Rebuilding my kit - shielded twisted pair options, and a film cap [resolved]

twofires · 55879

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Offline Doc B.

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Offline twofires

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https://forum.bottlehead.com/index.php?topic=8888.0

I have a dremel and a tube of Autosol so I can definitely make this happen. Thanks!

Also no pops so far today with the GE tubes. I'm not willing to call it yet, but I'm starting to move towards cautious optimism.

Simon N


Offline Paul Birkeland

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It is completely possible that running with the conductive flux could do some weird stuff to the tubes themselves, though the kits I've fixed with these issues haven't shown tube damage (that I can remember at least).

Paul "PB" Birkeland

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Offline twofires

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It is completely possible that running with the conductive flux could do some weird stuff to the tubes themselves, though the kits I've fixed with these issues haven't shown tube damage (that I can remember at least).

For sure. I'm keeping the Sylvania aside until I'm satisfied the amp is issue-free with other tubes, at which point I'll clean them and see if they behave. They're in the '?' box at the moment. It would be nice if they can be salvaged, as unlike the GE and RCA I've received from the folks at Vacuum Tubes Inc., the glowy bits on the Sylvania face forward when installed in the SEX. Which is just nicer to look at.

That said, the GE seem to be really nicely constructed.

Just as an aside, if I'm not the only dummy to fall victim to this water-soluble flux issue, I wonder if it's worth adding a disclaimer about it under the one about plumber's solder (unless it's there somewhere and I missed it). This really has been an ordeal I'd like to help others avoid, however much of a edge case it might be. For reference, I got to the idea of using ChipQuik by hearing younger folks working exclusively with SMD PCBs talk about it. It never occurred to me that dropping a PCB into an ultrasonic cleaner is a part of their process, and a lot easier than cleaning a point to point kit. There's also a lot of fear-mongering about rosin solder and corrosion out there, and it took me a long time to realise that RMA solder manufacturers will put it right there in the datasheet that cleaning is unnecessary outside of specialist industry (which audio ain't).

I'm also wondering now whether the pin cleaning method linked above might also work for prepping the lower eyelets of those Keystone 8 terminal tagstrips I had the trouble with that drove me to use extra flux in the first place. I might have to test that with a spare tagstrip at some point.

Edit: That's in no way an attempt to blame you folks for my mistake by the way - that's 100% on me.
« Last Edit: October 28, 2024, 07:46:37 PM by twofires »

Simon N


Offline Paul Birkeland

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The disclaimer is on page 7 and specifies that rosin core solder is to be used and nothing else or it will ruin your kit. 


Paul "PB" Birkeland

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Offline Doc B.

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There is also a video dedicated to soldering techniques specific to our kits on our youtube channel. The newer manuals include a link to that video.

https://youtu.be/EN16Pi7pcfk?si=x1-9aWg8UfsTL3lG

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline twofires

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There is also a video dedicated to soldering techniques specific to our kits on our youtube channel. The newer manuals include a link to that video.

https://youtu.be/EN16Pi7pcfk?si=x1-9aWg8UfsTL3lG

Rewatching I can see that you do mention flux as part of your disclaimer about plumbing solder "and we are not talking about any kinds of additional flux that you would apply, stay away from those". I missed that, and that's on me.

The disclaimer is on page 7 and specifies that rosin core solder is to be used and nothing else or it will ruin your kit. 

To be fair, I did use rosin core solder - it was the additional (non-rosin) flux that did me in. In retrospect it's obvious that 'flux is the stuff that is in the solder, and if I say only rosin core solder I mean only rosin flux'. I didn't know enough to make that connection at the time - if you flush all the knowledge and experience from your mind and read the warning on page 7 with the question "can I use this water soluble flux?" in your head, it doesn't rule it out. It also doesn't rule out eating your own shoes, so I am saying this understanding that there are reasonable limits to the warnings a customer should expect. I'm open to the possibility that I'm just especially dense. It probably doesn't help that there are quite a few people out there using 'flux' and 'rosin' interchangeably, making it harder for the novice the understand that there is a difference.

What I should have done, when I had trouble getting a good joint on H2U-H7U, was come here and talk it through. Lesson learned.

I don't know if it's helpful, but the warnings that stick out in my mind are the ones on page 20 because they spell out the consequences of using plumbing or lead free solder.

Simon N


Offline Paul Birkeland

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Water soluble flux that's conductive is plumbing flux.

Paul "PB" Birkeland

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Offline twofires

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Water soluble flux that's conductive is plumbing flux.

Hang on a sec. I've clearly got this all confused, as it definitely wasn't plumbing stuff...

*checks old Mouser invoices*

This is the stuff I used: https://www.mouser.com/datasheet/2/73/SMD491_10M-2511050.pdf

Now I'm reading the datasheet and it says it's non-conductive, so I guess it got into the socket and was preventing pins from conducting, rather than shorting them?

