Transformer from Sony A/V Receiver - what's up with these windings?

[Stephen Morgan]

A friend gave me a transformer from a Sony A/V receiver. He didn't know the Sony model, I think it was 7 channels, or maybe 7.1, possibly 100 Watts per channel. I figure if Sony was claiming 7 channels of 100 Watts, it might be a good start for a 2 channel 100 Watt amplifier. Output devices are MP1620 / MN2488.

The secondary high current winding has 5 wires, with voltage as follows, measured with 120 VAC on primary, no load on secondary:

Orange - 44
Yellow - 27.4
Black - 0
Blue - 27.4
Red - 44

So, we have the makings of a +/- 62 VDC or +/- 38 VDC supply. According to my math, that would be about 240 Watts or 90 Watts into 8 ohms.

Anybody know how this thing was used? Guesses also welcomed.

 

[XEAGLEKEEPER]

Sounds about right. If there is a part number you could call sonys techline and maybe find out the VA rating?

 

[stoN_Cold]

Hi !

Measured dimension of that transformator.
Maybe we can calculate VA rate(transform in mm ).
Regards zeoN_Rider

 

[XEAGLEKEEPER]

Have you tried googling that part number?

 

[Stephen Morgan]

Actually, what I was wondering about was the voltages - one pair seems too low for a 100 Watt amplifier, the other pair seems way too high.

I was hoping maybe someone had seen one of these before and knew what Sony did with those taps.

 

[XEAGLEKEEPER]

Have a look at these amps
http://sound.westhost.com/project3a.htm 100watt 38vdc
http://sound.westhost.com/project101.htm 180-200 watt 66vdc

 

[Stephen Morgan]

Thanks for the amplifier recommendations XEagleKeeper, but allow me to drag this back on-topic:

Why are there two sets of taps on the secondary?

 

[XEAGLEKEEPER]

Probably because the sony required two different supply voltages.Real hard to say without a schematic!Possibly lower voltage for the preamp,flatamps and higher voltage for the poweramps???

 

[Stephen Morgan]

Hmmm. +/- 38 VDC is a bit high for a preamp, and I have no idea what a flatamp is (neither does Google 🙂 ). And this is the high current winding - there is a separate low current winding measuring 14-0-14 that is almost certainly for the low-level stuff.

Thanks.

 

[djk]

Voltages sound right for a 5-ch 100W class H amplifier.

 

[XEAGLEKEEPER]

Instead of guessing get a service manual! Flat amp term used to decribe a driver section of a preamp( yamaha's term anyway) as in flat response no coloration of source signal. My yamaha C-4 PREAMP runs a +/- 45vdc so 38vdc is not out of the question.Have you tried a Sony techline.....

 

[ostie01]

Maybe this is crazy, forgive me but somebody told me last year that sony had some models with switching power supply.

 

[sam9]

A number of AVR's including Sony have a switch on the back labeled 4 0hm vs. 8 ohm. The purpose is to get the user to use lower rail voltages with 4 ohm speakers. This indicates to me either that there are heat dissipation issues with a 4 ohm load or SOAR issues or both.

Such a switch would change which set of windings connect to the rails. I can't say this is the case in the example at hand, but it is a possibility.

 

[XEAGLEKEEPER]

I have a Yamaha HTR5560 that has a similar switch for 8 & 6 ohm combinations. I guess that could also be a possibility.

 

[unclejed613]

the higher voltage is for 8 ohm, the lower for 4 ohm and for the surround amps.
60V is correct for a 100W/8r amp (44*1.414=62) and 38V is about right for 100W/4r.

 

[Stephen Morgan]

Thanks, UncleJed. That sounds good, except that's a 44-0-44 winding (88 VCT), which would give a +/- 62 VDC supply, which would be more like 240 Watts into 8 ohms. Oh, well, I'll find a use for it.