Service Centre for David Eden and Nemesis bass amplification

Hey folks – just a reminder that we also service the needs of working and recording bass players, which includes not only valve (tube) amplification, which always has been and always will be our specialised area of interest, but also solid-state amplification. We have long been an authorised service centre for Ampeg and Peavey amplification, and also Marshall, Laney and Hartke. We provide non-warranty repairs to many other brands of bass amps, for example Fender, Orange, SWR, Labsystems, and more recently the products of David Eden and their budget off-shoot brand, Nemesis. We do not provide service to amps with switched-mode-power-supplies (SMPSU), or switching amps in general. Check with us first, if in doubt.

Recently a David Eden WT800C bass amp was delivered to our Wyoming workshop for repair by Grove Studios, a Central Coast (NSW) recording facility formerly owned by Gary Beers of INXS fame. Grove Studios have become a regular customer in recent times, as amps quite often choose the worst possible time to develop a fault, ie in the middle of a recording session. We always strive for the best possible turn-around time in these situations, depending on availability of parts, as required.

The WT800C in question was blowing fuses, which after initial investigation was found to be a melt-down in the left-hand power amplifier. The power amp board had some short-circuit (S/C) output devices plus some other smaller collateral damage, and worst of all there was damage to the printed circuit board (PCB), with some destroyed tracks and solder pads. This PCB damage appeared to be from a previous unknown repair and not from this particular incident. Another example of heavy-handed soldering/de-soldering technique (or lack thereof).

I had to order in the output devices which were 3 each of the Sanken 2SA1492/2SC3856 complementary pairs, which unfortunately held up progress of the repair for a few days. To ensure equal load sharing between the output devices, I never mix and match new and old devices, or different brands of the same device. That way, I know the repair will hold up under rawk’n’roll conditions. It’s also important for the same reasons to clean up the forced-air cooling system. After replacing the output and driver devices, plus diodes, etc, and repairing the damaged PCB the best way I could, ie, with wire links to replace the blown tracks, etc, etc, we powered up and readjusted the bias setting as per the sevice manual. The amp passed its power output test, burn-in test and electrical safety test with flying colours ! With one channel only driven at a time, this amp puts out approx 500 watts into a 4 ohm load, and therefore potentially delivers over 800 watts with both channels driven.

Many thanks to Markus Salisbury of Grove Studios, and Eric Grothe of Shinobi.

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