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
Plug it in and run. Kidding. There is a toggle switch on the back to switch between SE and Balanced.
You may need to hook up a pair of cheap test speakers as tube amps generally require a load when powered up.
Buy a variac and use it to apply power over a period of 24 hours slowly increasing the voltage over the period of time. This will help reform the electrolytic capacitors. Get hold of the manual as you'll need to bias the tubes for correct operation.
One other thing; these things will kill you if you mess around inside. 

Why not find an ARC dealer (or even ARC) and let them check it out for you?
Never turn on a tube amp without a load (speaker or resistor) connected! Otherwise damage will result to the output transformer!
I keep seeing "Never turn on a tube amp without a load". I don't think this is correct. I had my Audio Research Classic-60 recapped at an authorized ARC dealer. I saw the amp turned on sitting on the workbench but not connected to speakers. The tech said "it's alright to have the amp on just don't give it an input signal without speakers attached". Can an AGon super tech member verify this please?
@dweller , you are correct. The exception might be if the amp is somehow unstable without a load but IMO such an amp would be borderline criminal to sell on the open market.

FWIW a variac is not needed to restart this amp. If you are concerned about the condition of the filter caps, remove the tubes in the amp, and get a 60 watt light bulb (incandescent) and wire that in series with the power cord (if you don't know how to do this, have someone that knows electricity to do it for you- its not hard).

Then turn the amp on. The bulb will light up, but as the caps charge it will dim out. This will prevent any dangerous currents from damaging anything. If the bulb stays lit, the amp needs service. If the bulb goes out, reinstall the tubes and run the amp normally. Let it play for a while before you take it seriously as it will need some 'break in' time.

That's a whole lot cheaper than a variac!
@irish_tim

First tube amp! Wow, did you pick doozy for your first tube power amp.

It should arrive with the tubes removed. You will need to install the tubes. You can’t just install the small 6922 tubes where ever want. Hopefully the guy you bought the amp from marked, identified, each of the 6922 for the tube socket they are biased for. Match the number on the tube to the appropriate tube socket number. Tube socket numbers are on the circuit board near the sockets.
DO NOT JUST STICK THE 6922 TUBES BLINDLY IN THE AMP. You will seriously damage the tubes, and or the circuit boards, and or resistors in the amp.

Hopefully the guy marked, identified, the 6550 power tubes as well. They also require biasing and are matched pairs or matched quads. Not sure on the VT200, can’t remember. Even if they are identified for the correct tube socket, they should be checked for proper bias. Power tubes are somewhat easy. That is for someone that has done it before. Lethal voltages inside.

If the guy did not mark, identify, the 6922 tubes when he pulled them you are screwed! You will have to either send the amp to ARC, or find someone locally that works on ARC VT series power amps.

How to bias an ARC VT200.
http://www.audioresearch.com/ContentsFiles/VT200_BiasAdjust.pdf

ARC VT200 schematic wiring diagram, download.
https://elektrotanya.com/audio-research_vt200_amplifier.pdf/download.html

http://www.arcdb.ws/VT200/VT200.html

Jim
Thank you everyone for the great information.  I feel much better now.  
I have huge respect for audiophiles that are going with tube amps. I think this is  THE WAY to go if someone wants real and full tube sound. I don t think going tube preamp and ss amp is the right way, as I beleive messing with tube in the preamp signal stage is not the purist way. ( same issue with messing with tubes in the dac).
@atmasphere I am surprised you dismissed using a variac especially with an expensive amp full of electrolytics not used for 3 years. Also surprised about not loading the outputs. If anything was to go wrong, it is good practice to protect the amp. Maybe you can get away with winging it in the lab but isn't it better to give an unwary first time monster tube amp the safest instruction?

I am surprised about the hesitation to power it up after being stored for only 3 years. That doesn't seem very long at all. We took my father's D-79 that wasn't powered-up for about 15 years and plugged it directly into the wall (didn't have a big enough variac available) and no problem. Maybe just got lucky but ARC tends to use high quality components especially back in those days. It seems 3 years is nothing.
I agree with j_stereo, that 3 years does not seem long enough to pose a problem for the caps. The 6922 tube bias thing is however, extremely real and they are a bit of a pain in the a$$ to bias, requiring 2 digital multi meters, some expertise and patience. Best left to someone with experience. Improper driver tube bias can/will take out output tube(s), final resistors and possible cause mini-fire.
@noromance , The technique I offered works just as well and is a lot cheaper. Based on your post I suspect you didn’t read my post all the way through.
@atmasphere I did read it all the way through. And with increasing incredulity with each sentence! However, I'll defer to your experience. I always play by the book when working on tube amps.
I always power up an old or used gear the first time using a DBT (Dim bulb tester) as atmasphere suggested:

http://www.geek-tips.com/2015/11/22/dim-bulb-tester/

Better safe than sorry!
@noromance  The technique I wrote about has been around for many decades as you can see from the post prior to this.

When the bulb is lit, the voltage drop is all on the bulb. This can happen if the filter caps are shorted or drawing current as they take a charge. But over time, eventually the lamp might go out- if it does, that means that the caps are no longer drawing current, so at that point they are fully charged. The lamp prevents the caps from being damaged should they draw current.

This is actually safer than using a variac, as you need to have an ammeter on that variac to monitor the current draw, and there is a serious judgment call about how much current is safe! So you are usually better off using the light bulb in this particular case- but because the tubes draw current, they can't be in the amp while this process is going on. You put them in only after the caps charged up and the lamp is off, and then power up the amp normally.

For an amplifier that has been sitting for decades, this technique is not so good, as the filter caps should simply be replaced. But for an amp that has been sitting for only three years this is the way to go.
Thanks @atmasphere . As the VT200 pulls 500w at rest, what wattage bulb would you use? I use a DMM to monitor current when using the variac.
If you read the link there is a guide for bulb wattage. 
Yes. So pass me the 700watt bulb! #variac

Use a power strip parallel a few incandescent bulb.
@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.
Thanks Ralph. Apologies for laboring the issue. 
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.
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I’m not sure the series light bulb thing will work on this amp.
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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.

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@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.