Thermal Faults

And so on.

What it comes down to is cost. And, in my experience, those who wish to believe that cost is not the issue will throw up all sorts of smoke and mirrors around audiophoolery.

Peter Wieck Melrose Park, PA

s have an excellent reliability record. I've

it's the worst way to use any resistor, but that is immaterial. When an EE needs a resistor with large pulse tolerance, carbon comp is the best candid ate for the job, and by a long way. There's no other reason to use them now adays, no other way in which they're better, and they certainly aren't chea per.

Are you really claiming to not know this stuff?

NT

Oh boy. Carbon comp is so much better at pulse work that a comp R with a given pulse rating is cheaper than a larger film type with the same pulse rating. THAT'S WHY THEY'RE USED.

NT

Operative word being "CHEAPER".

Which is what I am getting to with the comment "kicking the can down the ro ad".

Being that this is a hobby for me, there are very few things that I purchas e in sufficient quantities that even a 100% premium (and it is nowhere near that for resistors) is not worth the extra cost for the avoidance of troub le. I just purchased a lot of electrolytic capacitors to go into tube equip ment - the premium for 105 C High-Hours caps vs. standard caps came to abou t 5% across 20 caps in total.

Peter Wieck Melrose Park, PA

Oh, that's right. I forgot you're never wrong.

Even when you are.

No, modern resistors used within their specs are very reliable. They're among the most reliable of electronic components. Further comment is just not worthwhile.

NT

Yet you persist on saying carbon composition resistors are better for a given application.

Make up your mind.

I'm not confused. Nor am I much concerned whether you read up on them or not. Good night.

Actually you are c>

Then you follow up with:

Yet carbon composition resistors are made the same way they've been made for the past 50 years. And with the same time and temperature drift that they've always had.

Whatever they all say this is the deal. First of all things that pop up when cold might be connections, if when hot they are almost always component failure.

You have to thermally cycle it several times, so go over your Grandma's place a steal an endtable. Take the case off and get a towel. Fire it up and maybe take some voltages. Cover with towel. Then when it fails take those voltages again.

Then find out where any missing voltages come from. Always remember, 70% of the time or more it only has one problem. I used to say almost all the time but that is no longer true. And things blow each other, but there is one ROOT cause of the problem.

If you can't find a case history on it you are just going to have to do it, all there is to it.

You can try Repairworld if they are still around for $11 a month. Just one month isn't going to break the bank I hope but they might not have anything on it.

Other than that, just troubleshot. Got a print ? Maybe we can look at ? I don't even know what the f*ck this thing is. It could be an ICBM or a toaster fr as I know.

which part of

did you not grasp? I don't need an answer.

It's an old HP 8565A RF spectrum analyser built with good old fashioned discrete components you can physically see. The problem I'm having is access. I have identified the failed board: the x-amplifier module. They've used plug-in boards which is great in one way, except that they're so closely juxtaposed with other plug-in boards it's impossible to carry out any traditional troubleshooting techniques whilst under power. Believe me, I've tried. Tacking on fine wires to various key connections and running them out for probing and whatnot but I'd end up with a right old rat's nest of a mess if I carry on like that much longer. I've discovered a lot of old tower computers use the same pitch of plug in board that HP used (3.96mm) so I've ordered a matching socket and will make up a patch lead that will enable me to probe the board under power out in the open where I can get at it. It's a PITA, but there's no alternative I can see.