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In Reply to: RE: In my direct-coupled 45 amp....some observations posted by drlowmu on March 11, 2017 at 13:56:36
Jeff, simply by observation and knowledge/experience in such things.
I see blobs on tube-socket terminals, blobs/balls else-ware, excessive solder wicking along wire, dull masses of solder on multiple-component terminations, and the terminations on the rats-nests of component leads, e.g. chassis RHS/above centreline is very poor practice and likely
to have dry-joints.
Attached is a solder joint inspection guide and also a pic showing good soldering work.
I hope you find this helpful.
What does your term " Chassis RHS / above centerline " mean, stand for ??
Off Topic :
The amp you choose to show us, is a very poor example. Oh, I will grant you, the soldering looks fine.
But this is the SET Forum, and there are HUGE and numerous mistakes, in that amp's LAY OUT. It is a good example of what NOT to do, in SET construction.
Only the unintiated would be impressed by that amp's underside photo. We have to LISTEN to a SET amp, and not LOOK at its wiring. Here, briefly, is what I see, as poor lay out and design practice, in this photo :
(a) Wires touching, indeed even bundled. One never has wires touching each other in SET lay out. In Push-Pull, there is inherently more bandwidth, so, one can do this. Not in SET. I see seven tie wraps, where there should be none. Wires should never touch, and cross at right angles, when necessary. NEVER would one bundle different wires together - into a group.
(b) The use of a component PC board. All this does, is ADD to lead lengths, which should be kept as SHORT as feasible in SET lay out. Point to point rules in SET lay out, with the lengths of the components REDUCE the needed lead lengths. 'Takes thought to position / envision it, but " form follows function".
(c) Non - optimized wire gauge choices. Throughout the entire amp. The red twisted pair on the far-left, AC leading to the power transformer's primary, could be more robust, advantageously. Observe the tiny wire gauge off of the power transformer's high voltage secondary ( red-black-red ). See how TINY that wire is ? This creates a loss in dynamics, peak instantaneous dynamics, which makes the amp no longer fun to listen to.
Also, we now know in 2017, complements of Jack Elliano and Dennis Fraker, not to twist the high voltage secondary leads of a SET amp together as shown, if we seek best sonics.
Getting back to my soldering: I agree with your observations. In the past, I have used large ( often 12 AWG ) wiring, and too-small of an iron. As of December 2016, I have gone to a new, more powerful soldering gun, which should give me what I need, heat and heat control-wise. I also stopped using mostly " one size fits all, 12 AWG wire ", so as to retain more of the highs in SET builds I do. I will read your provided tutorial, thank you, and proceed as I can. Regards,
The pics can be loaded into your favourite picture viewer and enlarged to get a better look.
A good guide on soldering, below.
The Weller website is worth a visit.
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