JTM 45 clone wiring question

[mikepukmel]

Most of the kits run most wiring to the bottom of the turret or eyelet. The mechanical connection isn't very good there.

Ive seen a few builds/kits like this, that run the wiring up through a hole near the eyelet/turret, then solder to the top of the board.

This puts an extra turn in the wire, where it has to go backwards, to the hole, down, then turn back towards the socket pin (or whatever the otehr end is soldered to).

Would these extra bends in the wiring cause more problems than having the wire run out the bottom of the turret or eyelet?



Thanks.
MP

[bob p]

No.

[soundmasterg]

A lot of the time where the wire comes from a socket, then goes into a hole in the bottom of the board then up the hole to the top and wraps around a turret, that is done for strain relief on the wire. If it is stranded wire it will be just fine....I wouldn't use solid core there though.

Greg

[bob p]

Solid core wire will probably be fine... until it breaks! It should be obvious that you shouldn't be straining a wire unnecessarily. Nothing good will come from that.

When Mike asked the question about whether the extra bends would cause more problems than having the wire run out of the bottom, I think he was asking the wrong question. Both of those methods are the wrong way to wire a turret. They both cause problems and are bad. They both introduce problems, and I don't think any one is worse than the other. The better question would have been to ask if the extra bends required to perform that crazy strain relief offer any advantage over the standard method of wrapping the wire around the turret. That answer would also be "No."

Unfortunately we live in an era where people learn by following others' examples, and many amateur amp builders don't follow good wiring techniques. The result is that people who don't have experience learn by emulating other DIY'ers techniques, which are often quite bad. There's been a trend in recent years to make amps that look visually appealing for showing them off on the internet, rather than focusing on function.

There are two ways to connect to a turret -- the right way and the wrong way. The right way is to wrap the wire tightly around the turret, making a strong mechanical connection, and then solder. Done. Mounting from above or below using the hole does not provide a strong solder-free connection and is wrong. Abusing the wire by knitting is also wrong. We recently discussed this in another thread, only a few days ago.

I don't understand why people knit wires through boards like that. It's never been part of the milspec wiring methods with turrets, and I don't remember seeing it in any commercially produced amps in the golden era. I think it's a somewhat new technique that's been invented in the era of DIY. If I had to guess, someone started doing it because he tugged too hard on his wires during assembly and broke them, and other people started copying his work.

I don't see any point in it. A wire that is soldered to a turret has a robust connection, and in use someone is going to have to break the wire to get it off. In service, it's quick and easy to remove. How much better does the connection need to be? Knitting the wire through the boards like that doesn't offer any added stability to the connection, it does stress the wire, and it adds to both assembly time and service time.

As Greg pointed out, the added bending back and forth is only likely to ruin the wire by breaking strand(s). To what end? To produce a visually appearing knitted look for anal-retentive amp gawkers? I just don't get it. Those sharp bends do produce a visually appealing result, but they do so at the expense of straining the wire and adding to manufacturing and repair time, without providing any real advantage to the circuit.

The oldest example that I can put my finger on that demonstrates this screwy knitting thing seems to have been the Bedrock amps. They've obtained legendary status, so people now emulate their quirky boards. If I were building one I wouldn't be using the knitting technique.

[soundmasterg]

Bob p, when you are talking about the knitting thing, are you talking about the areas I circled in red in the picture? If so I've seen that on old Marshalls among others...if its not that that the knitting is referring to, please enlighten.

Thanks,

Greg

[bob p]

Yes, I was referring to what you circled. I don't like amps that have wires "woven" like that. I've actually seen some far more extreme examples where the wires have 3 bends through the board instead of 2, as if that makes a better strain relief.

I used the photo of the Bedrock because I had that photo handy on my PC and it is literally the only amp that I have on-hand that has an example of that woven wiring. I'm sure there are lots of other amp makers who did that sort of thing that pre-dated the Bedrock. I didn't mean to imply that the Bedrock was the first amp to do it, just that it was the only example that I have on-hand. I was using the "put my finger on it" metaphor in the literal sense. I probably should have used "lay my hands on it" to be more precise.

I hadn't thought of Marshall doing that, but now that you mention it I seem to recall seeing photos of those old perfboard Marshalls that did tuck their wires into the perfboard like that. Thanks for pointing it out. I have to admit, I'd be at a loss to create a list of other amps that were like that. I might have known that once upon a time, but I've forgotten it by now. In light of my previous comments, I have to ask a question -- would Jim Marshall quality as a DIY copycat guy who was copying other peoples' amps and using bad building techniques? Dare I say it, I think so.

