Bottlehead Forum
Bottlehead Kits => S.E.X. Kit => Topic started by: twofires on September 25, 2024, 11:16:07 PM
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Hi Bottleheads,
So, my SEX amp has an intermittent popping issue (through headphones and speakers) that is maybe once every hour of use, and is concerning enough that I'm just going to strip the whole thing down and start again. There was a water-soluble flux issue during the build, brought about by my inexperience, that may be causing intermittent shorts, and so I just want to clean the whole thing out, try again, and hope the transformers and chokes are okay.
Anyway, I'm able to account for pretty much every part, except for the shielded twisted pair power wiring w/drain wire. The closest I've found that isn't AUD$400 for a massive reel is this stuff:
https://catalog.belden.com/techdata/EN/8450_techdata.pdf (https://catalog.belden.com/techdata/EN/8450_techdata.pdf)
It's about AUD$95 for a 15m cut shipped from the US, but I can live with that.
The tech data says it's rated to 300V, but as there's around 400V flying around inside the amp, I thought I'd check if this is an appropriate substitute.
Also it seems 1.5uF 630V+ PP film caps are hard to find outside of this general purpose Vishay:
https://au.mouser.com/ProductDetail/Vishay-Roederstein/MKP1839515084HQ?qs=5W%252BGeepUzoc9cdLA%252BylF3g%3D%3D (https://au.mouser.com/ProductDetail/Vishay-Roederstein/MKP1839515084HQ?qs=5W%252BGeepUzoc9cdLA%252BylF3g%3D%3D)
and a rather chunky and expensive Mundorf M-Cap Supreme:
https://www.soundlabsgroup.com.au/p/Mundorf-MCAP-Supreme-1u5-600V-Capacitor.html (https://www.soundlabsgroup.com.au/p/Mundorf-MCAP-Supreme-1u5-600V-Capacitor.html)
Is there any leeway with capacitance with that cap? What would raising it to 2uF do to the circuit?
Thanks in advance,
Simon
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Also it seems 1.5uF 630V+ PP film caps are hard to find outside of this general purpose Vishay:
https://au.mouser.com/ProductDetail/Vishay-Roederstein/MKP1839515084HQ?qs=5W%252BGeepUzoc9cdLA%252BylF3g%3D%3D (https://au.mouser.com/ProductDetail/Vishay-Roederstein/MKP1839515084HQ?qs=5W%252BGeepUzoc9cdLA%252BylF3g%3D%3D)
and a rather chunky and expensive Mundorf M-Cap Supreme:
https://www.soundlabsgroup.com.au/p/Mundorf-MCAP-Supreme-1u5-600V-Capacitor.html (https://www.soundlabsgroup.com.au/p/Mundorf-MCAP-Supreme-1u5-600V-Capacitor.html)
Is there any leeway with capacitance with that cap? What would raising it to 2uF do to the circuit?
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There is considerable leeway. The calculated value is 1.25uF, and anything between half that and twice that is acceptable. Larger values give slightly deeper bass with slightly less power on the deepest bass - neither is likely to be audible in ordinary use.
I'll defer to PB on the wire. You can also ask at replacmentparts <at> bottlehead.com for the cable and capacitor. Mention this thread when you email.
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That wire will do the job, the STP in the SEX amp doesn't carry much voltage.
Water soluble flux can ruin a build, but I have brought kits back to life by running them through a dishwasher cycle without soap.
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There is considerable leeway. The calculated value is 1.25uF, and anything between half that and twice that is acceptable. Larger values give slightly deeper bass with slightly less power on the deepest bass - neither is likely to be audible in ordinary use.
I'll defer to PB on the wire. You can also ask at replacmentparts <at> bottlehead.com for the cable and capacitor. Mention this thread when you email.
Thank you for that, Paul. It seems that the options for caps increase a fair bit if 2uF is acceptable, so I might go with that. I'll keep the replacement parts thing in mind, too. It all comes down to shipping in the end.
That wire will do the job, the STP in the SEX amp doesn't carry much voltage.
Water soluble flux can ruin a build, but I have brought kits back to life by running them through a dishwasher cycle without soap.
Excellent. Thanks for that PB. Finding an equivalent wire down here in Oz is pretty much impossible - too small a market for many specialty products I guess.
