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In Reply to: RE: Vintage SE OPT hook up confusion posted by DAK on September 22, 2014 at 20:10:33
63 Ohms seems awfully low for a primary resistance - are they treble transformers for bi-amp? Moto made quite a few three channel amps. And 48 ohms seems awfully high for a secondary. But likely was used for feedback. Got a part number?
Primary tap is probably for hum cancellation - was cheaper than adding capacitance, which the rectifier tube wouldn't have liked anyway..
Follow Ups:
Sorry, for the extra confusion. My DMM had a low battery and was giving bad results. The OPT resistance is actually 620 ohms. The part number is
95-1660 and 343926.
Is it possible that the second B+ tap is an integral choke and used for the driver tube or the screen grids? cheers, Dak
I googled around some and found your transformer number matches up with a Zenith console amp 3D32. There may be other Zenith amps that used the same transformer as well. Here is what one person did with the amp, including the schematic he used. Hope this helps.
His schematic is
http://www.angelfire.com/vt/audio/se6bq5schem.gif
Thanx for the tip. Yep the pictures are spot on. In my amp I will be using the RH84 schematic. I still don't understand the purpose of the dual secondaries. cheers, Dak
Sometimes it's that way with repurposed iron. If you had the original schematic, it might become clearer, or maybe not. I couldn't find a free original schematic, but it may be out there. Tom Bavis is probably right that it had to do with humbucking.
The main thing is to make sure you identify the phase of the two windings so you don't have them "fighting" each other if you use both. Or just use one and insulate the other. Have fun!
RH84 gets good reviews. I may try that one myself one day. Let us know how it comes out.
John
I have made 2 identical RH84 on the same RCA console amps and they turned out very nice sounding. I was pleasantly surprised since the circuit is rather simple. I made a pair of monoblocks that were stereo/mono switchable so I could double the power. I found that was just an ok situation. But in stereo they are a great sounding amp. cheers, Dak
Hi TB, thanks for the info. I will go to the shop and get the serial number off the trans. But, I am pretty sure these trannies are not from a 3 channel amp. Any idea about the dual secondaries? On the primary if I just leave the lower impedance tap unconnected would be ok? thanx for the help, cheers, Dak
Some chance the lower impedance tap on the primary is for ultralinear operation. I think I have an old SE Sony tape deck that runs the 6AQ5s in UL. Just a guess though.
Are the transformers big or small? For a small transformer the resistance of the primary seems pretty low. Have you applied voltage to calculate the turns ratio?
Hi, I did no testing other than measuring the DCR. I saw a pic of the stereo amp and it looked like one of those standard type console amps. The opt are not especially small about 2 x 2 1/2 x 2.
Try this:
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