FWIW, what I refer to as the "Golden Age of Tubes" was ending by the time that Marshall was founded in 1962. In what I like to think of as the "Golden Era" era everything was built the way that Matchless builds their amps, with true PTP wiring (see the example of my old Cardwell below) or mil-spec turret board wiring. There wasn't any of that low cost eyelet board stuff that Fender made so popular to decrease manufacturing costs.

Which brings up a question -- can anyone point who invented the use of eyelet boards?

On a side note, I was looking at transistor history to get a better grasp on when transistors first began to ring the death knell for the vacuum tube. According to Wikipedia the first transistor manufacturing plant was opened in 1951, in Allentown PA, making germanium transistors. TI had created the first portable transistor radio by 1952 and the shirtpocket portable went into widespread production by 1955. Chrysler started putting Philco all-transistor radios in their cars that same year.

Many of us like to think of the 50s a being a big era in tubes because we use musical instrument electronics and the birth of Rock and Roll as our our reference points. That's when Fender underwent explosive growth. But by the mid-late 50s when Fender really got going strong, tubes were already on the way out. Dare I say it, Fender was using them because they were cheap and plentiful, and transistors were still quite expensive. From a tonal standpoint, I think we're quite lucky that Leo Fender was such a cheepskate.

[mikepukmel]

Thanks Bob, Greg. I think I didn't phrase the question correctly, but ended up getting the answer I was looking for.
The kit maker/seller, recommended (for bottom mounted wiring connections) to strip, then fold the wire back and crimp, then stuff that in the bottom of the turret. Which I now know (thanks you your many comments on this) is no good since there is basically no mechanical connection there, just a little bit of an interference fit.

The main part of the question, that wasn't phrased correctly, is: is it better to

A) drill a hole in the board, in back of the turret, run the wire up through that hole then do a nice wire wrap around the turrent and solder to the turret that way (which causes an extra turn the wire).

vs

B) just strip, tin and wrap the wire to the turret, then run the wire over the top of the board, bend, down to the chassis, then to the socket pins.

I was worried that with method A the electrons would get confused going around the corner like that

Seriously, with method A the wire would have a longer path along the chassis, with method B shorter path.


With eyelets, on another build, for bottom mounted wiring, I stripped and tinned a little longer section of wire, ran up through the eyelet, so I could crimp a little piece of the wire onto the eyelet to get a good mechanical connection. The problem here is that the component leads on the top of the board mostly did not have a good mechanical connection since some were inevitably dangling in one of the eyelet holes and not crimped around the eyelet.

[mikepukmel]

I got the feeling it was for appearance, but would there be a problem electrically, running the wiring to the top of the board, like in the following edits:



Using their method, the wiring hits the chassis, and has a longer piece of the wire running along the chassis, rather than in the air.

[bob p]

The reason that the old-style milspec wiring methods evolved the way that they did was because the military wanted robust products that could stand physical and environmental abuse; they were also intended to be easy to service in the field.

They were built rugged, extra-rugged. But even with extra-rugged construction the military repair techs still had to perform service on electronics in the field. It was not at all uncommon for the guy in the radio hut to have to service electronics that failed. Such was the nature of electronics in the era when tube gear got bounced around hard and caps didn't last as long as they do today.

Part of the reason that the milspec wiring evolved to require ONE component per turret was to facilitate removing one part without having to effect another part. In a "proper" design there's only one component mounted to a 2-rung turret, on the top rung, with any necessary connecting wire being mounted to the bottom rung. When a component failed this made it possible to remove the faulty component without effecting any other component, as those components were presumably working and needed to be left alone.

In the interest of making the repair process quick and as easy as possible, wires were not woven back and forth through holes. Doing that doesn't really add any significant strength to the connection, though it does make it a time-consuming PITB to remove the wire if that should be necessary.

I like milspec turret board constrution that isolates one component per turret. IMO that's the gold-standard for ease of servicability. I don't like the woven wire technique. It adds effort to servicing the amp. I also don't like Fender's sloppy eyelet board methods that stuff several component leads into one hole and then gang-solders them. That method is great when your concern is fast and cheap manufacturing, but it's not so great when it's time to service the amp. It's an asspain to have to deal with an eylet that has 4 different component leads and two wires running into it at the same time. Heating up the eyelet to remove a component subjects several different components to unnecessary thermal stress, so you've got to alligator clip everything, which makes access to the workspace even more difficult.

Most people selling amp kits optimize their designs for ease of build and visual appeal rather than ease of service. When I build my own amps, I plan on keeping them for my lifetime and servicing them myself, so I make an up-front effort to make my life easier further on down the road.

