Using a variac when testing always wise?

[Bazz4CQJ]

So, if you would like to use a Variac on something with auto mains select, proceed on the basis that you need to stay at the lowest voltage on offer.

Of course, not many vintage radios have auto mains select.

B

[SiriusHardware]

One of the cheapish camera modules available for the Raspberry Pi series of computers is specifically an I/R sensitive one, although probably intended to work with scenes which are lit with infrared light - security applications or wildlife 'camera traps' for example.

[GMB]

I am pretty sure that thermal imaging cameras are way different to near-infrared cameras.

But why spend thousands on a thermal imaghing camera when you can get (very cheaply these days) a pyrothermometer. That is basically a 1-pixel thermal imaging camera (so to speak). They work brilliantly and are great for spotting hot components.

My wife bought me one years ago and then promptly acquired it for checking the temperature of things being cooked.

They typically have a laser pointer attached to show you what it is looking at, but bear in mind that its angle of view is not so narrow.

[lightning]

When l was a kid l got hold of a variac and thought it would be great as a bench power supply in my shed.

The first thing l connected up to it was a transistor radio. l thought l would turn the variac up just a little bit and get 9v

The bang was impressive and blew the back open on the radio. lt was actually my dad's Hacker, l put the batteries back in and returned it to the kitchen.

l never owned up to it and fortunately the radio was never taken to a repair shop, which would have revealed my sins.

[Bazz4CQJ]

Originally Posted by GMB

But why spend thousands on a thermal imaghing camera when you can get (very cheaply these days) a pyrothermometer. That is basically a 1-pixel thermal imaging camera (so to speak). They work brilliantly and are great for spotting hot components..

Can we just be clear that nobody (certainly not me) suggested buying a thermal image camera just to use on VRRR stuff. As for prices, there are small modules on the market now for <£100. The camera which I have is a quality "FLIR" model and that was £500 12 years ago, but it was bought by my business for other applications.

Your point about the pyrothermometer is interesting, but it cannot easily look at a large PCB and instantly pick out anomalies.

Whether or not an inexpensive thermal image camera would pay for itself in an electronics service shop I don't know, but it is another tool in the box, especially if you have multiple uses for it.

B

[Richardgr]

I suppose it is horses for courses. A variac is invaluable for a piece of valve gear that has been modified or newly built, just to see voltages settle in ballpark areas. Call me a cautious Old Hector, but I use it with a filament bulb in series the very first time I power up a new build.

Another useful role is starting up an old radio the first time just to verify the transformer is OK. Upping the voltage slowly over a period of time is not as rigorous as reforming the electrolytics, but I think it is a confidence builder if the equipment has been lying dormant for years, maybe in non-ideal storage.

[CambridgeWorks]

I think there is agreement about the use with valve radios etc.
I wonder if anyone has caused damage to such as a complex audio power output stage in a solid state amp? Or damage to a piece of complex circuit solid state test gear?
I haven't, but don't think I ever used my metered variac in such situations, just in case.......
Rob