BWRX said:
Of course you are correct, and safety practises and good judgement should always accompany working with mains voltage or high voltage circuitry. In fact the same care is due low voltage circuits which can deliver large amounts of current which can melt metals, start fires and burn flesh.
My post was made tongue-in-cheek because our friend did not seem open to the idea that tubes can be good.
Well, I just bumped into these transformers again after forgetting about them in the back of my closet. I just couldn't throw them away for some reason.
Against my better judgment I decided to to feed 120VAC into the 100V tap. I know I said these were 70V, but at the time I only had a short look at them and didn't see the 100V marking on the other tab. Anyway, after applying power I checked the voltage across the the secondary 8 ohm tap. I measured 40VAC, which is a decent usable voltage for some amps I have.
I threw caution to the wind and wired up a 5R test load. With the 5R load the voltage dropped to 35VAC. Not bad, that's 245W. I let the test load toast for around 30 minutes and then felt the transformer with my hand; it wasn't even warm and the voltage had only dropped to 34.5VAC. I left it plugged in without the load connected for a few hours and it was barely warm enough to notice.
Am I setting myself up for a Darwin award, or can I use these as power transformers?
Against my better judgment I decided to to feed 120VAC into the 100V tap. I know I said these were 70V, but at the time I only had a short look at them and didn't see the 100V marking on the other tab. Anyway, after applying power I checked the voltage across the the secondary 8 ohm tap. I measured 40VAC, which is a decent usable voltage for some amps I have.
I threw caution to the wind and wired up a 5R test load. With the 5R load the voltage dropped to 35VAC. Not bad, that's 245W. I let the test load toast for around 30 minutes and then felt the transformer with my hand; it wasn't even warm and the voltage had only dropped to 34.5VAC. I left it plugged in without the load connected for a few hours and it was barely warm enough to notice.
Am I setting myself up for a Darwin award, or can I use these as power transformers?
Anonymous1, be careful in touching the transformers while there is power applied, they could be poorly insulated. Although, you are on to something. What I did with some I had lying around (rated at 10 watts each) is use them for the B+ supply in a tube amp. I had a 13.5 volt 6 amp AC wallwart that I didn't need so what I did is connect to two 70V transformers wired in series. Then I rectified it with a voltage doubler circuit and now I have a good B+ supply around 260 volts for the cost of various junk I have lying around. I ran these transformers backwards. If you do want to use it for power transformer purposes I guess if you could isolate them fairly well you should be safe it seems like you're getting a good deal of power out of them. You can also use them in an electrostatic speaker if you want to go that route as well. If anything you shouldn't throw anything working away, junk comes in handy in this hobby.
I didn't actually touch the frame of the transformer when it was powered up. There are plenty of things I don't completely understand, but I'm not completely stupid.
Actually, I should probably measure to see if there is any leakage. I would think they would be insulated enough to handle 120V if they were built to handle 100V.
These will be in a properly grounded chassis and they won't be pushed anywhere near the 245W I tested them at. I'll post a pic of my monstrosity when it's finished.
Actually, I should probably measure to see if there is any leakage. I would think they would be insulated enough to handle 120V if they were built to handle 100V.
These will be in a properly grounded chassis and they won't be pushed anywhere near the 245W I tested them at. I'll post a pic of my monstrosity when it's finished.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.