Step down transformer for stereo amplifier

vmscbe1974

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Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions :
1. Brand to be used for the amplifier in India
2. What KVA rating of step down transformer should be used when it’s mentioned as 140 watts on the rear panel of the amplifier
3. Is it wise enough to buy the step down transformer generating no hum in speakers or let go of this amplifier and look out for Indian wattage adaptability.
A confused member .
regards
Srinivasan
 

yugaaa

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Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers . Three questions :
1. Brand to be used for the amplifier in India
2. What KVA rating of step down transformer should be used when it’s mentioned as 140 watts on the rear panel of the amplifier
3. Is it wise enough to buy the step down transformer generating no hum in speakers or let go of this amplifier and look out for Indian wattage adaptability.
A confused member .
regards
Srinivasan
Why dont you get it rewound ? It would be cheaper and fit in the same place ? Since the amp is used , you do not have to be bothered about warranty . It would also be a good time to check bias , electrolytics etc .
 

vmscbe1974

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Why dont you get it rewound ? It would be cheaper and fit in the same place ? Since the amp is used , you do not have to be bothered about warranty . It would also be a good time to check bias , electrolytics etc .
Oh okay . Will check with few techies who can do it here at my hometown
 

analogadikt

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Recently purchased a pioneer amplifier sa8900 rated at 110 watts (Japanese market ) obviously from the used market . After buying I read a thread in Hifivision for hum generated from step down transformers .
Srinivasan
Hi!
Your question is about a stepdown transformer while you seem to be referring to the output figures of the amplifier.
To get this straight, let's check what the spec sheets on the net say.

1)Output. : 60+60 watts @ 8 ohms load

2) Voltage. : 100 volts 50/60Hz

3) Consumption : 145 watts rated 380 max

You have to look into #2 and 3 to get a correct trafo.

Specs
Primary 240 volts, Secondary 100 volts capacity 500 watts (it should in VA but am in a hurry )

Get a transformer wound on EI core or toridal from a good transformer tech.
After that if hum problem occurrs the problem shall be somewhere else, not the transformer.

Regards,

Anwesh
 

IndianEars

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Perfect reply by analogadikt, viz:
Specs
Primary 240 volts, Secondary 100 volts, Capacity 500 watts



There should be NO Concern for Hum.

Please DO NOT get yr amplifier's internal transformer rewound, it will effectively no longer be the original as Both Primary & Secondary windings will be rewound, and if not done correct, it could even damage your amp when you re install the rewound transformer.

Just get an external transfo as recommended by analogadikt.
 

vmscbe1974

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Hi!
Your question is about a stepdown transformer while you seem to be referring to the output figures of the amplifier.
To get this straight, let's check what the spec sheets on the net say.

1)Output. : 60+60 watts @ 8 ohms load

2) Voltage. : 100 volts 50/60Hz

3) Consumption : 145 watts rated 380 max

You have to look into #2 and 3 to get a correct trafo.

Specs
Primary 240 volts, Secondary 100 volts capacity 500 watts (it should in VA but am in a hurry )

Get a transformer wound on EI core or toridal from a good transformer tech.
After that if hum problem occurrs the problem shall be somewhere else, not the transformer.

Regards,

Anwesh
Thanks Anwesh for your guidance technically . Will now look out as mentioned by you .
 

greenhorn

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Check what the primary winding of the trafo looks like. If there are two windings in series, they could be wired in parallel as a 230v
 

analogadikt

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Check what the primary winding of the trafo looks like. If there are two windings in series, they could be wired in parallel as a 230v
Hi greenhorn,

The transformer has a 100 volts primary. If it is made up of two windings in series, then each winding shall be rated at 50 volts, so connecting them in parallel shall make the primary 50 volts, a no go situation.

If the primary is two 100 volts windings in parallel, connecting those in series would result in a 200 volts primary, which also would not work with 240/250 volts supply that is common in urban areas nowadays.

Changing the internal trafo's primary would also entail that all other components on the primary side would need to be looked at. The power switch on the front panel, would it be rated at 250 volts? The fuse rating would need to reworked and a new fuse installed.

IMO an external stepdown is the safest solution. I would also suggest to the op that before commissioning the job of building the trafo, he should monitor the actual voltage he is receiving at various times of day and night and share the information here. It would help to fine-tune the stepdown trafo specs.

Regards,

Anwesh
 

greenhorn

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Whoops I got the series and parallel mixed up. Generally stuff like pio stuff off that vintage tends to be built with components that would work with 230v, so you just might get lucky.


But 100v is something I suppose still makes a difference. Especially if you're lucky to live in a place which actually delivers 230v. In my house we get 180-200ish due to being far away from the greatest transformer, so I guess it would be a feature !
 

yugaaa

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Perfect reply by analogadikt, viz:
Specs
Primary 240 volts, Secondary 100 volts, Capacity 500 watts



There should be NO Concern for Hum.

Please DO NOT get yr amplifier's internal transformer rewound, it will effectively no longer be the original as Both Primary & Secondary windings will be rewound, and if not done correct, it could even damage your amp when you re install the rewound transformer.

