Under the board wiring - good practice or not?

[PharmRock]

I've seen a lot of quality builds (and assembled some kit amps) where there are a few under-the-board wire runs.  A common one is the bias supply to the 220K grid leak resistors in a Plexi style circuit.  I've always thought the under-board wires presented a problem especially for diagnostic purposes.  For example, there is no easy way to tell if a wire "dropped out" of the turret, or is loose.  And then, to confirm the problem and fix, you need to pull the board.  I've seen versions where a hole is drilled next to the turret, and the wire is run up through the hole and the connection made on top of the board. 

Is there a "best practice" for under-board wire connections or how to run them?  I've seen instances where the wires make a straight-line path from point A to point B, and others where the wire takes a twisty-turny path to avoid turrets along the way. 

Any reason that we just don't make the entire run on top of the board so the connections can be easily seen? Might not be as aesthetically pleasing, but would seem to serve a purpose.

I'm guessing that these questions could all be answered with a "depends" or "whatever you prefer".  Just wondering what the general consensus is on this. 
Thanks!

[acheld]

I don't know the right answer for you, but I do think using the underboard wiring makes it easier to keep the aboveboard components straight and neat.   Tried both, prefer to use judicious underboard wiring for stuff that will NOT be changed later. 

I do have to make sure there is no chance for the underboard wire to drop out of its turret if the turret is heated too much.   

Underboard wiring makes it more difficult to know where your traces go if you need to troubleshoot the circuit later, and it's best to keep it to a minimum, as Hoffman and Sluckey builds do.

[sluckey]

Look here to see how I do under board jumpers...

     http://sluckeyamps.com/VAC15/ac15.htm

[PharmRock]

Underboard wiring makes it more difficult to know where your traces go if you need to troubleshoot the circuit later, and it's best to keep it to a minimum, as Hoffman and Sluckey builds do.

Look here to see how I do under board jumpers...

     http://sluckeyamps.com/VAC15/ac15.htm

Thanks for the responses.  I'm using one of Doug's Plexi boards, and there is only 1 under-board jumper on the whole thing, compared to other layouts where there's quite a few. 

As acheld mentioned, I'm concerned about wires "falling through" due to soldering/resoldering of components.  As an example, in the Plexi build I am doing, I have a Lar/Mar PPIMV I plan to do.  I was going to do this mod after the amp was up and running, but given that I would have to remove the grid leak resistors (where the under-board bias supply connection is), I elected to just incorporate it right from the start to avoid potential problems later.

Sluckey...that link really illustrates a nice way to do it.  The practice of running the under-board wire up through the turret and back down the top-side is something I'll definitely do. 

Also...while not related to this thread topic...Sluckey I've noticed on your builds where you have a buss bar for grounding, as in the one for the ac15 link.  It looks like it is elevated with some stand-offs or chassis-isolated turrets.  It is hard to tell.  Do you mind sharing how you secure the buss bar to the chassis?  Or perhaps point me to a website where I can see a more close-up picture?
Thanks!

[sluckey]

The AC-15 was a special case since the input jacks were in the middle of the front panel. The right end of the buss is soldered to an insulated standoff turret for support only with no connection to chassis at this point. My preamp chassis ground lug is bolted to the chassis right under the input jacks and the buss is connected to that ground lug.

Most of my stuff has the input jack located at the end of the chassis. I install a preamp ground lug right near the input jack. Sometimes I bend the buss and solder directly to the preamp ground lug. Sometimes I solder the buss directly to the input jack.

In all cases the other end of the buss is not connected to chassis. It is just dangling but supported by the various connections from the pots, etc. My goal is to have the preamp buss connect to the chassis at or very near the input jack. Here are some more examples. There's even one with a split buss, one for the preamp, another for the power amp.

http://sluckeyamps.com/supro/supro_02_big.jpg

http://sluckeyamps.com/phoenix/p11_big.jpg

http://sluckeyamps.com/lil_maggie/m-04.jpg

[Ethan]

Under-board wire runs don't offend me any as long as the runs are done neatly and cross other wires according to good practices.
In fact, as Acheld points out, it can really clean up an otherwise messy layout and make it easier, rather than harder, to troubleshoot.

If there's a concern about a wire falling out when reheating a turret then the wire's not sufficiently secured.  Solder isn't glue.  It's there to make an electrical connection, not a mechanical one.  We (amp builders) bend that rule all the time when we use eyelet boards - at least I know I do! - but it's not a very good practice.  Sluckey's method of securing the wires is excellent and it's just one way to approach the problem.  Coming up through a hole in the board as you mention in your OP, coming up around the side or anything else you can come up with is fair game but, in any arrangement, the wire's got to be mechanically secured somehow.

[acheld]

I've been using a 1/4" dab of Permatex to secure the wire to the underside of the board.  Works well, but if you're not careful, it can be messy.

I like Sluckey's method -- with the only problem being that the wires can fill the turret.  Proper planning should take care of that.