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Pipes in the peaks Compton

PostPosted: Tue Nov 21, 2017 12:03 am
by mcmurdo
Pipes in the Peaks, Near Ashbourne, Derbs. Ex Derby Regal/ABC Compton, greatly expanded.

When I first visited here a few years ago I saw a Melotone unit, not wired, stuck up a corner. On a recent visit it's gone. I wonder if it's been installed?

Always worth a visit especially when they have well-known guest organists. The residents are very enthusiastic about their organ and usually introduce unusual features during the concerts, before demonstarting the particular rank or effect within a tune.

The organ includes a rare cello.

Re: Pipes in the peaks Compton

PostPosted: Thu Nov 30, 2017 11:36 am
by Lucien Nunes
Yes it's installed and working. It came down to London first, for Richard Cole and I to give it an overhaul, during which time we had it standing in my workshop next to the ABC Plymouth unit as in the attached pic (Plymouth left, Derby right). It gave us cause for some head-scratching though. After all the normal problems were sorted out (leaky waxies and drifted high value resistors replaced, stator tracks repaired etc) it produced music but with an unacceptably high hum level. The earthing / grounding configuration of amplifier and generators was non-standard (the original is not terribly logical anyway) but I reverted to that as it works OK on Plymouth and others. However, this made ithe SNR worse, so we set out with a series of experiments to identify the cause. Long story short, I made a couple of changes to the earth bus termination that cleaned it up dramatically, that when replicated on Plymouth made that worse. IIRC my conclusion was that different transformers and chokes with different flux leakage patterns cause different eddy currents in the panel and chassis, making the first stage and pickup wiring more or less sensitive to particular grounding points.

One of the most fascinating things I find about restoring equipment that was never 100% perfect in one or more parameters, such as SNR, is working out what is 'right' even without the benefit of experience of it in its prime. The popular perception of old technology is often one of almost comedic deficiency. When I run a good old film print on a good mech, many younger people seem surprised that it's not scratched and unsteady with flash frames all over the place. When they hear 1950s HiFi they expect it to sound like a wax cylinder recording, not clear and open with a full flat response and minimal surface noise. For the trained ear it is not hard to set realistic performance targets for something that compares well to modern equivalents. OTOH Compton knew their tone generators suffered from rather high background noise - they added muting devices to the more serious offenders and Wally Fair noted that it was a significant issue with the otherwise superb type 350 generators. But how good were they when new? Same with hum; there are numerous 'leaks' where it gets in, some due to limitations in the method of construction, which they would have known how to solve but obviously didn't feel the need to. Eventually one has to say 'It'll do, let's hear a tune on it!'

Two Melos.jpg
Melotone units under evaluation - ex. ABC Plymouth on the left, Regal Derby (now at Pipes in the Peaks) on the right.
Two Melos.jpg (265.1 KiB) Viewed 20549 times

Re: Pipes in the peaks Compton

PostPosted: Sat Dec 02, 2017 5:17 pm
by mcmurdo
I did wonder if they'd had to get experts in. Christian up there seems to like his technology if the drumkit and control desk is anything to go by!