184.6.48.13
This Post Has Been Edited by the Author
In Reply to: RE: I'm Melting... What a world, what a world... posted by jjhaz on December 18, 2011 at 21:18:27
Hi Jeff,I'm Jeff also. I custom design SE special custom power transformers for ultra-discriminating audio people and I will be the first to tell you there is nothing at all wrong with using Hammond Power Transformers..... IF you know how to spec them, and under-use their ratings by a fair margin. Your 372BX was only rated to do 92 VA / 100 mA. on the secondary.
Question one, are you really needing an INTERNATIONAL primary ??
By that, I mean do you need choices from 110 VAC home line voltage to 240 VAC home line voltage,... as in Europe? If so, simply use the 3XX series and just UP the current rating. Order the 372JX which does 250 mA. and costs $149.95 Your melted trannie, rated at 92 VA / 100 mA. cost you $100.78. and its a total loss now.
If you are USA only, or nominally use 120 VAC only, NEVER order the 3XX numbered series of Hammonds - ever, (with all the fancy un-used primary taps hanging off them). Order the 2XX Hammond series, with the 115 and 125 VAC primaries only....MUCH more trannie for the money, and you can easily and cheaply upgrade the VA rating, so the trannie LOAFS and runs cool, rather than strain and spill its guts out.
Would you rather drive a 49 CC China scooter up a hill, or a 1,300 cc BMW cycle ??
Your upgrade route, if you are in the USA, is to order a Hammond 272JX, it is rated at 236 VA and it can do 600 VCT at 287 mA. of current!!!!! Guess what, it retails for $65.54!!!!!!! A fraction in cost of the 100 mA. melted one, and 2.36 times HIGHER in VA rating.
Three important questions need to be answered still:
(1) Can you fit it on your chassis?? It will be physically larger that the "P.U.ny" 100 mA./92 VA power trannie. If it does not fit, rebuild the amp on a larger chassis, or modify mounting holes and locations on your existing chassis.... so it will fit.
The amp (with the new trannie) will run cool to the touch, and it will sound at least 10 to 30 percent better. Why? Well, the HEART of the amp, the power transformer, is STRONG and will self-regulate the B+ under the demands of music reproduction. Wait till you hear this !!
Two other questions need to be answered :
2) Has another part failed, that caused this transformer to have a ultra high load, and thus fail. If so, that problem area needs to be fixed!!! FIRST.
3) Was the size of the safety fuse in your amp so high in Ampere ratings, such that the power trannie blew BEFORE the safety fuse? If so, by all means, reduce the value of the fuse for MORE protection.
If you have questions, feel free to contact me. 272JX wow, $65.54 a TOTAL steal. It is my observation that most people on this Forum and in audio in general (99%) build their amps narrow-band and dynamically challenged, FAR WORSE than the limits of Hammond Transformers, including Hammond output transformers. Smoke on that, for awhile folks.
Cheers,
Jeff Medwin
Edits: 12/18/11 12/18/11Follow Ups:
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