I think I understand now what's happened. Clearly edge-case stuff outside the scope of what you'd need to warn about. My apologies. I feel pretty thick right now.

Simon N


Offline Paul Birkeland

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That stuff is just generally a bad product.  It is minimally conductive for low voltage circuits but not at all OK for high voltage products.  Still, this is a product for surface mount soldering of low voltage circuitry.
https://www.reddit.com/r/electronics/comments/p9ajhi/til_that_flux_is_quite_conductive/

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline twofires

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Yeah, for sure. Trying to cast my mind back to when I bought it, I think the fact it was tacky was about all that made me pick it. I completely ignored the SMD part.

I have made so many bad choices in building this amp I might actually make a video for future kit builders. Real 'Don't Do What Donny Don't Does' sort of stuff.

That said, I haven't heard another pop since I swapped those tubes over, so I think I'm finally winning.

Thanks again to all of you for your patience and understanding.

Simon N


Offline 2wo

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I have used that very flux In SMD work and it works very well for that purpose. It never would have occurred to me that it could be an issue in point to point work.

I Don't understand Where this, "need extra flux" came from, must be one of those "Internet things"... John

John S.


Offline twofires

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I have used that very flux In SMD work and it works very well for that purpose. It never would have occurred to me that it could be an issue in point to point work.

I Don't understand Where this, "need extra flux" came from, must be one of those "Internet things"... John

It wasn't until Paul pointed it out that I realised , yeah, 400V across a couple hundred ohms is very different to 4V across the same resistance.

As for the extra flux thing, it came about due to having a lot of trouble with the joints at H2U-H7U. It was in part due to those Keystone strips being a bit oxidised vs the other kind, but in pondering all of this I think I know what actually happened. In an effort to get the diodes in those positions neat and straight (because I wanted to do a 'good job'), I spent a fair bit of time bending the legs just so. What I wasn't thinking about was that the jaunty angle they sit on in the manual is actually pushing the legs into the eyelets with enough force for a good mechanical connection - I traded that away needlessly, for a straight row of diodes. The legs still touched the eyelets, but not well enough to transfer heat sufficient to overcome the oxidation issue. Solder would glob onto the legs of the diodes, and the narrow back of the eyelet, but not the front.

That's not a common problem for PCB and SMD work, where the bulk on internet wisdom is focused, and so most googling around 'how do I get this joint to take' returns results about flux and adding more of it.

It all seems very silly now, but somehow it all appeared perfectly reasonable to me at the time. I suppose this is the downside of doing this stuff in isolation with only the internet for advice, versus what I imagine the old days were like. I imagine back then your mate would pop around, take one look at what you were trying to do, and quickly set you straight. And then you'd repay them with beer.

Simon N


Offline 2wo

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I agree with your take on it.

It's easier to goggle knowledge than experience.


John S.


Offline Doc B.

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Yup, Google is a two edged sword. In the old days the solution was to find an Elmer. An Elmer was typically an old ham operator or electronic engineer (or both) who would advise you and show you the tricks. I've had many, most notably John "Buddha" Camille back in the 90s. Finding an Elmer took some initiative and because of this I suspect a lot of electronics kits purchased by tyros back in the 50s and 60s never got put together to completion. Back in the "golden age" Dynaco supposedly employed two full time guys who fixed kits that were sent in for repairs. That doesn't sound like a very high completion success rate - except for the repair techs. I also recall a friend taking a lot of the Heathkits he built into the tech at Zack Electronics in San Francisco to get them working back in the 70s.

If you came from that pre-www era like me the potential of the internet as a resource for developing new skills seemed like magic. And I was excited to use it as a resource for our customers, to empower them to complete a kit build successfully. That's why we had one of the first 25 thousand websites on the planet in 1997 (there are around 200 million these days) and one of the first electronics tech support forums in 1999. But just like anything in life you have to consider the source of the information you receive. These days I spend more time SMH and saying "why are you doing it that way?" when I watch the plethora of DIY videos on any subject on youtube than saying "wow, makes sense". Sometimes the videos by a pro may seem less entertaining and more serious but chances are good that you will get better info than from the "relatable" guy who titles his video "can we build this kit without destroying the solar system?" You really have to weigh the value of what you are watching with this stuff if you plan to use the info given. I vinyl wrapped a car for the first time this year and watched a zillion videos before. Most of them had educational value as a way NOT to do it, and the best info seemed to come from shops that were very successful rather than guys who were amateurs or starting out in the business.

I find myself pretty dry and boring in the video we made about soldering one of our kits. But your gear will be put together successfully if you use the info we give on point to point soldering technique. It's, unfortunately, a dying art form like a lot of things that were common DIY skills in the past.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.