JonM Posted January 12, 2003 Share Posted January 12, 2003 I'm asking this here just because this seems to be the forum with the most Dyna postings. Maybe one of you can help. A year or two ago both of my Dynaco Mk IV amps (they're the 40 watt mono ones, sort of half a Stereo 70) suffered the exact same catastrophic failure at the exact same instant. The power transformers shorted out! One moment they were quietly playing Sunday morning background music, the next moment there was silence. I cannot for the life of me figure what happened (weird harmonics on the power line?), but the primaries of both shorted out (yup, I disconnected all secondaries and plugged them in, and the fuses still instantly blew), and I am still looking for replacements. Any idea whom to contact? I tried Magnequest, and Hammond - the usual suspects. No luck - either the wrong voltages, or no bias voltage tap, or simply the wrong dimensions to fit the chassis. The rest of the amps are in beautiful condition, and I like the sound (not as sweet as my ST-70, but still very listenable), so you can imagine I'd love to find new transformers and get these units running again. As they are now, they are collecting dust. :-( Any ideas are much appreciated. I'm using SS to feed my Khorns for now, and I know they'd like to be tube-fed again :-) Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 12, 2003 Share Posted January 12, 2003 You can buy bolt in replacement Magnaquest's from Triode http://store.yahoo.com/triodeel/index.html Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted January 12, 2003 Share Posted January 12, 2003 Not sure if these are for the MkIV. Know you can for the Mk III. I could be wrong. MagneQuest makes GREAT iron, though. I've been involved with them since 99. TAlk about talking your ear off! IF you can get off the phone withe Mike LaFevre in under two hours, you are a rare soul. kh Quote Link to comment Share on other sites More sharing options...
lynnm Posted January 12, 2003 Share Posted January 12, 2003 I am with mdeneen (as usual). The odds of power xformers in 2 separate amplifiers failing in the same manner at the same moment are worse than my opening my door and finding Cameron Diaz lying on the floor yelling Do Me ! Do Me! Do Me! Are you certain that the problem is with the amps ? Have you hooked them up to a different preamp ? Have you taken the pre that you were using and tried it with a different amp or amps ? What makes you think the primaries are shorted ? Continuity checking will not give a valid distinction between a simple closed circuit and a short. Both will read the same unless a very good ohmmeter is used.A simple check with an ordinary multimeter will likely show 0 ohms or a very little more resistance. In other words an ordinary ohmmeter will show continuity but will not accurately measure the resistance of those primary windings. I can pretty much guarantee that if when measuring the resistance of the primaries you get an inductive kick (for a lack of a better term - mdeneen ?) that the primaries are intact - ( This phenomena occurs when a DC source such as a battery is connected across the windings of an xformer or a choke and the circuit is broken. At times the use of a strong battery and a coil with many turns is used the resulting voltage can be astoundingly strong. ) I honestly believe that the problem is not with the power amps but is related to something upstream - preamp,sources etc. or very much less likely downstream - ie speakers . The likelihood of the problem being in the speakers is even less than being with the amps. Both Cameron Diaz and Julia Roberts craving me would be more likely. Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted January 12, 2003 Share Posted January 12, 2003 I have to admit, I agree too. The chances of BOTH power trans going at the same time is highly unlikely, unless something ELSE went in your system that caused the blowout. You didnt specify anything so it seems circumspect. Still, I am not sure if MQ makes the iron for the MK IV. Call Ned. kh Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 12, 2003 Share Posted January 12, 2003 Oops my goof I thought it said Mark III Quote Link to comment Share on other sites More sharing options...
sunnysal Posted January 13, 2003 Share Posted January 13, 2003 you might want to try Joe Curcio @: curcioj@earthlink.net He repairs and restores dynaco equipment and might be able to help you troubleshoot the mark IVs and find trannies for you if they are, in fact, both blown. regards, tony found this on his site: "Magnequest Replacement Output Transformer Ultra high quality direct drop in replacement output transformer for your Mark 4· Output Transformer Replaces Dynaco A-470 (P/N MQ-470) @ $150/ ea" http://www.curcioaudio.com/dynadr_3.htm Quote Link to comment Share on other sites More sharing options...
mobile homeless Posted January 13, 2003 Share Posted January 13, 2003 He is looking for POWER TRANSFORMERS, however. kh Quote Link to comment Share on other sites More sharing options...
sunnysal Posted January 13, 2003 Share Posted January 13, 2003 oops...I will look some more...lol! tony how about this german site? http://www.hde-gmbh.de/dyna2.html 464008 Power X-former MK-IV (120V) - PA-135 105,00 or triode electronics? http://store.yahoo.com/triodeel/index.html Quote Link to comment Share on other sites More sharing options...
JonM Posted January 14, 2003 Author Share Posted January 14, 2003 I appreciate all the feedback (no pun intended). I, too, am completely baffled that both went at the same instant. But that's what makes me think it was something in the AC feed. They were both protected by 2 amp fast blow fuses on the primaries, and I'd have thought that would have prevented any currents needed to do real damage. They were, I admit, plugged into a Tripplite surge protector/AC filter (not a UPS), and I wonder if some weird resonance started in the surge protector's circuitry at a very high frequency that...no, the windings of the transformer would be a high impedance to that...oh, I really am baffled! I determined it's a short in the primary by the very simple test of disconnecting *all* the secondaries, putting in a new fuse, and plugging it in. Pff - fuse blows instantly. The preamp is fine - everything else works with a different power amp. Nothing else that was being fed by the same surge protector that day was damaged (I no longer use it - I can't say it's guilty, but I'd rather not find out by damaging something else with it). I guess getting the transformers rewound is a possibility, but I was hoping to find a way that's less expensive. And yeah, the Mk IV uses a different power transformer than either the Mk III or the ST 70. My transformers were made by "Custom Coil" (marked on the case) DING DING DING!!! I just did a google search and found Custom Coil is still in business, in Ohio. Time to drop them an email. Thanks guys - it wouldn't have occurred to me to look if I hadn't had this exchange with you. I'll let you know what happens when I talk to the folks at Custom Coil! Quote Link to comment Share on other sites More sharing options...
JonM Posted January 16, 2003 Author Share Posted January 16, 2003 I know I sounded like a ding dong in my last posting, but frankly I looked a couple of years ago when the amps originally failed, and there was no hint of Custom Coil. Their web site must be relatively new. They appear to be a small shop, and small businesses are often the last to "webify". Quote Link to comment Share on other sites More sharing options...
Clipped and Shorn Posted January 16, 2003 Share Posted January 16, 2003 If it really turns out the transformers are shot, you did suggest that replacements existed but would not fit right. Have you considered a rebuild upgrade project onto a new chassis with more room to work. You could even add other upgrades to help motivate the project. C&S Quote Link to comment Share on other sites More sharing options...
JonM Posted January 26, 2003 Author Share Posted January 26, 2003 I've been in touch with the original manufacturer of the transformers (Custom Coil in Zanesville, Ohio) and they found replacements I think in inventory, though they are missing the bell covers. I am still working with them on getting things arranged (which may involve making new covers, or using the ones from my transformers). They have been very helpful - will let you know how it turns out. Quote Link to comment Share on other sites More sharing options...
NOSValves Posted January 26, 2003 Share Posted January 26, 2003 Why couldn't you use the bells off your original transformer ?? Keep us up to date on what happens Craig Quote Link to comment Share on other sites More sharing options...
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