Question about Crate Blackheart BH5-112 Little Giant Guitar Amp Combo, 5W All Tube with Attitude

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Zero output, no noise, no hum, no nothing I've tested with various speakers I've checked the fuses I've check the power tranny I've changed the tubes.

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Rommel Cana

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Then you may need to measure plate voltages

there is a possibility of open resistors or changed- value

Posted on Nov 07, 2009

  • 1 more comment 
  • Rommel Cana
    Rommel Cana Nov 07, 2009

    here is a simple guide:




  • Rommel Cana
    Rommel Cana Nov 07, 2009

    a) you can inject audio with a series capacitor on the blue arrow., to test the main amp

    if there is no sound , have a resistance check on the resistors ( orange arrow)

    need to measure the B+, should have at least 250V

    b) if there is audio on blue arrow then trace circuits backwards going to the input.


    it might take about 5 minutes for the tubes to warm up and to produce sound on the speakers





  • Rommel Cana
    Rommel Cana Nov 09, 2009

    when having a resistance check,

    unplugged the unit and safer to discharge first the filter capacitor with a 4.7K 5W resistor.

    if your having trouble reading the resistor color coding, post the colors and will decipher it for you.


    you can use an analog multimeter or either a digital one , both is OK


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Can't be fuses, as it comes back on!

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i) Does it go off when run continuously with volume controls at zero?
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ii) When the unit does operate, is the sound good on both speakers?

iii) Does the fault occur more when outdoors (wind noise tripping the power protection). If so, reduce the low freq EQ setting.

iii) Do the EQ lights flutter when the fault occurs?

This fault has been reported on the Escort 3000 too, see link
Peavey Escort 3000 sound cutting out - Peavey Forum
suggesting this may need a 'electronic modification' to put it right.

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I have a Crate CR212 it started to hum/buzz today. It would not play out any sounds other than the noise. I unplugged everything and still it hummed. I unplugged the unit, check the fuse and replugged and...


Are all the tubes lighting up? they should glow like dim light bulbs. If not, replace them with the same model type (12ax7, or EL34 for example).

Often there are two fuses, one to protect the speaker and another to protect everything, it sounds like the latter fuse may be burned out. take it out and take it to radio Shack for exact replacement.

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Likely the filter capacitors have a problem. Best to take this in for repair... it is ODD that there is noise with the standby switch is in standby... That makes no sense... In standby it appears that power is removed from the power amp high voltage so nothing should come through the speaker... Unles maybe one off the power tubes had a total meltdown which should have blown the fuse.

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You need to confirm and replace the specific stages or outputs. If not there can be issues in the mother board, maybe the protect circuit by itself is shutting off due to a faulty bias , maybe a leak in any voltage/current sensing circuit. Also disconnect the speakers and test, if the protect is off then check for short on the speakers.

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