Boys and girls, and glen,
There are three constants in the world.
time
labor
material
No matter what you do, when you do it, or how you do it, it will aways boil
down to;
time
labor
material
If I have a problem with the AGC hang time and I know it's a capacitor that's
out of spec, I don't check it, I replace it. Now if that assembly is buried
deep way down and I have to pull a band switch shaft to remove the pcb, then
I'll replace the capacitors that are associated with the AGC. Are they bad?
More than likely not, but since I have the time and labor into removing the
pcb, it's cheaper to do it now than later.
On this Paragon I picked up at Dayton, the display was not working correctly.
History proves that there are one or two capacitors in the driver circuit that
fail. These did as well. Instead of just replacing the ones that were bad. (i
could tell, they got hot to the touch) I replaced all the caps in the driver
circuit. The material was inexpensive, the time was the same no replace just
the bad ones and all it required was a bit more labor.
Do I replace every electrolytic capacitor on the pcb? No, just the ones that
either experience or history of failure suggest.
However, I will check transistors. I use a small black box from Msquared and
while I don't believe they sell it any more, it's slicker than snot on a
polished doorknob. Not only will this device tell you what the pin out is of
the device under test, but the Hfe, current and other parameters I could care
less about. Not only does it test transistors, but will do mosfets, diodes and
other semiconductors.
I use another tool. This one is a APP for my ipad. It's called "electronic tool
box' and has an incredible semiconductor database. You can type in a number
such as MPS6514 and it will tell you if it's NPN or PNP and the case style and
any other important information such as if it's a darlington or bipolar.
I'm like Glen. I too have piles of expensive hi-tech test gear. But sometimes
the best tools are a simple transistor checker, a good meter and the gray stuff
between the ears.
mike, wb8vge
On Jun 2, 2012, at 12:17 PM, Glenn wrote:
>
>
>
>
>
> Hi Group,
>
>
> FYI: I repair a lot of Ten Tec boards and especially Omni 6 logic boards and
> Paragon boards in general.
> About 2 years ago, I bought an ESR meter to better evaluate the electrolytic
> capacitors on these boards in areas
> where I was finding faults. As suspected, MANY of the electrolytic caps are
> measuring high AC resistance. I find almost 3 to 4
> caps reading above 15 ohms on every board. And replacements I install are
> typically well under 2 ohms.
>
>
> The question becomes how necessary is it to replace these caps. In some
> cases, I see improved filtering and resolve go no go faults.
> In other cases, little to no difference is observed in functionality.
>
>
> Given the age of theses boards, it is not unusual for some of these caps to
> be marginal. In my case, I replace any cap that is not measuring
> below 3 to 4 ohms. Just because it works today does NOT mean it will continue
> to work. If I can save a client a headache in a year or two I am happy
> to do so. This adds some cost to the final invoice but over time it is a win
> win deal for the client and my business; My back log is always long and I
> hope our customers have excellent results from our work.
>
>
> I built my first ESR meter and had an analog meter but decided to buy one by
> ANATEKCORP dot com. It is called the Blue ESR meter.
> It was a kit and cost $80 or $100 assembled. It took about 4 hours to build
> and align and it works GREAT.
> I did toss the cheap test lead wire that came with the kit and used real Test
> Lead cable and like that MUCH better. I also tossed the alligator clips that
> were supposed to be used fro grabbing cap leads and replaced them with self
> locking logic clips; MUCH BETTER.
>
>
> I find I use this piece of equipment almost as much at I use my DVM or trusty
> Simpson 260P.
>
>
> Just one other note. I buy a lot of caps on line from epray many or maybe all
> made in Asia. I have to say they work great and have LOW ESR values of
> typically less than 1.5 ohms and spec to correct values on my Wavetek
> Capacitor tester. They are speced at 20% but my readings always indicate
> better than 2%.
>
>
> I am in NO way related to or do any work/ business with Anatek but they do
> have some great products. I just bought the inductor ring tester ($52 kit)
> which I can simulate with a function generator and AC volt meter but this
> unit is a calculator size box that I can quickly take from bench to bench. It
> has been invaluable to find leaky caps across coils sinking back EMF as well
> as coils with faults. I have found numerous bad caps and coils on R 390A
> receivers I work on with this cheap tester.
>
>
> They also have a slick transistor/FET tester. I have used analog meters for
> decades to test these devices and I have a Curve tracer as well but again,
> this is a small box that moves around my lab easily. My Tektronix 576 curve
> tracer is great but weighs 90 pounds. I have not purchased the transistor
> tester yet but will do so soon. It has a processor and will ID the device you
> hook up as an NPN, PNP, Darlington and on and on. My Simpson requires my to
> find out what I am testing by other means.
>
>
> Hope this helps.
>
>
> 73,
>
>
> Glenn WA4AOS
>
>
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