Help identifying this transformer

[charlie_bird]

This is a mains transformer in a Audire 2M power amp (made in the US in the eighties). I'm keen to find the manufacturer and or specifications. The only markings on it are 7256-71A. I've been googling like crazy and the only reference I found is the transformer was also used on Quartre amps. If anyone can help identifying the manufacturer  i'd be very grateful. Thanks 

[Addicted to music]

What is the reason to replace this transformer?

[Guest]

Ok

What do you want to know about the Transformer ? They are fairly basic things.

 

Normally (suspect) it would have 1 primary, secondary auxiliary (control and indication power) and a centre tapped secondary to power the stereo amplifier modules.

Being from USA it may or may not have dual windings for the primary that can be either series connected for 220vac or parallel for 110vac mains supply

 

Edited December 15, 2017 by Guest

[Addicted to music]

37 minutes ago, 125dBmonster said:

Ok

What do you want to know about the Transformer ? They are fairly basic things.

 

Normally (suspect) it would have 1 primary, secondary auxiliary (control and indication power) and a centre tapped secondary to power the stereo amplifier modules.

Being from USA it may or may not have dual windings for the primary that can be either series connected for 220vac or parallel for 110vac mains supply

 

Rough guess as to what is the pic provided in the OP and this link:

 

http://www.audioreview.com/cat/amplification/amplifiers/audire/model-2/prd_425296_1583crx.aspx

 

I doubt that looking at the size that the link provided says it's a 1000w transformer.  That's typical laminated  and it doesn't justify the size for 1kW.  More toward 300-500w especially for a 100WPC,   I have not seen a commercial amp use 1000W back in the 80s and definately not one that's for a 100wpc!     2ndly the  model 2 is rated at 100 wpc but no speaker impedance given, so assume 8ohms.  

 

This is not concrete as there is no measurements done and the op hasn't provided rail voltage measurements.  But for a typical 100 wpc amp they normally operate with rail voltages around the +/- 40-50V rails.  Let's assume 50V, the primaries are likely to be 50 \ 1.41 = 35V.  So this would have a typical 35-0-35 on the secondary winding of the transformer.  This is just a rough guess as no other info is provided! 

Edited December 15, 2017 by Addicted to music

[Guest]

1 hour ago, Addicted to music said:

Rough guess as to what is the pic provided in the OP and this link:

 

http://www.audioreview.com/cat/amplification/amplifiers/audire/model-2/prd_425296_1583crx.aspx

 

I doubt that looking at the size that the link provided says it's a 1000w transformer.  That's typical laminated  and it doesn't justify the size for 1kW.  More toward 300-500w especially for a 100WPC,   I have not seen a commercial amp use 1000W back in the 80s and definately not one that's for a 100wpc!     2ndly the  model 2 is rated at 100 wpc but no speaker impedance given, so assume 8ohms.  

 

This is not concrete as there is no measurements done and the op hasn't provided rail voltage measurements.  But for a typical 100 wpc amp they normally operate with rail voltages around the +/- 40-50V rails.  Let's assume 50V, the primaries are likely to be 50 \ 1.41 = 35V.  So this would have a typical 35-0-35 on the secondary winding of the transformer.  This is just a rough guess as no other info is provided! 

Yep, right you are, similar to this beasty yoinked from a fried Yamaha, rated at 100wPC, which I find errr, enthusiastic at best.

All sorts of good taps on that one suitable for linear supply for say, a PC

Pictured next to a 200va Isolation E Isolation Tx for scale

 

I have never ever seen that many mass produced commercial amps have really great transformers either, always "barely" enough

 

OP seems to have baled

[charlie_bird]

5 hours ago, 125dBmonster said:

Ok

What do you want to know about the Transformer ? They are fairly basic things.

 

Normally (suspect) it would have 1 primary, secondary auxiliary (control and indication power) and a centre tapped secondary to power the stereo amplifier modules.

Being from USA it may or may not have dual windings for the primary that can be either series connected for 220vac or parallel for 110vac mains supply

 

 

No haven't bailed, just been busy through the morning.   I'm exploring the idea of converting to 240 mains and if that isn't technically or financial feasible, need to work out a suitable step down transformer (not my first choice). 

 

The primary winding is 120V and it doesn't appear to have and additional primary allowing for 240V operation ( its matching pre-amp does). I did take some measurements using a standard step-down transformer. With an input voltage of 123VAC the first secondary output  voltage is 76.5V and the other secondary is 7.25V .  There is additional terminal on the transformer (that I believe is ground) and it connects to the negative (middle) of the filter capacitors which are series connected. I can't post some additional pictures and a block diagram if required. 

 

I guess the specification I'm missing is the secondary current rating, particularly the 76V output. From what I've read on the internet, these amps are know for being 'overbuilt' and this transformer is physically pretty massive. I measure 14cm x 14cm x 12cm .  There a couple of places on the net saying the transformer is 1KW... I have also attached a picture of the back of the amp showing the stated input fuse size and power consumption if that helps. 

  

Its a pretty cool amp and sounds great. Unlike your vintage Sansui's (or whatever), there is no information on the net for these amps. The company is long out of business and the owner is approaching his nineties. I have not tried to contact him.
 

