I like good test equipment and when I started in the 1950s good was
homebrew, war surplus and the local radio TV shop. Then in the RCAF it was
a Tek 545 and later at university it was a Tek 545B. (I worked my way thru
college as a TV repairman working 20 to 30 hrs per week!) After university
and when I had spare cash I graduated from homebrew and surplus to kits.
Then my first good bad scope was an HP 120. Nothing but problems with the
HV supply. Now unwllingly retired at 63 one of my passions is to build a up
a small lab for personal enjoyment by finding at good prices test equipment
made by the best mfgs such as Tektronix , GR, HP, Fluke, Boonton, and
others, but the others usually don't hold a candle to the top 4. Others
include Wavetek, Racal, Philips, Systron Donner, etc. There's a third class
that includes Heathkit, Eico, RCA, Sencore, B&K and others who furnish radio
and TV test bench eqpt and I have some that is very, very good. A fourth
class is foreign like Marconi, Meguro, Siemens, Rohde & Schwarz, all
excellent but that I generally shy away from them because information and
parts are in the unobtanium category.
Generally finding a very good deal at a swapmeet means there's something
wrong with it, either unknown or undisclosed by the previous owner.
Finding docs for the best is hard enough but an order of magnitude harder
for the others and that goes another order of mag for parts. Sometimes one
needs 2 or 3 junkers to succeed or give up.
I don't like to leave a swapmeet without some good deal that I can take
home and plug into the Variac to see what it does. Generally I'll look
inside to see if it's complete with no obvious missing parts and no char
babies. Then I turn the Variac up and watch the current and look and smell
to see if all the smoke the the factory sealed-in is still there. If it is
but it doesn't work I check power supply voltages. It never ceases to amaze
me that very few of the mfgs have figured out how to build a reliable power
supply. In my work, Telecom, most critical hicap stuff had dual supplies
so it could still operate if one supply failed and to top that off they
migrated to hot swapable supplies! My own theory on power supply
unreliability is that the companies assign newly graduated engineers to
design power supplies and those guys don't have enough experience to
understand the ravages of long term heat, continual cycling and the crazy
stuff that can come down the AC power line! One exception today may be PC
power supplies as I don't see boatloads at the meets like I used to but
maybe it's because I'm not looking!
First, I check the supply voltages and if they're down I check the
rectifiers and capacitors. Many times I'm lucky and find the problem right
away but other times if its a short it a arduos process on pcb. After much
wasted time the bad cap is found, an Al electrolytic if there are no or few
tantalums but if there's lot of tants there's a very good chance it's one of
the tantalums with a dead short and not exploded. Partial short are best
because they make char babies!
If the fault isn't in the power supply or on a supply rail it soon
becomes a waste of time without a manual.
To end this mild diatribe, obsolescence of test eqpt is a matter of
economics for business and sadly me! I still like my Boonton 260 Q meter but
I'd rather have an HP 4342A and I'd rather have an HP 8921A to replace my HP
141T, a newer Tektronix TDS to replace my Tek 465. Space, time, dollars,
and performance all suffer in my lab but it's there for my enjoyment and
entertainment. and most likely to be upgraded with smaller, higher
performing, newer, less obsolete gadgets.
73
hank wd5jfr

Many companies view power supply design as unchallenging, and many engineers
see it as boring. So power supply design often gets relegated to dull
people or new grads. There is a grain of truth there, in that power supply
design is a lot about remembering all the ways that previous designs have
failed and not doing that again, and not so much about applying the latest
technology that's coming down the pike.

The two best power supplier designers that I can bring to mind are (one) a
guy who never did get his BS in EE, but designed power supplies for decades
and could tell you every possible way that one could fail and what to do
about it, and (two) a guy who usually does video design, but only because he
does _everything_ right -- and when he does a power supply or is the
technical lead over someone doing a power supply it always works. Both of
these guys are technically paranoid and have long memories, which is really
what it takes.

"Henry Kolesnik" wrote in message
...

snip some

My own theory on power supply
unreliability is that the companies assign newly graduated engineers to
design power supplies and those guys don't have enough experience to
understand the ravages of long term heat, continual cycling and the crazy
stuff that can come down the AC power line!

snip some more

73
hank wd5jfr

One thing I forgot to ask is how good are old, burned-in tantalums that test
good if salvaged for reuse from older equipment. Anyone have any data?
tnx
hank wd5jfr
"Tim Wescott" wrote in message
...
Many companies view power supply design as unchallenging, and many
engineers
see it as boring. So power supply design often gets relegated to dull
people or new grads. There is a grain of truth there, in that power
supply
design is a lot about remembering all the ways that previous designs have
failed and not doing that again, and not so much about applying the latest
technology that's coming down the pike.

