Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Gene Heskett]

On Tuesday 02 April 2019 11:11:13 Jon Elson wrote:

> On 04/02/2019 03:25 AM, Gene Heskett wrote:
> > The powerstat was losing contact at the slip ring. I put
> > the circuit in straight thru connection and took the stat
> > out and apart to find that ring burnt to ashes. A sliding
> > contact, on alu? Boggles the mind.
>
> A sliding ELECTRICAL POWER contact on aluminum??!!??  Yes,
> boggles my mind, too!
> Maybe it would work on a manually-controlled dimmer, but not
> an automatically-adjusted one.
>
The frying sound accompanied by the jerking as you were breaking the 
microwelds that would be the actual contact as you turned it by hand 
when it was under power would have rang all the alarm klaxons in my 
mind.

> > I told the guy who specced that transformer off explaining
> > in great, but vulgar detail exactly what was wrong with
> > his education.
>
> Well, it probably wasn't Harris' fault, they bought an
> off-the-shelf powerstat and expected Superior Electric knew
> how to build them. Obviously, NOT!
>
> Jon
>
I don't recall now, but I don't think that POS ever saw a Superior 
assembly line.  I have a couple samples of their stuff and some chinese 
versions all of which are made better that that was. It was NOT up to 
their quality level on several fronts. The clock motor driving it had a 
Cramer stamp on it, but I don't recall if there was a stamp on anything 
in the stat itself.

You know me well enough, Jon, to know I'm a sloppy working perfectionist.  
An oxymoron but call it what it is.  That, nearly 40 years later, still 
upsets me. If I was to find it again, I'm likely NOT mellowed enough to 
keep me from calling him and asking which of his mothers legs the best 
part of him ran down.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 



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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Jon Elson]

On 04/02/2019 03:25 AM, Gene Heskett wrote:
The powerstat was losing contact at the slip ring. I put 
the circuit in straight thru connection and took the stat 
out and apart to find that ring burnt to ashes. A sliding 
contact, on alu? Boggles the mind. 
A sliding ELECTRICAL POWER contact on aluminum??!!??  Yes, 
boggles my mind, too!
Maybe it would work on a manually-controlled dimmer, but not 
an automatically-adjusted one.


I told the guy who specced that transformer off explaining 
in great, but vulgar detail exactly what was wrong with 
his education.
Well, it probably wasn't Harris' fault, they bought an 
off-the-shelf powerstat and expected Superior Electric knew 
how to build them. Obviously, NOT!


Jon


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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Gene Heskett]

On Monday 01 April 2019 22:16:11 Jon Elson wrote:

> On 04/01/2019 11:27 AM, Gene Heskett wrote:
> > I'd have done the same, except I'd have added a flyback diode across
> > the solenoid to absorb the shutoff pulse from the solenoid. Perhaps
> > with a small r in series to absorb more of the stored energy in the
> > R.
>
> I'm pretty sure the diode must have been there, or it would
> have only operated ONE time!

But thats assuming it was a fast switch too, Jon. Many times the response 
of the cell to the flame can be measured in seconds, and that would be a 
pretty slow switch. But I'd like to CMA with the diode anyway.  Belt and 
suspenders approach. :)
 
> >> Since this was in a safety system, I was a bit hesitant to
> >> be so bold with this change, but, my circuit WORKED, the
> >> original required frequent tweaking, maybe as room
> >> temperature changed or like voltage changed.
> >
> > Actually, it seems like you did exactly what a good designer should
> > have done in the first place.
>
> Yup, that's what I thought, too.
>
> Jon

And yet, I have been plumb amazed at the stupidity exhibited in the 
finished product. Harris MW1A transmitter, designed for the 1 kw 
daytimers. Teeny little 100 watt motorised powerstat designed to be an 
automatic voltage regulator, run by a geared down electric clock motor. 
Stator contact, the ring the armature contacted, made out of aluminum by 
stamping. Took me a year of running the 3 miles out to the site because 
it was off the air, and finding it back on the air when I got there. 
Finally I decided to sit down in a chair and wait it out. Took most of 2 
hours. The powerstat was losing contact at the slip ring.  I put the 
circuit in straight thru connection and took the stat out and apart to 
find that ring burnt to ashes. A sliding contact, on alu? Boggles the 
mind. Even with a slather of deoxit on it is not going to work 
dependably, ever and certainly not for a year.  I ordered a new stat 
from Harris as thats the only way I could get a pristine pattern, went 
to the scrap yard and got some sheet brass, and made a brass version to 
put in the new stat. AFAIK, its still working, maybe. If the whole 
transmitter hasn't been replaced in the ensuing time from '82 till now.

