Repair Job #318 Steelphon GA810

I had this very unusual Italian Steelphon GA810 come in for repair and couldn’t seem to find too much info online about it, particularly in English. So I thought I better write up a blog post on it with some photos and take some voltage readings etc that might be of use to somebody out there.

When it came in the amp was humming dreadfully when powered on. This later turned out to be a faulty Electrolytic can capacitor. These types of can caps that have a single plastic thread at the bottom for mounting are not readily available so I had to widen the existing mounting hole and install a clamp style can capacitor in its place.

The output stage of this amp is a pair of 2N3055’s with rails at +40VDC and -40VDC. This particular example seems to be missing one of the output transistor PCB's as can be seen in the photos.

The preamp is driven by an ECL86 and 2 12AX7’s.

12AX7 plates measured at 182V, 139V, 100V and 101V.
ECL86 triode plate measured at 80V and pentode plate measured at 149V.

Overall, this amplifier sounds very nice, jangly and sparkling with tons of reverb on call. There is even an internal reverb depth control so you can set your max reverb where you like it. The tone turns to a nice crunch at higher volume.

The reverb pan is a delicate arrangement!

Rectification and filter stage

Preamp PCB underside

Preamp PCB top view

2N5322

2N5320

Power stage PCB top view

Output PCB

Seems to be missing an output PCB

This hardware keeps the two cabinet halves clamped

Faulty Faccon cap

New F&T 50+50uF cap installed

With thanks to Richard Walsh.