Please review my turrent board layout

[dbishopbliss]

I'm finishing up the layout for my AB763 Bandmaster turret board but I would like a second (or third, fourth, fifth) pair of eyes to review the layout before I submit my order.

I have followed the Hoffman style board pretty closely, but I eliminated the lugs for the reverb circuit.  In addition I adjusted the spacing so that the Mallory 150 capacitors and the 1W resistors I have will fit between lugs rather than bending the leads.  Maybe I shouldn't care, but I like things to look neat - fewer mistakes that way and easier to make modifications.

Also, the Bandmaster uses a solid state rectifier.  I was wondering if it is ok to put the diodes on the board with the rest of my components, or should I make a separate board like Fender did originally.

Thanks for your feedback... getting so close.

[Willabe]

I was wondering if it is ok to put the diodes on the board with the rest of my components, or should I make a separate board like Fender did originally.

Company's/guys do put B+ diodes on the end of the board sometimes but....

Your going to have a problem putting any eyelets/turrets too close to the edge of the board. You will lose the strength of the board and it's ability to hold the eyelet/turret, it could break lose. Turrets will be more unstable/risky than eyelets because of leverage. You could even break the board just setting/crimping the eyelet/turret.  

I like to leave at least 3/16" from the edge of the board to the outside of the eyelet/turret closest to the boards outside edge.

In addition I adjusted the spacing so that the Mallory 150 capacitors and the 1W resistors I have will fit between lugs rather than bending the leads.

Some might disagree with me about this but......

Your still going to have to bend the leads (at least on the 3 @ .01 from looking at your drawing) on the caps. I'd be very worried about soldering them in place so close to a turret because of heat, it could kill/burn up the cap. The heat will run right up that very short cap lead and into the cap where it connects to the caps inner/start or outer/finish wind. I would not feel comfortable with less than at least a 1/4" of lead between the caps end and the turret. And that's even cutting it too close for comfort for me.

Modern caps use a plastic film for the dielectric (insulator) between the conductors. That film doesn't take much to melt. Silver mica caps don't use film construction but seem to be even more sensitive to heat.

I'd be less worried about MF or MO R's but I still like some lead space between the R and the eyelet/turret.

Looks like you could move the B+ and ground rails/buss further back, closer to the edge of the board and gain some more room.  

If your very good at soldering and can get a good solder joint by going in and getting out very quickly you can probable get away with 1/4" of lead. Some guys use a heat sink on the lead when their very short to keep the cap from getting burned up.  

Maybe I shouldn't care, but I like things to look neat - fewer mistakes that way and easier to make modifications.

That's a good thing to me.            


Brad    

[dbishopbliss]

I like to leave at least 3/16" from the edge of the board to the outside of the eyelet/turret closest to the boards outside edge.

There is 1cm between the turrets and the edge of the board as drawn.  The diode turrets look as if they are right on the edge, but that is because Visio makes the image only as big as the items in the diagram.

Looks like you could move the B+ and ground rails/buss further back, closer to the edge of the board and gain some more room. 

I can move the rails/buss down but that will leave 0.5cm  between the turret center and the edge of the board.  It would be a drag to break the board.  In addition, that would mean the rails are only 0.5cm away from the ground buss (I'm not sure if that is a concern). 

I suppose the other option is to buy smaller resistors, but that would seem like a waste.

[Willabe]

There is 1cm between the turrets and the edge of the board as drawn.

That's about 3/8"? So 0.5 cm is ~3/16"? You have a little room to gain. And I just checked my Sch layout drawings and I've been going with 1/4" to center of eyelet/turret from boards edge. Which leave about 3/16" from the edge of the board to the outside edge of the eyelet/turret.

I don't have Visio can't afford it, so I use the free Sch program.    

I set up the dot grid so it's on a 1/16"x1/16" and then you can put your starting point of any part or wire in between and get to a 32"x32" grid for scale layouts.

If you 1st set up all the turrets that go around the edges of the board at 1/4" to center then you'll know how much room you have left to play with.

This is why I set the dot grid so fine/small. So if space is tight I can move things and know it will still work.

I can move the rails/buss down but that will leave 0.5cm  between the turret center and the edge of the board.

How did you get to that, you said you have 1cm from turret center to the boards edge? You can only move things 0.5cm at a time?

Also I not sure that Doug is set up for using cm.     Which might throw things off. You might need to send him your board in inches?

that would mean the rails are only 0.5cm away from the ground buss (I'm not sure if that is a concern).

The B+ and ground rails if close should only help to cancel out noise. The only thing to worry about is to make sure they can't short out. As long as you keep any turrets and bare wire leads spaced apart they should be fine. Just move them to the left or right if possible as needed.


             Brad            

[Willabe]

I high lighted a few options for re-arranging for more space.

1. in red 2 turrets could become 1.

2. Purple could be moved up. ^ Far left end B+/ground rail you would move only 1 of the 2.   

3. Yellow not needed?

4. Blue 3 could become 1.

There's space to be opened up if you make 2 parts into a Y and get ride of some redundant turrets. You can also stand a resistor up on 1 end at a 45 degree angle.

