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Ashdown ABM 600 Evo IV Problem - Power but no sound.


RnRDave
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Hi all

 

So I got to rehearsal last night and set up - amp powers on fine and VU meter shows there's input sound but no sound out of the cab. Assume a fuse must have blown. 

 

I've got home and plugged it into my home cab and still nothing - taken it out of the sleeve but can't see any of the fuses have blown.

 

I'd be fuming if it's in the bin time - wondered if anyone has any troubleshooting tips for me to try?

 

 

PXL_20230510_133302955.jpg

PXL_20230510_131742542.jpg

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Ashdown have the best customer service in the business. They can repair anything they have ever made and are pretty inexpensive.

Speak to DG and if he can't troubleshoot over the phone just get it to Ashdown HQ and it'll be sorted.

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19 minutes ago, RnRDave said:

Just wondering if there's likely to be a fuse on this PCB at the back? 

 

EVO III and EVO IV  heads have a speaker fuse on a small auxilliary circuit board beneath the back board for the send/return / footswitch sockets. I've seen this a few times on EVO III in particular where the output fuse works loose or the fuse clip looses tension causing no output. Or it might have blown but you'd need to be going some for that to happen. Earlier models had a T12A fuse ( 575 watt versions ) later models seem to have a smaller T10A fuse, 20mm type. From the pic the amp looks about six years old so I wouldn't expect fuses to be working loose at that age.

If you hear absolutely nothing from the speakers with a bass plugged in and power on, and I mean absolutely nothing then good chance its something on the output. As the red pen says, the heatsinks are live so don't get fingers anywhere near them even when switched off! You can also check the pre-amp by making sure the meter registers if you cranck the input and if you have another combo or amp, run a cable from the line/tuner out to the other amp and make sure signal is going through the pre-amp section. Pic below shows roughly where the speaker fuse is located on most models, on EVO IV its usually on the back board assembly which tricky getting access to as it usually means loosning the transformer and the rear back board nuts and screws. Worth making sure there are no loose wires either. 

 

  Screenshot2023-05-10at16_04_15.thumb.png.c0f2221a54c10d4a58d15f3027b94d49.png

Edited by DGBass
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15 minutes ago, DGBass said:

EVO III and EVO IV  heads have a speaker fuse on a small auxilliary circuit board beneath the back board for the send/return / footswitch sockets. I've seen this a few times on EVO III in particular where the output fuse works loose or the fuse clip looses tension causing no output. Or it might have blown but you'd need to be going some for that to happen. Earlier models had a T12A fuse ( 575 watt versions ) later models seem to have a smaller T10A fuse, 20mm type. From the pic the amp looks about six years old so I wouldn't expect fuses to be working loose at that age.

If you hear absolutely nothing from the speakers with a bass plugged in and power on, and I mean absolutely nothing then good chance its something on the output. As the red pen says, the heatsinks are live so don't get fingers anywhere near them even when switched off! You can also check the pre-amp by making sure the meter registers if you cranck the input and if you have another combo or amp, run a cable from the line/tuner out to the other amp and make sure signal is going through the pre-amp section. Pic below shows roughly where the speaker fuse is located on most models, on EVO IV its usually on the back board assembly.

 

  Screenshot2023-05-10at16_04_15.thumb.png.c0f2221a54c10d4a58d15f3027b94d49.png

 

Amazing! I'm gonna go to work and get the back board off tonight then as I can't see any accessible fuse like what's circled there.

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2 hours ago, RnRDave said:

I'd be fuming if it's in the bin time

These amps are some of the easiest to repair that are currently in production.  if you draw a blank with fuses and there are no obviously loose wire connectors, Ashdown or any reputable tech would be able to get your ABM working again 🙂

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 I've had a blown output fuse using my own amp with a rehearshal room or venue cab and/or cables on several occasions. I always use my own speaker cables if I have to use someone elses cab. Same goes for power cables 🙂

Edited by DGBass
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On 10/05/2023 at 20:14, RnRDave said:

Finally got the fuse out from the output board after lots of fiddling (and my wife's small nimble hands).

 

Fuse has definitely blown so fingers crossed that's the problem! Now to eBay for fuses!

PXL_20230510_190439784.jpg

Nice style there using your wife's nimble fingers to poke about in the live bit! Us bass players are pretty indispensable so any personal risk should definitely be avoided 

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So it's still not working. 

 

There's a small click sound about 10 seconds after I switch the amp head on, not sure if that happened before as I'm usually at rehearsal and not paying attention.

 

Any ideas?

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You did well finding the blown fuse. ABM's do click after switching on but its usually within a second or two at most. Thats the speaker output relay switching on that normally makes a click. If you hear a click after ten seconds, that doesn't sound right. It could be the output fuse blowing again. If it has gone again, then the fuse blowing is only a syptom of another problem but still good evidence that its likely to be in the output stage.  At this point, I'd be getting out the test meter to run through a checklist and start faulting. Or, i'd quickly swap out the entire output board with a good working spare I have on hand if all the supply voltages were good. Otherwise, its probably time to get help from a tech who can fault it for you. As many folks have said, Ashdown service is excellent and giving them a call and posting your unit to them for a service might be the best course of action especially if there is no one local you know of who could look at it.

The speaker output relay is the little transparent box next to the red and black speaker wires. 

 

 

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