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Thread: Furman Punch-10 transformer

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    Furman Punch-10 transformer

    I recently acquired a Furman Punch-10 rackmount unit missing its transformer. I was able to get the schematic for the unit, it shows the windings of the transformer, but no further detail (see attached pic). My question is, is there anyway to determine what kind of transformer I need to use since I know what the output voltages are supposed to be (+ and - 15V) and I know all the values of components in the power supply? It's a relatively simple design with very few components..
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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Hook it up to a bench power supply and measure the current demand for the +15 and - 15V rails. Next look as the physical size of the transformer. Go and search for transformers of that size with secondaries in the range 15-0-15 to 18-0-18 (guess for now) and note the the maximum secondary current, primary and secondary DC resistance ( or regulation if not available).

    Now download Duncan's PSU designer tool (search for it) and plug your transformer data in to see if will work. Your goal is to ensure that the input to the regulators is not less than 18V at full load and lowest expected line voltage. On the other hand you don't want the voltage too much higher else you might overheat the regulators.

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    Last edited by nickb; 09-29-2019 at 11:41 PM.
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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by StormLord11 View Post
    I recently acquired a Furman Punch-10 rackmount unit missing its transformer. I was able to get the schematic for the unit, it shows the windings of the transformer, but no further detail (see attached pic). My question is, is there anyway to determine what kind of transformer I need to use since I know what the output voltages are supposed to be (+ and - 15V) and I know all the values of components in the power supply? It's a relatively simple design with very few components..
    Agree and add: please post the FULL Punch 10 schematic, may help reasonably estimate current/power consumption demands.

    Yes, the supply is simple, but we know nothing about its load .

    Thanks.

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    Juan Manuel Fahey

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    Quote Originally Posted by nickb View Post
    Hook it up to a bench power supply and measure the current demand for the +15 and - 15V rails. Next look as the physical size of the transformer. Go and search for transformers of that size with secondaries in the range 15-0-15 to 18-0-18 (guess for now) and note the the maximum secondary current, primary and secondary DC resistance ( or regulation if not available).

    Now download Duncan's PSU designer tool (search for it) and plug your transformer data in to see if will work. Your goal is to ensure that the input to the regulators is not less than 18V at full load and lowest expected line voltage. On the other hand you don't want the voltage too much higher else you might overheat the regulators.

    Good idea, I'll try this. Probably going to need to get another bench power supply though because I don't think I can get + and - 15V out of one channel, right?

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    Quote Originally Posted by J M Fahey View Post
    Agree and add: please post the FULL Punch 10 schematic, may help reasonably estimate current/power consumption demands.

    Yes, the supply is simple, but we know nothing about its load .

    Thanks.
    OK, here's the full schematic Furman PUNCH-10 - Schematic.pdf

    Thanks

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    "Thermionic Apocalypse" -JT nickb's Avatar
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    Quote Originally Posted by StormLord11 View Post
    Good idea, I'll try this. Probably going to need to get another bench power supply though because I don't think I can get + and - 15V out of one channel, right?
    You will need two ( or a dual output supply). As Juan said, it may be possible to get an estimate looking at the schematic, thanks for that. It can get a bit time consuming and is prone to error.

    PS: Just took a look at the schematic. It looks like there are 10 x TL084, 1 x CD4013 and U12. The tyoe if U12 is not specified so can you take a look at the board and tells us what it is. Provisionally, the current it going to be really low. if we allow a typical 1.5mA / opamp that's 60mA. If we said 100mA max I think that would be pretty safe. This implies a transformer of at least 250mA due to ineffeciency of the rectifers. So, go see what you can find that fits and post the candidate's data.

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    Last edited by nickb; 10-02-2019 at 10:20 AM.
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