Please help... problem with Ashdown MAG 300

[crward77]

[color=#141823][font=helvetica, arial, sans-serif][size=3]I was trying to do some recording earlier but I had some issues.I use an Ashdown Mag 300 head and a 200w cab I think I may have connected the cab output cable to the line out cable. There was a couple of sparks. Power l[/size][/font][/color][color=#141823][font=helvetica, arial, sans-serif][size=3]ights are on, speaker is humming ok, but the signal isn't there. If i turn it on max the signal needled flickers very slightly. Had the top off and no sign of any blown fuses (and the front). [/size][/font][/color]

[color=#141823][font=helvetica, arial, sans-serif][size=3]Thought I could smell a light electrical burn smell but no sign inside. [/size][/font][/color]

[color=#141823][font=helvetica, arial, sans-serif][size=3]Any ideas, I am absolutely gutted. Any help appreciated. [/size][/font][/color]



[color=#141823][font=helvetica, arial, sans-serif][size=3]Chris Ward[/size][/font][/color]
[color=#141823][font=helvetica, arial, sans-serif][size=3] [/size][/font][/color]
[color=#141823][font=helvetica, arial, sans-serif][size=3]frown emoticon[/size][/font][/color]

[EBS_freak]

Think that's one for the service department at Ashdown...

[sunburstjazz1967]

Thinking out loud here but could it just have blown the preamp valve by trying to power the speaker cab? Cheap and easy fix if it's possible.

[crward77]

do you know what the valve looks like?

[barkin]

If it's a MAG, I'm pretty sure it doesn't have any valves...

[sunburstjazz1967]

It's stuffed then :-( I get confused with the models, I once had a mag evo and that did have a valve.

[ben4343]

Definitely worth getting in touch with Ashdown and asking for some advice on how to progress with this; their customer service is top notch in my (thankfully) limited experience (MAG 420 user).

[jezzaboy]

Take it down to your local amp guy if you have one that is! I imagine that is what Ashdown will say. Or else buy a Toneman 300 from Thomman for £207.

http://www.thomann.de/gb/ashdown_toneman_300_evo_iii.htm

[crward77]

All the fuses look fine. Replaced the smaller fuses (the big one at the back also looks fine) and checkeed the components behind the knobs. Can't spot anything. The capactors have a glue on the side, but should there be so much at the base? Are these blown? Is this the problem? I don't know if they are supposed to look like this. cheers.

I

[JapanAxe]

The big caps look normal. The gunk around the base of each cap is to stop them vibrating and breaking the circuit board tracks.

Can you clarify which output socket you plugged your cable into, and what was on the other end of it?

[crward77]

I think (i got into a muddle and discovered it wasn't working a little afterwards) I plugged the cab le that goes to the power amp into the tuner/line out on the front. (I thought I was plugging the line out into my recording box at the time) - realised when there was a plug-like spark that wasn't the case.

[Merton]

So you plugged the speaker output into the line output? (This will be a bad thing).

Or you hooked the amp up to your recording device via the line out and didn't have a speaker load present? (This shouldn't be an issue).

[crward77]

[font=arial, sans-serif][size=3]Option A[/size][/font]

[Merton]

sh*te, I suspect one of the output transistors has gone wonky. The only time I've blown an output tranny I couldn't tell just by looking at it ... It'll need a tech. Ashdown are very very good to deal with on these sorts of things though (I know because they're the ones who fixed my blown-up GK amp haha!)

[crward77]

Do you know what the transistors look like. I've had it open a load of times but can't spot any obvious signs.

[Merton]

See the big silver metal fins which look like the back of a radiator (that's essentially what they are!), the output transistors are the little black components attached to them and the PCB

[crward77]

thanks for that. i see em. that's some of the components i can't see too well so will investigate further.

cheers a lot.

[Merton]

Good luck with it - let us know how you get on

Edited January 16, 2016 by Merton

[MoonBassAlpha]

More likely something in the preamp has got blown up. The voltage level from the speaker out will most likely be too high for the input op amp. I think it's highly unlikely the output transistors will be blown as it would represent a high impedance load. This could be good news, as op amp cost peanuts.
Try putting a line level signal into the effects return socket. See if the power amp section is working at least.

Edited January 16, 2016 by MoonBassAlpha

[JapanAxe]

Chris, where do you live? There may be a local BassChatter who can help you narrow down the possibilities.

[crward77]

yeah good thinking dude. I live in durham

[Merton]

[quote name='MoonBassAlpha' timestamp='1452982989' post='2955373']
More likely something in the preamp has got blown up. The voltage level from the speaker out will most likely be too high for the input op amp. I think it's highly unlikely the output transistors will be blown as it would represent a high impedance load. This could be good news, as op amp cost peanuts.
Try putting a line level signal into the effects return socket. See if the power amp section is working at least.
[/quote]

Good call

[sunburstjazz1967]

[quote name='MoonBassAlpha' timestamp='1452982989' post='2955373']
More likely something in the preamp has got blown up. The voltage level from the speaker out will most likely be too high for the input op amp. I think it's highly unlikely the output transistors will be blown as it would represent a high impedance load. This could be good news, as op amp cost peanuts.
Try putting a line level signal into the effects return socket. See if the power amp section is working at least.
[/quote]
This was my initial thought regarding the preamp valve as I didn't realise it was not a mag evo but just a mag, so it's done the same thing but to the component preamp rather than the valve.

Long live speakon connectors!

[4stringslow]

[quote name='sunburstjazz1967' timestamp='1453029347' post='2955627']
Long live speakon connectors!
[/quote]

I agree. I've seen people with no idea (I'm not saying that's the problem in this case) attempt to cable up a small PA system and simply plug in cables at random, the main criterion seemingly being that connectors actually fit regardless of the types of signals they may be carrying. Thus, speakers into line outs is quite common

I wonder if it's a hangover from the PC world? The PC industry has done a pretty good job to ensure that different signals are carried on different connectors such that it's almost impossible to hook up a PC, screw, keyboard, mouse, network and external hard drive incorrectly, while the music world still embraces a Victorian era connector!

[crward77]

First of all, thanks again for your amazing support. I had a look for an Op Amp. But i couldn't see anything that looks like this...



which is an op amp on wikipedia.

Also, i connected cables to the effects return ans get jack in crackles, so I think the speaker is working.

I have obtained the amp schematic from here (http://music-electronics-forum.com/attachments/23084d1366992849-mag300.pdf) can anyone spot the op amo, which may help me actually locate it on the amp.

Once again, I cannot thank you enough for your support.

Chris