Sudden loud buzzing on Ashdown bass amp

[Baldrick]

Hi

My Ashdown EB150 has on a few occasions suddenly made an extremely loud buzzing noise. At one rehearsal it did it twice within 15 mins of each other. Then again a month later at another rehearsal just the once.

It does not go away by turning down the volume or by pulling the jack plug out - only by switching it off. It goes back to normal as soon as it's turned on within a very short while.

Has anyone got any suggestions what might be causing it or what I could do to try and recreate the fault for someone to have something to work with?

Cheers

Rick

[txstrat]

Had the same thing happen in a guitar amp. Turned out to be the PI tube, but more likely seems to be a bad power tube.
Does whacking the top of the amp bring the buzz back?
Would try to change the power tubes for known good ones (one by one to determine which is the bad one).

[Enzo]

Solid state, no power tubes or PI.

Look for cracked solder on you main filter caps.

[Baldrick]

re: main filter caps

Thanks Enzo - I'm going to take a closer look at this but might need some help.

I've had a chat with a friend who knows a little about amps. Am I right in thinking the main filter caps are to do with the main power supply and by 'caps' you mean capacitors?

I'm trying to find a diagram for my amp but I suppose many solid state amps might have similar layouts for the power supply. Any chance you could point me towards one please?

Many thanks

Rick

[izzybell2810]

Hi,
Ashdown don't release schematics you have to be authorised to access them. If you let me know which model you have I can point you in the right direction.

Dave.

[Baldrick]

re: Schematics

Hi Dave

Actually I have received some diagrams from Ashdown but any information you have I'd gratefully follow up. What I could really do with is a photo of my board to know which component is what.

My amp is an Ashdown Electric Blue EB150 with a 15" Speaker.

Cheers

Rick

[Gtr_tech]

Boy this Ashdown stuff seems to be pretty unreliable. Haven't been inside one yet but just from the amt people looking for awnsers to problems with these I'd advise avoiding 'em.

[Baldrick]

to be honest, what I've read has been pretty good so far - this particular amp I've bought is second hand and is a few years old - so 'fingers crossed' if it's just a bit of cracked solder it can be nursed back into full health

it's never failed on a gig (yet)

[schraedertr]

I would have to disagree with you, I've been through a number of Ashdown amps and even the Chinese made models are better than the low end Fender.

The English made Ashdown stuff is very good: quality plywood cabinets, quality Celestion speakers, good components, and great lead dress. I had an Ashdown Acoustic Radiator that looked like mil spec equipment inside.

I will say however that I've never seen one of their Peacemaker amps without the VU meter broken! I did buy a new VU from them, and the part with shipping from England was more reasonable the Yamaha parts from California.

They have also been very good about emailing schmatics when I have requested them.

The Chinese built amps, the Fallen Angel guitar and MAG bass series, are average quality, the cabinets are MDF and parts blow up. I've had a couple of MAG amps with bad op amps.

They have now dropped the guitar amps from the Ashdown name, and are only using it for bass amps.

For what it's worth,

[Enzo]

I don't think looking online is a good measure of quality. it is more a measure of a lack of information. No one has to go online looking for a schematic or parts for a Fender Twin. But Ashdown doesn;t have that parts and information infrastructure.

[izzybell2810]

The filter caps are C9 and C10 as marked on the board. They're 4700uf 63v Elecrolytic caps located on the small board at the rear of the chassis by the fan. They're the largest caps on the board and close to the bridge rectifier which has a fuse mouted to each side of it.

If you have a maplin close by you can walk in and get them over the counter
Code: TX84F or you can order them from RS.

Dave.

[Baldrick]

Hi Dave

I've attached one of the diagrams I received from Ashdown. It doesn't seem to tie in exactly with my board of which I've included photos.

I believe the filter caps in question are C12 and C16 on the diagram. The large black ones in the photos (I removed the board for the second pic). I've found them on the Maplin website and there's a store 20 minutes away from me.

Do you think they should be replaced or is it just a cracked solder joint? I can't get the amp to make the noise on demand. It's just done it a few times during rehearsals and stops only after switching the amp off and on. Giving it a friendly thump doesn't stop it. Although last time it started after someone put something on the amp. If that did cause it, why doesn't my Gibson EB0 pounding away cause enough vibration to upset it? Puzzling!

Many thanks for your assistance and everone else's.

Cheers

Rick

[izzybell2810]

Hi Rick, yeah they're the ones! I'd replace them! Let us now how it goes.

Dave.

[Enzo]

Have yout TRIED resoldering them? I find very low failure rates in filter caps like that, but solder failures are not rare at all. Especially in this day of RoHS solder.

Large parts like that, especially taller ones with their higher center of gravity, vobrate and crack their solder.

[Baldrick]

Re-soldered

After taking out the board I discovered one of the connectors on one of the capacitors was dull so I've re-soldered that one for the time being and it passed a 3 hour test at rehearsals this morning.

So far so good - fingers crossed!

many thanks for all your help

Rick