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Post by bluebird on Nov 27, 2013 1:35:01 GMT -7
Hi all, Just wanted to check something with you. I noticed when changing tubes that the transformer (large - behind the rectifier tube from rear) doesn't seem to be mounted flush with the frame. The "ears" closest to the rectifier tube are bent and I'm just wondering if this is normal or do I need to do something about it. So effectively the transformer is tilted towards the grill cloth. The amp plays fine, actually plays stunning but if you could have a look at your transformer and see is it the same on your amp i would greatly appreciate it. Many thanks
Dec.
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Post by lowbudget on Nov 27, 2013 8:36:51 GMT -7
It's not "normal" but it's very common on Dr. Z amps. It has three basic causes, all acting in concert:
1. Very heavy transformers
2. Extremely protective shipping boxes
3. Inertia
In the immortal words of Percy Sledge, "It's not the fall at all but it's the sudden stop". Invariably, well almost invariably, UPS will drop the amp boxes. Due to the very highly protective Dr. Z boxes the amp inside isn't normally damaged but what you are describing is often the result. The amp stops when the box hits, but the heavy tranny wants to keep moving. I'm guessing that the Doc specs those mounting ears out of a softer material to keep from bending the chassis when this happens, so they bend instead of the chassis. I'll bet you a high percentage of the Doc's amps exhibit this. I know mine have.
It normally is not a problem, but it makes me crazy too. You can try a home-brew fix that helps sometimes. Loosen up the screws that hold the mounting ears to the chassis and push down hard on the tranny on the side where it's sitting high, then tighten everything back up. This may help a little, some, or a lot-you just have to try it and see. The doc has volunteered to fix some of mine before but I've never sent them in. There's no guarantee that it wouldn't happen again on the return trip to you.
The guaranteed fix of course would be to double-box the existing shipping box inside a second larger box with a cushioning layer of foam between the two boxes to absorb the shock, kinda like an air bag. But this would make the outside box very cumbersome and probably add $50.00 or more to the shipping costs. I'd gladly pay it myself, but that's just me.
Good luck, and let us know how it works out.
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Post by bluebird on Nov 27, 2013 10:34:22 GMT -7
Hi Fasteddie, Glad to hear mine's not the only one, as said before the amp plays well so it doesn't cause any problems so I think I'll leave well enough alone! Once I know it's not something to worry about. Thanks for great reply. Dec.
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Post by bluzman on Nov 27, 2013 13:08:24 GMT -7
I thought they were mounted like that to limit eddy currents, hysteresis and skin effect of any close wiring...
I stayed at a Holiday Inn Express before ya know!
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Post by mfirst on Nov 27, 2013 13:44:42 GMT -7
I thought they were mounted like that to limit eddy currents, hysteresis and skin effect of any close wiring... I stayed at a Holiday Inn Express before ya know! What he said. I didn't know what any of those things were called, but I have heard that mounting the transformers slightly off axis helps to eliminate annoying little electronic issues. Maybe Doc can help clear this one up.
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Post by BritInvasion on Nov 27, 2013 13:55:50 GMT -7
I always thought it was due to shipping concussion too. My Maz PT is just a *tad* tipped to one side - just barely noticeable. I looked closely at the mounting feet and washers and couldn't see any traces of a scrape mark so I really wondered if it was installed that way. I'd be real interested in knowing what the deal is.
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Post by lowbudget on Nov 27, 2013 14:37:15 GMT -7
I thought they were mounted like that to limit eddy currents, hysteresis and skin effect of any close wiring... I stayed at a Holiday Inn Express before ya know! What he said. I didn't know what any of those things were called, but I have heard that mounting the transformers slightly off axis helps to eliminate annoying little electronic issues. Maybe Doc can help clear this one up. I've talked to the Doc about it before. It's shipping.
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Post by gplayer1965 on Nov 27, 2013 15:44:36 GMT -7
mine as well, just a bit, but plays like an angel
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Post by BritInvasion on Nov 27, 2013 18:18:16 GMT -7
They sound better with the tranny tilted.
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Post by bluzman on Nov 27, 2013 22:27:45 GMT -7
I still stayed at a Holiday Inn Express before though!
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Post by prspastor on Nov 28, 2013 8:25:13 GMT -7
I agree with the shipping damage opinion.
There is a trick, when you are building amps, to put 120v on the primary of the power transformer that is already bolted to the chassis. You then wire a set of headphones to the primary of the output transformer and then you listen for hum while you turn and manipulate the OT on the chassis. Typically, the OT windings are turned 90 degrees to the windings of the power transformer. When you find the quietest position, you mark it, drill and bolt down the OT. I've never seen people purposefully tilt a transformer to reduce hum, thus the shipping damage seems more relevant to me.
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Post by bluzman on Nov 28, 2013 11:44:56 GMT -7
Transformers: Robots in disguise...or is it Robots in the skies?
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