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In Reply to: RE: I basically McShaned it and it worked very well. posted by Michael Samra on May 14, 2017 at 20:30:13
Thanks Mike, I changed diodes and added capacitance to PS, stepped attenuator, bypassed tone controls, gold plated connectors, better grid resistors, worked on RIAA curve, tried Vitamin Q's for the coupling caps, but ended up with Mundorf's. I didn't try K40Y's, didn't know they made 1uF at higher voltages. Just wish I had a stock unit to compare to.
What were your impressions of the sound? I didn't get to where I wanted to be and moved on.
Follow Ups:
Hi,
I'm finally going to start a Dyna Mark 3 rebuild. This project started in 1984 when the UPS delivered them on the hottest day of our planet to me on the 4th floor,C.O.D., and I didn't have the money on me. They were in one box. You could see it in his face and eyes he was about ready to swing at me! The saga continued......
I was finally ready to build when I saw the Blueglow video. I had one more chore to finish, paint the bells on the transformers. So as complete as this guy Mark's videos I have to ask you pros 2 questions I have that maybe were not addressed as much.
1. Years ago when I took the amps apart I nipped the transformer lead wires close to the tube sockets off without thinking I should of de-soldered as I could run out of lead length when re building them.I know the rule is before soldering you should have a good physical connection. If I have to extend some transformer wire leads what would be the best physical way to connect those 2 wires before solder and shrink tubing....side by side(abutted), hook into hook ends and crimp, or twisted?
2. When it came time to strip teflon wires he had a fancy heated wire stripper that seems a little costly for me to get. Could I just heat up my little Radio Shack strippers and use a kitchen mitt glove and the flame of my gas stove? I bought some Teflon wire from Dynaparts....thought you guys might have some stripping tips as I heard most of you hang out in stripper bars?.....
If they put those Blueglow videos on major TV networks do you think the ratings would be off the charts or would people think it's to nerdy and switch over to the Big Bang show.....thanks for any help.....Mark K.
1. My experience it depends on the wire, but basically either way is fine and yes it is good to have a good physical connection, but solder does really well. And if you can find them, vintage equipment uses a lot of terminal strips that screw to the chassis.
http://www.ebay.com/itm/10-Pieces-TS-3-Terminal-Strip-2-Lug-Bakelite-1-Grounded-2-Ungrounded-375-/252675460503?hash=item3ad4a18d97:g:RJEAAOSwA3dYSzc-
2. I just use regular wire strippers with teflon insulation.
I've never had any luck with any of the wire strippers I've tried, not where Teflon is concerned. It always just stretches it out at the end, and makes a mess.
What type of strippers do you use?
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
I found if you use a heat gun before stripping helps.
I've never heard of doing that before.
Using a utility knife, or a single edge razor blade works OK on the 18 gauge Teflon I have. But I bought some 20 or perhaps 22 gauge (I can't remember which) for a project, and haven't had a bit of luck going at it with the knife.
I'll give your pre-heat method a go. Thanks again!
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
I use two types:
https://www.digikey.com/product-detail/en/apex-tool-group/SAS3210/SAS3210-ND/1500292
https://www.digikey.com/product-detail/en/jonard-tools/JIC-125/JIC-125-ND/1007221
Neither are the exact strippers, just so you can get an idea of the styles. The second type, I use most of the time, inexpensive and works pretty well across range of size, just rotate the wire and squeeze a couple of times before pulling.
My two closely resemble these, and either pair will only serve to mangle Teflon wire. They work great on standard PVC though.
And for those who fell for my subject line, sorry. Here's a little something for you.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
Hi,
thanks for the info. I'll practice before applying the final solder job.
Shovel, the board I'm putting in for the large aluminum electrolytic is from this guy Chart Chong which I got 8 years ago. It looks simular to the board in the video.
You won't believe this Shovel but my favorite preamp, not a passive one I built, is the Last Pas by David Vorhis. I got mine hooked up to a ST-35 in my bedroom. A friend wired mine in a trade for another PAS and a faceplate I made to hide missing switches and controls back in 1990. I still have the article on it if you need a copy. I got to get you a picture. Take care....Mark K.
I'm not at all surprised that you enjoy your "Last PAS". I enjoy mine too, and I've been using it problem free for at least 25 years. It's good to know someone else out there actually built it. You're the first other Inmate I recall ever mentioning it. Thanks for the offer of the article, but I still have mine, unfortunately not in PDF form, but a hard copy.
Have you tried the EFB mod on your ST-35? If not, I recommend it, and your tubes will thank you!
At the risk of redundancy, please look hard into the AC wiring of your upcoming MK-III project, and put the fuse, thermistor and switch all on the hot leg.
Be safe, and have fun.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
Hi,
Shovel, my pad 5 years ago. Try and find the Last Pas, it's got my home made faceplate....Mark K.
