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Old 11th December 2014, 01:10 AM   #1
tiomilo is offline tiomilo  Costa Rica
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Default Behaivior under voltage ??

hi to all, working atm with one amplifier designed to run at +/- 100V DC. measured identical working amplifier is: no load +/- 120v dc loaded at 8 ohm +/- 100V 50% ( 27V rms out ) +/- 85V DC ( 80% 47V rms out ) original toroid secondary unloaded is +/- 80V, no further data can get, don't know the amperage there is no datasheet original part number XT-373 chain-mate industrial . now i found one similar size, but different output secondary twin 50V 0V 50V part number LVD021875 doing test only with diodes and capacitors run at +/- 75VDC unloaded, it could work ? is very hard to replace a toroid in my country, even if i can get it outside don't know how to looking for it. many thanks in advance.
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Old 11th December 2014, 01:36 AM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by tiomilo View Post
hi to all, working atm with one amplifier designed to run at +/- 100V DC. measured identical working amplifier is: no load +/- 120v dc loaded at 8 ohm +/- 100V 50% ( 27V rms out ) +/- 85V DC ( 80% 47V rms out ) original toroid secondary unloaded is +/- 80V, different output secondary twin 50V 0V 50V part number LVD021875 doing test only with diodes and capacitors run at +/- 75VDC unloaded, it could work ?
Toroidal transformer voltage regulation from no load to full load typically is -5% to -10%, with smaller toroids being worse.
The bulk capacitors in your amp must be somewhat undervalued for that large a drop under load.
Certainly the operation will be affected by about 1/3 less supply voltage, lower power output being the most obvious thing, but it could be acceptable.
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Old 11th December 2014, 02:24 AM   #3
JMFahey is offline JMFahey  Argentina
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Your measurements are way too high and you confuse DC with AC .

Please state:

1) what is the amp you are talking about.
2) What power out does it claim, into what ohms load.
3) What line power does it state it uses (in Watts or VA) .

Chain Mate is a Taiwan OEM supplier which obviously was used by your presumably Taiwan made amplifier.
They won't deal with a single transformer and maybe not even remember what it was, they build under Customer's specs, deliver, and that's it.

Why do you think that transformer is bad?

And as I said, +/-120V DC rails sound impossibly high, good for >1000W RMS amps

REAL 1000W, not "Taiwan Watts".
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Old 11th December 2014, 04:57 AM   #4
tiomilo is offline tiomilo  Costa Rica
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Join Date: Apr 2012
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Quote:
Originally Posted by JMFahey View Post
Your measurements are way too high and you confuse DC with AC .

Please state:

1) what is the amp you are talking about.
2) What power out does it claim, into what ohms load.
3) What line power does it state it uses (in Watts or VA) .

Chain Mate is a Taiwan OEM supplier which obviously was used by your presumably Taiwan made amplifier.
They won't deal with a single transformer and maybe not even remember what it was, they build under Customer's specs, deliver, and that's it.

Why do you think that transformer is bad?

And as I said, +/-120V DC rails sound impossibly high, good for >1000W RMS amps

REAL 1000W, not "Taiwan Watts".
hi and thanks for response,my bad the amplifier is a Yamaha P4500 take borrow my cousin's amplifier is the very same model, the toroid from mine have both primary 115v open, just made the measurements because the schematic diagrams don't have the values of secondary output, found too this post with almost the same results of mine: Reparatie si testare Amplificator Yamaha P4500 - Teste & Review-uri - Comunitatea Tehnium Azi
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