Variacs N Stuff

nakdoc

Chief Journeyman
Joined
May 11, 2011
Messages
619
Location
Nashville, TN Music City
Tagline
highly biased
#26
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.
 

WOPL Sniffer

Veteran and General Yakker
Joined
Aug 10, 2015
Messages
11,223
Location
Minnie-Soda
Tagline
Screw it
#27
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.

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.
 

WOPL Sniffer

Veteran and General Yakker
Joined
Aug 10, 2015
Messages
11,223
Location
Minnie-Soda
Tagline
Screw it
#28
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.
 

Wheel-right

Chief Journeyman
Joined
Jun 24, 2019
Messages
781
Location
SoCal
Tagline
Man, Ya shoulda been here yesterday
#30
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.
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:

wattsabundant

Chief Journeyman
Joined
Apr 26, 2011
Messages
842
Location
Central Ohio
#33
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.
 

WOPL Sniffer

Veteran and General Yakker
Joined
Aug 10, 2015
Messages
11,223
Location
Minnie-Soda
Tagline
Screw it
#35
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
 
Top