Ashdown fault

[Pookus]

Can anyone suggest a possible cause and solution? I have a 5 year old Ashdown ABM Evo II 900 head going into an ABM 810 cab. Up until yesterday I've never had any problems. However, during a practice session the sound cut out. The power still going to the amp, the VU responding to input etc. I checked the line out signal to another amp and that worked. What should I check? What could be the problem? Thanks, Jamie

[icastle]

I'd start off by checking out the speaker cable and then try an alternative cab.

[Protium]

If the above doesn't yield anything, check the fuses on the power board inside the amp. They're glass, about 1.5inch long and will be blackened if they're blown.

[Pookus]

Thanks for your suggestions. It's not the cable. The amp works thru a different cab. So it must be the cab where the fault lies. What next? Is there a fuse in the cab? I can't see how the speakers could have blown (I was playing very quietly) and the cab is rated at 1200w.

[icastle]

[quote name='Pookus' timestamp='1324755185' post='1477662']
Thanks for your suggestions. It's not the cable. The amp works thru a different cab. So it must be the cab where the fault lies. What next? Is there a fuse in the cab? I can't see how the speakers could have blown (I was playing very quietly) and the cab is rated at 1200w.
[/quote]

I don't think there's a fuse in the ABM810, but if there is then it'll be on the reverse side of the connection plate.
If you're going to take a look in there then check to make sure that none of the wires from the jack socket are floating around loose - that could cause the whole thing to stop working...

[Pookus]

[quote name='icastle' timestamp='1324757608' post='1477693']
I don't think there's a fuse in the ABM810, but if there is then it'll be on the reverse side of the connection plate.
If you're going to take a look in there then check to make sure that none of the wires from the jack socket are floating around loose - that could cause the whole thing to stop working...
[/quote]

Yeah thanks, I've had a look in there - no fuse and the wires are all secure.

[icastle]

This is starting to sound a little ominous.

The next step is to remove the front grille and start releasing the speakers one at a time.
Take a look at the connections on the rear of each speaker - are they both connected?

If you have a multimeter handy, switch it to the 'Ω' setting, disconnect a wire from the speaker and take a meter reading directly across the speaker terminals - don't worry if it doesn't exactly match the impedance rating stamped on the back of the speaker - you just want to see that there is a resistance there (thereby eliminating the possibility of an open circuit).

If you don't have a multimeter then use a couple of scraps of wire and a battery - if the + end of the battery is connected to the + terminal of the speaker then the driver should 'click' and move forwards as soon as you attach the negative lead.

If the driver doesn't show a resistance or doesn't 'click' and jump forward then that speaker is blown.

Work your way through each speaker like this.

[LawrenceH]

There is no way you will have blown all 8 of the drivers...I'd guess they'll be wired parallel too in which case even if one failed the rest would still output. I'd start by assuming it's a problem with the input socket or attached cabling, and rule that out before looking further.

[MarkBassChat]

This could be a power amp failure. But since you say that the amp works with another speaker I would look at the jack (or speakon) socket in the cabinet. Is there a parallel output (link) that you can connect to another cab? If you do it, this will verify the socket.
Did you play loud when the amp was cutting out? I'm asking because this is a typical problem with power amps (not only Ashdown) not properly cooled. Over-temperature protection circuit disconnects the speaker. And this may happen when the fan is not cooling properly the heatsink in the power amp.

Mark

[thepurpleblob]

There's not much you can do without a multimeter.

If it's *definitely* the cab (i.e. it works perfectly with another one, for a reasonable time, at a reasonably high volume). You need to put a meter on ohms over the input to the cab (plug a speaker cable in and put the meter across the two jack 'pins'). I'm not sure what impedance those cabs are, but you should get a resistance reading of the order of 75% of the specified rating (e.g. a 4 ohm cab will read about 3-3.5 ohms - dc resistance is different to ac impedance but this will do).

If you find it's short (ie substantially less than that) then you are pulling the cab apart, checking the reading on each speaker and the wiring. I'm sceptical that a single shorted speaker could be the cause but you never know.

If the cab checks out then it's your amp. Under the circumstances you need a proper repairer as it's (effectively) an intermittent fault.

