Bass amp overload, help

[kulabula]

Hi there, I need advice please.
I have a hartke ha5500 into two hydrive 112's. Twice now I have clicked on my boss bass overdrive pedal and the thermal protection has kicked in after about a minute and everything goes quiet. Full shut down!! Not cool mid gig.
Anybody got any ideas???

Thanks

[Dad3353]

[quote name='kulabula' timestamp='1396188401' post='2410728']...Anybody got any ideas???...[/quote]

Good afternoon, kulabula...

Not much can go wrong, imo, excepting the obvious. Assuming the total load to the amp to be within spec (are both cabs 8 ohm or more..?), it can only be a simple case of over-heating. Does the ventilator fan turn permanently..? They can become noisy, which incites some to disable it. It should always be 'on'. Is there a sufficient source of fresh air around to enable cooling..? No towel left lying on top, restricting air flow..? Not too close to a back wall..? Unplug and open the amp; is it full of fluff and dust..? A good blow through with a compressed-air line could help (wear goggles, or shut your eyes if doing this...).
That's it, really, unles the temperature sensor is badly calibrated. That seems unlikely, but technically possible, I suppose. I've yet to see one, though.
Hope this helps; subject to completion, correction and/or contradiction from others.

[HowieBass]

Looking at the spec for the cabs they're switchable between 4 and 8 ohms... I'm sure you've checked but could one or other of the cabs have been switched from 8 to 4 ohm mode in error? Reading up on Hartke amps other people have had overheating problems due to the fan not running properly.

[rogerstodge]

[quote name='HowieBass' timestamp='1396190885' post='2410755']
Looking at the spec for the cabs they're switchable between 4 and 8 ohms... I'm sure you've checked but could one or other of the cabs have been switched from 8 to 4 ohm mode in error? Reading up on Hartke amps other people have had overheating problems due to the fan not running properly.
[/quote]yea, i had 2 peavey cabs that both said 8 ohm on the back, i took the back off the 1x15 and it was a 4 ohm speaker, my amp was forever cutting out.

[kulabula]

Everything was set up properly. It seemed to be when the overdrive was switched on. Bizarre. .
All I could decide after some advice was that that pedal is overpowering the amp??

[HowieBass]

What's the compression LED doing when you switch the overdrive on? If it's limiting the input signal it should start flashing or be continuously red and I'd assume that limiting function ought to protect the rest of the amp's circuitry?

[kulabula]

Oh God, I don't know. I was too busy rocking out haha haha haha haha haha

[HowieBass]

Time to experiment then

[kulabula]

So, can I ascertain that if the gain and mix is set too high on the overdrive pedal it will cause the amp to overload?

[HowieBass]

Well, assuming you're running the amp with the compressor enabled, you'll see from the LED what it thinks of the signal level first without, and then with the overdrive present, which tells you if the overdrive is giving it a really hot signal... but I imagine that anything hot enough to overload the amp would be pretty obvious to the ear?

[Dad3353]

[quote name='kulabula' timestamp='1396214052' post='2411117']
So, can I ascertain that if the gain and mix is set too high on the overdrive pedal it will cause the amp to overload?
[/quote]

If your amp's thermal protection is cutting in, it's not that the amp is 'overloaded', it's that the amp is too hot. It's true that, if you play with all pots dimed in a hot club with no ventilation around the amp, it'll heat up more than the makers bargained for, and will (indeed, should..!) cut to prevent permanent damage to the amp's components.
To get an amp such as your Hartke to overheat, the causes have been mentioned above. If the fan is running, the air around is cool and there are no obstructions to air circulation, you're playing pretty damned loud if it gets that hot.
As I said, though, it just might be the thermal sensor gone wonky. You can't do anything about that except get it serviced.
When it's cut out, is the back plate hot to touch or not..? Be careful, though; you could get burned checking this.

Edited March 31, 2014 by Dad3353

[kulabula]

Yes, the back of the amp was hot, and it was also smelly! The pre amps and master were set exactly half way. I didn't think that that was too excessive? My other band are a bit quieter and so the master is usually on around 3.

[Musky]

It's an odd one for sure. Thermal protection kicks in when the power amp get to hot for all the reasons Dad has mentioned and I wouldn't expect a properly functioning amp to cut out at full power under normal circumstances. Although feeding the amp with a hot signal won't coax anymore power from it (it's limited by it's maximum voltage swing) it is possible the Boss is making it reach full power. The position of the volume knobs isn't a reliable indicator of an amp's output, and it's far from unknown for manufacturers to load the controls so most of the action happens in the first half of the pot's travel. In other words it's quite possible that with the volume knobs up halfway and feeding the amp with a boosted signal you'll be making as much power as the amp is capable of.

It still shouldn't be cutting out in the way you're describing though. Try all the steps Dad has mentioned, especially cleaning out any dust. It's amazing how much amps with fans can accumulate.