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Rack Cooling GK2001RB?

Discussion in 'Amps and Cabs [BG]' started by George Law, Apr 15, 2018 at 9:10 AM.


  1. George Law

    George Law

    Jul 16, 2017
    Hey Everyone, I'm using a rack case with my GK 2001RB which is exactly the right size (no free units), I've been having a little bit of trouble on gigs recently and I was advised by GK to take the amp out of the rack as it may be overheating (I've been playing in particularly warm pubs with radiators on etc), this seems to have solved the problem however, the 2001RB is pretty awkward to move about without a rack case, I'm looking to go to a bigger rack case and use a rackmount fan cooler underneath the amp, the fans would be blowing up onto the bottom of the amp as that is the only part that gets warm (2001 has decent fans that seem to push the cool air in and warm air out fairly well, I'm just thinking if I cool the bottom, it will act as a heat sink as the entire amp is made of metal) has anyone tried using these rack unit fans? will it actually make any difference?, is there anything I should look out for, noisy supplies that will make my amp hum etc? cheers :)
     
  2. Paulabass

    Paulabass

    Sep 18, 2017
    I wrote GK about using a two space rack and got a snarky answer. Right now, I've got a three space effects rack and it works perfectly, even with a freakin huge radiator on my side of the stage :) I run it hard, sometimes for six hours at a time.

    Edit- A newer Korg tuner fits without blocking the fan, it's only 2" deep, I've got one on order.

    IMG_0229.
     
    George Law likes this.
  3. George Law

    George Law

    Jul 16, 2017
    hmm, that's odd, they were really helpful with me (they basically had to explain how the 2001rb works because I'm an idiot haha), I'm using a 3u rack at the moment but it' doesnt leave much airspace around the unit, however, the 2001rb has the intake for the fans at the back of the unit, not on the top like the 1001rb, I don't really see how much of a difference it makes, I'm Ideally going to use something like a 6u rack with a 1u fan at the bottom, a 1u gap for airflow, the 3u 2001rb on top of that with a 1u rack tuner on top of that :)
     
  4. Paulabass

    Paulabass

    Sep 18, 2017
    Quite frankly, I didn't notice you said 2001rb. My bad. More cooling is NEVER a bad thing.
     
    George Law likes this.
  5. George Law

    George Law

    Jul 16, 2017
    No worries, cheers for the reply :)
     
  6. Wasnex

    Wasnex

    Dec 25, 2011
    All of the GK RB series heads I have opened up have stand offs that lift the circuit cards off the chassis, so I doubt cooling the bottom will do much unless the amp is vented on the bottom.

    Have you had your amp cleaned/serviced. The typical GK power amp has a fan that blows air across a large metal heat sink with fins that can clog up with dust, especially if you work in an environment with hazers or foggers. Also, if the amp has lots of hours on it, the fans may be tired and reluctant to start. I bought a couple of old 2000RB and the fans did not want to start without me giving them a bump with my finger. I put fresh fans in the amps, and now they run perfect. The amp has a temperature sensing circuit and the fans are variable speed. They only run when the amps are hot. All of the old fans I pulled out of my amps would easily start with a 9V battery.

    Regarding keeping the amp in a case. I don't know how the air flows with this amp. You need to make sure none of the amp's vents are blocked and that the fan is not recycling hot air. A rack fan can help express hot air from the case, but make sure it is working with the GK's air flow instead of against it.
     
    George Law likes this.
  7. George Law

    George Law

    Jul 16, 2017
    My 2001RB does have stand offs but is not vented at the bottom, I just thought that maybe keeping the base as cool as possible would allow better heat dissipation, perhaps not, the fans definitely work, I checked at the end of a gig on friday, the fans were definitely going, so thats something I suppose, I don't actually find that the amp feels like it is getting "hot", just a little bit warm on the bottom, the rest of the chassis is cool :) the rack I am using is a gator 3u which has a removable front and back which means that there is nothing blocking the fans air intake, I assume the air is then expelled out of the front grill of the amp which is also not blocked, the only thing is that there is not a lot of air flow around the outside of the chassis of the amp because it is physically in the rack which is 3u (the 2001RB is also 3U) but like I said the chassis feels cool apart from the bottom which is just a bit warm
     
  8. Wasnex

    Wasnex

    Dec 25, 2011
    The 2000RB amps I have do not flow a lot of air and I would not say they are very good about expelling it from the case. The bottom side of these amps gets a little warm because when the air exits the heat sink on top of the power amp module, it hits the side of the case. The left power amp module is close to the edge of the case. There is also a small vent here and you can barely feel the air flow with the side of your face.

    There is also a warm spot on the back panel where two large transistors are bolted down for heat sinking. Not sure if the 2001RB has similar transistors. The screws had fallen out of these resistors on the last amp I received and were bouncing around in the bottom of the amp. Good thing I found the loose screws and washers, as a short on the output module tends to cause a catastrophic failure...I learned that the hard way. Also, there's probably a good reason why those two transistors are heat sinked to the case. I touched one of them and it was painfully hot and the amp had only been on for a short while.

    What symptoms is your amp exhibiting?

