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Jeffrey D. Medwin

Thinking of doing a Dynaco / DYNA PAS Preamp

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1 hour ago, codewritinfool said:

At the risk of sounding like I have a big head, I have certainly been soldering for at least 40 years.  For the last 30, I've been doing it professionally as part of my job.

Still, I learn something new almost every day, and I will never stop learning.

 

I maintain that a 350W soldering gun is WAY overkill for most of this work (if not all of it), and it can actually encourage cold joints by overheating followed by micro-movements until the phase temp is reached on the way down.  Not only that, but many of those items like tube sockets and RCA jacks can definitely be damaged by overheating. 

 

Just looked up your Alpha Reliacore 15 solder and it notes this in the technical bulletin available from this page https://alphaassembly.com/Products/Cored-Wire/Reliacore-15 :

  • Do not overheat as this causes an increase in the depth of the inter-metallic layer, which in turn weakens the joint.

Just my 2 cents.

None of that really matters.....................................

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Right, you do not overheat the tip or the joint.  Apply 120 VAC for just a matter of seconds.  I am totally aware of that.   Use of 0.62 diameter solder, fed in, helps cool the tip a bit too. 

 

There are advantages when using such a 325 Watt unit, that no one has yet acknowledged or thought about .

 

My audio mentor, Dennis Fraker, tells me he has used a WELLER D-550 for about 50 years now, for perhaps 90% of his amplifier work.   Dennis finds its use to be indespensable. 

 

Jeff 

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9 hours ago, Jeffrey D. Medwin said:

Right, you do not overheat the tip or the joint.  Apply 120 VAC for just a matter of seconds.  I am totally aware of that.   Use of 0.62 diameter solder, fed in, helps cool the tip a bit too. 

 

There are advantages when using such a 325 Watt unit, that no one has yet acknowledged or thought about .

 

My audio mentor, Dennis Fraker, tells me he has used a WELLER D-550 for about 50 years now, for perhaps 90% of his amplifier work.   Dennis finds its use to be indespensable. 

 

Jeff 

Jeff, you wont like this, but to solder correctly, you need consistency in both temperature and technique.  A trigger switch on a 300+ W gun that can no doubt glow cherry red won't give you temperature control.  On some of those joints, you'll no doubt overshoot it, and probably have.  I see joints with too much solder, joints that look cold, and plenty of joints that appear to have no mechanical connection when they could.  I know the photo is not of the best quality, but honestly I can see enough to know that I'd reject nearly every one of those joints. 

 

As far as the "advantages when using such a 325 Watt unit, that no one has yet acknowledged or thought about", I'd love to know what they are.  Maybe for repairing copper gutters, but probably zero for tube sockets and RCA connectors.  But what do I know?

 

I gave you reasons, including a technical note from the manufacturer of your solder of why excessive heat is a serious problem, yet because your mentor did it this way, it is somehow ok or even superior.  It isn't.  To play a card from your deck, it could be better.  I feel we could learn a lot from you in some ways, but I also feel you could learn from some people here  Why you seemingly dismiss attempts to help or critique, all in the name of / because of your mentor, is beyond me.  You aren't your mentor.  You can take his input as a base and expand and do better.  Wouldn't you WANT to?

 

But I have good news, too!  This isn't my preamp. It doesn't have to look or sound good to me, only to you.  With that, I wish you success and I sincerely hope that the preamp sounds amazing.

 

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99% of my connections are made with either a 25 watt or 35 watt pencil iron with a 1mm tip.  At the power supply company we never used anything over 40 watts.  
 

 

Maynard

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When soldering guns are outlawed, only outlaws will have soldering guns.

 

It’s a toss up between using a Bernz-O-Matic or a soldering gun for that delicate surface mount soldering of IC chips or capacitors.  Any tyro can get good results from a 35 watt pencil iron.  It takes a special talent to get blobs of solder using a torch.

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I do things differently than you and other fellows do . 

 

The last amp I built, the 2019 KT88 DC amp, had 8 AWG m22759/11 wire for its ground bus, and certain ground returns.  That 8 AWG is 133 strands of wire.  We four guys all clearly heard that result in Montana.   I loved it .  That 2019 effort easily set brand new audio performance standards, to my ears, as far as being able to render dynamic contrasting.  "High dynamic definition " I termed it.   Yes, I really liked it a lot fellas.   None of us in audio....... had ever heard that ..........before !!  