[stereo coffee]

I seem to recall ATCO being a manufacturer of such C core transformers.  As for stepping voltage down

the rear panel suggests that there is a primary tap at 240v indicated by the fuse markings. Could be just a matter of contacting Audire  http://www.audire.in/index.html#about

 

Hopefully Audire now apparently based in India, is the same firm that made the 2M

[Guest]

1 hour ago, charlie_bird said:

 

No haven't bailed, just been busy through the morning.   I'm exploring the idea of converting to 240 mains and if that isn't technically or financial feasible, need to work out a suitable step down transformer (not my first choice). 

 

The primary winding is 120V and it doesn't appear to have and additional primary allowing for 240V operation ( its matching pre-amp does). I did take some measurements using a standard step-down transformer. With an input voltage of 123VAC the first secondary output  voltage is 76.5V and the other secondary is 7.25V .  There is additional terminal on the transformer (that I believe is ground) and it connects to the negative (middle) of the filter capacitors which are series connected. I can't post some additional pictures and a block diagram if required. 

 

I guess the specification I'm missing is the secondary current rating, particularly the 76V output. From what I've read on the internet, these amps are know for being 'overbuilt' and this transformer is physically pretty massive. I measure 14cm x 14cm x 12cm .  There a couple of places on the net saying the transformer is 1KW... I have also attached a picture of the back of the amp showing the stated input fuse size and power consumption if that helps. 

  

Its a pretty cool amp and sounds great. Unlike your vintage Sansui's (or whatever), there is no information on the net for these amps. The company is long out of business and the owner is approaching his nineties. I have not tried to contact him.
 

Yea, cool

You explained the transformer and it's connections ok, so the only thing I suggest in light of the fuse ratings is have a really good look inside the case around the transformer primary to see if there are another pair of wires. Particularly good if there are 2 wires in parallel, that would indicate voltage change possible, probably

Sounds like a nice enough piece of kit.

Ask the Forum you might turn over a step down transformer, cheap if you have no luck otherwise.

 

cheers

[charlie_bird]

1 hour ago, stereo coffee said:

Could be just a matter of contacting Audire  http://www.audire.in/index.html#about

Hopefully Audire now apparently based in India, is the same firm that made the 2M

Yes I saw that, thanks. Not sure about the naming rights, but I'm pretty certain that the mob in India doesn't have anything to do with the Julius Siksnius - Audire amps

27 minutes ago, 125dBmonster said:

have a really good look inside the case around the transformer primary to see if there are another pair of wires. Particularly good if there are 2 wires in parallel, that would indicate voltage change possible

 

Here are some more pics and a bonus nudie.. 

 

The second primary is not apparent unless the terminals are tucked up inside somehow. I will need to completely disconnect the transformer to get a real close look. 

 

[Guest]

mmmmm ok

Taps 4,5 and 6 are fairly well unmistakable as the amp drive supply, center tapped, probably around the 55vac mark

If not mistaken, Taps 1 and 3 are the primary winding input (tell is the little filter cap) , 7 and 8 are is the auxiliary supply

 

Looks like you need an update or a step down unfortunately

 

Excellent photos well done.

 

 

Edited December 16, 2017 by Guest

[Guest]

If you really get into bother finding a reasonable alternative or step down, I have a 1Kw 240/115v transformer buried somewhere, but it's heavy and the paint on it a little sad. Otherwise functional and doesn't hum all that much. Could sort out something via PM as a last resort if you come up with nothing, locally

 

[charlie_bird]

39 minutes ago, 125dBmonster said:

If you really get into bother finding a reasonable alternative or step down, I have a 1Kw 240/115v transformer buried somewhere, but it's heavy and the paint on it a little sad. Otherwise functional and doesn't hum all that much. Could sort out something via PM as a last resort if you come up with nothing, locally

 

Thanks for the thought, much appreciated. I'll keep going and see how it comes up. 

[Sub Sonic]

@charlie_bird it looks like quite an interesting amplifier. Any chance of some more internal/external photos?

 

Regards,

 

SS

[charlie_bird]

9 hours ago, Sub Sonic said:

@charlie_bird it looks like quite an interesting amplifier. Any chance of some more internal/external photos?

 

Regards,

 

SS

Will do. I only have pictures of the innards of these amps, I'll grab some others and post them. 

[charlie_bird]

Getting back to the original topic, I think I need a 240V transformer with a 70V center tapped secondary i.e 35-0-35 and an additional secondary winding of 7VAC (or is it 6?, the lamps behind the meters are 6.3V). After thinking about my previous post, the power consumption figure stamped on the back of the amp, I'm guessing the power transformer rating should be no less than 500VA? 

 

1) Where would I purchase such a transformer? 

2) Would a Torroidal transformer with 2 @ 35V secondary windings be the same (35-0-35) ? and could I use a big torroidal for the 70V and a separate small one for the 7V ? 

 

Whilst most folks on this forum have more experience in these matters than I do, this youtube video explains the topology of my amplifier in very simple terms. Its a good video.. btw I think I have worked out who manufactured the original transformer in this amp and I will try to ring them next week, hopefully they are still in business !!