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Progress on Tim Mellow 25W OTL Tube Amplifier

(Added Video Files of meter's working , unable to load in the original Red Plating Post)


Tim Mellow - 25W OTL Tube Amplifier Build / Progress Just got some more kit that I may use for this Amp.

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All holes for Tube bases Done.

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Chassis now formed using my home made sheet metal bender.

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Seen this Double VU Meter with driver board on Ebay , ooh, thought I'll incorporate it in the design. Original design had 2 x 1Amp meter's for biasing only, no VU Meter's. I have read in some of the forums these meter's were replaced by resistors and not fitted after initial set up. I'm going to use a switch were I can switch between the resistors and meters so as to check the biasing now and again when needed. Trying to fit the 1 Amp meters any where on the chassis just did not look aesthetically right.

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Hole cutout for the Meter, took about an hour to complete , took extra care not to mark the chassis as this will be in full view when complete.

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Deciding were the I/P'S and O/P'S are going.

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Final Placement Decided on this layout in the end.

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I ordered a pair of these with driver board some time ago to go with the Boyuurange A09

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No Lamp adjustment with this PCB

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Dam Big Holes to drill in the Face Plate

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Made the mistake of measuring the resistance of all the meters and testing their deflection. 2 Pairs and I Double all varying resistances and deflections with the same current.The only consistency with parts from China is the Inconsistency. Best use these as "Indication Only" as they look like 20-30% variation between then. Having in the past calibrated Medical equipment these would be a nightmare to calibrate correctly and would be scraped but we'll use just to show some indication.

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Tested using another PCB with lamp adjustment


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Low level adjustment

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High level adjustment

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Blue meter's Illuminated

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Added Some Tape for better affect

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Chassis Size comparison to the Boyuurange A09

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Giving the Meters workout


Take Care and have fun. Will.

277 Views
Skunkie
Skunkie
01 abr 2022

Nice job!!

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