 

That particular power amp used GTO film caps, to the KT88s, caps capable of doing 1,500 AMPERES Peak Instantaneous. 

 

This preamp, breaks with tradition in its build, hopefully to get similar dynamic contrasting results as the 2019 amplifier's build !! 

 

I really won't know the preamp result fellas, .............until its up and running .

 

I have my own vision with this design.  After hearing that particular KT88 amp, this preamp with similar design by me applied, is certainly not destined to become your typical tube phono preamp !! 

 

Jeff 

 

609976695_P1010076dated.thumb.jpg.b5ab519d2433fc13dbd37c0c17922ddd.jpg

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2 hours ago, codewritinfool said:

Jeff, you wont like this, but to solder correctly, you need consistency in both temperature and technique.  A trigger switch on a 300+ W gun that can no doubt glow cherry red won't give you temperature control.  On some of those joints, you'll no doubt overshoot it, and probably have.  I see joints with too much solder, joints that look cold, and plenty of joints that appear to have no mechanical connection when they could.  I know the photo is not of the best quality, but honestly I can see enough to know that I'd reject nearly every one of those joints. 

 

As far as the "advantages when using such a 325 Watt unit, that no one has yet acknowledged or thought about", I'd love to know what they are.  Maybe for repairing copper gutters, but probably zero for tube sockets and RCA connectors.  But what do I know?

 

I gave you reasons, including a technical note from the manufacturer of your solder of why excessive heat is a serious problem, yet because your mentor did it this way, it is somehow ok or even superior.  It isn't.  To play a card from your deck, it could be better.  I feel we could learn a lot from you in some ways, but I also feel you could learn from some people here  Why you seemingly dismiss attempts to help or critique, all in the name of / because of your mentor, is beyond me.  You aren't your mentor.  You can take his input as a base and expand and do better.  Wouldn't you WANT to?

 

But I have good news, too!  This isn't my preamp. It doesn't have to look or sound good to me, only to you.  With that, I wish you success and I sincerely hope that the preamp sounds amazing.

 

 

Thanks for your good wishes, and your positive intent.  Appreciated.  Since my Mentor is known to produce world class equipment, over several decades to me now,  to good mention, I tend to follow him.   Realize also please, I've never seen nor heard your audio work.

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56 minutes ago, DizRotus said:

surface mount soldering of IC chips or capacitors.

 

ya need a magnifier to see SMDs well enough to solder. I've tried to put components the size of a pin head back after they popped off the board... Rotsa ruck. These were R/C control boards. Not really built for.. well, in R/C there is a saying

"If you build a helicopter that is crash-proof, it will be too heavy to fly"    the weight vs durability trade-off

 

they use a technique called "wave soldering" to do surface mount 

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20 minutes ago, grasshopper said:

they use a technique called "wave soldering" to do surface mount 

 

G. Marsh, the builder of my “Wiener” TPA3118 class-D chip amp, used a toaster oven to solder all surface mount components at once. Is that anything like “wave soldering?”

 

I’ve successfully replaced the capacitors in an Onkyo AVR with the HDMI issue.  They had to be done as surface mounts using a soldering pencil.

 

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I can only speak to through-hole wave soldering, but it's basically running a populated PCB on a conveyor through a "wave" of solder. The conveyor is adjusted so that flowing solder contacts the bottom of the board, and wicks up the through-holes. Masking is applied to any lands/through-holes that are to be populated by hand later on. That's the old way, I assume SMT must have some process similarities.

 

Solder training can be helpful. I had to be certified annually to IPC-A-610 when I worked on the bench in a manufacturing environment, and found it to be very useful. It may change how you execute your solder work for the better.

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07-14-2020                               PROGRESS PHOTOS

 

 

 

 

 

Installed LINE IN wiring, ......................................................RCA Input Jacks to Source  Selector Switch and  Ground Buss Bars.

 

1516511748_7-14-20A.thumb.jpg.26e6457e21bc40437f83efecd211a715.jpg

 

279241693_7-14-20B.thumb.jpg.bca32477de52f70bfd024e99c5cefda2.jpg

 

Notice the short wire lead lengths, compared to other preamps you have seen ??  .  Wire is Insulated Wonder Wire, available from Michael Percy. 

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