Just get an external transfo as recommended by analogadikt.
Transformer rewinding is not a big deal . It is easy and a proper rewinding shop in an electronics market will do the job . At the factory the transformers are wound with respect to the geography destination of the amplifier . so 100v and 230v does not matter . Since the current required for the 230v will be lower than the current required for the 100v the wire thickness will be lower and there will be more windings but overall core winding will be the same . A real professional can handle the windings and it should not cost much to get the job done .
 

yugaaa

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Hi greenhorn,

The transformer has a 100 volts primary. If it is made up of two windings in series, then each winding shall be rated at 50 volts, so connecting them in parallel shall make the primary 50 volts, a no go situation.

If the primary is two 100 volts windings in parallel, connecting those in series would result in a 200 volts primary, which also would not work with 240/250 volts supply that is common in urban areas nowadays.

Changing the internal trafo's primary would also entail that all other components on the primary side would need to be looked at. The power switch on the front panel, would it be rated at 250 volts? The fuse rating would need to reworked and a new fuse installed.

IMO an external stepdown is the safest solution. I would also suggest to the op that before commissioning the job of building the trafo, he should monitor the actual voltage he is receiving at various times of day and night and share the information here. It would help to fine-tune the stepdown trafo specs.

Regards,

Anwesh
There is no power switch "rating" per se . We just need to know if the switch can handle the current . Since the switch handles 110v I am sure it can handle 230v . Else a switch should not cost more than Rs.100 .
 

greenhorn

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There is no power switch "rating" per se . We just need to know if the switch can handle the current . Since the switch handles 110v I am sure it can handle 230v . Else a switch should not cost more than Rs.100 .
Power switches do have a voltage rating. if you search for switches on mouser etc, you will see most of them have a max rated voltage
 

reubensm

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whenever i come across 100v or 110v equipment, i go in the following order

1) look to see if there is a voltage selector switch
2) look up the schematics to check if the transformer has multiple primary taps for multiple voltages - usually amplifier manufacturers included multiple voltage options on European and Asian (non-Japanese) models while they preferred dedicated 110v or 100v for the American/Canadian and Japanese market. However in most cases (not all), the same transformer was used in all models
3) look for a original transformer spare part, obviously the multiple voltage primary or 220v version
4) ascertain whether 220v transformer substitutes are available or the possibly of rewinding professionally
5) using a step-down transformer (usually and personally speaking, I avoid buying if I have exhausted the top-4)
 

IndianEars

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Have been reading & following this thread, which addresses a typical and frequent problem of using 110 Volt equipment in India.

vmscbe1974 does not seem to be comfortable with a soldering iron or multimeter and asked for advice on the way forward.

I believe (and stated so in my post) analogadikt (post #4 bin this thread) provided perfect advice... Particularly, to get an external step down transformer rather than rewind the existing internal transformer.

I am quite surprised to see repeated advice to rewind the existing transformer rather than buy an external step down transformer, hence this post.

A good hefty (atleast 500VA) 220 Volts to 110 Volts external transformer is practically essential kit for any buff dabbling in pre-owned HiFi. It can be used universally with any 110 Volt equipment.

Some technical facts:

The Power Transformer in an amplifier is an important component. Some classic amps like the budget NAD 3020 had tailored the power transformer to provide Punchy (transient) mid bass, even though it did not have the juice to sustain deep bass. Rewinding such a transformer would completely change the sonics of such amplifier.

I researched the amp in question and it does not seem to have split primary windings that can be jumpered for 220 V operation.... Hence I did not mention this course of action (particularly for someone who is not technically conversant).

*REWINDING A TRANSFORMER FOR 220 VOLTS OPERATION*

I suspect that many who recommend rewinding, do not intimately know the process. Simply stating that it should be entrusted to a professional rewinder is evading the issue.

vmscbe1974 does not seem to be comfortable with a soldering iron or multimeter and he would simply hand over the amp to a repair shop. He will have no say or control over who rewinds the transformer and the quality of the rewinding Job.


THE REWINDING PROCESS
Do have a Look at this video which details the process of completely stripping down a transformer for rewinding. The 110 Volt Primary is located in the CORE of the bobbin (i.e. the inner most winding). To rewind it, ALL the other windings MUST be completely removed and rewound!

Do also observe the tedious labour to separate & disassemble the laminations, one by one. This is a REAL world transformer with Varnish to hold the laminations together and prevent mechanical hum of the transformer. The Varnish cannot be completely removed, it remains as a coating on each lamination.

This video does NOT show how the transformer is put together (!), because it will reveal that all the laminations with Varnish will NEVER refit in place due to the added thickness of the varnish on the laminations. Hence the rebuilt Transformer will never have all the laminations, and its characteristics will always be poorer.


This second video (after 3 minutes) shows the process of reassembling the laminations. Do observe that the laminations shown are brand new... WITHOUT Varnish ... You will observe the process of hammering in place the laminations, and even with new (unvarnished) laminations, the reinsertion is tough.

To summarise, I would Strongly recommend that rewinding an Internal transformer be avoided at all cost, and retorted to only if a transformer burns out.
 

