There is PCB and then there is PCB

[Enzo]

Leo turning over in his grave? Not likely.

No I don;t consider the pcb a "slap in the face" to Leo. He had nothing against them, He would have used them, his eyelet board was not some sort of anti-pcb statement. He didn't use them then precisely BECAUSE he was being cheap.


One could even make a case that the truest copy of the amp would be to make it the cheapest way possible.

[teemuk]

If Leo turns in his grave due to amps using printed circuit boards then please explain Music Man amps...

[Steve Conner]

That's not possible! They don't exist!

[R.G.]

The problem we face is that if a person ever once believes the "PCB is Evil" myth, they generally become a True Believer because they don't have the background to think about it on their own, and are afraid that the real cognoscenti will laugh at them if they ever accept that PCBs may not, after all, be Evil. So they become truly impervious to accepting anything else, or even considering the possibility.

"PCB is Evil" becomes a religion, and therfore immune to logic.

[kg]

pcb IS evil!

The toxicity of PCBs had been known since before its first commercial production through research done by producing companies themselves in the 1930s; however, these conclusions were dismissed as negligible.

The toxicity of PCBs to animals was first noticed in the 1970s, when emaciated seabird corpses with very high PCB body burdens washed up on beaches. Since seabirds may die far out at sea and still wash ashore, the true sources of the PCBs were unknown. Where they were found was not a reliable indicator of where they had died.

<snip>

PCBs also have shown toxic and mutagenic effects by interfering with hormones in the body. PCBs, depending on the specific congener, have been shown to both inhibit and imitate estradiol, the main sex hormone in females. Imitation of the estrogen compound can feed estrogen-dependent breast cancer cells, and possibly cause other cancers, such as uterine or cervical. Inhibition of estradiol can lead to serious developmental problems for both males and females, including sexual, skeletal, and mental development issues.

link

[Alex/Tubewonder]

One could even make a case that the truest copy of the amp would be to make it the cheapest way possible.

Imagine an amp vendor advertising his products as "manufactured in true adherence to Leo Fenders methods and principles using the cheapest surplus parts available and cheapest unskilled manual labor we could hire. However, locating all these bargain components is extremely time consuming and does reflect in the high price of our amps".
That will be the day.....

[g1]

pcb IS evil!



link

And thats why the power utility companies have removed all pcb's from their transformers and refitted them with ptp or turret boards. http://music-electronics-forum.com/i...ilies/wink.png

[R.G.]

pcb IS evil!

Oh, sure, that one...

'Course, the "organic is always good" crowd never lived near skunks or pigs.

And turkey buzzards are organic, too.

[dai h.]

The problem we face is that if a person ever once believes the "PCB is Evil" myth, they generally become a True Believer because they don't have the background to think about it on their own

right, (to be kind of blunt) how can anyone even discuss anything of significance if they have no inkling about the issues involved? If the goal is to replicate something "vintage exact" without considering cost, practicality, effect on operation, sonics, etc. (or with some sort of belief that even the tiniest deviation is an abomination against the amp gods or whatever) then that is more of a religious issue, not electronics.

About Leo, from what I understand he was a practical guy, not some mojo chaser. He would apparently buy cans of (tuna or whatever it was) to give as gifts to his employees and tell them to give the cans back after they had eaten the contents (so he could use them to store parts). Or look at something like the Strat with the interchangeable parts. He wasn't even a guitar player, if memory serves.

Just wonder if this "PCB is bad" again goes back to GW/Vintage Guitar mag and the "co-planar traces", etc. business.

[Alex/Tubewonder]

right, (to be kind of blunt) how can anyone even discuss anything of significance if they have no inkling about the issues involved?

That's simple. The less they know the stronger opinions they have and can not be bothered with facts. This applies universally from amps to politics, religions, cooking etc.
This is my opinion, if you don't like this one I have many more.

[Chuck H]

The "PCB=bad" mentality that persists has merit. It didn't happen for no reason. PCB tube amps simply break more often than eyelet board or turret board amps. As already expressed, this is because they're made as cheaply as possible. They also suffer more layout problem like hum, hiss and buzz noise. Are these gross generalizations that don't apply to all PCB amps? You bet. But they are generally true so the general opinion is representative of this.

