Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Roukedou on November 16, 2017, 05:33:50 pm
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I have made a .dwg file of my layouts, for a 6g13a (Fender Vibrasonic) and 6g15 (Standalone reverb), with actual measurments taken from the components I'll be using, the biggest ones being the blue Sozo's cap.
When comparing my layout with the one Doug made for his eyelet boards, there is a significant difference (17.5" vs 12.5" for the Vibrasonic). I included a 1-2mm spacing between components that are close to one another, but still, that is a big difference.
I'm not using the smallest components (carbon comp resistors and sozo blue caps), but I don't think I am that far bigger than the components used on the actual amp made by Fender, if not smaller.
From your experience, would I be ok using a 12.5" board (turrets)? I am not far from making a cardboard test board, but making that test is almost as much work than assembling the actual board...
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Are you using equal spacing between all your turrets, or equally scaling up the space between each set of turrets?
If you have larger caps it makes sense that you might need a larger board... the only obvious mistake I can think of is if you also increase space between turrets that don't need to be further apart, like ones simply holding resistors.
Whether you can get away with the 12 inch board totally depends on how big those caps are.
Double-check your measurements. Also keep in mind, the part is centered on the turret so only 1/2 of it protrudes towards the next row.
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The original 6G13a board is 14.625" by 2.5". Your board needs to work together with the chassis size and layout. I would not try to put a 17" long board in a standard size 6G13a chassis.
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I have not started the chassis yet, waiting to have the turret board done to make a cardboard test chassis first.
I did not use an equal spacing for turrets. My process was to measure each component, and then draw the board in autocad, inspired on the original layout (as the circuit is mostly the same), including 1-2mm minimum space between components and turrets. I am confident that my layout is correct (confirmed in various ways), but what puzzles me is that the blue molded caps are the same if not bigger than the blue sozos I'm using, and the carbon comp resistors are the same size, but I arrive at a 17" while the stock version is 2.4" shorter and Doug's is 4" shorter... Should my spacing be smaller than 1-2mm?
(https://i.imgur.com/k7W4JmB.png)
I know my design is a bit longer, since I tried to avoid bending the components leads too extremely, keeping most of them straight, but I don't think this is what creates the 2.4" difference...
Thank you
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mounting points? the first thing to do when designing any board is to decide where to place your mounting holes, then work within those confines. however, before starting with the concept of your board, you should have already hand sketched what dimensions the chassis will be, then build within those limits, if you can't then you scale up. if you have too much room, then scale down. 1-2mm spacing between components dissipating 1=<W is fine. variable pitch is fine as long as you keep a minimum distance with high voltage. minimum spacing depends on working voltage. 1/8" (3.18mm) or more is a conservative spacing for 500V.
--pete
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Yes, I did not include mounting points at this step, but there is more than enough room to find spots to locate them. Also, I'm building everything from scratch, so I have no size constraint. I don't want to compromise on the result, but still I aim for an efficient use of space.
I will trace the high voltage paths, an adjust spacing accordingly. When drawing this, I also kept in mind the location and angle of the wires running under the board. I assume this was done with good lead dress in mind.
Thank you for the tips.
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I found that if I put two turrets close together, my turret staking tool would not fit on the second one. Several on your plan look unstakable for that reason.
--Craig
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Funny, the last thing I do after laying out the turrets on a board is locate the mounting holes for the chassis. I find that as long as I have at least a 3" wide board and I keep the top and bottom rows of turrets one down and one up from Doug's old drilling guide there is plenty room for them. On Doug's old drilling guide the turrets for the small bias pots are the closest together and are still stakable. Also, I find using Visio to do all my amp design including board layout to be much easier than AutoCAD. This is especially true given all of the scaled component templates everyone has shared in here. I start with Doug's template, position the components to see which holes I need, eliminate the unused holes, group the board and holes as well as put them on their own layer then put the components in place. After that, I find the best locations for the standoffs which don't interfere with transformers or other components on the chassis and done. Making sure the components and board are on different layers makes it easy to turn the components off for the board drilling print out and on for the component loading layout. Attached is the old drilling guide in multiple formats and a board example from the recent Hoffman DR I have been building.
Barry
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I looked at my 6G13A Vibrasonic board again
The dimensions are wrong on the eyelet board page
Is is supposed to say 3 inches x 14.625 inches