I just picked up some really big potted Chicago Standard Transformer Company OPT's. I've heard alot about the BO-14, but not sure if these are the same. They are big!
Can anyone tell me if these are of the same quality and any more details?
And should I plan to build something high end with them or don't bother?
Can anyone tell me if these are of the same quality and any more details?
And should I plan to build something high end with them or don't bother?
Last edited:
Picture uploaded!
Not much of a picture, but you can compare the tools and in the upper right corner is a pop can to give you a sense of size. I don't have them in my hot little hands and no pics of any print, but they say 65 watts on them and have UL taps. Octal sockets and the guy said they ran 6550 tubes. The BO-14 were supposed to be 100 watt if my reading is correct, but that info's from the internet, so if could be wrong.
Not much of a picture, but you can compare the tools and in the upper right corner is a pop can to give you a sense of size. I don't have them in my hot little hands and no pics of any print, but they say 65 watts on them and have UL taps. Octal sockets and the guy said they ran 6550 tubes. The BO-14 were supposed to be 100 watt if my reading is correct, but that info's from the internet, so if could be wrong.
Attachments
Last edited:
From a 1966 Radio Master Catalog the Stancor Commercial BO-14 is indeed a 100 watt unit. The BO-15 is a 65 watter. Both have screen taps and a cathode feedback winding. Below are figures for each. The weight and dimensions will be the key in lieu of a number.
BO-14: 5000 ohm CT/8,16 ohm & 70 volt, 150mA. 21 Lbs, 5.312x4.75x6.062 high.
BO-15: 4300 ohm CT/8-16 ohms, 150mA, 12 Lbs, 4.56x4.125x5.312 high.
BO-14: 5000 ohm CT/8,16 ohm & 70 volt, 150mA. 21 Lbs, 5.312x4.75x6.062 high.
BO-15: 4300 ohm CT/8-16 ohms, 150mA, 12 Lbs, 4.56x4.125x5.312 high.
Last edited:
Wow! I am always amazed at the info people have here! Called to confirmed its a BO-15 dimensions and sure enough, it is a BO-15.
So now my question narrows. Is the BO-15 in the same league as the BO-14, and I guess more importantly, could this trafo be the foundation for something nice?
Any experience with this trafo out there?
So now my question narrows. Is the BO-15 in the same league as the BO-14, and I guess more importantly, could this trafo be the foundation for something nice?
Any experience with this trafo out there?
I say definitely yes to both. I have a pair of BO-14 that I've had for years as well as the PCR-300 power transformers. Below is a scan from the Nov. 1955 issue of Radio & Television News magazine that contained an article for an amplifier that used the BO-14. The 15 could be adapted to something similar. Perhaps copy and enlarge them.
Attachments
Sorry, no I don't. Even after some searching round on line in the catalogs and other forums no number is given for percent of turns. But in the article it's mentioned that for the pentode version the cathode winding is providing about 20dB of feedback. And about 7dB in the triode connected one because of less gain. There is 14dB of global in both cases.
Picked up a NiB Stancor OPT at the Dayton Hamvention for a few bucks. Its 4400 : 8 impedance ratio was a nearly perfect fit for a new project (though at 30W, it's a bit on the low side). Was a bit concerned it might've been a PA OPT, given the secondary taps (4R, 8R, 16R, 32R, 125R, 500R) but that wasn't the case, as it measured quite well indeed. Included two "tertiary" windings for lNFB (Ultralinear? Cathode?) that I didn't need, as the 6BQ6 finals didn't need any extra help for distortion performance (almost all h3 with very little high order harmonics). It looks like it was originally intended for Class A 6L6s, which would explain the tertiaries since the 6L6 does need some extra help in the form of lNFB to sound their best, and the screen voltage rating is limited.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.