Audio Research VT-100
This VT100 came into the store
with 1 dead channel. Many of these AR amplifiers have been
unsuccessfully repaired by previous attempts elsewhere.
Audio Research has always been
difficult because the company prefers to see all units go back to the
factory's repair department. Nevertheless, we have a
friendly and cooperative relationship with AR, and they will sell
parts to us albeit expensive at times.
The VT-100 is a hybrid design
utilizing transistors as a constant current source.
Sometimes when the tube goes, it takes out the transistors.
Replacing the transistors are difficult due to the industrial engineering
design of the amplifier. It has to be completely disassembled.
The transistors are common but the identification codes are rubbed off and
replaced with AR's in-house color codes.
After we replaced the
transistors, the tubes were replaced with a specific narrow range
requirement which meant not every tube will work for this amplifier.
You need to know the specific bias range of the tube.
We replaced the defective parts,
re-biased the amplifier, followed by a 48 hour stability test.
Subsequent bench test met factory
specification. The problem the repair job took us 6x
longer than quoted, nevertheless we charge by a per job rather than a per
hour basis. We lose money on the job but customer
satisfaction is No. 1 and we always keep our promises.
We are proud of the work which we