It was Harris's first transistorized transmitter, and used the poorest 
transistors that would still do the job and the failure rate was pretty 
high when the stick it was driving had no coils across the eggs in the 
guy wires and was the tallest thing for a mile around in lightning 
country.

Driver transistor failed, I went to the shack and got a cb radio final in 
a to-202 package.  Only had about 10x the gain of the one Harris used, 
put it in and instantly made a 1600 watt transmitter out of it. Took 
half an hour detuning it to get it down to a kilowatt. And it did it on 
less amps into the finals, increasing the transmitters efficiency by 
around 10%. Typical, and I think that and the transformer debacle 
explains why Harris is no more. I told the guy who specced that 
transformer off explaining in great, but vulgar detail exactly what was 
wrong with his education.

War stories. Been there, done that.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 



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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Jon Elson]

On 04/01/2019 11:27 AM, Gene Heskett wrote:

I'd have done the same, except I'd have added a flyback diode across the
solenoid to absorb the shutoff pulse from the solenoid. Perhaps with a
small r in series to absorb more of the stored energy in the R.
I'm pretty sure the diode must have been there, or it would 
have only operated ONE time!

Since this was in a safety system, I was a bit hesitant to
be so bold with this change, but, my circuit WORKED, the
original required frequent tweaking, maybe as room
temperature changed or like voltage changed.


Actually, it seems like you did exactly what a good designer should have
done in the first place.

Yup, that's what I thought, too.

Jon


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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Gene Heskett]

On Monday 01 April 2019 11:31:08 Jon Elson wrote:

> On 04/01/2019 06:24 AM, Gene Heskett wrote:
> > It once took me around 3 years to find an engineering
> > goofup by Chyron.
>
> Well, here's one crazy fault that I finally debugged.  It
> was a rack-mount mag tape controller for a PDP-11, made by
> Datum. Basically one huge 15" square board in an aluminum 3U
> or so cabinet.
> It was stuck in reset.  The reset/ line ran all over the
> board, but only to inputs, the driver was on the system
> bus.  And, reset/ was stuck low, and even when powered off,
> it was just a couple Ohms to ground.  I started cutting the
> reset/ trace in spots to isolate it, and pulled the last 2
> chips, but it was still grounded.  Finally, I had it down to
> a 2" strip of copper trace, and this was a 2-layer board,
> and there was nothing on the other side, and no ground trace
> nearby.  I finally peeled the trace off the board, and you
> could not see ANYTHING odd there!  Replaced the chips,
> soldered a piece of wire-wrap wire (with the insulation LEFT
> ON in the middle) and it worked fine for years.
>
> That was certainly one of the odder faults I ever had to
> debug!  Not an engineering goof, just a weird defect.
>
> A piece of gear I worked on had a photomultiplier that
> sensed a green light from a flame to indicate the sulfur
> content of the air. This also provided a flame on/off
> signal.  The range of the signal from flame on to flame off
> was about .6 V.  They set up two transistors, one lit a
> flame-out light, the other held the gas solenoid open.  So,
> either one transistor should be on, or the other one should
> be on.  But, the .6 V difference was almost the entire
> signal swing, so the circuit was really flaky.  I eventually
> figured out how to do it with ONE transistor, as the lamp
> drew so little current it could not possibly hold the
> solenoid open.  I put the lamp across the transistor that
> switched the solenoid valve.