[icastle]

[quote name='thepurpleblob' timestamp='1325113659' post='1480041']
I'm sceptical that a single shorted speaker could be the cause but you never know.
[/quote]

Other way round.
An open circuit speaker wouldn't affect the entire cab, at worst it would only stop half the speakers from working as 8x10s are wired in series and parallel.
A short circuit one would take the whole thing down as the amp will just see a short and shut down.

[thepurpleblob]

[quote name='icastle' timestamp='1325114287' post='1480053']
Other way round.
An open circuit speaker wouldn't affect the entire cab, at worst it would only stop half the speakers from working as 8x10s are wired in series and parallel.
A short circuit one would take the whole thing down as the amp will just see a short and shut down.
[/quote]

This actually depends on how they are wired internally. That would be the case if the speakers where all in parallel but they won't be. A shorted speaker will drop the overall impedance somewhat. It won't be a dead short but, yes, it might just be enough to make the difference.

EDIT:
These cabs are 4ohms I think. The only way I can think to do that (correct me if I'm wrong) is with 8ohm drivers. Each pair is in series (giving 16ohms) and then each 16ohm pair is wired in parallel giving an overall 4 ohms. A single short speaker will reduce the impedance to 3.2ohms. I doubt that would be a problem.

Edited December 29, 2011 by thepurpleblob

[Pookus]

I used a multimeter on a speaker cable (one that I know works) plugged into the cab - the ohm reading stayed at '1'. I did the same with my GK cab to check the multimeter and got a reading close to 8 (it's an 8 ohm cab). Therefore there must be a fault with the cab. Next I'll have to check each speaker.

[Pookus]

Blimey! Those speaker screws are tight - my DeWalt won't budge them and I can't undo them by hand. I've got an impact driver but am afraid I might damage something if I start bashing the screws. Time for some professional intervention. Can anyone recommend someone who could take a look at my cab in the Faversham area - Kent?

[Protium]

[quote name='Pookus' timestamp='1327827000' post='1517177']
Blimey! Those speaker screws are tight - my DeWalt won't budge them and I can't undo them by hand. I've got an impact driver but am afraid I might damage something if I start bashing the screws. Time for some professional intervention. Can anyone recommend someone who could take a look at my cab in the Faversham area - Kent?
[/quote]

I found the ones in my old ABM410 were super tight when I added damping foam, brute force undoing them by hand eventually worked. Sucks for you that there are 8 speakers!

[Luke's dad]

Did you resolve the issue with your Ashdown? I've had a similar problem with a new ABM500 Evo III. I set it up with an ABM 1x15 cab in the house, played at low volume for 5 minutes when the sound cut out. Signal still getting through, VU meter moving etc. Tested the speaker and found it had blown. Relieved it was the speaker rather than amp, I sent it back for repair. Subsequently used amp with an Ampeg 2x10 classic (300w, 8ohm) at a gig. Half way through the 1st half the sound cut out again. Could continue as signal still going through DI and into pa. Tested speakers again and found they were blown. The shop has now taken the amp back for a "repair".

On a side note, does anyone know where I stand legally if the amp I bought was faulty and has blown a cab I already owned?

Cheers!

Dave

[Musky]

[quote name='Luke's dad' timestamp='1352488883' post='1863844']
Did you resolve the issue with your Ashdown? I've had a similar problem with a new ABM500 Evo III. I set it up with an ABM 1x15 cab in the house, played at low volume for 5 minutes when the sound cut out. Signal still getting through, VU meter moving etc. Tested the speaker and found it had blown. Relieved it was the speaker rather than amp, I sent it back for repair. Subsequently used amp with an Ampeg 2x10 classic (300w, 8ohm) at a gig. Half way through the 1st half the sound cut out again. Could continue as signal still going through DI and into pa. Tested speakers again and found they were blown. The shop has now taken the amp back for a "repair".

On a side note, does anyone know where I stand legally if the amp I bought was faulty and has blown a cab I already owned?

Cheers!

Dave
[/quote]
Good question. [url="http://www.findlaw.co.uk/law/consumer/consumer_protection/139.html"]This site[/url] suggests that you can make a claim against the manufacturer, but you might do better posting this as a separate thread in the General Bass Discussion forum. There are a few legal types about and others may have some experience of similar situations.

If not, the CAB is your friend.