Temperature related measurements:
Two thermocouples were installed in the chassis of the amplifier under test. One attached to the top of the transformer to measure the surface temperature, the other suspended at a mid point within the chassis to measure internal ambient.
Room Temperature...
After quite a bit of playing around, measuring, and calculating, I've learned quite a bit about the small transformer I'm trying to reverse engineer. Again, a big thanks to The Electrician who directed me to much of the information I needed.
Pursuing the cold vs. hot resistance of the windings...
I'm back again, and feeling a bit sheepish for further imposing on your time. In continuing with reverse engineering this little transformer I've arrived at the point where I would like to make a determination of the power rating by means of core dimensions. Although there are formulas to...
This could well be the only transformer I'll ever be testing in this way, which is why I was most interested in a suitable low cost solution. I could not justify purchasing expensive instrumentation for a one time event. The Kill a Watt would seem to be the answer in my case. Having only the...
Ok, so my Kill a Watt has arrived and I've done some preliminary testing. I must say, this thing is way better than I was expecting. Perhaps I got one that wasn't made on a Friday afternoon. It's quite possible that I may not need to modify it for my specific purpose. I don't need accuracy down...
I've seen internal photos of the Kill a Watt, and it looks like it should not be too difficult to modify. I just happen to have some 5408 diodes on hand, which should do just fine. I will be in wait mode until the meter arrives, then I'll assess the shunt resistor value. Looking forward to...
Thanks for the links. The comparison of your scope related readings to the modified Kill a Watt was very interesting. I found one on Amazon for 10.99 and ordered it. From reading the comments of others who have performed the modification, it would seem there is some variation in the value of the...
It would seem that the typical low cost consumer grade power meters will have poor resolution at low power levels. There's lots of them available, and some really low cost ones on ebay. Some use a sense resistor and others a current transformer, but all are intended for higher power than what I...
It's time to fess up. It finally did come down to performing a recount on another transformer sample. It turns out I had, indeed, made an error in the count, and on the winding with the least turns no less. Still not sure how it happened, but it did. The real count for the 12V secondary is 94...
It would have been nice to be able to determine the core loss, just to fully characterize the transformer, since things have gone this far. But I'm not sure how practical that would be given the equipment I have to work with. I can measure RMS current and voltage, I have a scope (analog) and a...
Unfortunately, I do not have a wattmeter. I know that it is common to employ one when trying to determine core loss since the reactive component, and phase shift, involved makes it a bit ugly to deduce otherwise. Just never had the need to go this far into that particular aspect of a...
I had already done the temperature rise by wire resistance change procedure, with the transformer operating fully loaded in its intended application. At room temperature, with the covers removed from the amplifier, and then again with covers installed. Two thermocouples were used to monitor both...
I agree with your rating assessment based on weight. I had already done some investigating in that regard. Based on the core area, though, the rating would be somewhat less. The reason I am going through this process is that it has often been claimed, on vintage audio forums, that the...
The transformer is layer wound with the primary on the core, of course, then the HV winding on top of that, and finally the 12V winding on the outside layer. The 12V winding has a resistance of 1.09 ohms, the meter has the capability to null out the lead resistance. The transformer weighs 1.20...
I am attempting to reverse engineer a small 1960's vintage power transformer that is employed in a vintage audio amplifier. It contains no marking to indicate operating voltage or current ratings, however I do have several sample transformers as well an an operational example of the amplifier...