Does anyone know how to convert voltage of Accuphase A-48 100v to 110/120v? Or does anyone provide information on voltage conversion table of Accuphase A-48?
All Accuphase amplifiers and preamplifiers I’ve seen use the same transformer type for US/EU/Japan markets, and therefore it is relatively easy to switch them to desired voltage.
Do you think both 100V and 120V are the same wiring?
No.
imhififan, do you have any reasons that looks like wired to 120V?
I was just guessing. Maybe the A-48 just changed
one set of
primary
winding
color of wires
(orange-red-gray)
only, and kept the second set
primary
winding
(yellow-brown-white) unchanged.
correct observation imhififan, Accus have different wiring colors, despite generic schematic is the same. not sure about resistance, using power VARIAC transformer starting with 0V AC and measuring major operational voltages (for example large cap banks) is the most reliable way to make sure no damage if wiring change is wrong.
1=white+orange 2= red 3= blue 4= black+yellow 5= brown 6=none
To measure DC resistance, you need to pull out all transformer primary winding wires from the quick connect terminals, make sure all wires not touching each others, using a DMM to measure the following resistance:
white - orange = ? ohm white - red = ? ohm
white - blue = ? ohm
white - black = ? ohm white - yellow = ? ohm
white - brown = ? ohm orange - red = ? ohm
orange - blue = ? ohm
orange - black = ? ohm
orange - yellow = ? ohm
orange - brown = ? ohm black - red = ? ohm
black - blue = ? ohm
black - yellow = ? ohm
black - brown = ? ohm
yellow - red = ? ohm
yellow - blue = ? ohm
yellow - brown = ? ohm
Please report back the result and see if we can figure out which wires belong to the two sets of
primary winding.
Plug in the amp to the mains (120v), measure voltage across terminal 1 and 3, if the voltage reading 140v or more the amp is wired to 100v, if the voltage is about 100v the amp is wired to 120v.
To measure DC resistance, you need to pull out all transformer primary winding wires from the quick connect terminals, make sure all wires not touching each others, using a DMM to measure the following resistance:
white - orange = ? ohm white - red = ? ohm white - blue = ? ohm white - black = ? ohm white - yellow = ? ohm white - brown = ? ohm orange - red = ? ohm orange - blue = ? ohm orange - black = ? ohm orange - yellow = ? ohm orange - brown = ? ohm black - red = ? ohm black - blue = ? ohm black - yellow = ? ohm black - brown = ? ohm yellow - red = ? ohm yellow - blue = ? ohm yellow - brown = ? ohm
Please report back the result and see if we can figure out which wires belong to the two sets of primary winding.
I tried to pull out all transformer primary winding wires from the quick connect terminals, but I could not pull them out since they are pushed into very tightly. Is there any way to pull them out easily? Or is it ok to pull them more strongly?
I tried to pull out all transformer primary winding wires from the quick
connect terminals, but I could not pull them out since they are pushed
into very tightly. Is there any way to pull them out easily? Or is it ok
to pull them more strongly?
Use a pliers on the connector metal crimp to pull and a flat head screw driver push on the connector tip should be able to release the connector.
From the picture of A-48 wiring, as @westcoastaudiophile pointed out,
the wiring scheme is the same as A-46, so I believe you can skip the resistance measurement, simply swap the black and brown wire, yellow and blue wire. The new wiring diagram will be:
1= white+orange 2= red 3= yellow 4= blue+brown 5= black 6= none
It is very important to make sure no damage
to the A-48
if wiring change is wrong!
I strongly recommend to use a Dim Bulb Tester to power up the amp.
to verify correct voltage can measure voltage on large capacitor terminals, which should be in a range 50V to 55V
As @westcoastaudiophil suggested,
measuring voltages across large filter cap is the most reliable way to be sure the conversion done right: power up the A-48 with 100V mains voltage before conversion and power up the A-48 with 120V mains voltage after conversion, the voltages across filter caps should measured
about the same.
Thank you very much, imhififan. I will appreciate very much if you would explain more about 'measuring voltages across large filter cap?' What should I do concretely to measure voltages across large filter cap?
The purpose of voltage conversion from 100v to 120v is to give the amplifier circuitry correct operation voltages.
https://1.bp.blogspot.com/-Yn62ubWAJB8/XZBPQoN1Z8I/AAAAAAADXY8/Fa5bof2bzGs7ECGh9lAp1qj-ddhNSw6dwCLcB... To measure voltages across large filter cap, use a DMM set to DC voltage measure voltage on 60000uF capacitor (RED probe on red wire connection, BLACK probe on the aluminum plate connection), you should get same or very close voltage reading by power up the A-48 with 100V mains voltage before conversion and power up the A-48 with 120V mains voltage after conversion.
BTW, I strongly recommend to use a Dim Bulb Tester to power up the amp at the first time after voltage conversion. If anything goes wrong the light bulb will simply light up instead of dimming and save the amplifier from any damage.
Although the Dim Bulb Tester is a low tech simple circuit connecting an incandescent light bulb in series from the mains to the amplifier, it is an amazing device works as a current limiter. Every one should have one in their tool box!
I am trying to convert an Accuphase A-48 from 100v to 120v as well. If anyone has a photo of the connections pre and post the conversion just like someone has posted, would be appreciated. Thanks.
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