Risk of shorting B+ to ground in hoffman layout

[pompeiisneaks]

I had an interesting discussion on facebook with someone insisting that the hoffman layout style with the 100k anode resistors going over ground to the B+ rail is a serious danger and should be modified to use shielded wire instead of buss wire.  I get it 'could' be problematic, but that means the lead has snapped and in theory, could be able to move almost anywhere in the amp and is a bigger problem in theory than it being 'over' the B+.   I wanted to get the consensus here on if that's a major issue and if I've been misunderstanding this and doing it wrong in the past, or if he's just overly sensitive?

~Phil

[sluckey]

I try to avoid that situation. But some of my earlier builds needed a little 'comfort' for me. Very easy to just slip a piece of Teflon insulation over a jumper. Look at this pic. The long red jumper has B+ on it. And I have also occasionally put black insulation on ground jumpers if they were exposed. Stuff I've built during the last 5 or 6 years usually have the ground buss on one edge of the board away from everything dangerous, kinda like your AC30.4 board.

[tubenit]

Not sure if I am understanding what you are saying but I would NOT use shielded wire for B+ rail.  I do what Sluckey does and simply slip on some teflon insulation over the wiring.

with respect, Tubenit

[John]

I think he said shielded when he meant insulated. Anyway, I don't like a lot of bare wire either. Any jumpers are almost/usually insulated if they're running close to something else. Under-board the same.


I think it makes up for my carelessness in other areas. 

[Tony Bones]

Yeah. A scrap of insulation stripped from some wire is too easy to slip over any leads that might need it. No reason to worry if you're paying attention.

[pompeiisneaks]

I definitely meant covered not shielded.  Ok so since I've done several that didn't have this coverage, are they at risk?

[sluckey]

If you can push on a component and make it's lead touch a naked buss wire underneath, well, what would Murphy say?

[drew]

Given how many Hoffman boards have been built and how long they've been in circulation, I have to think that if this was an actual issue rather than a theoretical one, it would have made itself apparent by now.


Realistically, once an amp is built and put into a cabinet, what is going to make those resistor leads touch the ground buss, short of some kind of Monty Python-esque 2000 lb weight falling out of the sky and landing on the amp kind of event?

[sluckey]

This type of failure is not likely to occur during normal use. But a lot of people that own a Hoffman board are tinkerers just like me. We can't keep our hands out of the guts. Chances of this happening increase quite a bit while poking this and tapping that or doing one more mod. To further complicate matters, a lot of people's boards do not look as neat as boards built by Doug.

[pompeiisneaks]

Yeah I think I'll just make sure for future boards I put some kind of cover over the leads of the anode resistors that go over the ground so they can't in theory touch even if they break. 

[Ed_Chambley]

Even though lacing B+ is pretty, I still would not use bare wire.  The feller that made the comment would probably start swinging his arms and saying Danger Danger Will Robinson if he ever saw the inside of a point wired radio.


Murphy says now that you know it you must correct it.  Before you knew it, it was not a problem.  Ignorance is bliss and Murphy overlooks ignorance.  Has to.  Ever wondered how those guys who have no tools at all even live?

[shooter]

Ever wondered how those guys who have no tools at all even live?

 

Those are the ones that pay more cuz you DO have 'em

[EL34]

I had an interesting discussion on facebook with someone insisting that the hoffman layout style with the 100k anode resistors going over ground to the B+ rail is a serious danger and should be modified to use shielded wire instead of buss wire.  I get it 'could' be problematic, but that means the lead has snapped and in theory, could be able to move almost anywhere in the amp and is a bigger problem in theory than it being 'over' the B+.   I wanted to get the consensus here on if that's a major issue and if I've been misunderstanding this and doing it wrong in the past, or if he's just overly sensitive?

~Phil

Never heard of this happening in 20+ years
I guess if someone is a total idiot and does loose sloppy workmanship, anything is possible

[vibrolax]

I've been designing and building nearly everything I do Hoffman style (with my best imitation of Doug's workmanship) for over 12 years, and am not at all concerned about the anode leads touching the ground buss.  I  use insulated wire for part of the B+ buss on some layouts, when I mount preamp filter caps right over the buss.
Jon

[EL34]

It's pretty easy to slide on some wire jacket material
.... If someone is concerned that a brick is going to be dropped on the board and force the parts down until they are mashed together

I would think the copper lead wires would break if you forced a component that far down

[pompeiisneaks]

Yeah Doug, that was somewhat my point too, if you hit it with a sledgehammer it may cause a problem, but then, the hit with the sledgehammer is likely to be destructive to ANY construction methods :P  OTOH, slipping on a bit of insulation can't hurt and only should take an extra few minutes, so I may take that route going forward, but it's not enough of a reason for me to go back and desolder and cover the existing amps :)

~Phil