AC50 serial number 1015B

Details of the chassis

The "B" in serial number denotes "Bass" - the amp's accompanying speaker cabinet can be seen on the main page, along with its covers. Further photos will be added soon.

Below, a selection of details of the chassis. Some prefatory observations: the chassis of this amp and of serial number 1005B differ in a number of respects from later two input amps - .

First, the cut-outs for the cage-nut nuts are long rectangles which extend into the upright of the plinth (see the pics below). Later amps have small square cut-outs - their normal form - on the front and back splays.

Second, the main 32uf filter caps for new AC50 were planned initially to be tall thin silver Hunts units (the originals survive in 1015B), which are 1" in diameter. One can see in the pic immediately below that 1005 was drilled first for these thinner caps, but subsequently drilled again to accommodate the squatter blue Hunts caps (which became standard).

Above, the underchassis of 1005. Note the holes for the filter cap clamps. The inner unused pair was obviously intended for 1" diameter Hunts caps. But then the 1 1/4" caps were chosen.

Third, the mains transformers have leads of a slightly different sort. 1005 and 1015 have long straight 5 volt feeds in red for the rectifier heaters. In later amps these are thinner and tightly twisted (sometimes one red wire, one black).

1015 has superfluous holes for its output transformer - clearly a taller unit was expected. The surrounding aluminium of the unused holes is clean, however - no sign of anything having been attached, no impressions of grip washers. See the pics below.

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Click as ever on the thumbnails for larger images.