Musicmanager
Well-Known Member
Hi Guys
Remembering I'm a novice can someone please help me with some advice.
A friend has given me a bench power supply, looks to be homemade - no manufacturers marks or numbers - single output 0 - 30vdc; there appears to be current limiting that works OK, analog volts and analog amps display but neither work.
It powers up OK and the voltage pot will adjust between approx. 1.5 and 33 volts and the amps pot will limit current with an LED indicator OK. When I opened the case neither analog meter is attached to anything which explains why they don't work and that's a project for later maybe. A good look over the PCB, all looks very clean and tidy and not very old - there is still some flux residue about in parts.
My immediate concern is the transformer - after the power has been on for a few minutes there is a considerable amount of heat - enough to make a slice of toast - which I don't think should be there (there is a heatsink on the main chip which gets warm but nothing outrageous). It is giving 24 vac out of 2 separate secondary sets ( only one of which is in use ) I'm guessing it's going to go belly up very soon so I need to find a replacement. There is a label on the frame but the language is outer mongolian or similar so no clue to identification from that.
Using a multimeter, I've measured maximum output of volts at 33.2 vdc which coincides with the scale on the analog volts display @ 30 vdc; I don't know how to assess the max amps limit, but the analog amps display scale goes up to 3 amps so I'm guessing that's right.
I've calculated my new transformer would need to be 100 VA based on max volts @ 30 x max amps @ 3 = 90 VA
Are there many flaws in my plan ?
Thanks
Remembering I'm a novice can someone please help me with some advice.
A friend has given me a bench power supply, looks to be homemade - no manufacturers marks or numbers - single output 0 - 30vdc; there appears to be current limiting that works OK, analog volts and analog amps display but neither work.
It powers up OK and the voltage pot will adjust between approx. 1.5 and 33 volts and the amps pot will limit current with an LED indicator OK. When I opened the case neither analog meter is attached to anything which explains why they don't work and that's a project for later maybe. A good look over the PCB, all looks very clean and tidy and not very old - there is still some flux residue about in parts.
My immediate concern is the transformer - after the power has been on for a few minutes there is a considerable amount of heat - enough to make a slice of toast - which I don't think should be there (there is a heatsink on the main chip which gets warm but nothing outrageous). It is giving 24 vac out of 2 separate secondary sets ( only one of which is in use ) I'm guessing it's going to go belly up very soon so I need to find a replacement. There is a label on the frame but the language is outer mongolian or similar so no clue to identification from that.
Using a multimeter, I've measured maximum output of volts at 33.2 vdc which coincides with the scale on the analog volts display @ 30 vdc; I don't know how to assess the max amps limit, but the analog amps display scale goes up to 3 amps so I'm guessing that's right.
I've calculated my new transformer would need to be 100 VA based on max volts @ 30 x max amps @ 3 = 90 VA
Are there many flaws in my plan ?
Thanks