Breadboarding a 1.65A circuit - but do not wish to use those human hair-sized jumpers

[Usable Thought]

So I'm going to put together a new 6.3VDC (actually 6.5VDC) heater supply for an amp of mine. The previous unregulated supply became too temperamental so at a suggestion by Randall Aiken I'm going to build a regulated supply around a switching module - say, like this one.

Previously I've prototyped by soldering on a turret board. Well, I'd rather not have to solder to put my little power circuit together - I will be testing it, maybe swapping a cap here & there, etc. So I'd love to breadboard it with pluggable wires instead.

But I just can't believe that a plastic breadboard of the typical kit type, with 0.1" grid and those tiny little jumpers the diameter of a human hair, can handle the roughly 1.65A output of this supply. The input wires won't have to carry quite that much due to higher voltage - with the 10A secondary I plan on using maybe they'll see something like 1.26A at most. But even so.

So, what do folks use for temporary assembly of something like this if you don't want to solder? I am thinking I could use a turret board with alligator clip jumpers - I can make my own jumpers to keep them short enough. Other ideas welcome!

[Enzo]

Some thoughts:

Just because you have a breadboard thingie, that doesn't mean you have to always use it. You can lay parts on a wooden plank and tack solder wires between them almost as easily. What's wrong with solder? If you are afraid of "wasting" resistors or something, don't trim their leads, just tack to the leg somewhere. Tagboard is neat and sturdy, but a breadboard circuit by definition isn't going on tour with you, so there is a lot less need to anchor parts to something other than each other.

Famous engineer Bob Pease was famous:
http://www.rfcafe.com/references/ele...Breadboard.jpg

Power supplies do not put out current, current is drawn from them. Your supply might be capable of 1.65A, but are your heaters going to DRAW that much? Two 12AX7s will draw 0.6A, and that is within those jumper wires ability.

Why are we regulating heater supply? That strikes me like calibrating my bench stool. The heater draw is pretty constant, regulators are good for maintaining a voltage over varying load. Minor variations like mains have won't be audible in terms of heaters. if you want DC for hum abatement, the steady load still is the case, so just setting the voltage with a resistor or a diode or two is simple and effective. DC heaters really only help noise in the first stage or two.

[martin manning]

The typical breadboard will accept 22 awg, which will handle 3 or 4 times that current. In fact that is the gauge of the pre-formed staple-like jumpers.

[Usable Thought]

It's 1.65A because it's all four tubes plus pilot not just the 12AX7s. And the reason for that is that the budget amp being rescued from its own shoddy design and build (Laney allegedly designed it and it was built in China) does not have room on its tiny PCB + cramped chassis for another Molex plug or similar to bring in a separate heater circuit for preamp vs output tubes. For other reasons it already has more jumpers on the back of the PCB than a Christmas tree has tinsel.

If you are curious as to the genesis of the heater supply you can read this very long thread over on The Gear Page. But that is just the latest entry among many in a 6 month operation to reduce noise on this little amp (successfully) - an operation I don't think a pro would ever do, but which is dear to me. Some people like vanilla, others chocolate.

[Usable Thought]

The typical breadboard will accept 22 awg, which will handle 3 or 4 times that current. In fact that is the gauge of the pre-formed staple-like jumpers.

Goodness. Then maybe it's the insulation which is so thin. Which can be gotten away with due to lots of air in between the wires? Good to know, thanks - I will jumper away now.

Meanwhile I found a couple of useful (well, to me at least) links about when & how to breadboard, just by Googling for Bob Pease:

Prototyping - when to When to avoid using a breadboard

Breadboard hints

[Usable Thought]

Just because you have a breadboard thingie, that doesn't mean you have to always use it . . . Famous engineer Bob Pease was famous

P.S. Once you showed me that pic of Bob Pease's Famous Breadboard, game over! Now I HAVE to breadboard this baby.

Although he also wrote a cautionary column about breadboards and switcher circuits: What's All This "SMWISICDSI" Stuff, Anyhow? Fortunately mine is not a high freq application & anyways the switcher I will be using is already an idiot-proof module, properly laid out so I can't mangle it.

