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Internal rewiring of Parasound Halo A21 120V --> 230V voltage conversion

Hello everyone,
I recently acquired a gorgeous Parasound A21 which I imported from the US, and as I am really into DIY and opening things to check how it's made, I deliberately looked for a 2nd hand amp from the US, so I would have to switch the voltage operation by myself. I believe I have almost solved the problem, but considering the different sources I found online (none were exactly for the A21, rather for A52), I came to doubt the final moves.
The circuit board is a B4170A, I have already moved the jumper cable JP13 to JP14, the former being for AC120 V and the latter for AC230 V.
Now I'm facing the change into the big transformer wiring. I have a red wire on P4 and a white on P1, both connections labelled as AC120V. The target connectors are P5 and P6, labelled as AC 230V.
The last two transformer wires, yellow and black, are plugged onto "To Transformer TP12" and "P3" respectively, along with a "AC120V" written above both.

There are 2 more wires, P2 and TP11 which connected to the external fuse. ( I have already swapped it for a 6.3A slow blow one)

I know that for 120V operation, the transformers are connected in parallel, and they must be linked in series for 230V operation. The thing I do not know which one exactly are primary and secondary and all the cable are pretty well coated with plastic and I'm not sure how could I do an efficient continuity test.

I believe that I should plug P4 to P5, and P3 to P6. Does anyone know exactly which cable must be switched to please ? Also, I think I could/should change the internal fuses but I have not thought about those yet...
As a safety measure, I have created a power outlet linked in series with a 500W incandescent light bulb, to avoid surge on the A21, if I would come to mismatch some cable, which I'd rather avoid, thanks to this forum hopefully.
Thank you all for reading and hopefully understanding my issue, I wish you all a very pleasant day !
Zeka
zeka
imhififan's avatar
imhififan
2,179 posts
 
The thing I do not know which one exactly are primary and secondary and all the cable are pretty well coated with plastic and I'm not sure how could I do an efficient continuity test.
Based on the photo provided by @jea48

https://www.stereo.net.au/forums/uploads/monthly_11_2013/post-106386-0-69609600-1385421328.jpg

Those two green and two yellow wires in between the power transformer and four rail fuses are secondary.The red, white, black and yellow wires go to the B4170A circuit board are primary.
Also, I think I could/should change the internal fuses but I have not thought about those yet...
No, the four rail fuses should not be changed to lower rating.

I believe that I should plug P4 to P5, and P3 to P6. Does anyone know exactly which cable must be switched to please ?
If you can provide some close up photo of the connections, maybe we can give you more help.

As a safety measure, I have created a power outlet linked in series with a 500W incandescent light bulb, to avoid surge on the A21, if I would come to mismatch some cable, which I'd rather avoid,
Good idea!
zeka OP
5 posts
 
Hello everyone ! Thank you very imhififan for your answer and details. Excellent news, I called Parasound on the phone, explaining my situation and they emailed me with the procedure for the conversion.

Imhififan, yes, after reading some more on the transformers I realized I had misunderstood primary and secondary wire and continuity test for identification.

Changing the railed fuses is definitely not on the menu indeed, a seller from Germany I called probably tried to prevent me from the operation, saying stuff about internal fuses ratings. Well since I am naïve I immediately thought about those 4.

I can upload some pictures I have taken for others who'd need to do the same procedure, though they are not perfect

It turns out I was right, but not completely as the connector labels do not matter as much as the color code of the cables. These instructions are for B4170 board only.

-jumper JP 13 to JP14 
-white lead should go to P5
-yellow lead should go to P6
-Red and black leads should stay connected where they are
-rear panel fuse should be changed accordingly from the writing on it, 6,3A slow blow


imhififan's avatar
imhififan
2,179 posts
 
@zeka
Great, thanks to let us know, it will help other members if they need to do voltage conversion. Also kudos to Parasound of their great customer services!

corteng
2 posts
 

@zeka , I am in the same situation. I need to do the power conversion . I wonder if you can send me the squematic and some photos. Thanks

zeka OP
5 posts
 

@corteng  Hey mate,

Welcome to the parasound family ! So, I'm curently not very much in my house and trying to move in another place urgently. I did not have any schematic with me. Opening the amp is not quite possible right now :x

Did you already take a look inside the beast ? First thing is to identify your board number, the instructions I received from Parasound were litteraly a mere word file with the instructions I quoted last year 😂

However if you have basic knowledge in the field that should do it right. Since I cannot really open my amp in the coming days, here are my advices

- Open the amp on a large table, sit comfortably and start scouting the main board. There is a jumper cable where you can read JP13 next to the plug on the board, this one should be rewired on JP14 which is very close if I remember.

Then it's all about finding the P5 and P6 plugs, and plugging on it the white and yellow cable respectively.

Then you need to change the fuse which you can order on ebay easily.

Take your time, don't rush anything yet. Take pictures and post them here if you are unsure !

One great thing at the time I built and still use whenever I'm not sure about my wiring, is a powerful filament lightbulb in serie to your device. The  idea is that as long as the filament is cold, it has a very low resistance. Hence, if everything is normal in your wiring, your device will be powered and the lamp should remain off. It is important to use a lamp that requires much more power than the device you want to protect. For the A21 I bought a 500W filament lamp.
If there is a default on your circuit, the power lightbulb will take on the charge and avoid frying your circuit. You'll notice it gets bright instantly, meaning you have done something wrong.
Here is a link explaining it, in french, in case you'd want to do that with more details.

Cheers and good luck mate !
Zeka


http://pafgadget.free.fr/bidouillages/astuces-bidouilles.htm

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