120V to 240V internally

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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.

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 ?

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.

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.
 
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What are the connections to it ?
When you say solid state do you mean a switch mode power supply ?

Its a transformer coil/unit within a domestic device.

so.. it have primary and secondary terminals.

curiously the secondary has two 250v glass fuses on the circuit board that's attached to the terminals.

I'd include a picture if this site would let me attach one.
 
1) if the service manual describes rewiring the primary side for 240 and leaving the secondary alone, that is perfectly correct

2) 250VAC is one of the standard voltages for fuse ratings, it does not mean the secondary voltage is 250V


thanks..

its just that the pin numbers on the schematic don't match the pin numbers on the primary board of the transformer connection.

there are only three terminals and two are connected for 120v. I presume switch over the neutral to the other and assume its a 'live' connection for 240.

perhaps I'm being too careful, the fuses ought to blow if there's any power problems and the house 'safety' switches should throw if its a short.
 
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.

Well I definitely don't want to destroy the electronics.. So at least my caution and protracted enquiries is warranted.

the schematic has the numbers 2, 3 and 5 next to the lines that represent the primary yet the actual circuit board have 3 and 5 as connected but 2 isn't connected nor is there a pin there and 6 is connected to the primary but nothing to the mains power wires.

the schematic isn't matching the circuit board on the unit via pin numbers, hence my caution. I figure there are only three terminals on the primary. two are connected, surely the solution is a specific permutation of 2 out of the 3 possibilities(excluding the current one).
 
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.
 
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.
 
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.

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.

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.

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 don´t 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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Bought a CT-W703RS.. a cunning plan to modify.

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.
 
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 don´t 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.
 
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.
 
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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.(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.
.
 
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.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.