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Post by RockAndRoll on Mar 11, 2021 6:58:44 GMT -5
Hi. I recently bought my first Marshall tube amp (Origin 50 head) and I'm thinking of eventually swapping the EL34's for 6CA7's. I've never biased an amp, so I've been doing as much research as I can and one of the questions I have involves supporting the chassis while biasing. I've seen where many folks prop the chassis on wooden blocks or paint cans, etc. I've also seen where some use an amp cradle. Just wanted to get some recommendations on how to safely support the chassis so I don't necessarily need to bring it to a tech. If a cradle is the best solution, any opinions on which one to purchase, or where to find plans to build one, would be great. Thanks!  |
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Post by Leftee on Mar 11, 2021 8:23:20 GMT -5
I’ve not had my Origin 50 out of its cab, but often you can use the cab itself. Just turn the chassis slightly so the corners sit on the back of the cab.
I’m not sure if this will work with this amp. I have used this method with many amps, though. Just make sure the chassis sits firmly in place and doesn’t teeter. Also make sure the cab is deep enough that the power tubes don’t touch the front.
Watch your fingers. Lots of high voltage stored in the caps!
Years ago I had some wood blocks screwed together to support a chassis. I don’t recall what they were. The blocks were tall enough so that power tubes and transformers cleared the bench top.
I could see old paint cans working, but I would only use the plastic ones - with the lids on.
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Post by RockAndRoll on Mar 11, 2021 8:32:20 GMT -5
Thanks Leftee. I appreciate the help! |
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Post by cedarchoper58 on Mar 14, 2021 17:27:23 GMT -5
i use books
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Amp cradle
Mar 14, 2021 20:33:38 GMT -5
via mobile
Post by RockAndRoll on Mar 14, 2021 20:33:38 GMT -5
Sounds good. Thanks cedarchoper58. |
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pdf64
Wholenote
Posts: 556
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Post by pdf64 on Mar 15, 2021 5:06:38 GMT -5
Book etc are fine for putting under the transformers to raise the valves away from the worktop. Some amps are fine with that but with others, it can be a bit wobbly / potentially unstable, thereby putting the valves at risk.
Amp cradles are complicated and pricey as they’re adjustable to fit a variety of chassis sizes, and some can tilt too.
But for a specific amp chassis, it’s a simple DIY job to cut and screw 3 spare bits of wood together. That’s a much better way to keep the chassis stable and the valves safe.
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Post by RockAndRoll on Mar 15, 2021 5:34:28 GMT -5
Thanks pdf64. I do have some lengths of scrap wood. When I get the chassis out, I'll take the measurements and assemble the support before tackling the biasing. Thanks again. |
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