1. Home
  2. amps-preamps
  3. 134896-34144

Please give me advice about an ARC VT 200 amp

In a few days I'll be the owner of an ARC VT 200.  I've never owned a tube amp, much less one of this size.  I'm reluctant to plug in this amp for fear that there may be some considerations that I'm overlooking.  I haven't found much info about the operation but I did read that a variac should be used to bring the voltage up, and that a shorting pin needs to be installed in the balanced inputs if the single ended inputs are used.  I've never heard of either a variac or shorting pin, and I'm wondering if you could please give me your thoughts about these items, as well as anything else that I should take into consideration before plugging it in, and during use.  

I will be using the single ended inputs.  The amp has not been turned on for 3 years.  I was told that the owner was fastidious about the maintenance of the electronics and the tubes.  Any thoughts would be greatly appreciated. 

Thanks
irish_tim
atmasphere's avatar
atmasphere
7,068 posts
 
@noromance a 60-100 watt bulb will do the job.

When the caps are fully charged, they won't draw current. The bulb goes out.

The bigger loads just take longer to put the bulb out.
noromance's avatar
noromance
1,780 posts
 
Thanks Ralph. Apologies for laboring the issue. 
jea48
2,944 posts
 
Did any of you guys look at the AC circuitry for the power supply of the VT200?
If has a soft start circuit that incorporates a triac (switch) that is in series with two parallel 10 ohm 20 watt resistors (5 ohms 40 watts) that feeds the Hot lead of the power transformer. For this circuit a 4 amp dual element, slow blow, fuse is used.
https://elektrotanya.com/audio-research_vt200_amplifier.pdf/download.html

The triac gate is powered by AC through a 100 ohm resistor. Main AC line fuse is a dual element, slow blow, 10 amp fuse.

Two relays RY1 and RY2 contacts are used in the AC power circuitry. A n/c contact on RY2 controls the triac gate and a n/o contact on RY1 controls full power to the hot lead of the power transformer.

Both RY1 and RY2 are controlled by the power transformer secondary windings DC power supplies.

The AC On/Off power switch is a DPST switch. In the ON position one set of contacts supplies power to the n/c contact of RY2 that feeds power to the gate of the triac. The other set of contacts, on the power switch, completes the circuit for the coil of RY1.
.
I’m not sure the series light bulb thing will work on this amp.
.

I will say I have used the series light bulb trick on simple across the line circuits in the past. It does a great job of reducing voltage and limiting current.

FWIW I have an old Marartz 5.1 multichannel amp I no longer use that I tried the series bulb thing on earlier today. It would not work on the amp. I used a 75 watt light bulb and when I energized the series bulb/amp circuit a relay in the amp started chattering causing the lamp to blink off and on. I could not get the amp to switch from standby to power on. Just a guess the relay was used somewhere in a protection circuit.

>>

@irish_tim ,

Have you received the Amp yet? How about an update.

.
atmasphere's avatar
atmasphere
7,068 posts
 
@jea48 - a very good point, and this also means that a variac won't work either!

Your Marantz can't be restarted in this fashion either- not unless you are willing to remove all the transistors! The light bulb trick only works with tube amps with all the tubes removed.
More to discover