Variacs N Stuff

Yamaha used to have national service training. One year, the B6 and "X power" were both introduced. B6 looks like Darth Vader. It has a Carver magnetic field power supply, and is rated at 250w/ch. Yamaha set it up on loads and plugged the power into a 30 amp variac. They had the amp running full power into 8 ohms, then began to lower the AC voltage on the variac. pretty soon the amp was grunting, and every light in the room was madly flickering as the switchmode was making up for low voltage by drawing more current. The demo was impressive! IIRC the AC voltage was reduced to 85 volts.
 
nakdoc said:
Yamaha used to have national service training. One year, the B6 and "X power" were both introduced. B6 looks like Darth Vader. It has a Carver magnetic field power supply, and is rated at 250w/ch. Yamaha set it up on loads and plugged the power into a 30 amp variac. They had the amp running full power into 8 ohms, then began to lower the AC voltage on the variac. pretty soon the amp was grunting, and every light in the room was madly flickering as the switchmode was making up for low voltage by drawing more current. The demo was impressive! IIRC the AC voltage was reduced to 85 volts.
Click to expand...


Well, I heard of reports that heat could cause issues in this amp. Shaped like a pyramid, and the transformer at the top, it may have killed itself and it may have just been a coincidence that it was on a Variac. I don't know if it's possible for that amp to "Try" to draw more current if the voltage is dropping with the way the Triac works or not. You could come up with a scenario in your head but whether it happens like that or not who knows. It was not a huge seller.
 
Don"t know also, whether they had the top off when they were "Testing" that amp and I think the top had the heat sink in it so the top NEEDS to be on. a just never know what they were doing.
 
nakdoc said:
Yamaha used to have national service training. One year, the B6 and "X power" were both introduced. B6 looks like Darth Vader. It has a Carver magnetic field power supply, and is rated at 250w/ch. Yamaha set it up on loads and plugged the power into a 30 amp variac. They had the amp running full power into 8 ohms, then began to lower the AC voltage on the variac. pretty soon the amp was grunting, and every light in the room was madly flickering as the switchmode was making up for low voltage by drawing more current. The demo was impressive! IIRC the AC voltage was reduced to 85 volts.
Click to expand...
Found this info on the B6, wasn't such a great one as shown by how fast it was gone away.
http://www.thevintageknob.org/yamaha-B-6.html
 
Last edited:
Variac Panel 1.jpgVariac Panel 2.jpgVariac Panel 3.jpgVariac Panel 4.jpg

Some I have grabbed shots of off the web. Thought these were cool but the OPs double meter with A or W option is slick, too.
 
All of my test equipment (load bank, power source, oscillators, scope etc) is rack mounted. The ac power source includes a voltmeter (taken on the output receptacle), and ammeter. I incorporated the series light bulb and switches into a 4 space chassis. I built the rack out of 3/4" plywood almost 40 years ago with oak rack rails. It's served me very well. A few years ago I upgraded the variac to something like 20 amps.

The rack keeps everything close while not taking up bench space. It's very efficient and flexible.
 
I have another winter project. I just score a 5 amp model with both an Amp Meter, AND a Watt Meter. This comes in handy for the preamps and smaller components besides Amps. Now I just got to get my friend to weld the 2 small holes shut , have it blasted and powder coated to match my other Variac. Ain't it cute??? After this, I'll find the 20 amp version and be done.... I also got a NIB transformer for it and if it's meters are beat (they appear to be fine), I have a couple. A new cord, some NOS fuse holders, and a new face applique..... 5ampVariac.jpg

She'll look nothing like this when I get done.


5ampVariac.jpg
 
Yes sir it does. I will preserve the integrity of that feature for sure. No cords from Cina on this baby.....
 
In the oilfield those are "perforated" power cords...
 
I think that three-meter beauty should go out for chrome plate!
 
You must log in or register to reply here.
Back
Top