rascalseven
Well-known member
I drew this based on the power supply in my modified Alesis 3630 compressor.
[EDIT - I actually used 10uF electros instead of the 50uF marked at the reg outputs]
This is the power supply design after implementing the 3630 mod by he-who-no-longer-wishes-to-be-named-on-this-forum.
I have a bunch of surplus power transformers with 14vac secondaries that I thought this might be a good design for (to make bipolar 15 and 18vdc from a single 14vac secondary). The transformers that would be good for this design, so I thought I'd give it a whirl. I have questions:
When I measure the voltage at pin 2 of the 7915 I get around -47vdc. At pin 1 of the 7815 I measure +46vdc. Wow.... that's a lot more voltage than I would normally expect at the front of these regulators.
Is this normal? When I measure the output of the 7915 I'm getting almost -18vdc, not -15. The + is fine at +15, however. I've double, triple, and quadruple checked my wiring, and was just wondering if the regulators are gonna fail or what. I'll stick another 7915 in to see if I got a mislabeled 7918 by any chance, but was really curious about the high voltage feeding these regulators, and specifically, if its a problem.
Can anyone shed light on this design? I remember Keith saying that this is not an ideal psu design, but I can't find his post and don't remember his reasoning. I just wanted to use my surplus transformers to make some bipolar psu's and thought this might be worth trying.
On another note, my transformers can be wired 28vac w/CT. Do you think it'd be okay to use a more typical design with 15v regs? That is do you think a 14vac transformer would provide enough rectified voltage to keep 15v regulators happy?
Thoughts??
Thanks,
JC
[EDIT - I actually used 10uF electros instead of the 50uF marked at the reg outputs]
This is the power supply design after implementing the 3630 mod by he-who-no-longer-wishes-to-be-named-on-this-forum.
I have a bunch of surplus power transformers with 14vac secondaries that I thought this might be a good design for (to make bipolar 15 and 18vdc from a single 14vac secondary). The transformers that would be good for this design, so I thought I'd give it a whirl. I have questions:
When I measure the voltage at pin 2 of the 7915 I get around -47vdc. At pin 1 of the 7815 I measure +46vdc. Wow.... that's a lot more voltage than I would normally expect at the front of these regulators.
Is this normal? When I measure the output of the 7915 I'm getting almost -18vdc, not -15. The + is fine at +15, however. I've double, triple, and quadruple checked my wiring, and was just wondering if the regulators are gonna fail or what. I'll stick another 7915 in to see if I got a mislabeled 7918 by any chance, but was really curious about the high voltage feeding these regulators, and specifically, if its a problem.
Can anyone shed light on this design? I remember Keith saying that this is not an ideal psu design, but I can't find his post and don't remember his reasoning. I just wanted to use my surplus transformers to make some bipolar psu's and thought this might be worth trying.
On another note, my transformers can be wired 28vac w/CT. Do you think it'd be okay to use a more typical design with 15v regs? That is do you think a 14vac transformer would provide enough rectified voltage to keep 15v regulators happy?
Thoughts??
Thanks,
JC