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Technics SU-7300 Replave 110V to 220V
Technics SU-7300 Replave 110V to 220V
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Old 14th January 2020, 04:21 PM   #1
nuno cesar is offline nuno cesar  Portugal
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Default Technics SU-7300 Replave 110V to 230V

Hello.
I have a Technics SU-7300 US version and is 110V, in very nasty condition. My goal is to practice and rebuild this amp, and if someting goes wrong i dont get very upset to blow up the amp.
But im based in Europe i canīt use it because we use 230V.
What option do i have?
Is possible to replace the transformer?
Should i get a cheap 230V to 110V converter?
For now i just opened and make a little clean.

Thanks
Attached Images
File Type: jpg SU-7300-1.jpg (984.5 KB, 68 views)
File Type: jpg SU-7300-2.jpg (791.9 KB, 68 views)
File Type: jpg SU-7300-3.jpg (988.3 KB, 70 views)
File Type: jpg transformador.JPG (66.0 KB, 77 views)

Last edited by nuno cesar; 14th January 2020 at 11:13 PM.
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Old 14th January 2020, 05:23 PM   #2
JonSnell Electronic is offline JonSnell Electronic  United Kingdom
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Hi.
I would find out why the fuses have blown but an auto transformer will be the most reliable option to power it, if the transformer is OK.
Here is the service manual; Download TECHNICS SU-7300 Service Manual
Before powering it up, check you have continuity between Black and Red, the primary of the transformer, you will know where to go from there.
A suitable auto transformer would be; RS PRO 50VA Enclosed Autotransformer, 230V ac Primary, 115V ac Secondary | RS Components
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Last edited by JonSnell Electronic; 14th January 2020 at 05:25 PM. Reason: More information added
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Old 14th January 2020, 05:46 PM   #3
Mark Tillotson is online now Mark Tillotson
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Well the cleaning work is impressive!
Have you checked the existing transformer primary and secondaries are intact? If its blown you'll need a replacement transformer anyway. You can check to see if its a dual primary, 'cause that would simplify things.
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Old 14th January 2020, 06:18 PM   #4
MAAC0 is offline MAAC0  Portugal
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Nuno:

Nominal Voltage in Portugal is 230 / 400 V and not 220 / 380 V.

Power consumption is 140W. So you'll need at least a trafo with this power, unless You don't krank up the volume.

A motor winding workshop could count the primary windings and rewind it for 230V operation. Just double the windings.
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Old 15th January 2020, 10:47 AM   #5
nuno cesar is offline nuno cesar  Portugal
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Quote:
Originally Posted by JonSnell Electronic View Post
Hi.
I would find out why the fuses have blown but an auto transformer will be the most reliable option to power it, if the transformer is OK.
Here is the service manual; Download TECHNICS SU-7300 Service Manual
Before powering it up, check you have continuity between Black and Red, the primary of the transformer, you will know where to go from there.
A suitable auto transformer would be; RS PRO 50VA Enclosed Autotransformer, 230V ac Primary, 115V ac Secondary | RS Components

Good morning . Thank you for the tip and links. I already download the service manual.
One fuse is blow. I will get replacement soon and make more test.


Quote:
Originally Posted by Mark Tillotson View Post
Well the cleaning work is impressive!
Have you checked the existing transformer primary and secondaries are intact? If its blown you'll need a replacement transformer anyway. You can check to see if its a dual primary, 'cause that would simplify things.

Not checked yet. What you mean by dual primary transformer?


Quote:
Originally Posted by MAAC0 View Post
Nuno:

Nominal Voltage in Portugal is 230 / 400 V and not 220 / 380 V.

Power consumption is 140W. So you'll need at least a trafo with this power, unless You don't krank up the volume.

A motor winding workshop could count the primary windings and rewind it for 230V operation. Just double the windings.



Yes, you are right. 230V. I will need a trafo to replace the inside transformer, or an external transformer?
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Old 15th January 2020, 11:17 AM   #6
Mark Tillotson is online now Mark Tillotson
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A dual primary transformer has dual primary windings, each 110V. You connect them in series for 220V operation and in parallel for 110V.
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Old 15th January 2020, 06:42 PM   #7
Holmer is offline Holmer  Germany
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Unfortunately this one has a single primary (after a look at the manual).

And it looks like it is potted, and even if not, the secondaries will probably be on top of the primary. Rewinding both makes little sense. Better disconnect it, measure the voltages (on a variac or with a light bulb in series, you only need the ratios) and get a replacement.
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Old 16th January 2020, 11:31 AM   #8
nuno cesar is offline nuno cesar  Portugal
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Good day. I decided to purchase a 230V to 110V transformer.


Is to much hassle to replace the 110V Transformer and i dont have the knowlege to do this.

to be honest i dont even know is the amp works or not.

Im still looking for a replacment of the 125V 3A glass fuse that is blew up.


Thank you all and have a nice day.
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