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

[twofires]

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.

 

[2wo]

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

 

[twofires]

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.

 

[2wo]

I agree with your take on it.

It's easier to goggle knowledge than experience.

 

[Doc B]

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.