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Old 19th Mar 2019, 12:22 pm   #59
Uncle Bulgaria
Join Date: May 2016
Location: Cornwall, UK.
Posts: 347
Default Re: Ferrograph 4A: Restoration advice needed

Thanks Bill.

You're right, I was using a DMM as my AVO 4 is under piles of cleared things (I'm restoring this on the floor around the place as we build a house and soldering sometimes takes second fiddle to making walls), and the AVO8 I've got from my grandfather has a snapped binding post!

I noticed the 'measured with an AVO8 at X ohms/Volt', but thought that couldn't account for the small measured difference at the HT and the wildly varying readings on the anodes. Wouldn't it be a linear progression?

I haven't touched the filter/reservoir capacitors as they seemed to be running along just fine - none of the dual cans have been changed as yet.

I couldn't resist, so powered it all up yesterday and had guitar playing through both inputs with a working volume control! The solenoid still wasn't sticking, but I think it's entirely my fault - I'd put a 250mA fuse in the back panel as a fail-safe and it must have been on the edge with the motors running as it blew. Replacing it with the circuit diagram's 1A now that I thought there was limited danger of escaping smoke, the solenoid holds and the motors run!
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