[Justin Thomas]

I guess I'm somewhere in the middle for eyelets; I don't mind 2 or maybe 3 parts in the same eyelet, but having 4 or 5 is a pain. Sometimes for a repair or mod you have to add more parts, or the lead thicknesses are different, or you have to bend every lead JUST right to make them all fit... Not so bad on an Ampeg, who used much bigger eyelets than Fender.

With turrets, I tried lacing a board. No more! I had to change some layout issues, and swap some component locations,and having to unlace all those wires was a real PITA. But I don't mind 2 components plus a wire on a turret; as long as that good mechanical connection can be had, I'm happy. I'm not really going for milspec. Another possibility with lacing all that wire: chafing the insulation during assembly, and in use from vibrations?

Justin

[bob p]

"lacing". that's the word I was looking for.

[Enzo]

Dare I say it, Fender was using them because they were cheap and plentiful, and transistors were still quite expensive

Not only were tubes cheap, they were very reliable, especially compared to the transistors of the era. Those were not reliable at all.

One transistor advantage was small size - an entire AM/FM radio was the size of two decks of cards stacked. There would be no advantage to Fender to fit a Deluxe into that tiny form factor.

[bob p]

There would be no advantage to Fender to fit a Deluxe into that tiny form factor.

Never say never. It only took Fender 50 more years to introduce the Mini-Twin.

[soundmasterg]

"lacing". that's the word I was looking for.

With the term "lacing" I think of vintage Sunns where they ran the lacing down a string of many wires such as a harness and the lacing ties it all together, much like zip ties today. I used to work at Rodgers Instruments (an organ company) and they did lacing the same way Sunn did it. They would have these platforms on the wall with nails in them and run their many colors of wire around the nails in whatever pattern they needed to run, along with the lacing string, and wrap the whole thing together and then stick it into their organs. It was a fascinating process to watch, but it is a lot of trouble to recreate it. I suppose you could say they are lacing the wire through the holes in the board as in your example bob p, but it isn't the approach I envision when someone says the term lacing in relation to wiring amps.

Mike, running the wire from a tube socket terminal along the chassis, then up through a hole in the board, then a quick bend to go to the turret and wrap around the turret properly isn't that bad. Some don't like it for the reasons that bob p mentioned, but it has been done many times. An engineer friend of mine who grew up in the 40's and 50's and was messing with electronics since age 9 told me that approach is for a strain relief purpose and was done in much equipment back in the day, including organs, consumer stuff, and some mil-spec stuff. I would have to hunt down some examples of mil-spec stuff with that approach however. I've used that approach myself when using turrets, and I have also run the wire from the socket up over the top edge of the board, and around a turret. I don't mind it going through a hole first as I can see where it adds strain relief, and while if you had to replace that wire, then yes it could be a PITA to do so, but wire is the least likely part to need replacement. Stranded wire can handle that bend ok without issue for decades, but solid core wire would likely fatigue and break sooner. I think it looks nicer in that it keeps the wires running close to the chassis and in a straight line, so it is helpful if you are going for the visual effect, especially if using PVC insulated wire, but cosmetics are rarely important in an amp unless you are trying to impress someone. I have some organ chassis at home but they are PTP for the most part. PTP is notoriously messy looking but very robust. It takes awhile to get the layout correct too, but once it is, it can be duplicated easily. I also have some old mil-spec stuff that is using turrets, but I would have to hunt around in my attic for it, and I don't have the time to do so right now as I am in the middle of a long term project fixing my daily driver and won't be done for several months still. If you are interested sometime this summer, remind me and I can get some pics of that stuff for you. One was a pressure tester of some sort that I've kept intact so I can refer to it as it was, and another was a tube powered Geiger counter with turret construction. The old Tektronics gear such as their tube scopes are a great example of stupendously good wiring techniques. The first time I saw some and the quality of components used in those my jaw dropped. I don't have any of those myself but there are pictures on the web that you could refer to.

Anyway, to summarize, for what you are doing, you could go either way and it would be fine. Just try to optimize your layout for quality of construction and keeping in mind good layout practices for electrical reasons, and don't take Fender's approach as gospel. After you get these clones built, try to build something of your own design from scratch, lay it out on paper before you build it, and you'll get a better idea of the trade-offs involved.

Greg

[bob p]

That Cardwell PA amp gut shot in Post # 6 shows the use of waxed string to bundle together wires using the method of "lacing" that was prominent from the 1920s to the 1950s.



The current PCB method of "lacing" is more like threading laces in a shoe.