So I have a build in progress. I was asked to reuse a power transformer from a 60's PA amp that was driving a pair of 6L6 power tubes and has a bias circuit tap as well.
When I measure the unloaded transformer I am getting 350-0-380 out of the high voltage leads. I am wondering if- after running to a GZ34 rectifier- if the unbalanced voltages are going to be a problem?
Anyone know?
Unbalanced voltages from Power transformer- Problem??
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Stevem
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Re: Unbalanced voltages from Power transformer- Problem??
Balance will not be so much a issue, but if that 350 volts is due to a shorted winding and not just a crappy winding job, than that PT is on it's way out and I do not know how you could find out!
May be others here will have a idea?
May be others here will have a idea?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Unbalanced voltages from Power transformer- Problem??
Agreed...time for the super secret thing.
http://www.premierguitar.com/articles/t ... r-tester-1
As I understand it, this test is very good for a PT and not so much for an OT.
http://www.premierguitar.com/articles/t ... r-tester-1
As I understand it, this test is very good for a PT and not so much for an OT.
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Stevem
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- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Unbalanced voltages from Power transformer- Problem??
I built that last year and have only had a chance until this week to test it on OTs and its not 100% right on as it passed a OT that I already knew was bad, but I just got a reissue jtm 45 in that needs a PT and I will see how it checks out on that!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Leo_Gnardo
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Re: Unbalanced voltages from Power transformer- Problem??
Are you absolutely sure you selected the correct leads for center tap and bias, not got 'em reversed? Yes, I've done that too... and it ain't pretty at all.mmmoser wrote: I was asked to reuse a power transformer from a 60's PA amp that was driving a pair of 6L6 power tubes and has a bias circuit tap as well. When I measure the unloaded transformer I am getting 350-0-380 out of the high voltage leads.
If you're sure you do have the CT & bias ID'd, I wouldn't commit to drilling holes to mount the oldie but goldie until you clip it in & see whether you get expected B+ and power levels from the amp. I've seen mismatches say 10V work out OK, 30V worries me.
down technical blind alleys . . .
Re: Unbalanced voltages from Power transformer- Problem??
Thanks for the link- I will give this a try and see if it indicates any potential winding problems. I'd hate to build out the amp only to have a failure in the PT after a short time of use.
Frugal Amps
Re: Unbalanced voltages from Power transformer- Problem??
Are you absolutely sure you selected the correct leads for center tap and bias, not got 'em reversed? Yes, I've done that too... and it ain't pretty at all.
If you're sure you do have the CT & bias ID'd, I wouldn't commit to drilling holes to mount the oldie but goldie until you clip it in & see whether you get expected B+ and power levels from the amp. I've seen mismatches say 10V work out OK, 30V worries me.
Yes- I am certain on all the leads and their jobs. I have not seen a variance this large either so that is why I asked.
If you're sure you do have the CT & bias ID'd, I wouldn't commit to drilling holes to mount the oldie but goldie until you clip it in & see whether you get expected B+ and power levels from the amp. I've seen mismatches say 10V work out OK, 30V worries me.
Yes- I am certain on all the leads and their jobs. I have not seen a variance this large either so that is why I asked.
Frugal Amps