Re the flux: yeah it was a lesson learned, for sure. The Keystone terminal strips were a bit oxidised and my wimpy no-clean solder didn't have strong enough flux to cut through, so I unwittingly added the water-soluble stuff. It worked in the short term, but then clagged everywhere, hid in places, and trapped forgotten lead cutoffs. The total immediate damage on first power on was one power resistor, a Dayton cap, and an RCA tube. It took out another tube before I got it clean enough to function, but it's not ideal and I'm looking forward to a clean slate. I have better RMA solder these days.
I've seen you mention the dishwasher thing before - how does that work exactly? Are we talking disassembling and desoldering and washing the hardware and passives? Or you just bung the whole thing in minus the wooden base and tubes? I always assumed that would destroy switches and pots and transformers and such.
I'm basically planning to bin everything but the transformers, chokes, tubes, base, top plate and mounting hardware, and replace the rest to rule out gremlins. This still leaves the possibility that I damaged the PT-10 when I (very gently) sanded the chickenwire marks & coating off the sides and repainted. I recall you folks telling someone this may damage the transformer - something about eddy currents? The transformer did get quite hot in operation, and there was a definite hum, but it also seems like these things are normal within certain limits. So maybe it's fine? I dunno if there's a test with a scope or meter or something to confirm.
Anyway, I can try working with the iron I have first - if I have to build it a third time I'm sure I'll have it down pat by then. :)
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Or you just bung the whole thing in minus the wooden base and tubes?
Yes, that will do it, and definitely run a dry cycle.
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I opted for the full teardown in the end. That water soluble flux (ChipQuik) was crusted on everywhere, in spite of my best cleaning efforts while the amp was whole. It's a miracle the amp worked at all in that condition. When I was desoldering leads and removing excess solder from the chokes and transformers I could still smell the stuff cooking off - a distinctive black bean stir fry sort of smell.
See the attached for a an example of how the flux caked on to a tag strip, and the horrified look on my now depopulated top plate.
Other than having to bin a lot of components, the transformers and chokes came out okay. The only minor note is that terminal 18 on the PT-10 is a little bit wiggly - I'm wondering if there's a high temp non-corrosive glue I can use to get it rock solid again. Probably not a concern but seeing as I have the thing apart anyway...
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You can use a little epoxy to secure the plastic piece of the bobbin that holds that power transformer terminal.
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You can use a little epoxy to secure the plastic piece of the bobbin that holds that power transformer terminal.
Thanks for that Paul. Something like JBWeld HighHeat? It says it can withstand up to about 290C. My iron is set to 370C at the tip, but I figure the point of contact should be significantly cooler than that unless I'm dwelling far too long. Unless you recommend epoxy only after soldering? It might be a bit trickier to glue up in situ but not impossible.
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I wouldn't even worry about buying high temp products, the heat will only be there for a handful of seconds.
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And it's epoxied. That stuff (JB Weld) actually goes on really well if you have something small enough to apply it. I used one of those tiny soldering tool spatula things and iced around the base of terminal like it was a tiny cupcake. Left to cure for 24hrs and now it's rock solid. I'm happy with that.
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Ah, JB WELD, let me tell you about the time my shift lever snapped off in West Virginia, or the crack in the mower or the grill handle or...
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Ah, JB WELD, let me tell you about the time my shift lever snapped off in West Virginia, or the crack in the mower or the grill handle or...
It does seem like supremely useful stuff. I especially like that it doesn't stink to hell like Araldite does.
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WE ARE BACK! I am an extremely happy camper. 8)
The best thing is, something I did this time around has dramatically reduced my transformer hum . Possibly that spot of JB Weld on PT terminal 18.
I added #10 stud solder tags (Keystone 4704) to the speaker terminals (between the two supplied nuts) to make soldering and speaker terminal replacement much easier. Removing the old ones when I stripped the amp taught me that is not a fun exercise when solder has clagged up the threads.
Also note that 400V .1uf Orange Drops (715P10454LD3) fit the layout just fine if you can't get the Daytons, although you need to bend the A side cap up just slightly once soldered to clear the lip of the base.
Voltages were a bit high (+6% or so), but that's likely due to Australian AC being nominal 230VAC, but usually 240VAC during non-peak times. I wired for 225-235 figuring it wouldn't hurt anything.
