There is PCB and then there is PCB

[MWJB]

"Not mentioned in the Leo Fender argument is that Fender continued to employ eyelet board construction LONG after every other MFG had gone to PCB. Hmmm?"

That is true but had nothing to do with Leo, he sold the company in '65, LONG BEFORE every other MFG had gone to PCB. After Leo left, Fender were very slow to introduce changes (especially after the lukewarm reception of the quasi-cathode biased amps & even that took them 3 years & no doubt increased their caution). In the cases of the Champ, Princeton, Deluxe, Vibrolux, these changes are barely worth mentioning, a couple of resistors, a couple of caps & a little more B+. It's fun, but ultimately pointless to speculate as to what might have occurred had he stayed with the company...based on the frequent updates right up to the point he left (it's more unusual than usual to see 2 brown/blonde amps that are the same), it's anyone's guess.

[big_teee]

I have enjoyed the read!
I'm sure glad I got Leo envolved!
We could get Jim Marshall in the conversation next.
After all he borrowed (Stole) most of his ideas from the Fender Klan!
Back on the PCB.
I myself don't have a problem with the components being mounted on a PCB for a Modern amp.
I just don't want any Tubes, or Pots, or switches mounted on the PCB, but that is strictly IMHO.
As far as old designs, I still contend that the PCB is out of step, and out of place.
Keep it up, I have enjoyed the discussion.
Later,
Make Rock Proud, Play It Loud!
Terry

[soundmasterg]

So what do you guys think of connectors for solder-lug pots, to allow panel mounting with easy disconnect for servicing of the PCB?

The reason I am asking is because I have seen both good and bad - those horrible insulation displacement connectors many amps use fail all the time, I wouldn't put them in anything, but I design in the newer small connectors like the 2mm Molex types into a lot of aircraft avionics equipment for one of my engineering consulting clients, and they never fail, even in heavy helicopter vibration or on the vibe/shock test table.

Got a link to those type of connectors Randall? I've got a 1972 Datsun 240Z that uses a ton of molex connectors on the wiring harness, and a late 70's MCI 24 track 2 inch reel to reel with lots of molex connectors, and both are famous for intermittant electrical gremlins. It would be nice to be able to solve those issues once I get around to it with some quality parts.

Greg

P.S. I've always liked your use of PCB's with turrets....I think thats a great approach that makes for a more robust and reliable amp, even after repairs are done down the road.

[jpfamps]

"Not mentioned in the Leo Fender argument is that Fender continued to employ eyelet board construction LONG after every other MFG had gone to PCB. Hmmm?"

That is true but had nothing to do with Leo, he sold the company in '65, LONG BEFORE every other MFG had gone to PCB. After Leo left, Fender were very slow to introduce changes (especially after the lukewarm reception of the quasi-cathode biased amps & even that took them 3 years & no doubt increased their caution). In the cases of the Champ, Princeton, Deluxe, Vibrolux, these changes are barely worth mentioning, a couple of resistors, a couple of caps & a little more B+. It's fun, but ultimately pointless to speculate as to what might have occurred had he stayed with the company...based on the frequent updates right up to the point he left (it's more unusual than usual to see 2 brown/blonde amps that are the same), it's anyone's guess.

Well CBS did update the Fender amp line with the solid state range.

These where an unmitigated disaster.

I expect it is this failure of these (rather than the cathode/fixed bias amps) that discouraged CBS from experimenting much with the amp line again.

[J M Fahey]

"... tiny inductance and capacitances between traces..." which is downright deceptive.

Deceptive indeed.

>> Inductance:
A straight 6 inch track on a PCB has the *exact* same inductance as a straight 6 inch piece of wire.

>> Capacitance:
"In a parallel plate capacitor, capacitance is directly proportional to the surface area of the conductor plates and inversely proportional to the separation distance between the plates." (Wiki)
*so*, when comparing two PCB tracks , say, 1mm wide (40 mils) , 0.1mm thick, separated by 1mm , and facing each other thin edge to thin edge, I'm sure their coupling capacity will be *less* or worst case the same than the one created by two regular insulated wires, 1mm thick (#18 ?), tied in a bundle and separated by 2x the insulation thickness.
Of course, the stupid/lazy designer who lets his PCB software place 2 parallel tracks, exactly superimposed on both sides of a PCB for any appreciable length deserves the 100pF capacitor he is creating.
But with just a handful of neurones still working, that must be corrected on screen, before 10000 boards are ordered.

Let me remind that tying wires in bundles is widely regarded, specially by "classic technology" lovers as the ultimate in construction quality, specially because of its use in "military" electronics.
The obsessive , visually stunning classic Hiwatt is an example, also Mesas and many others.