    It sounds like you have opened your amp up. Are the heat sinks clear of dust and lint, and does it sound like there is anything loose inside the chassis...like the screws and washers mentioned above?

    Here's an image I found (see below). It doesn't look like the 2000RB really flows air through the case any better than the 2000RB. Maybe a small case fan would help. It probably just needs to be powerful enough to ensure hot air is not pooling in the case.

    GKRB2001.2-300x225.
     
    George Law likes this.
  9. George Law

    George Law

    Jul 16, 2017
    Basically the protection circuit is triggering every now and then (like twice on a gig or something), I've opened it up and it's clean inside, there's also nothing rattling around, I spoke to a guy at a GK repair place and he said to try the amp without the case as they do overheat sometimes, he also said it could be a shorted turn in the speaker cab? not too sure what that is, he explained to me something to the effect of as the voice coil in the speaker heats up, it changes the resistance and that change can cause the protection circuit in the 2001rb to trigger, I'm using an ashdown 8 ohm cab wih it that has a 50 watt horn, on the next couple of gigs I'm going to test it without using the horn to see if it still triggers, maybe I'm just feeding too much to the horn?
     
  10. Wasnex

    Wasnex

    Dec 25, 2011
    You can't use the GK biamp feature with an Ashdown cab, the tweeter amp should not be doing anything. You could use a two conductor Speakon chord to ensure the tweeter amp is not accidentally connected and shorted out. Turn the master volume for the tweeter amp off, so no voltage is developed across the output.

    An 8 ohm load, should not be overly taxing for the amp even if you are bridging the output. It's rated for 4 ohms in bridge mode. If using bridge mode the manual is very specific about how the amp must be connected to operate without malfunction.

    From the manual:
    "Note: To operate the 2001RB in bridge mode, you must use the L/BR Speakon outputs only. Using the Left channel, 1/4” outputs will not work, since the ground for those jacks are internally disconected when in bridge mode. Using any of the Right channel 1/4” or Speakon outputs is not recommended as this will result in a malfunction, or undesired operation of the amplifier."

    Also from the manual:
    "DO NOT USE 'BRIDGED MODE' SPEAKON CABLES WITH THIS AMP!!!"

    How long is the shut down? Instantaneous or does it take awhile for the amp to reset. If it's instantaneous, I could see it possibly being related to an impedance issue, especially if you are really flogging the speaker beyond it's mechanical limits.
     
    Last edited: Apr 15, 2018 at 4:19 PM
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    There is nothing to gain by blowing air on the bottom of the amp. There needs to be at least 1 rack space free and clear above the amp however.
     
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  12. George Law

    George Law

    Jul 16, 2017
    yeah, sorry I should have specified, I have a standard +1/-1 speakon cable going from amp to cab via the left/bridge mode speakon connectors, the tweeter amp (+2/-2) is not connected to anything and I have the tweeter volume turned all the way down, the cab itself has a control to turn the horn on or off (off/low/high)

    it shuts down for a few seconds, the protection light (red flashing) comes on and then it will go back to normal, the cab is a 650 watt cab (600 when not using the horn) the 2001rb is supposedly rated at 650 watts into an 8 ohm load, I have the master up about half way usually, so I'm not really gunning it and I'm not clipping the input, I use an active 5 string bass but I don't boost much on there, just some mids when I need to cut through
     
  13. George Law

    George Law

    Jul 16, 2017
    @agedhorse is that the same for the 2001rb which doesn't have vents on the top? cheers
     
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    No, it's only true for the models with the fan and vents on the top. I was addressing the comments about the 2000RB, sorry.

    IIRC, the 2001RB is front to back cooling. The first thing I would look at is the impedance of your speaker... I see enough speakers improperly repaired and mis-marked to suggest that you might have a 4 ohm speaker cabinet rather than an 8 ohm one. What model is it? Can you measure the DC resistance oft he cabinet at the speaker input terminals?
     
  15. George Law

    George Law

    Jul 16, 2017
    I'm not sure whether it is front to back or back to front cooling, I was under the impression that air was being pulled in from the back and vented out the front but I may be wrong, it's an 8 ohm cab, bought new and never modified, even if it were a 4 ohm cab, the amp is capable of driving a 4 ohm load in bridged mode and I have experienced the problem when using the left or right side (seperately) in dual mono where each side can take a 2 ohm load
     
  16. Wasnex

    Wasnex

    Dec 25, 2011

    Per the manual, the 2001RB is rated for 1080 watts/4 ohm operation in bridge mode.

    Totally agree about racking the 2000RB...it needs a bit of space to breath.
     
    George Law likes this.
  17. Even with extra space, I found by adding a fan, blowing onto the back of the amp, helped tremendously.
     
    shodan and George Law like this.
  18. George Law

    George Law

    Jul 16, 2017
    Hey @Duanestuermer are you talking about the 2001rb or the 2000rb?
     
  19. Don't remember what mine was (it was a few years back), it had those cooling fins on the back, but hey weren't enough to keep it from clipping, and shutting down without the fan.
     
  20. Wasnex

    Wasnex

    Dec 25, 2011
    That sounds like the old 800RB or 400RB. The newer amps have the cooling fins inside the case.