Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: eetechTom on December 13, 2020, 01:01:38 pm
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Hello, I am looking for a instruction sheet/wiring diagram for a Thordarson 13S41 output transformer. It’s a P-P type, universal replacement type. I recently bought a Peerless cathedral speaker, and am hoping to use the transformer to do a sound check. The Peerless has a high impedance, and sounds like crap connected to my little AA5 radio speaker terminals.
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I checked a few of their catalogs, but the didn’t supply PIN number data in any of them. It has pins labeled 1-6 on the secondary, and P, P B on the primary side.
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Let's see if I can get pg. 24 of the cat to attach. Can't too much wacky loading.
If you have the number: 400-FX 1942 catalog, reference pg. 24 and notice the wiring diagram on the upper left corner of the page. If you don't have the catalog, it should be out there on the net.
silverfox.
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PG 24
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.... I recently bought a Peerless cathedral speaker, and am hoping to use the transformer to do a sound check. The Peerless has a high impedance, and sounds like crap connected to my little AA5 radio speaker terminals.
Let's skip the details. What IS the Peerless speaker impedance? I assume the AA5 is 3 or 4 Ohms.
If the speaker is anything like 400 Ohms, try a 120VAC:12VAC 1A power transformer *backward*. If closer to 1,500 Ohms, try 120:6.
It is of course entirely possible the Peerless is sick or needs some odd bias. Particularly a magnet.
https://www.antiqueradios.com/forums/viewtopic.php?f=1&t=230307
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Thanks silver fox and resistor, I was able to guesstimate the speaker taps with my DMM. Also wanted data for future reference. Didn’t seem to work well with the speaker.
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PRR, I measure 2 Henry’s, and 1,800 ohms with my DM27XT DMM. The speaker was manufactured in the late 1920’s. As a side note, I want to brag about my trusty Wavetek DMM for a sec. It has enough output to drive that speaker with a decent tone when testing inductance. Used that feature to test a few speakers when buying vintage gear. Anyway, I will try the power transformer trick tomorrow. Thanks for the tip!
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Here is a photo, better late than never.