Of course, the problematic bundle can be untied and wires separated at will, if a problem arises.
Tracks can also be separated at will .... by the designer.
Afterwards they will remain so forever; but in a handwired amp I would not be so sure, it depends on the "hand".

Given that 90% industrial manufacturing is being moved to the Far East, to modern cheap automated factories (which of course will rely on PCBs), with abundant and cheap production impossible to compete with on even terms; then one of the few still open paths for an American Technician or Engineer to use his beloved and hardly acquired skills is to resort to semi-obsolete technologies "not cost-effective to the Chinese", to "Mojo" (whatever that is) and to Patriotism, with abundant calls to (justly) famous former American glories.
Problem is, the Chinese already own illustrious classic names as Vox, Celestion, Wharfedale, and many others, so they can use them too; even pin small American (or British) flags in their ads if they wish so.
Sad but true.

[Chuck H]

On the issue of small inductance and capacitance issues with PCB's I would say that (as JM pots it) anyone "with just a handful of neurones still working" recognizes that these issues are much more random and problematic in hand wired amps AND this effect can be used as a tool. It's been shown here MANY times that layout is critical in certain designs and there have been many failures due to lack of attention to this detail. A PCB solves this issue as opposed to the popular lore that it is a problem. The effect of inductance and capacitance due to lead and component proximity is a relevant design application attributed to the relative goodness of any amp design. Since we can't always accurately identify EVERY small effect that happens due to a specific layout why not at least render the effect consistent by using PCB's instead of hand wiring? If an amp sounds and performs good these effects become a relevant part of the design. How did it become a "problem"? And why is it exclusively attributed to PCB amps by the anti PCB ilk?

That said I will concede that it is due to inductance and capacitances of typical PCB tube amps that accounts for their general tendancy to be noisier than hand wired amps. But this due to poor layout and ground planes found in most PCB designs. So it's a design issue, not a PCB issue.

[Alex/Tubewonder]

In the end it all boils down to the skill and experience of the designer. PCB design is an art. PTP design is an art too. It's easy to see the difference between an artful execution of each method and a hack job by a dilletant.
Also, the issue of ease of repairing a PCB amplifier that is brought up ever so often. It's non issue. The issue is with the repair person not willing to learn proper techniques and using right tools for the job.
As a side note: I am surpised to see single sided PCB on phenolic paper still being used in some (no names) amplifiers. This belongs in a museum.

[Ronsonic]

In the end it all boils down to the skill and experience of the designer. PCB design is an art. PTP design is an art too. It's easy to see the difference between an artful execution of each method and a hack job by a dilletant.

More often than dilletantism what we see is some guy who has no real idea of the final application under immense pressure to get his design done for the lowest design cost and the lowest production cost. His only other restriction is that it survive the warranty period. Field repair is not a concern, only cost of design and manufacture.

Also, the issue of ease of repairing a PCB amplifier that is brought up ever so often. It's non issue. The issue is with the repair person not willing to learn proper techniques and using right tools for the job.

I've got the right tools, I have the techniques and skills. There's more to it. Replace a component on the main PCB of a Music Man amp. Simple and fast, a couple of screws and the board flips up. The guys who designed that considered the need for field service and provided for it at almost no additional production cost. Almost ironic that nearly forty years later hardly anything ever fails on those boards. Now replace a component on any, ANY, PCB Marshall. Whole 'nother job. Then when you get to the hastily designed, truly cheap stuff it gets even worse. Much worse.

As a side note: I am surpised to see single sided PCB on phenolic paper still being used in some (no names) amplifiers. This belongs in a museum.

Agreed. That single-sided parchment-colored board is nature's way of screaming cheap crap. Even if you don't need traces on both sides of the board, the through-plated holes of a double sided board are vastly more reliable. It can also permit service from the component side of the board. Again, a consideration for the guy who has to keep it running.

[Alex/Tubewonder]

Since we can't always accurately identify EVERY small effect that happens due to a specific layout why not at least render the effect consistent by using PCB's instead of hand wiring? If an amp sounds and performs good these effects become a relevant part of the design. How did it become a "problem"? And why is it exclusively attributed to PCB amps by the anti PCB ilk?

That said I will concede that it is due to inductance and capacitances of typical PCB tube amps that accounts for their general tendancy to be noisier than hand wired amps. But this due to poor layout and ground planes found in most PCB designs. So it's a design issue, not a PCB issue.

