Ashdown EVO II 300 Bass Head Repair

This British-made bass head was dead to the world.  After looking at the fuses, nobody would dare open it for service, possibly because there was no service literature available in this hemisphere, or perhaps out of reverence for the brand.  This is a hybrid amplifier, with a tube in the preamp chain and a solid state power amplifier.  Would the Unbrokenstring Crew run where angels fear to tread?

01ASH the patientThe owner said that he would clean up the front panel.  Just get the thing working.

02ASH backsideThe steel chassis was just the ticket to keep everything in its place.  You can see the Trace Elliot heritage in this brand.

03ASH back closeHere’s a close-up of the rear panel.  The footswitch must have a pair of switches and a pair of quarter-inch plugs.  The line input jack is an interesting feature.

04ASH chassis scrThese plastic caps covered the screws that secured the chassis to the case.  Well, it appears someone has been here before us!

05ASH scrA little care and a #3 Phillips was enough to bite into these screws and get the unit open.

06ASH power supplyHere, the power amp board is pulled free for inspection.  That’s some big wire!

07ASH cookedCan you see the failed solder joint?  The four elongated tabs are the terminals on a large full-wave bridge rectifier.

08ASH repairEach of the solder joints were de-soldered and then re-soldered with fresh solder.  The joint that failed may have been on an ever-so-slightly thinner trace, so a jumper wire adds some circular mils of copper to that part of the circuit to keep the temperature rise of the circuit board down.

09ASH on the airBehold!  Everything comes alive!  This meter is really a nice-looking feature.

10ASH finishedThis unit is conservatively rated at 300 watts.  The unit barely got warm after four hours at that power level.  I think we fixed it!

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626

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