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TC electronic BH500 humming problem


sykilz
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So, the amp was bought last year used, and most of the time its fine, but occasionally when switching on, usually after a bouncy car trip or vibrations on top of cab with wheels, theres a fairly loud hum, which is not linked to the volume or gain controls, it stays at the same volume, instrument plugged in and also not plugged in. When the hum is evident, you can play through the amp, but its very under powered and sounds distorted, more or less unusable live. Sometimes the hum goes if you give a sharp whack on the top rear edge! Last gig I had to do this then lie it on the floor away from the cab, as the vibrations of playing set it off again! Any ideas before I hit the repair shops? Theres nothing on google at all!

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Thanks, my guitarist friend went all over it with a multimeter but could only find a small voltage drop over the transformer, though a guy at Essex amp repairs told me over the phone that it was unlikely to be a transformer as they either work or don't. Thing is, these are 290£ new at the moment, so wondering if its worth repairing or just get a new one with 3 year warranty from DV247. Thats the gamble....

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  • 7 months later...

Sorry to resurrect an old thread, but my BH500 just started exhibiting similar symptoms. Did you ever get to the bottom of this?
Playing at a quiet volume practicing, and I noticed a sudden drop in volume. Cranked it up a little, but sounded distorted, even with the gain and tube tone down. The constant hum you describe is also there. It doesn't however, appear to be affected by movement.
So far I've tried:-

Swapping instrument cables
Swapping cabs
Swapping basses
Tried through headphones - the buzz stops and can't be heard through the headphones.

Any help appreciated!

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I think I may have been mistaken regarding the distortion, but the buzz and volume drop were definitely there. It was pitched roughly at A, (55 or 110 hz) - so I'd guess it it was probably 50 cycle mains hum.
Out of curiosity, i opened it up and had a look inside. Nothing visibly suspect at all, however i put it back together, and the problem is gone! Scared it'll happen mid-gig though...
Any suggestions?

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  • 2 weeks later...

It seems like a few of the connections in this amp, instead of being soldered, are just push fits, kinda like spade plugs, and they lose connection when not seated properly, think mine shook loose as I used to wheel it on top of my cab which has castors fitted. The amp repairers told me that they see a lot of amps that have been damaged by wheeling/shaking/vibration!!!!!

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[quote name='MoonBassAlpha' timestamp='1401645415' post='2465511']
Sounds like a dry joint somewhere. I'd look for large components like caps and power transistors, big resistors etc. and reflow the joints.
[/quote]
I had a similar thing happen on a Fender guitar amp a few years back.. an amp repairer I knew at the time said it was a pain of a job and he was really busy, so I should get to the circuit board and re-solder every single joint as it would be pretty much impossible to identify just which one was causing the problem. I did what he said, and the amp was still working fine when I sold it a couple of years later. Time-consuming but not actually hard.

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[size=3]Thanks for the information guys.[/size]

[size=3][color=#282828][font=helvetica, arial, sans-serif]I've had the head to three rehearsals since it had it[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'s little [/font][/color][font="helvetica, arial, sans-serif"][color="#282828"]hiccup. It[/color][/font][color=#282828][font=helvetica, arial, sans-serif]'s had a 25 mile round trip each time, and the problem still hasn[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'t come back, which I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'m obviously relieved about. I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'d still like to figure out exactly what caused it though - I have a corporate gig this Thursday with 1000+ people there, I just [i]know[/i] that if it decides to go again, it[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'ll be then! The venue has a decent PA and sound guy, so if the worst does happen, I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'ll have some Zoom B3 amp-sim patches lined up just in case![/font][/color][/size]


[size=3]I[color=#282828][font=helvetica, arial, sans-serif]'ll try and open it again this week and look for the spade type connections that were mentioned, along with any dry solder joints etc. I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'m guessing that the fault is going to be somewhere in the power section - the preamp in this is all surface mount digital type stuff - not a place I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'d attack with a soldering iron! (Since I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'m clumsy!)[/font][/color][/size]

[size=3][color=#282828][font=helvetica, arial, sans-serif]On a side note, I[/font][/color][color=#282828][font=helvetica, arial, sans-serif]'m actually shocked at how loud this thing is, never had it above 3 in a rehearsal or gig! (Through either two TC 2x10s at gigs or an Ampeg 8x10 at the rehearsal room)[/font][/color][/size]

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Its sooo loud, isn't it...! I use the TC BC4x10 for most gigs, but for very large pubs, like this weekned, also have the 2x12 to stack up, seriously nice rumble from a very affordable set up. When mine was in for repair I borrowed a friends Ampeg.... I think SVT PRO7... Supposedly 1000 watts aginst the TC bh500 which allegedly has about 250 watts and lots of compression, and the Ampeg really struggled to keep up with the band volume wise, was so glad to get the TC back.

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