I'd have done the same, except I'd have added a flyback diode across the 
solenoid to absorb the shutoff pulse from the solenoid. Perhaps with a 
small r in series to absorb more of the stored energy in the R.
>
> Since this was in a safety system, I was a bit hesitant to
> be so bold with this change, but, my circuit WORKED, the
> original required frequent tweaking, maybe as room
> temperature changed or like voltage changed.
>
Actually, it seems like you did exactly what a good designer should have 
done in the first place.

I always ask myself will I lose any sleep worrying about it. If the 
answer is no, it gets done. I will fix a blown circuit according to the 
schematic maybe twice. The 3rd time it fails, I'll redo the design to 
remove that failure. Case in point, a balancing relay with platinum 
points that cost a couple hundred a set was used to run the motor of a 
10kw powerstat in an RCA TT-25 transmitter for automatic line voltage 
control.  But the thing was mounted on a transmitter wall that had a 
constant vibration from the belt driven 10 hp cooling blower. Contact 
life was about 6 months and you could see the fire between the contacts.

I thought about it, looked up a starting and extinguishing voltage of an 
NE-2, and put a network of 5 NE-2's from each contact to a 2200 ohm 5 
watt fire proof R connected to the common point. It was sorta 
entertaining to watch the NE-2's flicker, but couldn't see any arcing at 
the contacts. It regulated closer than it ever did new, and for all I 
know, that was in the early 60's at KOTA-tv in RCSD, it could have been 
running yet on the same contacts when they shut it off for the final 
time at midnight June 30 2008 when the digital switch was made. I was 
there till about '70 when I went to KXNE-tv-19 for Nebraska ETV and 
learned about high power klystrons.

Thats a whole nother story. Lets just say that they confirm E=MC2 as 
their major distortion source. And tuning adjustment mistakes can 
destroy a $125,000 klystron in 10 milliseconds. Never had to explain 
that, only tube I lost in 8 years was due to a heineman breaker single 
phasing its cooling pump. We designed a 50 kilovolt vacuum relay to 
detect that. On test, it ran the filter caps, used to 20kv, up to almost 
40kv, but they survived. They were a LOT cheaper than klystrons in any 
event.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 



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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Jon Elson]

On 04/01/2019 06:24 AM, Gene Heskett wrote:
It once took me around 3 years to find an engineering 
goofup by Chyron.
Well, here's one crazy fault that I finally debugged.  It 
was a rack-mount mag tape controller for a PDP-11, made by 
Datum. Basically one huge 15" square board in an aluminum 3U 
or so cabinet.
It was stuck in reset.  The reset/ line ran all over the 
board, but only to inputs, the driver was on the system 
bus.  And, reset/ was stuck low, and even when powered off, 
it was just a couple Ohms to ground.  I started cutting the 
reset/ trace in spots to isolate it, and pulled the last 2 
chips, but it was still grounded.  Finally, I had it down to 
a 2" strip of copper trace, and this was a 2-layer board, 
and there was nothing on the other side, and no ground trace 
nearby.  I finally peeled the trace off the board, and you 
could not see ANYTHING odd there!  Replaced the chips, 
soldered a piece of wire-wrap wire (with the insulation LEFT 
ON in the middle) and it worked fine for years.


That was certainly one of the odder faults I ever had to 
debug!  Not an engineering goof, just a weird defect.


A piece of gear I worked on had a photomultiplier that 
sensed a green light from a flame to indicate the sulfur 
content of the air. This also provided a flame on/off 
signal.  The range of the signal from flame on to flame off 
was about .6 V.  They set up two transistors, one lit a 
flame-out light, the other held the gas solenoid open.  So, 
either one transistor should be on, or the other one should 
be on.  But, the .6 V difference was almost the entire 
signal swing, so the circuit was really flaky.  I eventually 
figured out how to do it with ONE transistor, as the lamp 
drew so little current it could not possibly hold the 
solenoid open.  I put the lamp across the transistor that 
switched the solenoid valve.


Since this was in a safety system, I was a bit hesitant to 
be so bold with this change, but, my circuit WORKED, the 
original required frequent tweaking, maybe as room 
temperature changed or like voltage changed.


