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Audio and Video Talk
The Vintage Audio Section
Leak, Quad, PYE, Dynaco, Radford - Transformer Iron Quality
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<blockquote data-quote="Ampdog" data-source="post: 847113" data-attributes="member: 144"><p>Neither have I (and I come from the 'era').</p><p></p><p>I read up somewhat, and cannot readily see that mentioned effects can be serious at normal valve output powers (hence transformer sizes).</p><p></p><p>BUT:</p><p></p><p>Possibly not very relevant here: Not long ago I had a problem with power transformer dissipation that I knew only the theory of and never experienced before. (I mentioned this under DIY.)</p><p></p><p>That was the 'shorting' effect of assembly screws through the stack, particularly with large stacks. As said the theory is there, but mostly in practice the 'shorting' resistance is high enough to avoid this problem. </p><p></p><p>Not so with a rather thick stack (about 90mm) power transformer. The laminations were well insulated, and the fixing srews/bolts through the four ends rapidly heated up to smelling point - measured at some 160?C ! Being somewhat amazed, I used insolating washers each end of the bolts: No excessive heat. My surprise was at never having encountered this over all the years in practice - but then power transformers also were not taken apart all that often.</p><p></p><p>Returning to your question: Again surprise at never having heard that mentioned as a factor. But it exists in theory at least. Reading up briefly I could not find much more than the theoretical analysis, particularly regarding figures. I will inquire on another forum I frequent; as said right now I cannot imagine that the aging effect of laminations (steel) could be much of a problem at low powers usually relevant to valve audio equipment. </p></blockquote><p></p>
[QUOTE="Ampdog, post: 847113, member: 144"] Neither have I (and I come from the 'era'). I read up somewhat, and cannot readily see that mentioned effects can be serious at normal valve output powers (hence transformer sizes). BUT: Possibly not very relevant here: Not long ago I had a problem with power transformer dissipation that I knew only the theory of and never experienced before. (I mentioned this under DIY.) That was the 'shorting' effect of assembly screws through the stack, particularly with large stacks. As said the theory is there, but mostly in practice the 'shorting' resistance is high enough to avoid this problem. Not so with a rather thick stack (about 90mm) power transformer. The laminations were well insulated, and the fixing srews/bolts through the four ends rapidly heated up to smelling point - measured at some 160?C ! Being somewhat amazed, I used insolating washers each end of the bolts: No excessive heat. My surprise was at never having encountered this over all the years in practice - but then power transformers also were not taken apart all that often. Returning to your question: Again surprise at never having heard that mentioned as a factor. But it exists in theory at least. Reading up briefly I could not find much more than the theoretical analysis, particularly regarding figures. I will inquire on another forum I frequent; as said right now I cannot imagine that the aging effect of laminations (steel) could be much of a problem at low powers usually relevant to valve audio equipment. [/QUOTE]
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Audio and Video Talk
The Vintage Audio Section
Leak, Quad, PYE, Dynaco, Radford - Transformer Iron Quality
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