The two best power supplier designers that I can bring to mind are (one) a
guy who never did get his BS in EE, but designed power supplies for
decades
and could tell you every possible way that one could fail and what to do
about it, and (two) a guy who usually does video design, but only because
he
does _everything_ right -- and when he does a power supply or is the
technical lead over someone doing a power supply it always works. Both of
these guys are technically paranoid and have long memories, which is
really
what it takes.

"Henry Kolesnik" wrote in message
...

snip some

My own theory on power supply
unreliability is that the companies assign newly graduated engineers to
design power supplies and those guys don't have enough experience to
understand the ravages of long term heat, continual cycling and the
crazy
stuff that can come down the AC power line!

snip some more

73
hank wd5jfr

On Fri, 23 Jan 2004 18:35:51 -0600 "Henry Kolesnik"
wrote:

One thing I forgot to ask is how good are old, burned-in tantalums that test
good if salvaged for reuse from older equipment. Anyone have any data?

I like the tantalums that come in the metal cylindrical cases with the
glass seals. I've never seen a bad one. Look for them at swap meets
and use them instead of small alum electrolytics as a higher
reliabilty replacement.

I've not had a lot of experience with the teardrop tantalums, but I
have seen a few bad ones.

While you will see aluminum electrolytics in all stages of ageing from
perfectly good to dead short or open, my impression of the teardrop
tantalums is that they are either perfectly good or completely bad.
There doesn't seem to be any middle ground.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

It would be nice to find a set of bath tub curves on each kink of old
tantalum. Maybe we'll get enough inof here to sort the good from the bad.
I don't even have a cluse as to how many mfgs there were and how many time
they improved their designs as they experienced failures. Iguess what we
need to know is which one fail themost.
73
hank wd5jfr
"Jim Adney" wrote in message
...
On Fri, 23 Jan 2004 18:35:51 -0600 "Henry Kolesnik"
wrote:

One thing I forgot to ask is how good are old, burned-in tantalums that
test
good if salvaged for reuse from older equipment. Anyone have any data?

I like the tantalums that come in the metal cylindrical cases with the
glass seals. I've never seen a bad one. Look for them at swap meets
and use them instead of small alum electrolytics as a higher
reliabilty replacement.

I've not had a lot of experience with the teardrop tantalums, but I
have seen a few bad ones.

While you will see aluminum electrolytics in all stages of ageing from
perfectly good to dead short or open, my impression of the teardrop
tantalums is that they are either perfectly good or completely bad.
There doesn't seem to be any middle ground.

-
-----------------------------------------------
Jim Adney
Madison, WI 53711 USA
-----------------------------------------------

Hi Henry,

I like what you write about test equipment. I have a nice collection of HP
stuff of my own. Maybe even more than 40 items. I like HP because it was
well known at my university at that time (the 70ties). Also it is well
documented and it can be repaired at times. There are many other good brands
available but I prefer HP. On the other hand: a lot of HP equipment needs
repair at present. And indeed: the power supply is the culprit in many
cases. Either tubes or caps. About tantalum: not much specific experience
available over here, but I seem to like the axial metal ones with glass
sealed terminations. So keep up the good work!
Btw: is there a site or community to exchange experience on how to repair HP
equipment and how to obtain spare parts?
regards,
Harke PA0HRK

Henry Kolesnik schreef in berichtnieuws
...

Yrrah wrote:

Hi Henry,

I like what you write about test equipment. I have a nice collection of HP
stuff of my own. Maybe even more than 40 items. I like HP because it was
well known at my university at that time (the 70ties). Also it is well
documented and it can be repaired at times. There are many other good brands
available but I prefer HP. On the other hand: a lot of HP equipment needs
repair at present. And indeed: the power supply is the culprit in many
cases. Either tubes or caps. About tantalum: not much specific experience
available over here, but I seem to like the axial metal ones with glass
sealed terminations. So keep up the good work!
Btw: is there a site or community to exchange experience on how to repair HP
equipment and how to obtain spare parts?
regards,
Harke PA0HRK

news:sci.electronics.equipment has some discussion about test equipment.


--
We now return you to our normally scheduled programming.

Michael A. Terrell
Central Florida

There's a Tektronix group on Yahoo Groups that's quite active but I've not
seen any on HP ;-)..
We need to keep hoping..
73
hank wd5jfr
"Yrrah" wrote in message
l...
Hi Henry,

I like what you write about test equipment. I have a nice collection of HP
stuff of my own. Maybe even more than 40 items. I like HP because it was
well known at my university at that time (the 70ties). Also it is well
documented and it can be repaired at times. There are many other good
brands
available but I prefer HP. On the other hand: a lot of HP equipment needs
repair at present. And indeed: the power supply is the culprit in many
cases. Either tubes or caps. About tantalum: not much specific experience
available over here, but I seem to like the axial metal ones with glass
sealed terminations. So keep up the good work!
Btw: is there a site or community to exchange experience on how to repair
HP
equipment and how to obtain spare parts?
regards,
Harke PA0HRK

Henry Kolesnik schreef in berichtnieuws
...