Jon


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Re: [Emc-users] Radio station stories -- Was RE: Posting order

[Gene Heskett]

On Monday 01 April 2019 01:09:59 John Dammeyer wrote:

> Hi Gene,
>
> > And yes that supply s/b installed so it can be swapped out for a
> > fresh one easily, the capacitors WILL die, sometimes a horribly
> > messy death. Least dependable part in any system. We need to invent
> > something more dependable for use as a large capacitance, but alu
> > foil, kraft paper, and a cc or less of technical grade ethylene
> > glycol is 100 years later, still the cheapest farad you can buy by
> > several magnitudes.
>
> I used the highest hour rated, highest temperature and 4x the needed
> value for the simple linear DC power supplies in this project.
> http://www.autoartisans.com/LGB/Lions%20Gate%20Bridge%20Pano1.jpg This
> summer it will have been running for 10 years without (AFAIK) any
> failures.  Granted the power factor sucked but a more complicated
> supply that would move the PF up to close to 100% would have added a
> major potential single point failure to 6 LED modules in each lamp.

Pretty impressive picture, John. Thanks.

> I'm also a
> > Certified Electronics Technician, now long since retired after
> > spending nearly 50 years keeping some tv station on the air.
>
> Spent a year as a disk jockey at CJOI 1440.  Evenings for the first
> 2.25 hours were boring playing religious "send me your money" tapes. 
> After that it was rock music till 1AM. I had the job because the
> automation system (International Good Music  IGM) was flakey and would
> play run the card reader empty and then just play the backup music
> tape and no commercials.
>
> Since I had two hours every night where all I had to do was queue
> tapes and keep the volume high enough to determine it was working I'd
> play with the automation system.  All RTL logic.  Two of the 4 fans in
> the cabinet were toast.  I replaced those.  (I had a high school
> diploma in Electronics Technology).
>
> Here's how the system worked.  A punched card reader.  An IBM
[...]
It once took me around 3 years to find an engineering goofup by Chyron.
They had used a cmos nand gate as an invertor, and left the 2nd input 
floating.  Thats a CS101 lesson. When I finally found it, I called the 
guy whose name was on the schematic and gave him a piece of my mind that 
by then was decidedly spare. Another time, much earlier, I found 2 
traces interchanged on a pcb in a Dynair video switcher that had a nasty 
habit of turningits power supply to charcoal. Schematicly it was 
supposed to be a foldback circuit to protect the supply from a shorted 
tally bulb, but the crossed traces turned the supply on full scale and 
let ALL the smoke out. And did it everytime a 327 bulb failed. I knew a 
good number of the folks at Dynair as they sponsored the annual party at 
the NAB for the Order of Iron Test Pattern Society, but I ragged them 
about it anyway. Totally tongue in cheek, as I'm a Brigadier General.

> And I'm willing to bet everyone on this list running CNC can 'feel'
> and 'hear' when something isn't quite right.  It's so subtle and often
> even difficult to explain to someone without experience.  But it's
> there.

Yup.

> > Its been quite a ride since I fixed my first tv in 1948, at 14 years
> > old. Yup, I was a geek before the word was invented. But now I've
> > had a couple health accidents that have slowed the thinker a bit.
> > Most recently a pacemaker, I was getting dizzy in between
> > heartbeats. Figured I had better get that fixed as I have a fading
> > wife to care for.
>
> Do take care of yourself.  And I'm still waiting for pictures... 
>  John

Somehow, I knew that was coming. :) If I ever get it working, I'll "clear 
the arena" and take some. Right now the bed is piled about 6" deep in 
tools and papers as I put the finishing but difficult touches on it. 
Working at my pace, often clocked by parts from China. Working on home 
switches and waiting for a 110 volt vfd. The one in it can't make up it 
mind which direction to turn the spindle, but despite its having clearly 
labeled FWD and REV terminals, they have no effect. I didn't want to 
spend the sheckles, but have anyway.

Take care John.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 



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[Emc-users] Radio station stories -- Was RE: Posting order

[John Dammeyer]

Hi Gene,
 
> And yes that supply s/b installed so it can be swapped out for a fresh
> one easily, the capacitors WILL die, sometimes a horribly messy death.
> Least dependable part in any system. We need to invent something more
> dependable for use as a large capacitance, but alu foil, kraft paper,
> and a cc or less of technical grade ethylene glycol is 100 years later,
> still the cheapest farad you can buy by several magnitudes. 