Now to run it in for a couple of weeks before chucking the C4S back into the mix.
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Sigh.
Might have to 'UN-resolve this' - I'm still getting the pop issue.
Every component is new other than the transformers and chokes, and the tubes, but after about 40 minutes of run time I occasionally get a loud pop in one channel or other. Just one loud pop, like someone flicked your headphone cup, then nothing. Like there's a slow and silent build up of energy that releases all at once.
Yesterday it was the right channel with Focal Clear headphones (55ohm 104dB), today it was the left channel with Fostex TH-X00 (25ohm 94dB). The random channel makes me think it's not the tubes, but I have a couple of spare pairs coming in the mail next week.
I'm very confident of all the joints and the wiring, and my mains are 236VAC at the moment so I figure I'm not over or under. My only other guess is my initial one, that either I damaged the power transformer when I removed some chicken wire marks on the side by lightly hand sanding before repainting, or, more likely, when I smoked one of the 3w resistors on my initial build due to the water soluble flux shorting things.
I'll try with new tubes, but failing that I might have to source a new transformer from you, unless you have other theories.
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Only other thing I can think is that there's something about my DAC it doesn't like. I'll try another source, too.
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Oddly enough, that is a noise I would expect from conductive flux arcing over periodically. I'd leave the amp on for a very extended period (10 days or so) to see if anything more concrete develops.
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Interesting. Pretty much the only place left that flux could be is inside the transformer itself, impregnated into the material around the guts of it. That could've happened when I tried to clean the initial build with isopropyl back before the rebuild. That mixture (ChipQuik and isopropyl) may have dripped in there and dried. I'm not sure that's the case, though, as I can't see any of the chalky residue that was everywhere else. That said, everything else is either new, or very, very thoroughly scrubbed, so if it's flux, the power transformer is likely where it is.
When you say something "more concrete", what kind of behaviour are we talking? I doubt I can leave it on that long as I can't keep an eye on it consistently. I should probably be close by if something dramatic could happen.
I'll see what can be done, though.
Strangely, when I bypassed my DAC (a Topping D90) and plugged the amp directly into the headphone out on my computer (so using the soundcard), I listened to music for another 2.5hrs without any pops. Hardly definitive, but, is there anything about a DAC with an internal switching supply that might cause issues like that popping? Doubtful I know, but I'm keen to rule it out.
Also hoping to rule out the thing with the sanding the sides of the power transformer - could sanding the coating off the sides and then blasting it with paint have caused some issues?
One other thing - it seems to be more common with more sensitive headphones than with speakers or high impedance headphones. That may be some other factor at play, but if it provides any clues...
Thanks for all your help.
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I seriously doubt that this will end up being the transformer.
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I seriously doubt that this will end up being the transformer.
That's certainly my hope, but I have to admit I'm stumped.
I realised the other component I kept was the Alps Pot I used, although I don't remember using any ChipQuik on that, and I was under the impression those are sealed anyway. I also cleaned and reflowed that breakout board pretty thoroughly.
At this point I'm holding out hope for either bad tube(s) or weird input issue, unlikely as those are.
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Quick question while I'm running this amp for extended periods:
Is it normal for the amp to have a bit of a fit when you unplug headphones to switch to the attached speakers?
I was listening with headphones, and needed to step away, but wanted to keep listening for issues, so I paused the music and pulled the headphones from the socket. This resulted in 'POPOPOP POP CRACKLE POP... POP... ... ... POP... ... ... ... POPOP' for at least 10 seconds from the speakers (mainly the left). When it seemed like it wasn't going to calm down easily, I turned the amp off (another single POP), waited a couple minutes and then turned in back on. No issues after that.
Is that an expected response to me doing something silly (like changing load from 55ohms to 8 ohms by pulling a jack out of a TRS socket), or is it unusual and indicative of some other issue?
This is the socket I used: https://www.digikey.com.au/en/products/detail/cliff-electronic-components-ltd/CL1323A/13663625
Note that powering it up again with headphones connected and then tapping on the headphone jack and twisting it in the socket didn't produce any pops, and all the joints look solid.
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Sure sounds like a bad or missing solder joint.
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That sounds a lot more like a soldering issue than a flux issue.