EDIT: This guy is a gem.

[Enzo]

Pease is a favorite of mine. His book Troubleshooting analog circuits is one of my favorite books on my shelf. I learn new things every time I read it, and I have read it many times.

I won't go look up a long thread elsewhere, but including the pilot light under regulation? That seems excessive. Are you regulating the B+?

[Usable Thought]

I won't go look up a long thread elsewhere, but including the pilot light under regulation? That seems excessive. Are you regulating the B+?

Same reason as before: It's the topology of the PCB tracks on the amp. Like many amps the pilot was fed by the 6.3VAC tap off the PT. You are right that only the input tubes are sensitive enough to justify DC in cases where that is the strategy . . . but again, given the alternatives, it would be a waste of time & effort to try and add jumpers / cut tracks just to cut the pilot out of the circuit and keep it on AC. Among other things this would have required (as I mentioned would have also been the case with the output tubes) adding a new mooring to an extremely overcrowded PCB for a Molex or similar connector. And for what - the scant 150mA of current it takes at 6.3V to feed a #47 bulb? Simpler is better: keep the heater circuit intact and change its power source. Me being the one doing the work, I get to make the call.

Really I prefer to get answers to the things I actually asked about & not have to defend things I didn't ask about that, esp. when they are not risks in any way but merely choices or preferences. Chocolate versus vanilla is a great debate to have . . . when the question is about chocolate vs. vanilla. On another forum (TGP) I once posted to the luthier's forum a question about how to improve shielding on a noisy guitar, in a case where the noise occurred when not touching the strings - and a luthier commented asking why was I taking my hands off the strings anyway? And went on to say I should get used to the noise and not let it bother me. Normally he is a very experienced fellow w/good advice in many areas. I guess he was having a bad day.

[Usable Thought]

The typical breadboard will accept 22 awg, which will handle 3 or 4 times that current. In fact that is the gauge of the pre-formed staple-like jumpers.

I misunderstood you in my first reply - your wording is quite accurate but I read too quickly. I was still thinking that the jumpers that come with a breadboard kit were 22AWG somehow - just now I chopped one in half just to be sure & clearly they are much more like 26AWG or even finer. Whereas I see that the "staple-like" preformed jumpers that you can buy from DigiKey etc. are indeed 22AWG. So now I can just cut up my own 22AWG solid wire and go that route. Again, thanks for the clear & simple answer.

[Enzo]

Usable, if you want to do something, I am not going to talk you out of it. But this is a forum, not an answer service. We post out thoughts and concerns here. You are free to ignore any of my suggestions. MAny times someone comes here fresh with an idea stuck in his head and never considered any alternatives. I am not criticizing your thought process, but I am considering all the lurkers reading this thread who may never have thought of wiring one tube socket separately before committing to a board art.

[Usable Thought]

I am not criticizing your thought process, but I am considering all the lurkers reading this thread who may never have thought of wiring one tube socket separately before committing to a board art.

That I am fine with & acknowledge is always a valid concern. However . . .

I've sometimes heard it expressed - and it's a sentiment I agree with - that commenting is a three-way struggle: responding to the original poster in a way that addresses their needs & interests while reminding them of things they may have overlooked; speaking also, as you say you are, to lurkers or future thread-browsers who might otherwise be misled by a particular decision having a very narrow scope (as mine does w/the heaters); and meanwhile separating our own personal biases and preferences from what the OP is interested on, tricky for most of us to do.

You will find I tend to argue in favor of the OP's needs much more than the other two. For me, those who are lurking or reading later need to read very carefully - a difficult and neglected skill & something I still don't do very well after nearly 60 years of trying. Witness how I misread martin manning's comment until I went back and read more carefully.

I hope you'll also find that when I am asking for input about a specific plan of action, I want all the critical input I can get and more. I'm eager but clueless - so "Didn't you consider Y and Z?" etc. is very much needed.

[Pdavis68]

Use barrier terminal blocks and test clips. Then you can use a screwdriver and alligator clips to connect things together.

You can breadboard entire amps this way.