[Amps] Re: The White Smoke

[Will Matney]

Hal,
You sure you don't have Gremlins? No, the transformer should not have 
done that. Even if it were out of phase, it should have just maid a loud 
moan, and then after a few seconds, tripped a breaker. It should have 
not burned up this easily! I have been building amplifiers since about 
1981-1982 and have never seen this. I have used two transformers in 
parallel time after time again and mistakenly hooked the phases up 
backwards. I never once burnt one up! Keep in mind that over my career, 
I have probably built from scratch, 200+ amplifiers! Even when in 
Vo-Tech school, I was learning how to design and wind transformers 
there, we had to calculate one by how the instructor gave us a spec, 
then build it from scratch. I had this happen there on one that I wound, 
and all it did was kick out a breaker after a few seconds. The primary 
coils didn't even get hot!

Now this is my opinion, and some may come down on me for this, but Peter 
Dahl is NO better then any other manufacturer. He has this Hypersil 
thing going which is not some big secret material. All hypersil is, is a 
C-Core lam that is cold rolled, grain oriented, 3.5% silicon steel, 18 
Kilogauss, nothing more. There are several other trade names for the 
same material, and M-6 is about the same in an EI core! Now this 
transformer should have been tested and "burnt in" before it was 
shipped. this includes double-checking the connections. I never let one 
out without testing when I was winding several years back. They should 
be tested with and without a load if they are a special. If they are a 
common one, they should be burnt in for at least 1-2 hours without a 
load. If something is going to happen, it should within that length of 
time. The burn in also switches the transformer on and off at least 4-5 
times.

Now if it were me, and that being their fault, I would not pay shipping 
again on the transformer. That is just too expensive to ship from where 
your at to Texas. I think if you check state law about warranties and 
guarantees, you don't have to as they're liable for it. This is despite 
what their warranty may contain. An ethical company would not charge you 
this either for at least 30 days after purchase. I'm not sure what their 
terms are, but that's how some try to do it. Besides, you paid about X2 
what the transformer was worth anyhow! This makes me wonder just how 
good is their quality control too! I can assure you of this, if I were 
running the joint, this would not slip through the cracks.

One of two things should show with a multimeter. Either a short or an 
open has occurred. I'm not sure which you found, but that's all that 
could have happened from this situation. This either from a bad winding 
or an incorrectly labeled transformer lead.

Will Matney

Harold B. Mandel wrote:

>Dear Will,
>
>>From the details Rich Measures asked, it is probable that
>a manufacturing error fabricated the primary windings with
>connections 180 degrees opposite for one of the windings
>than the schematic pins-out and this caused the two
>windings to be out-of-phase when 240 vac was applied,
>hence the smoke.
>
>Contrary to your posting, the a.c. breaker did not trip.
>The room light dimmed slightly when the breaker was closed,
>and then the sizzle, the smoke and a soft "pop."
>
>After performing resistance checks with a calibrated DMM
>on all the leads, once again I assumed all would be pristine
>and kosher for a power-up. This is the same error I made
>when trusting the bleeder resistor network to be operative.
>
>Rhetorically, how far does this all need to go? Can I not trust
>any electronic component without a thorough examination?
>I have years of building experience, but this is the first project
>that has presented situation after situation of supposedly new
>and pristine hardware being defective.
>
>Has anyone else had similar experiences? How do I invoke
>the Rule of the Final Inch? What would you do in this case?
>
>Thanks,
>
>Hal Mandel 
>
>
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