I see a couple of contenders, but I'm not spotting it, Mark. My first choice was the piece directly above the turntable, but that looks too short to be a PAS chassis. Not that it couldn't have been built in something else though.
The gold unit next to that looks like a possibility, but the number of knobs doesn't equate. I built mine with one knob for the volume control, and three small switches; Line Stage/Phono, two auxiliary inputs (functional when first switch is in "Line Stage" position), and a Stereo/Mono switch.
I don't see the mammoth filament cap bank sitting behind any of them, which is also hindering my search for yours.
You're going to have to tell me which one it is.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
Hi Shovel,
I don't know what to tell you but the wiring is from the Last PAS. I know what you mean about the big cap banks, mine came without them...I saw them in the article.
It's in the middle. I traded an extra PAS to a new friend from the old Audiomart. He wired the preamp and a Stereo 70 Purist Audio mod for me. In return I made up a faceplate.
I went to a trophy store and had a little brass plate made up that said (Modification by Bob Gates) just big enough to cover the tone controls. A little strip of wood covers 2 slide switches. I only have on/off and tape monitor. I ran out of PAS-2 knobs so I used some from a SCA-80Q or PAT-4. It used to be spit -shine bright but now may look like Grandpa Munsters old little dusty Eico.
I still talk to Bob all the time, an audio penpal from the early eighties. He was room mates in college or the Air Force with Jim Aud who runs Purist Audio. If something differs from the original Last PAS it's okay with me. I look in awe at some of his soldering.
I know a year ago you tried to show me how to send a picture, I still have the instructions written down. Well Vinnie made it simple enough for simply me to do it now....but he might of awakened a sleeping giant as now I could attack with quirky audio project pictures much like the boring slide shows Fred Rutherford projects for the Cleavers...take care Mark K.
I've now watched the Blueglow MK-III rebuild videos. He does nice work, and I generally agree with most everything he said. Thanks again for alerting us to them.A few things I noticed. If you go with the SDS power supply boards (which I recommend over the multi-section can cap), be aware that Triode has stenciled them incorrectly. Or, at least the two I bought were. Caps one and two are meant to be in series, but that's not the way the boards are numbered. It won't matter at all if you're using all the same value caps, but I used a slightly lower value as the first cap(s), so my smaller value caps actually went in positions one and five, rather than my board's indicated positions of one and two. I bring this up because, although Blueglow stuffed his own boards, he made no mention of them being mis-marked. Perhaps Triode's corrected this on the newer boards.
The second change I would make would be to do the "Diode mod" (shown below) and add a couple of UF4007s to the socket of the 5AR4. Eli Duttman has frequently recommended this as cheap insurance against today's "less robust" 5AR4s. Total cost, about 40 cents or less.
The last thing I took note of, and the biggest thing I take exception to, is his AC wiring. I really like his idea of installing a thermistor, and would encourage you to follow his suggestion. But he then wires up the power cord the same way Dynaco did it fifty+ years ago, which is the hot through the fuse, and the neutral through the switch (or vice versa).There was a long thread on DIY Tube Asylum some time back about which should come first, the fuse or the switch. Although there was no universal consensus (although the majority said "fuse first"), everyone agreed that by today's safety standards, the hot leg should be wired to the fuse and switch, and neural directly to the power transformer.
That's not the way Dynaco did it, and BlueGlow simply followed their antiquated method. Take note that at the 43:18 point of video #7, he wires the hot (black) to the thermistor and then the switch, while the neutral (white) is wired to the fuse holder. It's simple enough to do it correctly, and I've changed any of the Dynaco pieces I've worked on to the proper method
I also noticed that he added a chassis ground to each amp, via the green wire of a three pronged power cord. Be aware that multiple grounds may cause you ground loop hum problems. I suppose you'll just have to see how that goes once you get yours built.
As to your two other questions, there's plenty of "joining two wires together" tutorials on youtube. Watch a few, and that should show you the best method for extending transformer wires.
Your other question about stripping Teflon wire, I have no good answer for. Blueglow's heated strippers looked tempting to me too. But I only do this for a hobby, so the investment wouldn't be worth it for me. I strip my Teflon wires by hand, using a razor knife. It's a pain in the ass, but works OK once you get the hang of it.
Good luck with your project, and please keep us posted.
Edit: One more thing I forgot to mention is that Blueglow had to reuse the original Dynaco 11.2 ohm bias resistors. I get that these amps were not his, but he was working on them for a customer. Perhaps the customer might be confused by the new bias setting. Dynaco's 1.56 battery test method was fine for testing a VOM fifty years ago, but today's digital meters are generally very accurate. I'd trust my meter more than a fresh battery checking exactly 1.56V. That said, I'd install a 10 ohm, 1W resistor in place of the "unobtanium" 11.2 It makes calculating the bias setting a whole lot easier.
"Suddenly, I'm not half the man I used to be. 'Cause now I'm an amputee" J. Lennon
Edits: 05/15/17 05/15/17
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