It's can be nice to put every thing side to side but sometimes you can't fit it all in that way.   
          

               Brad    

[dbishopbliss]

How did you get to that, you said you have 1cm from turret center to the boards edge? You can only move things 0.5cm at a time?

Also I not sure that Doug is set up for using cm.     Which might throw things off. You might need to send him your board in inches?

I'm basing my scale off of the image found on the Turret Board Design Program.  I printed it out and used a ruler to measure the distance between the guidelines.  The lines didn't quite line up when I was using inches - a hair over 3/8" vertically, a hair under 5/16" horizontally.  Then I realized that 3/8" is 0.9525cm and 5/16" is 0.79375cm.  So I flipped the ruler over and they lined up quite nicely with 1cm and 0.75cm. 

I will send Doug an email to verify.  I printed the diagram out 100% as he instructs, but you never know, my printer could be off although I do measure 7.75" and 10.25" inches as he indicates on the diagram.

[Willabe]

I'm basing my scale off of the image found on the Turret Board Design Program.  I printed it out and used a ruler to measure the distance between the guidelines.  The lines didn't quite line up when I was using inches - a hair over 3/8" vertically, a hair under 5/16" horizontally.  Then I realized that 3/8" is 0.9525cm and 5/16" is 0.79375cm.  So I flipped the ruler over and they lined up quite nicely with 1cm and 0.75cm.

OK, I see now. Your fine.

I make my own boards so I never really looked at that before.

Still you might find some space with the suggestions I gave you.

I don't always see it at 1st, in fact most times I have to move something then I see something else I can move. Might take 4 or 5 moves for me to get there. I keep a copy of the drawing before I start moving parts so if it doesn't work I can get back to what I had before.

I also use eyelets and turrets on the same board. That way I can put a part left to right or on a 45 on turrets lifted above the part(s) below in eyelets. If they were all turrets it would get in the way in some spots. With turrets your already thinking in 3D, this is just an extension on the same 3D idea.


                  Brad          

[Willabe]

Here's an example, not saying it will work but you could move parts like this.

R on left ends up going left to right, purple box gets moved down the get turrets out of the way of the moved L/R R.

Are you missing a lead from 1M R to where I put a yellow box? It would go to 22K.


               Brad        

[Willabe]

Is the red line/wire supposed to go there? There's no wire in your drawing.

Are the 470R's in the blue box the screen grid stopper R's? If so they could be mounted on the tube socket (if your using 6L6) and get you some more space on the board.


             Brad     

[dbishopbliss]

Yes, I was missing a few lines.  I've updated the diagram with some of your suggestions.  I've hightlighted a couple of resistors that will be crowded, but I completely forgot about those caps on the right that you pointed out.

I could move the 470R's but the board is around 14" wide now so I don't really need the space at the moment I can go 16" wide I believe.  Thanks for helping with this.

[Willabe]

The 22k and 100R can be lifted up at a 45 degree angle if needed. The other 2 R's are light weight and can be floated in the air for a little more lead length. They won't go any where.

If your putting in tip jacks for measuring the bias you can more the 2, 1ohm R's onto the tip jacks.

I would not put the 1ohm R's right next to the 470ohm screen grid R's because of heat from them.

They will also do a better job mounted on the tube sockets as they are grid stoppers. Plus you it can make it easer and neater wiring up the output tube sockets that way. Keep the screen grid R's lead very short at the sockets pin and lift the other end up in the air at a 45 degree angle to help get it away from the heat. Very common to do this.

I have not gone over your boards layout, I know that's where you started this thread.


              Brad    
                    

[dbishopbliss]

Last changes for the day.  I moved the 4.7K and 1K resistors down to outermost row available in the turret board designer tool.  This let me give the 0.1uF caps some breathing room.  This layout will leave me with only 4 crowded resistors and 3 turrets close to the edge.  I will look at moving the 470R resistors to the sockets.  I hadn't really considered that since I was following Doug's layout.

By the way, the black circles in the corners are where I will put the standoffs.  They also give the image the proper horizontal spacing.

I've attached the schematic I am using.  Its not exactly an AB763 because I'm using a more Tweed-like tone stack in one channel and I have removed the reverb circuit.  I think it is correct but again, if you notice anything, please let me know.

Thanks again!!!

[Willabe]

Are the 2 @100ohm R's next to the B+ diodes for the heaters faux CT? If so they could be mounted on the pilot light in a Y shape with the Y stem soldered together with a wire going to the PT B+ CT ground. Then you could move the -bias over towards the B+ diodes.

If your board is correct than I still say the thing I would worry about most is the 3 coupling caps lead length on the far right of the board. You have a number of parts that could be moved off the board and to me should be, plus there's a number of turrets that could be left out and parts could be moved a little this way or that way.

Now there is more than 1 way to skin a cat, I'm just saying how I would build it and have done it before with no problems.

You'd be surprised how much you can room you can find if you move this a little this way and that a little that way. But it takes time to play with it.

Building an amp that has a per-punched chassis and a pre-made already laid out board is about as easy as it gets as long as you wire it up like it's supposed to be and do it neatly.

Laying out your own board is the next step and a little to a lot harder, depending on what your building, IMO.


             Brad