Hi All,
I got a Denon DP-3000 from Japan and need to step down the AC voltage from 120V to 100V. Can this be done with a resistor? If I do the math, it draws 14W, so to drop 20V I would need a 28.57 ohm resistor, rated for 20W? Sure I can purchase a step down transformer and in the long run, I will, but I need to test the operation before I spend any more money.
I got a Denon DP-3000 from Japan and need to step down the AC voltage from 120V to 100V. Can this be done with a resistor? If I do the math, it draws 14W, so to drop 20V I would need a 28.57 ohm resistor, rated for 20W? Sure I can purchase a step down transformer and in the long run, I will, but I need to test the operation before I spend any more money.
Variac is the way to go.
https://www.amazon.com/dp/B078Z7XYT2/ref=twister_B07G5BHXYV?_encoding=UTF8&th=1
https://www.amazon.com/dp/B078Z7XYT2/ref=twister_B07G5BHXYV?_encoding=UTF8&th=1
Dropping with a resistor does not give a stable drop. You need to use a 20 volt transformer of appropriate current rating to drop the line by 20 volts. It will not be as large as a 120 to 100 volt transformer.
Hoping someone here posts a simple schematic before I start scribbling on a piece of paper.
Hoping someone here posts a simple schematic before I start scribbling on a piece of paper.
A VERY common problem in Brazil.
It has the largest amount of Japanese descendants (Nisei) in the World, and customarily Nisei kids travel to Japan for 1 year after finishing high school,so around 18-19 y.o. , to work at Toyota - Nissan - Sony - Yamaha, etc.
MANY bring back their rocker youth dream:"a Marshall!!!!" 😉 , which is almost impossi9ble to buy in Brazil (high Tariff barriers) and easy in Japan, just a couple Months salary.
BIG problem is they bring the 100V version, complicated because Brazil is slowly switching its nominal 110V mains to hot 127VAC .... amp head damage is widespread and the normal solution is a bucking transformer.
In that case, they use a 24VAC secondary one, easy to find over the counter, since they have to nominally drop 27V , go figure.
Same arrangement as shown above.
It has the largest amount of Japanese descendants (Nisei) in the World, and customarily Nisei kids travel to Japan for 1 year after finishing high school,so around 18-19 y.o. , to work at Toyota - Nissan - Sony - Yamaha, etc.
MANY bring back their rocker youth dream:"a Marshall!!!!" 😉 , which is almost impossi9ble to buy in Brazil (high Tariff barriers) and easy in Japan, just a couple Months salary.
BIG problem is they bring the 100V version, complicated because Brazil is slowly switching its nominal 110V mains to hot 127VAC .... amp head damage is widespread and the normal solution is a bucking transformer.
In that case, they use a 24VAC secondary one, easy to find over the counter, since they have to nominally drop 27V , go figure.
Same arrangement as shown above.
A resistor will get hot enough to cause a fire! If you do a variac you can use it for lots of other stuff. A bucking transformer is fine too and less expensive but it is a one use item.
It's common to use a Buck/Boost transformer for this task.
But it takes knowledge and skill to do it safely.
Rod Elliott has lots of info:
" Bucking (And Boosting) Transformers"
https://sound-au.com/articles/buck-xfmr.htm
But it takes knowledge and skill to do it safely.
Rod Elliott has lots of info:
" Bucking (And Boosting) Transformers"
https://sound-au.com/articles/buck-xfmr.htm
Show your work. I don't think this is right.
(Aside from the fact that the "14W" may be only nominal. It is mostly motor, motor draw varies with load, from start-up to over-run.)
14W at 100V is 0.14 Amps. 20V at 0.14A is 143 Ohms and 2.8 Watts. Use a 150r 10 Watt resistor with a 3k 1/2W in shunt.
Plan B: get the schematic/service manual.
Very much doubt motor is straight Mains voltage, guess it´s a Servo controlled DC one, the whole (motor and controller) fed from a lower DC voltge, think 24V DC or so, fed from a stepdown transformer into a regulated power supply.
Meaning the stepdown transformer could have several primary taps (or at least 100-120VAC) OR if secondary is an "easy" one, say 24VAC , you could buy a 120>24V one (or whatever´s needed) from one of the usual suppliers.
Getting a proper PT will be less clumsy/kludgy than any external Variac or Bucking trafo any day of he week, it can sit unobtrusively inside the TT itself.
Post some gut picture 😉
Juan,
Good idea, but it looks like only a 100 volt input winding. So a buck transformer is the best way. I would not try to replace a turntable transformer as isolation and shielding requirements are quite stringent.
However I would measure the actual AC line voltage as it really is above 120 volts in many U.S. places and then use probably a common 24 volt transformer to buck it. Schematic seems to me to be able to tolerate a slightly low voltage. However I personally would use an 18 volt transformer and add a few turns. However that seems a bit beyond most.
https://www.diyaudio.com/community/threads/denon-dp-3000-service-manual-or-schematic-needed.368411/
Good idea, but it looks like only a 100 volt input winding. So a buck transformer is the best way. I would not try to replace a turntable transformer as isolation and shielding requirements are quite stringent.
However I would measure the actual AC line voltage as it really is above 120 volts in many U.S. places and then use probably a common 24 volt transformer to buck it. Schematic seems to me to be able to tolerate a slightly low voltage. However I personally would use an 18 volt transformer and add a few turns. However that seems a bit beyond most.
https://www.diyaudio.com/community/threads/denon-dp-3000-service-manual-or-schematic-needed.368411/
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IF, the load current is substansially constant, a voltage dropping capacitor can be a good solution. This is a technique used for some antique radios that used the resistance of a special line cord to lower voltages. Those line cords were known as curtain burners due to the fires that were inevitable.
A motor run capacitor is generally used. No heat is generated unlike a resistor.
A calculator can be found at, https://vintage-radio.com/repair-restore-information/valve_dropper-calcs.html
A motor run capacitor is generally used. No heat is generated unlike a resistor.
A calculator can be found at, https://vintage-radio.com/repair-restore-information/valve_dropper-calcs.html
A couple of these back to back inline with the 120V nput wuold work.
20V5W Zener
https://www.digikey.com/en/products/detail/micro-commercial-co/1N5357B-TP/1114299?utm_adgroup=Diodes - Zener - Single&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Discrete Semiconductor Products_NEW&utm_term=&utm_content=Diodes - Zener - Single&gclid=EAIaIQobChMI_4O8htXq-wIVU8OGCh102ACoEAQYBCABEgLSJ_D_BwE
20V5W Zener
https://www.digikey.com/en/products/detail/micro-commercial-co/1N5357B-TP/1114299?utm_adgroup=Diodes - Zener - Single&utm_source=google&utm_medium=cpc&utm_campaign=Shopping_Product_Discrete Semiconductor Products_NEW&utm_term=&utm_content=Diodes - Zener - Single&gclid=EAIaIQobChMI_4O8htXq-wIVU8OGCh102ACoEAQYBCABEgLSJ_D_BwE
The diode trick interests me. You say back to back, you mean back to back in series or parallel?