Accuphase A-48S

@imhififan 

I think you also need to following photos to figure out.

A-48S (1).JPG

A-48S (2).JPG

A-48S (3).JPG

A-48S (4).JPG

A-48S (5).JPG

A-48S (6).JPG

A-48S (10).JPG

A-48S (11).JPG

A-48S (12).JPG

Thank you in advance.

Why didn't you send him a PM or put this on the thread where it started? This is a first..

Making Frankenamps out of wonderful Accuphase equipment - you are messing with perfection in a less than perfect way.

Making Frankenamps out of wonderful Accuphase equipment - you are messing with perfection in a less than perfect way.

Thank you for your valuable opinion. I have no intention of opposing it or arguing with it. Let's get along, anyway. What I am interested in is only quality of sound.

@imhififan 

Since it's not easy to pull out the transformer wires (although I know I must pull out the transformer wires when I actually do conversion), a friend of mine who is familiar with PCB of electronics arranged an image which explains the connector layout for me.

Here's a link of the image:

A-48S_wires (003).jpg

Also, here are links for markings/part number of the component on the 716-1362-00:

716-1362-00 (1).JPG

716-1362-00 (2).JPG

According to him, the component on the 716-1362-00 is perhaps the bridge diode for rectification.

Hopefully, these photos will help you figure out.

Thank you.

@foolishman ,

Thanks for the photos, this time Accuphase is using a PCB instead of terminal block like before. Its connection method is still the same.

Looks like your friend already understands how these connectors work! Simply swap the positions of the black and yellow wires and swap the positions of the brown and orange wires to convert the power transformer primary winding from 100V to 120V.

On the #716-0962-01 board you will need to replace the small 100V transformer with a 120V one, or simply use a resistor to drop the input voltage.

IMHO, Accuphase products are certainly state of the art in terms of build and design, and if pricing was more affordable outside of Japan, I think more Accuphase enthusiasts would be able to enjoy it.

@imhififan 

Thank you very much for providing information on how to convert 100V to 120V. I have done accordingly, and I confirm I have successfully converted voltage to 120V. According to my friend, there's another way to convert to 120V, which is to swap the positions of the orange and yellow wires and swap the positions of the brown and black wires. Do you think it is OK?

Accuphase products are certainly state of the art in terms of build and design, and if pricing was more affordable outside of Japan, I think more Accuphase enthusiasts would be able to enjoy it.

I agree.

Information you provide always helps me. 

Thank you very much again.

there's another way to convert to 120V, which is to swap the positions of the orange and yellow wires and swap the positions of the brown and black wires. Do you think it is OK?

Yes, both the 100V and 120V setups have the two primary windings in parallel, swapping the position of the orange and yellow wires and swapping the position of the brown and black wires should also work.

@imhififan 

Thank you for your response. I will let him know about it. He will be glad to hear it.

Thank you again.

What can't I see the photo's. When I click on them it just takes me to Onedrive

@imhififan 

Would it be possible to convert the A-48S from 100V to 230V given that it has a soft start #716-0962-01 requiring a replacement transformer?

Could you advise what the wiring changes would be to the transformer to convert the primary winding to 230V

Thanks, Andy

@andyf

Convert 100V to 230/240V, in addition to replacing the standby circuit transformer on #716-0962-01,

1. You will also need to find out which wires belong to which set of primary windings using an ohmmeter.

2. Remove jumpers J1 and J3 and install jumper on J2, change fuse on board #716-1364-01 from 10Amp to 5Amp.

Thanks @imhififan 

I might be a bit slow, just what would I install on J2, as it only has a single tab.

Also, I believe that the standby circuit transformer has 3 pins on one side and 4 on the other. Does this suggest that it may be a center tap so can accommodate both 100V and 230V? It just needs wiring up differently.

Not being experienced, how would I go about finding a replacement transformer?

Thanks in advance for any help you can give.

Cheers, Andy

just what would I install on J2, as it only has a single tab.

716-1374-01 is a soft start resistor board. Based on my previous experience, two sets of resistors are connected in parallel via J1 and J3 (100/120V setting), and two sets of resistors are connected in series via J2 (220/240V setting).

I believe that the standby circuit transformer has 3 pins on one side and 4 on the other. Does this suggest that it may be a center tap so can accommodate both 100V and 230V? It just needs wiring up differently.

Sorry I don’t have an A-48S in front of me, I just based it on the photo provided by @foolishman, if the transformer does have a multi-tap primary winding, that would make voltage conversion much easier!

Can you post front and back pictures of your #716-0962-01 board?

how would I go about finding a replacement transformer?

This is the real challenge! Measure the secondary winding voltage, transformer size and its pin spacing, search for 230V versions on Digikey, Mouser, etc.

Thank you. Makes sense. I was going off the specs on the NMD website which says that the transformer is a 3 pin input 4 pin output.

https://www.nmd-trans.co.jp/p2_PinTypePowerTransformaer.html

HTP-35-12 transformer.

Looks like there are a lot of transformers available that will fit this package format from various manufacturers with a good selection of output voltages.

I'll continue to use my amps with a step down transformer for the moment, but think I will have a look at converting to 230V sometime in the next few months as it sure would be more convenient.

Has anyone measured the output voltages from the transformer, do you know?

Cheers, Andy

@andyf 

Thank you for providing the transformer spec. Sorry, I don't know the output voltage of the transformer, maybe @foolishman  has measurements.

However, I remember there was a post from an old thread mentioned that the relay was a 18VDC relay, so I'm guessing the output voltage of the transformer is probably about 13.6 to 14V.

If you decide to convert the voltage to 230V, please post your findings and some pictures of the voltage conversion, I'm sure Audiogon forum members who want to do something similar will find your post helpful and appreciated.

I have some free time tonight, so let’s discuss some details on how to connect the transformer to 240V.

1. Remove all the six transformer primary winding wires from the circuit board.
2. Use a multimeter to perform a continuity test to confirm which wires belong to which primary winding.
3. Connect the transformer primary winding wires as shown below.