HIEND-Raja

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I agreed use external step down transformer instead of rewinding existing Original transformer. I have some worst experience even replaced new in India on my Denon amplifier 100V to 220V. Best solution you can find Maxine step down (220V to 100V) transformer available in market there are many range. You can find shop in Chennai - Ritchie Street also available in Amazon.in Maxine 2000W (2kva) with Toroidal Transformer price 9450R.
 

frend2001

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Have been reading & following this thread, which addresses a typical and frequent problem of using 110 Volt equipment in India.

vmscbe1974 does not seem to be comfortable with a soldering iron or multimeter and asked for advice on the way forward.

I believe (and stated so in my post) analogadikt (post #4 bin this thread) provided perfect advice... Particularly, to get an external step down transformer rather than rewind the existing internal transformer.

I am quite surprised to see repeated advice to rewind the existing transformer rather than buy an external step down transformer, hence this post.

A good hefty (atleast 500VA) 220 Volts to 110 Volts external transformer is practically essential kit for any buff dabbling in pre-owned HiFi. It can be used universally with any 110 Volt equipment.

Some technical facts:

The Power Transformer in an amplifier is an important component. Some classic amps like the budget NAD 3020 had tailored the power transformer to provide Punchy (transient) mid bass, even though it did not have the juice to sustain deep bass. Rewinding such a transformer would completely change the sonics of such amplifier.

I researched the amp in question and it does not seem to have split primary windings that can be jumpered for 220 V operation.... Hence I did not mention this course of action (particularly for someone who is not technically conversant).

*REWINDING A TRANSFORMER FOR 220 VOLTS OPERATION*

I suspect that many who recommend rewinding, do not intimately know the process. Simply stating that it should be entrusted to a professional rewinder is evading the issue.

vmscbe1974 does not seem to be comfortable with a soldering iron or multimeter and he would simply hand over the amp to a repair shop. He will have no say or control over who rewinds the transformer and the quality of the rewinding Job.


THE REWINDING PROCESS
Do have a Look at this video which details the process of completely stripping down a transformer for rewinding. The 110 Volt Primary is located in the CORE of the bobbin (i.e. the inner most winding). To rewind it, ALL the other windings MUST be completely removed and rewound!

Do also observe the tedious labour to separate & disassemble the laminations, one by one. This is a REAL world transformer with Varnish to hold the laminations together and prevent mechanical hum of the transformer. The Varnish cannot be completely removed, it remains as a coating on each lamination.

This video does NOT show how the transformer is put together (!), because it will reveal that all the laminations with Varnish will NEVER refit in place due to the added thickness of the varnish on the laminations. Hence the rebuilt Transformer will never have all the laminations, and its characteristics will always be poorer.


This second video (after 3 minutes) shows the process of reassembling the laminations. Do observe that the laminations shown are brand new... WITHOUT Varnish ... You will observe the process of hammering in place the laminations, and even with new (unvarnished) laminations, the reinsertion is tough.

To summarise, I would Strongly recommend that rewinding an Internal transformer be avoided at all cost, and retorted to only if a transformer burns out.
Getting a Step Down is the best way to go rather then fiddling with original winding of transformer any day.

I had imported a JDM Sansui D707 which was 100 V. Since there's friend who owns a transformer mfg company I took the Sansui transformer to him for rewinding. One look at the Sansui transformer and he told me that rewinding is a bad idea. It will almost impossible to match the quality and workmanship of original sansui transformer

Mind you before getting into Audio, Sansui were famous for their transformers. So I simply got a step down and slept peacefully after that.

Also a transformer will hum, its the nature of the thing. Hum could be imperceptible or loud but transformers do hum.

A general idea is to get a step down with at least double ratings then the amplifier transformer. So you can figure.

Hope this helps.
 

nikhilblr

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I've used normal step-down transformers available at loca hardware / electric stores for 800 rs without encountering any issues. I've used them for guitar amps and not stereo amps
 

AKT

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Option 1 (Recommended):
As mentioned earlier, if there is an option for multiple taps, any good mechanic can change that for you to 230v in about 30 mins. Some Japanese amps have jumper settings for selecting voltage taps, which a skilled user can even do himself. It's a 50/60Hz unit so you do not need to worry about voltage frequency anyhow which is usually the cause of hum.

Option 2 (Preferred):
I have been using Universal step down transformer (from BLR) for my sub and TV (one each) with great results. They have never been switched off in the last 6 years. No hum, no heat issues. Same goes with Maxine. Both would ship to Coimbatore.

Option 3:
I generally do not prefer to get the transformer rewound unless it's a table top radio kind of thing. It's just my idiosyncrasy, not to mean rewinding is always fraught with problems.
 

reubensm

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rewinding, if attempted, must be done professionally, i have come across quite a few rewound trannies that produce a gentle hum

By far the best rewinding job which i have come across is with one of our FM's amplifier's toroidal tranny. The job done was exactly like the original. I think he got it done somewhere in Pune. I checked the specs of the rewound tranny with the original NAD tranny and they were a perfect match. The tranny was also dead silent.
 
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