I think the reason this is even a discussion today is that PCB amps are the norm and the uber gain monsters that have become so popular simply couldn't be made effectively or economically on eyelet or turret boards. I'd rather spend a week finding new and inventive ways to punch myself in the a$$h0!e before wiring up a Peavey 5150 on a turret board. So with respect to modern designs PCB construction is plainly superior. Are they less durable than the eyelet and turret board amps of yesteryear? Yup. Who could argue that? With PCB mounted pots, jacks and tube sockets, ribbon cable connections, thin board material, thin copper traces and layouts that often fail to take heat into consideration a higher failure rate is given. Are all PCB amps built this way? Nope, but most of them are.

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?

I'm not in the PCB=bad camp only because I'm aware of why current PCB amps suck and how one could be made that didn't. But to the lay-person the details are lost so the argument becomes moot. Because the general opinion regarding PCB amps is absolutely correct relative to the examples that have been demonstrated.

When you consider that nearly every eyelet or turret board amp that hasn't suffered a catastrophe is either still working or can be made to work with just a few component replacements I have to ask... What ratio of the PCB tube amps will still be that viable in fifty years?

Would "I" build a PCB amp? Sure, without hesitation or concearn for the stereotype. I'm just saying that the generalization exists for good reason so you can't really fault people for it.

[MWJB]

Well put Chuck.

[raiken]

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.

[R.G.]

It was well put Chuck. And I agree with you on almost all issues.

There is another reason that non-PCB style amps are viewed by the uninformed public as bad in general instead of poorly executed is that their techs tell them that PCB=bad. The techs do this because they (1) see the shortcomings (2) have no ability at all to fix the shortcomings (3) have to go to extra trouble and expense to do fixes on PCBs, as the techniques are not as simple and obvious and (4) can't do the lucrative mod business with nearly as much simplicity. Techs don't like them, for reasons that are valid inside their part of the world, but are not the entire world.

On this issue:

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?

the explanation is pretty simple: inertia. If you have a going concern, good rep, good sales and a trained staff producing the stuff as is, don't change it. This is a huge effect in businesses of all kinds after they are old enough to get set in their ways, and Fender was well and truly set in its ways, especially after the first whispers of "PCB is bad" got out. The lag in PCB use by Fender should get mentioned, but the reasons behind it should get explored too.

I get irritated by techno-myths and half truths. The PCB amp debate is constructed almost but not entirely out of these. If what you said was where these things got started, the discussions would be much shorter. But what usually gets trotted out is "... tiny inductance and capacitances between traces..." which is downright deceptive.

Good comment.

[R.G.]

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.

A number of things spring to mind.
1. Yep, easy removal of pots from PCB is a good thing. However this is very much subordinate to the bigger objective of why one is disconnecting the pot and PCB - presumably you're either replacing the pot or need to get at the PCB. If you're replacing the pot, a connector is not all that much simpler and easier than unsoldering three wires, and costs a lot more for good connectors. If you're removing the PCB, you have to be sure that just unplugging the pot does let you get the PCB out to work on it after the PCB is unplugged. I say this because I've seen situations where the pot body will still prevent removal of the PCB on other equipment. The mechanical design still has to be done with servicing in mind.
2. Good connectors cost money, and their reliability is necessarily less than the reliability of the uninterrupted strands of wire they replace. It's only worth the cost if the ease of working on the PCB is better, as in 1.
3. This still leaves the issue of servicing the PCB. Even if you can unplug all the pots and other stuff easily and remove the PCB easily, it's no help if you now have not been able to do all the debugging on the PCB down to only needing to remove/replace a component. If you have to do any debug with the PCB out of the box, you're still stuck with removing the pots from the panel to get them attached to the PCB that's now out of the box, too.

I went through exactly this train of thought in great detail before deciding that the right thing to do was to make the PCB nearly impossible to get out of the chassis - the Workhorse amp PCB is held in with sixteen screws! - but to make a removable panel and flying-wire controls so the controls (which are the vast majority of replacements) were trivial to replace without removing the PCB, but to make an access panel in the chassis so you could get at both sides of the PCB without ever removing it from the chassis, or in fact having to remove the pots, etc., to replace PCB parts.

So I think good connectors are great; I think no connector at all is better unless you simply have to have a connector. In most cases, the thinking about how to do without a connector is not complete enough.