Thanks David. It's fixed now. What's impressive is the care that goes into these old instruments even though they are still manufactured. Follow the link in the first paragraph and see the rest of the story.
Hi Martin...I can understand tubes in a megohmmeter, for the high impedance, but you'd think they'd be able to transitorise a Tach. Then again, if it works (and you can still get the tubes) don't fix it....
That's the thing about test equipment. Not only does "If it works, don't fix it" apply, but most people buying these already have them. They know what to expect from the equipment. Even if you can make it better, you don't. Well, not always. Why? Because having something better might reveal faults that would otherwise go undetected. Igorance is bliss.
One thing surprises me is that how they are able to maintain their staff or train their new staff. As the fresh grads coming out of colleges wouldn't 'have seen something called Vacuum tube, they need to have some retrograde training on basics of electronics and components of the older generation.
On the top of my cube wall is perched a 6201 / 12AT7 dual triode for all the younger staff to see. They may not know how it works, but they can now say they have actually seen a real vacuum tube (valve).
The old test equipment just keeps on going - and going - and going. No flash memory to degrade and guarantee failure in just a few years.
When I was a TA in charge of the physics lab, we had a closet with old but working equipment, including some voltmeters that were made in the thirties. What really impressed me though is the note inside stating that it was made to a design by Lord Kelvin from 1870s. That's longevity.
@prabhakar_deosthali, that may be the one thing that puts a company like IET out of business. Everyione who works there is an expert at his or her job and has been doing it for many years. When they reture, who will replace them?
There's another issue and that is because these people have a unique skill that's not necessarily transferable to other jobs. Thus, they have a job for life as long as the company stays in business, but there's little room for advancement or for changing jobs.