another 220v to 110v question

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I found the exact opposite of what I'm trying to accomplish through the search function, but it helped nonetheless.

http://www.diyaudio.com/forums/showthread.php?threadid=8141&highlight=transformer+220v

The unit is a Bose 901 equalizer from 1993 and I had Bose rewire it from 110v to 220v and now I want to change it back. It uses a (Markings: Pikatron D 6390 USINGEN NP 1076 QV 120993) transformer that currently is wired (on the primary) to the incoming wires on its outside taps and the 2 inside ones are shorted to create a series connection. It leads me to believe I have 2 equal windings together handling the 220v.

My question is: Can I disconnect the series connector and wire the 2 primary windings in parallel - to get it back to 110v operation? or is that a bad assumption? are there any gotcha's in phasing etc.?

sorry, i'm a rank amateur and it's been 20+ years since I've done this..I could of course send it back to Bose but on principle and pride feel I've already paid once to do this and I should be able to do it myself...:cannotbe:
 
Hi

You're quite right in saying you should be able to connect the primaries in parallel for 110V operation. Again, you are also right in assuming there are gotcha's with phasing! You must make sure that the beginning and end of the two windings are connected together, not vice versa. This should be quite simple since you already have them wired in series - the end of one winding will currently be connected to the beginning of the next, so you can work out what connection you need.

There may also be a mains fuse value to change. If this is so, it would involve a current rating increase. Try and determine what the present value of the fuse rating is and see if it's appropriate for the power drawn by the unit for 110V operation.

Take care,
Tim.

PS - Maybe Bose could provide a service manual that would help?

EDIT: Just so I'm clear, I mean both the winding beginnings and both the winding ends connected. :)
 
Hi,

Your assumption is correct. The phasing of the windings is of course vitaly important, but easily determined by deduction:
Lets call these primaries winding A and winding B.
At present, one end of winding A is connected to one end of winding B.
Disconnect that end of winding A, and connect it to the other end of winding B.
The 2 remaining winding ends can then be connected.

Clear as mud?

Cheers,
 
1 picture>=100 words
;)
 

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Thanks for the advice. I just converted my Bose 901 Series VI equalizer from 220V to 110V. Here are some specifics. Next to the primary of the transformer (the side where the power cord is soldered), there are three places for jumpers. For 220 volt operation, the one labeled LK1 is installed. To convert to 110 volt operation, remove the LK1 jumper. There are two spots (without jumpers in them, but with lines indicating there could be one) labeled 1-2 and 3-4. Next solder a jumper from hole 1 to hole 2, and a second jumper from hole 3 to hole 4.

I tested mine by checking voltage at testpoints indicated on the PCB for GND, +15V and -15V (located in the area behind the switches).

Hope this helps someone.

Al
 
To convert to 110 volt operation, remove the LK1 jumper. There are two spots (without jumpers in them, but with lines indicating there could be one) labeled 1-2 and 3-4. Next solder a jumper from hole 1 to hole 2, and a second jumper from hole 3 to hole 4.

Hmmmmm....

I'm looking at mine and see two holes to the the left and right of the LK1 jumper. Based upon the picture posted earlier, it looks to me like if you disconnect LK1, which seems to jump 2-3 and follows the picture, one would need to jump 1-3 and 2-4???

Any thoughts???

attachment.php
 

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'Tarzan' both voltage and a circuit require two conductors.
A US home has a 240V center-tapped AC power system. Large appliances use 240V while everything else operates on 120V.
The old 110V /220V is now ancient history.
So a 240V audio component could be used by connecting to a 240V appliance circuit.
 
Hello Speedskater,
As I wrote then, I was in a Good Mood and hence the "cheap" solution.
And yeah, we are moving or even moved to 240V AC.
Not so good for very old equipment. But few are in use today.
However I have to do some changes to these old radio's for the nostalgic customers.
Good looking antique radios are very sought after.
 
Yes it seems that much of the world is moving to higher & higher line voltages. Seven decades ago, the nominal US line voltage was 110V, then 115 or 117V, it leveled of at 120V for a long period of time. Now all new products are rated at 125V, which is what I sometimes see at my home.
The problem is, old tube equipment and legacy equipment have transformers designed for 110/115V. So plugging them into a 125V circuit overloads some transformers.
 
110, 115 117 and 125 are all the same voltage.

The equipment should be built to operate safely and correctly with any mains voltage from 110Vac to 125Vac.

The european harmonised supply requires all product sold into the EU to operate from 216Vac to 253Vac.That is the equivalent to 108Vac to 126.5Vac. It should be easy for any USA manufacturer/importer to meet a similar range of supply standard.

Prior to adopting the harmonised standard, the UK manufacturers had to guarantee safe and correct operation from 226Vac to 254Vac.
 
Thanks for the advice. I just converted my Bose 901 Series VI equalizer from 220V to 110V. Here are some specifics. Next to the primary of the transformer (the side where the power cord is soldered), there are three places for jumpers. For 220 volt operation, the one labeled LK1 is installed. To convert to 110 volt operation, remove the LK1 jumper. There are two spots (without jumpers in them, but with lines indicating there could be one) labeled 1-2 and 3-4. Next solder a jumper from hole 1 to hole 2, and a second jumper from hole 3 to hole 4.

I tested mine by checking voltage at testpoints indicated on the PCB for GND, +15V and -15V (located in the area behind the switches).

Hope this helps someone.

Al

For us late comers this is correct for 110v for Series VI I'm trying to convert mine back to 220v after 20 years and I forgotten what I had did. :) I'll try to put a photo of my 110v with LK1 removed since that helps. So looks like I need to put LK1 back in and remove the other two jumpers and I'll be back in business. 👍🏿
 

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