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120V to 240V internally
120V to 240V internally
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Old 7th December 2017, 10:19 AM   #11
AndrewT is offline AndrewT  Scotland
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first:
build a Mains Bulb Tester (MBT).
Power ON via the MBT to check your wiring.
Even completely incorrect wiring will not damage anything, not even the mains fuse when powered via the MBT.

second:
wiring a dual primary transformer incorrectly and powering directly from the mains can irreparably damage your transformer and your downstream circuits.

Before you power ON you can check some windings.
Preparing to measure the resistance of the windings.
You said there are 6 tags.
Find which ones are connected.
let's suppose your find that A, B & E are connected and that C, D & F are connected.
That tells you you have two windings and each winding has multiple tapping points.
Do that first and report back.
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Old 7th December 2017, 11:20 AM   #12
JMFahey is offline JMFahey  Argentina
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Quote:
Originally Posted by armarra1 View Post
Hi,
I apologise if this is in the wrong section , however I am trying to modify a 110v USA cassette deck to run on Australian 240v main input.

I've paid to download the service manual which includes the 'instructions' for changing voltage.

well.. the instructions are not that clear in identifying the pins to reconnect but it does mention the primary pins soley.
Please cut and paste here the page(s) dealing with voltage conversion so we can read what they actually say.

Quote:
what makes me worried is that the secondary has 250v glass fuses and clearly labeled 250v on its circuit board that's straight onto the secondary pins.

if this is step up, then what happens if I put 240volts across its primary ?
As explained above, this does NOT mean you have 250V at the secondary.

And in any case, the purpose of rewiting primary is to have no change on secondary voltage.

Quote:
I am assuming that by changing the primary to be across the two live pins instead of a live and neutral, that I get well.... 220v and that this goes to 250v at the secondary also.
With due respect, you have no clue but are messing with dangerous deadly voltage, stop messing with that cassette deck until you have a *clear* notion of what you are doing.

Quote:
as the voltages are high and I don't want to bugger the electronics can anyone suggest a course of action.

attached(at least I think so) is the downloaded pdf service manual. I refer to page 22 for relevant schematics. note.

holes 3 , 5 and 6 on the circuit board are the only ones that have terminals with pins on the transformer beneath and that pins 3 and 5 are connected to 120v plug and labelled live and neutral respectively.
Ok, please donīt touch the mains side (so for now refrain from working with that unit) until you have a clear set of instructions to follow.

EDIT: no service manual attached, please upload it.
Follow Forum instructions on how to do that successfully.
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Last edited by JMFahey; 7th December 2017 at 11:23 AM. Reason: Canīt find service manual
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Old 7th December 2017, 02:44 PM   #13
kodabmx is online now kodabmx  Canada
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It's less elegant, but using one of these would just be easier, no?

Just make sure the internal transformer is rated for 50Hz. 110V North American voltage is at 60Hz and running it from 50Hz will overheat the transformer is it's not rated for it.



Step Down Transformer US AC 220V To 110V Voltage Converter Travel Adapter 50W | eBay
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Old 7th December 2017, 10:16 PM   #14
armarra1 is offline armarra1  Australia
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Default Bought a CT-W703RS.. a cunning plan to modify.

Quote:
Originally Posted by nigelwright7557 View Post
If you measure primary impedance for 110v then it will be right when it is connected to give twice that impedance for 240v.

If its wrong it will likely destroy the electronics.
measured at already connected 120v and it was 35ohms

then measured the neutral to the only other spare terminal and it was 1 ohm(a short).

so lucky I measured.


there are about 6 taps all connected on secondary.
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Old 7th December 2017, 10:38 PM   #15
leadbelly is offline leadbelly  Canada
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120V to 240V internally
Again, don't jump to conclusions, the 1 ohm is likely not a short.

If there are 3 primary terminals, what is the resistance between any 2 terminals? Report back with 3 values.
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Old 7th December 2017, 10:53 PM   #16
armarra1 is offline armarra1  Australia
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Quote:
Originally Posted by JMFahey View Post
Please cut and paste here the page(s) dealing with voltage conversion so we can read what they actually say.


As explained above, this does NOT mean you have 250V at the secondary. got that, thanks.