It is not a problem for modern EDA software to calculate and model/simulate the effects of whatever parasitic impedance there can be between tracks on a PCB. How & why do you think those small wiggles on data bus tracks om PC mainboards came about? By design and simualtion, they are there to compensate pulse propagation times diffrences due to diffrences in individula track length. A tube amp PCB and its track-track capacitances or individual track inductances are pretty basic to analyze for todays PCB software. OK, initial investment can be substantial but can be avoided with "pay per use" licensing schemes. But you need to learn how to use the software on you own dime & time and that's a bitch.
The real question is: do we really need to do this kind of deep simulations on a tube amp PCB? I don't think so, not if you know what you're doing. And if you don't the best EDA software in the world won't help you a bit.

[Chuck H]

I agree. My point was that PCB's are consistent and hand wired methods are not. Even if we can isolate all the effects of tracing and layout, which AFAIK isn't a reasonable thing to do for most amp designers, your right that we don't really have to. We never did for hand wired amps either. I try to design for as little effect as possible. In some designs layout and lead dress IS a problem, like the SF Fenders for example. On others the effect is a happy accident nd there is a positive effect, like the Trainwreck Express (The designer insisted that tweaking the amps was partly in the lead dress and layout). Also there's the Marshall trick of tacking the plate and grid leads for V1 side by side on the chassis. Of course this creates a capacitance and probably improves stability. You get the point though.

[J M Fahey]

I'm slow minded but after certain time, ideas *do* get to the surface, I had this just at the tip of my tongue.
Consider this: in every "age", military construction is "top of the tops" by definition, simply because it *has* to have the utmost reliability considering what's at stake, and cost is not a point.
What was military construction like in Leo's era? : Turret or similar "solder terminal riveted to an insulating base" boards, (of which eyelet boards is a subset), plus tied up wire bundles.
There were some connectors used, where indispensable, and they were of the highest quality.
Harry Joyce (Hiwatt), uncrowned king of wirers, was an ex-RAF wirer.
Now to the million dollar question: what do the military use today?
PTP in any of its forms or PCB?
I leave the question open for anybody qualified to answer.

[R.G.]

... in every "age", military construction is "top of the tops" by definition, simply because it *has* to have the utmost reliability
...
Now to the million dollar question: what do the military use today? PTP in any of its forms or PCB?

That's a great way of stating something that I mistakenly thought was too obvious to say!!

I do have an example: the time/altitude/impact fusing circuit in smart artillery shells. These things have to withstand both the acceleration and *change of accelleration* when the shell is fired and still work when the shell reached the target. I haven't done the calculation, but I vaguely remember the accelleration of artillery shells as between 1000 and 10,000 times the force of gravity. That's pretty brutal stuff.

Yep, no hand wiring in artillery shells. 8-)

[big_teee]

That's a great way of stating something that I mistakenly thought was too obvious to say!!

I do have an example: the time/altitude/impact fusing circuit in smart artillery shells. These things have to withstand both the acceleration and *change of accelleration* when the shell is fired and still work when the shell reached the target. I haven't done the calculation, but I vaguely remember the accelleration of artillery shells as between 1000 and 10,000 times the force of gravity. That's pretty brutal stuff.

Yep, no hand wiring in artillery shells. 8-)

I agree with what you said,but!
Just to be the Devils Advocate.
Handwiring would be too big and cumbersome.
Handwiring, and PTP would be good if you had to do maintenance on it.
Did you ever hear of anyone needing to work on a Artillery shell after it was fired (Unless they are trying to de-fuse it).
It would be too little too late!
If it don't go off they will probably just lobb another one.
Later,
Rock Steady!
Terry

[J M Fahey]

Well, I didn't refer exactly to that, but to 99.999% of *all* other military electronics.
¿Field-repairing?
Not much; if you have to repair it you are already dead.
At most, full module swap, at least full board swap, and that in preventive maintenance, as in avionics.
In the battlefield, forget it.
You'd better be sure it does not fail, period.
And there you find PCBs.
If anything, encapsulated for toughness, which precludes repair.

[Alex/Tubewonder]

"Military electronics" means absolutely nothing unless you identify the Mil Std given equipment is compliant with. Requirement/standards for ground use non-critical piece oof gear and airborne mission critical are world apart, then you have distinction between manned and unmanned mission. Nowadays defense systems are using more and more OTS gear and going away from strictly mil std compliant in favor of compliance with requirements for automotive safety electronics.
You will find a whole variety of assembly techniques in "approved for use by defense forces" but I doubt PTP hand wired qualifies even in desktop office equipment. It's multilayer SMT PCB assembled by robots in your reliable trusty USB memory stick - which you are not allowed to bring with you to the base. As for the proximity fuses in a modern artillery shell - I'd like to see an earthling do manual assembly on that. Multilayer ceramic on metal carrier board, all SMT and a several 100s pin flip chip DSP powerful enough to do the AXE-FX thing. Guitar amps and tubes are technological throwbacks, even with double sided boards and plated through holes. Haven't you noticed the diminishing availability of through hole components?