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Okay. If that's the case I'm honestly sorry to be taking up your time with the most obvious problem. I really did try to double check everything. Any hints on where I could look based on the symptoms, or how I might diagnose? Everything really does look intact to me on the surface (I will visually inspect again though). Should I be powering it on upside down and tapping things with a chopstick or similar?
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I would start by reflowing all of the headphone jack and speaker binding post connections as well as the output transformer secondary connections.
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Thank you. Will do.
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So I reflowed the headphone jack (all), the OT secondaries (all), speaker terminals (all), H1 & H8, and both sides of both output caps. The headphone plug/unplug pops are now completely gone, and it feels like maybe the noise floor is a touch lower.
All those joints looked pretty shiny already (definitely nothing like the 'bad' examples in the manual) so I'm at a loss as to which it was that resolved it, but I'm also very happy to eat humble pie and nail that one down.
I'm unsure if this issue is the same as the once-hourly pop, so I'll continue to monitor for that and post back if I either hear it again, or feel it's gone completely. It would be wonderful (if embarrassing) if they were the same issue, and unrelated to the problem with the original build. Faulty reasoning on my part I suppose, trying to connect unrelated dots.
Thank you both for your help.
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Nope. The random popping persists. :-\ This time I turned the amp on and just sat here with the headphones on and no music playing while typing an email. Maybe 10 minutes in, with no movement or change of any kind, the left channel went 'pop'.
I just received a few extra sets of tubes today, so I'll see if I have any more luck with them.
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You might want to poke around in the circuit with a wooden chopstick to see if you can actuate the popping by moving anything.
I'd also use very, very hot water to clean off the tube pins on the tubes that were originally used in the amp, as there may be some flux remaining there.
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Is it possible that this popping comes from outside the amp itself? Easy to check - remove all inputs and turn the volume all the way down and see if it stops.
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So the GE tubes I swapped in didn't give me any grief for the hour I was able to listen last night, although that's not enough time to be certain, and I'm also mindful that reseating tubes is a confounding variable every time I do it. I'll listen more today.
You might want to poke around in the circuit with a wooden chopstick to see if you can actuate the popping by moving anything.
I'd also use very, very hot water to clean off the tube pins on the tubes that were originally used in the amp, as there may be some flux remaining there.
Flux on the pins of the old Sylvania tubes is certainly possible. I remember that back during the first build there was definitely flux on them - jostling the tubes before I realised that elicited a thunderous sound like a box of heavy books being kicked down a flight of carpeted stairs. This time around I gave them a bit of a clean with iso but it may not have been sufficient. I'll try the water thing. Would standing them in 80C water for a bit and then taking to them with a (clean) toothbrush do the job? I'm hoping they haven't contaminated the new sockets - if I have to pull the thing apart to replace those I might need to go swear loudly for a while. I don't think it's likely, though. Jostling the new GE tubes did nothing at all on the B side, and only elicited the slightest of susurrus noises I would expect is normal on the A side. Definitely no pops.
Is it possible that this popping comes from outside the amp itself? Easy to check - remove all inputs and turn the volume all the way down and see if it stops.
I did have that thought (earlier in this thread) about my DAC. It has an internal switching supply and I understand that sometimes those can do unexpected things re: ground. I wasn't sure if having nothing on the inputs was good for the amp but if it's fine I'll certainly give it a try.
I think my plan of attack will be:
- Keep listening with the GE tubes. If there are still pops...
- Remove the input and keep listening. If there are still pops after that...
- Poke with a chopstick until pops happen.
Thanks again everyone. We're gonna figure it out eventually!
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https://forum.bottlehead.com/index.php?topic=8888.0 (https://forum.bottlehead.com/index.php?topic=8888.0)
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https://forum.bottlehead.com/index.php?topic=8888.0 (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.
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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).
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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.
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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.
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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 (https://youtu.be/EN16Pi7pcfk?si=x1-9aWg8UfsTL3lG)
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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 (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.
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Water soluble flux that's conductive is plumbing flux.
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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.
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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/ (https://www.reddit.com/r/electronics/comments/p9ajhi/til_that_flux_is_quite_conductive/)
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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.
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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
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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.
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I agree with your take on it.
It's easier to goggle knowledge than experience.
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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.