And in any case, the purpose of rewiting primary is to have no change on secondary voltage. I know I know.. that's the idea but I'm just cautious


With due respect, you have no clue but are messing with dangerous deadly voltage, stop messing with that cassette deck until you have a *clear* notion of what you are doing.
I'm sending this forum question because I'm unsure. you needn't worry that I'm taking action without first checking. Else I'd have not posted here are we in agreement there ?

Ok, please donīt touch the mains side (so for now refrain from working with that unit) until you have a clear set of instructions to follow.

EDIT: no service manual attached, please upload it. I would if this site would let me do so. clicked browse, saw the file name in the list, clicked upload, no action/response. I'm using windows 10 and using Microsoft edge.

Follow Forum instructions on how to do that successfully.
thanks JM for your concern.

I'm thinking that if the primary has only three terminals one labelled neutral, the other live and the third not labelled then its possible that this is a multiple tap primary for 120 or 240 volts. but I'm being careful with that assumption and certainly not connecting to mains without checking first.
the fact that the service manual mentions to change the wiring on the primary side of this ACTUAL MODEL NUMBER of cassette player fills me with hope but I'm not yet fully convinced as the schematic doesn't identify the terminals enough.
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Old 7th December 2017, 11:01 PM   #17
armarra1 is offline armarra1  Australia
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Quote:
Originally Posted by leadbelly View Post
Again, don't jump to conclusions, the 1 ohm is likely not a short.

If there are 3 primary terminals, what is the resistance between any 2 terminals? Report back with 3 values.
So glad to hear you say that but puzzled as to why.


there are primary pins identified by

6 5 and 3.

5 says neutral on the board.
3 says live on the board.

the spare is 6 and says nothing.


3-5 is 35.6 ohms. 110volt power plug connected across 3 and 5.
3-6 is 35.6 ohms.
5-6 is 1 ohm.

also my multimeter leads say 1 ohm when I short them together.

Last edited by armarra1; 7th December 2017 at 11:21 PM. Reason: adding multimeter dead short ohms.
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Old 7th December 2017, 11:02 PM   #18
armarra1 is offline armarra1  Australia
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Quote:
Originally Posted by kodabmx View Post
It's less elegant, but using one of these would just be easier, no?

Just make sure the internal transformer is rated for 50Hz. 110V North American voltage is at 60Hz and running it from 50Hz will overheat the transformer is it's not rated for it.

thanks for the input, I've considered that... too easy

Step Down Transformer US AC 220V To 110V Voltage Converter Travel Adapter 50W | eBay
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Old 7th December 2017, 11:19 PM   #19
armarra1 is offline armarra1  Australia
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Join Date: Mar 2016
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Quote:
Originally Posted by AndrewT View Post
first:
build a Mains Bulb Tester (MBT).
Power ON via the MBT to check your wiring.
Even completely incorrect wiring will not damage anything, not even the mains fuse when powered via the MBT.

second:
wiring a dual primary transformer incorrectly and powering directly from the mains can irreparably damage your transformer and your downstream circuits.

Before you power ON you can check some windings.
Preparing to measure the resistance of the windings.
You said there are 6 tags.(yes actually.. 6 + [2 that go through the glass fuses] 8 in total but 1 isn't connected so 7 all up.
Find which ones are connected. All of them are to a ribbon cable that goes to the main board near the voltage regulators. oh I get it, check for resistance across the secondary taps to count the windings .. fine.
let's suppose your find that A, B & E are connected and that C, D & F are connected.
That tells you you have two windings and each winding has multiple tapping points.
Do that first and report back.
I am not sure about which are connected to eachother because the ribbon cable down to the main board cant be disconnected so I'm not measuring the secondary in isolation.
.
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Old 7th December 2017, 11:44 PM   #20
armarra1 is offline armarra1  Australia
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Quote:
Originally Posted by multi View Post
You could always use a 120 volt step down. I have ordered Tube amps from China and they tell you are 240 volts but I never trust them so use a step down to check. I always use a 240 volt 60 watt globe old type not a led in series with the amp with a switch, just to make sure after changing the wiring. If the wiring is correct the light globe will only light up a little if wrong very bright. Never tried it with transistor equipment.
thanks for the input. pun intended.
I'll keep it in mind.
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