Advice on Repairs for Audio Research VT100 Mk II

There are 8 power tube 100 ohm 5% 3 watt screen resistors. (Part # 43100208) ARC uses the resistors as fuses. The wattage value should never be increased.

@fsonicsmith @jea48 

The resistors should be adequate to survive a tube failure. Series fuses should be employed as well. When the fuses start blowing you know you have a bad tube. The fuses should be placed so that replacing them isn't a royal pain the rear. This is proper engineering; it prevents frustration with the product and allows the user to understand that tubes fail and are mounted in sockets for a reason.

From a manufacturing point of view, the less you see of the product once it ships out the better. When it returns under warranty, it eats into the bottom line and is 100% avoidable in this case. 

Letting the resistor be the fuse isn't (my opinion of course) proper engineering. It requires a trip to the service department to do something that the user should be able to do in the home without tools. It risks damage to the equipment along the way and encourages the user to seek alternatives away from the product. Some users might get frustrated and try to replace the resistors themselves- this can result in all sorts of headaches/liabilities for the manufacturer.

I agree with you Ralph and have a great Thanksgiving. As I said, ARC made some clunkers. Some of their amps were almost impossible to bias without taking to a good technician. And many dealers were forced to become proficient at replacing power tube resistors. I still maintain that for a large (by relative standards) tube amp specialist, their build quality is good and many have been reliable designs, again all things being relative. I know that your own tube amps are at the far spectrum of reliability. Kudos to you. At the end of the day, any electronic component will eventually need service unless pitched for something else, particularly tube amps. 

I've never heard of biasing the small signal tubes in an amp just power tubes, that design seems very user unfriendly to me.

@cleeds - thanks for pointing to the warranty, I obviously missed that. 

@jea48 raises a very good point about the caps. 

Sorry for your troubles, OP. It may be throwing good money after bad if that makes any sense. But perhaps worth asking about recap cost-- what else would normally go wrong in these? That old Dual 75a I have has no chips that I'm aware of-- but it was recapped a while ago and will probably need another go-over before I consider running it again. 

Op,

I definitely understand your dilemma. Honestly, I think the repair estimate is absurd. thirteen hours.

Also, calling ARC is in no way “going behind your repairman’s back”. That is an absurd quote. 

Audio Research makes some of the best amplifiers… regardless of the technology. You are talking about a 20 year old amp. A couple repairs and it is obviously got problems.

I would not loose faith on tube amps, or Audio Research for that matter. I have owned quite a few Audio Research components over the last forty years and have gotten. Nothing but incredible sound quality and reliability. I would get something more contemporary. I own all Audio Research equipment, and have enjoyed their sound and reliability for decades.