I used the highest hour rated, highest temperature and 4x the needed value for 
the simple linear DC power supplies in this project.  
http://www.autoartisans.com/LGB/Lions%20Gate%20Bridge%20Pano1.jpg
This summer it will have been running for 10 years without (AFAIK) any 
failures.  Granted the power factor sucked but a more complicated supply that 
would move the PF up to close to 100% would have added a major potential single 
point failure to 6 LED modules in each lamp.

I'm also a
> Certified Electronics Technician, now long since retired after spending
> nearly 50 years keeping some tv station on the air.

Spent a year as a disk jockey at CJOI 1440.  Evenings for the first 2.25 hours 
were boring playing religious "send me your money" tapes.  After that it was 
rock music till 1AM. I had the job because the automation system (International 
Good Music  IGM) was flakey and would play run the card reader empty and then 
just play the backup music tape and no commercials.

Since I had two hours every night where all I had to do was queue tapes and 
keep the volume high enough to determine it was working I'd play with the 
automation system.  All RTL logic.  Two of the 4 fans in the cabinet were 
toast.  I replaced those.  (I had a high school diploma in Electronics 
Technology).

Here's how the system worked.  A punched card reader.  An IBM Selectric 735 
computer controlled typewriter. Two reel-reel tape machines with music.  Two 
large cartridge machines (like 8 track but huge) one with odd minute messages 
and one with even minute messages.  Each message was about 8 seconds long.  
Then a series of rotary carousels with cartridges holding the commercials and 
promos.  Like 8 track but the pin roller was part of the player and not inside 
the cartridge.  It could take up to 25 seconds to rotate around and find the 
cartridge and cue it.

So a punch card would have and ID in the first 3 columns  like E21 or B12 for 
the cartridge carousels.  A T00 for a Time Card and a L00 or L01 for the reel 
to reel machines.  The program director would organize the music, commercials 
and time announcements  The rest of the punch card had information like client 
or song or whatever.

The card reader would index through the first three columns of the card and 
that would then select the carousel or tape machine getting it ready for the 
end of the previous selection.  Once the music or commercial started the card 
would be read at the speed of the Selectric which printed out the 3 digit 
number, and the rest of the text on the card onto the log printout.  Then the 3 
columns of the next card would be read and the corresponding hardware would be 
queued.

Finding that next selection took 25 seconds and didn't matter because the music 
and commercials were at least 30 seconds long.  The problem was the time 
announcements.  At about 8 seconds they'd be done before the next commercial 
was queued.  So the electronics (micro-processors didn't exist yet) would read 
the T00 time card, latch that a time announcement was needed.  Either ODD or 
EVEN, and then eject the T00 card and read the 3 columns of the next card.

And there was the problem.  Once it hit a time card, it would read it, eject it 
and then eject the entire pile in the reader too.  All the commercials were 
gone. With an empty card reader the music tape would default and play with a 
few seconds gap between songs.  And when it ran out, dead air.

Replacing the fans didn't really do anything.  But when one of the boards was 
on an extender card out in free air suddenly the system worked and sounded 
different.   A bit of time with a scope and freeze spray and I found the 
offending chip.  Once replaced the 3 column punch card read which had taken 
about 1/4 second suddenly sounded like it was a single column read it was so 
fast.  Kind of a blurp rather than a tick tick tick.  

There was another timer circuit.  If  took too long to read a card and the T 
column latched an EJECT signal for the card out went all of them. Once the new 
RTL chip was installed the read was so fast the timeout never happened.

All discovered because a slight change in temperature with the card out in 
ambient air on the extender card made the card reader sound ever so slightly 
different which set me onto the path with freeze spray.

And I'm willing to bet everyone on this list running CNC can 'feel' and 'hear' 
when something isn't quite right.  It's so subtle and often even difficult to 
explain to someone without experience.  But it's there.
>