, then it is a problem with the driver (speaker), or maybe the connections to the driver.

    Amps with headphone jacks have been known to lose output to the driver b/c the headphone jack itself gets worn or dirty contacts.

    Let me know how it goes.
     
  3. NOTa-bassplayer

    NOTa-bassplayer

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    Tried everything you suggested and still nothing. Thanks for the ideas.
     
  4. DogBone

    DogBone

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    Ugh, that's frustrating. So is the amp actually powering up? If so does the tuner on the top do anything?

    Here's the Loud service statement from their website, hopefully you can call them to request a schematic.



    For any questions concerning owners manuals or schematics please contact the LOUD Technologies Inc. Service Center at 1-800-898-3211
     
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  6. NOTa-bassplayer

    NOTa-bassplayer

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  7. BloozBass

    BloozBass

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    I used to have one of each. The only difference is the speaker jacks in the 220H are in parallel, but the extension jack in the 220 is in series with the built-in 15. That might be a spot to check - the extension jack opens the circuit to add an extra speaker in series, similar to the way the headphone jack opens the circuit to eliminate the speaker. If there's something wedged in there between the contacts, that would keep the speaker from getting signal. However, the line in/out should still function properly, so that's probably not it. (Sorry, we geezers have to think out loud before realizing we don't have the solution to the problem!!!)

    Blooz :bassist:
     
  8. DogBone

    DogBone

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    I've been thinking about this today and trying to come up with a safe way to recommend testing for a bad headphone jack or external speaker jack, which I'm thinking more and more is what this problem is.

    Plugging the bass in the effects *Return* like I suggested earlier should have bypassed both the clean and distorted channels, and the OP said the tuner works so that means the bass, chord, and input jack are all working.

    If it were me, I'd plug a cheap set of headphones in the effects *Send* on the back and try playing the bass (start with the volume low as not to damage the headphones), this should eliminate everything from the power amp to the speaker driver. If the bass is heard in the headphones, this means it's a problem with the power amp, the headphone jack, the external speaker jack, wiring to the driver, or the driver itself.

    If this doesn't work, it's schematic time.

    Good luck.
     
  9. NOTa-bassplayer

    NOTa-bassplayer

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    Was told that it could be a transister issue. Trying to rule out the easily fixed before I attempt trouble shooting the difficult. My degree in electronics is old and alot has changed in the last 25 yrs. I'll take it in if I can't find it. I haven't had time to contact crate about a schematic yet. I guess thats the next step.
     
  10. DogBone

    DogBone

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    Yeah, give them a call and hopefully they'll email you the prints. :)

    I called a few years ago when I bought a used, non-functional Crate Taxi, and they hooked me up with an owners manual and schematics, again that was SLM before Loud took over. BTW, the problem w/ my Taxi was a blown Op-Amp which I replaced.

    And like I mentioned before, I bought my BT220 for parts (it had rolled off the back of the truck, damage to cabinet wood and would power up but no sound). That problem was one of the input jacks had a broken connection to the PC board, easy fix.
     
  11. hogansokol

    hogansokol

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    I have the exact same problem as notabassplayer. I took the advice to plug the bass in the back and plug in headphones in the headphone jack. I had sound through the headphones. When I unplugged headphones I had sound. Plugged bass in the front and got sound, then it cut out. put headphone jacks in and then out and got sound again. How do I get at the back of that headphone jack?
     
  12. Krtalaz91

    Krtalaz91

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    I'm having similar problems as well and would like to know exactly how you get the Amp head out of the "crate," so to speak.

    The Amp intermittently stopped outputting sound through the driver, and at this point I don't get anything out of the main speaker. Everything lights up, and I get the original sound output when I plug into the normal input and use headphones through the actual headphone jack. I tried the previously mentioned check-ups with plugging the the bass into "return" outlet and then later trying to get output from headphones through the "send" outlet.

    I want to take a quick look at general connectivity issues in the amp as I have at least some decent troubleshooting skills with electronics (I'd rather not have the problem be some small integrated component that I really cant see or test though).

    I almost have the amp head out, but the built in tuner on the top of the combo is blocking it from coming out. I don't know if this just pops out or what. I don't really want to break something that doesn't need to be broken.

    Please, :help:

    -Krtalaz (a.k.a: Jovan)
     
  13. DogBone

    DogBone

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    I'm only going from memory, but I'm pretty sure you have to unplug the tuner to slide the amp all the way out of the chassis. It plugs into one of the PC boards.

    Once it's unplugged, you can then pop the tuner up and out the top.

    Again, just going from memory. Good luck.
     
  14. eb3mike

    eb3mike

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    I have a similar Crate 80 that was given to me because it was not producing sound. When you plug into the input that allows you to connect to another device like a recorder or Ipod... there is sound but much lower than the original input jack. I have not opened it up yet. Ideas?

    Thanks
     
  15. Krtalaz91

    Krtalaz91

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    I have noticed the same thing with my BT220. I'm really not sure what it is. Perhaps that input is just generally higher impedance... I really wish getting a schematic for one of these things was a bit easier. I'm still having audio issues with mine in that it sounds distorted on and off, and it seems to respond better to higher frequency input (using a pick seems to give better response than finger picking). :crying:
     
  16. NYCbassist

    NYCbassist Supporting Member

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  17. weddra

    weddra

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    I have a BT220 and have a similar issue. My issue is that at the amp heats up, the higher frequency strings begin to drop out. If I play the string open, the amp cuts out. The lower frequency strings will ring true for a while before cutting out. With time, eventually each string (in order) will stop working at all and then I have to let the unit cool down to start working again. Any ideas?
     

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