Yamaha A-550

[angel]

Has anyone had any experience with the Yamaha A-550? I recently got my hands on one, and it works like a charm. It has a rather laid-back/warm sound, and for once, my better half even approves.

However, it is worn, and before starting to change parts, I would like to know more about the design, so I don't screw anything up. Searching around the net for information, especially schematics, yielded no real information. One site refers to it as a class A integrated amplifier, but the heatsink would suggest class B. The transistors used appear to be older types, with a four digit designation, not even listed on my equivalents list.

If anyone has the schematics, or any hints about it in general, I'd be most grateful.

[6502dude]

I found this msg on search for info on A-550.

A neighbour put one of these out for the trash pick up tonight.

It is in excellent shape and works fine.

Anybody got specs on this unit???

[KBK]

Look to the voltage of the main PS capacitors. If it is 63 Volts, then it is likely to be 'about' 75 watts per channel. I believe the A-550 was that wattage..and all the 5 series were 70-75W/Ch. (500, 550, etc)

They were overall...well built. Back when the world was still seen as an endless supply of natural reserves..and an endless garbage dump..and we could afford to put quality into gear for reasonable costs.

[anatech]

Hi angel,
I used to service Yamaha under warranty. With most manufacturers, class A only meant "turned the bias up way too high and now it will not last as long". In class A, it's still a class AB amplifier. There was no difference in sound quality, it was all marketing.

Yamaha service manuals were not expensive in Canada, try your distributor.

-Chris

[6502dude]

Originally posted by KBK
Look to the voltage of the main PS capacitors. If it is 63 Volts, then it is likely to be 'about' 75 watts per channel. I believe the A-550 was that wattage..and all the 5 series were 70-75W/Ch. (500, 550, etc)

They were overall...well built. Back when the world was still seen as an endless supply of natural reserves..and an endless garbage dump..and we could afford to put quality into gear for reasonable costs.

Thanks for idea on checking out power supply.

Power supply is +/- 41VDC

Power output transistors are 1 x NEC B616A (PNP) and 1 x NEC D586A (NPN) per channel.

Max collector current spec appears to be 5A and power diss. spec is 80watts for these devices.

There is not tolerance for over voltage with capacitors in power supply. They are only 6,800uf @ 50Vdc