Kemet mil-spec cap ???

[Elias]

larsson.elias@telia.com (Elias) wrote in message news:<64434408.0403081331.668d716d@posting.google.com>...

I am somewhat of a beginner to the world of electronics, never dealt
with coils or transformers or such before.
Could anyone be so kind and explain to me what the following symbol
represents?
http://www.manicsexposed.com/t.gif
That it is a transformer of some sort is rather obvious, but the
built-in capacitor and the middle pin on the secondary coil puzzles
me.
The diagram claims this is a 455 kc IF (intermediate frequency, I
presume) transformer, although I have never seen such a transformer -
with a knob on it.

Thank you - all of you - for your help!
However, I still don't have much of an idea what an adjustable
transformer actually looks like.

http://img-europe.electrocomponents.com/largeimages/C278816-01.jpg
I did find this, but I suspect this is an adjustable _inductor_ with
only one coil.
A Farnell/RS Components order code, or even a picture would be highly
appreciated!

I curse myself for not taking those courses in electronics when I was
young(er).

\\Elias

 

[Senso]

Which variety are you looking for? I have a few Burr-Brown
DAC71-CCD-V, new/unused, antistat packaging.
Conversely, I'm looking for a DAC80-CCD-V (yes I realise that I could
use the 16-bit DAC71, but its for replacement in a piece of equipment,
and the pinning is different, unsurprisingly)

Pete.

Hi Pete,

I'm looking for Burr-Brown CSB's, such as DAC71-CSB-I-3 and
DAC71-CSB-I-V. I'm still trying to find out exactly which other ones
can be used for replacement.

Senso

 

[Jim Adney]

On Tue, 09 Mar 2004 14:28:56 GMT Al <no.spam@here.com> wrote:

In article <hr3q40dilmqp9bhs3g2vvgm68hjkqiguei@4ax.com>,
Jim Adney <jadney@vwtype3.org> wrote:

Okay, but why pick an identifiction method that requires a manual?
Most other components this size, including theirs, just have the
relevant numbers printed on them.

OK, let me give you a few example lines from the manual:

uF Case tol. Failure Rate (%/1000hrs) DC Leakage in uA
Code % 1.0 0.1 0.01 0.001 25C 85C 125C

5.6 A 5 5001 5201 5401 5601 0.3 6 7.5
5.6 A 10 2241 2481 2721 2961 0.3 6 7.5
6.8 A 5 5002 5202 5402 5602 0.3 6 7.5
6.8 A 10 2242 2482 2722 2962 0.3 6 7.5
6.8 A 20 2243 2483 2723 2963 0.3 6 7.5

So a M38003/01-5001 is unique. I left out the dissipation factor for
simplicty.

As you can see, there is much more information in this code number than
just the capacitance value and the voltage. When a component is bought
to this specification, it will meet it. If you buy a random FF uF VV
volt capacitor, you have no clue as to what you have with respect to
leakage, reliability, dissipation factor and the like.

I have a similar page here from the Sprague/Vishay catalog. In this
case it just happens to be for some caps which I picked up surplus
which are marked M39006/25-xxxx.

In this case the xxxx code pins down the tolerance and failure rate,
just as the Kemet does above (note that everything else above is the
same.) OTOH, the Sprague/Vishay caps are also labeled with their C and
V ratings, as well as the tolerance. Only the failure rate is left
unexplained. There is also an H-code for high vibration which you
might need the catalog page to interpret.

BTW, both manufacturers have a code for an M failure rate, which is
1.0% per 1000 hours. I find it hard to believe that anyone would buy
such a device, especially the military. The ones I got were the R
rate, .01% per 1000 hours. Those are the best that they offer and I'll
bet those are the only ones that ever get sold.

So I still don't think it's too much to ask that the most important
data be printed out separately.

Obviously, I don't tend to think like the military....

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Roy Lewallen]

Jim Adney wrote:

. . .
So I still don't think it's too much to ask that the most important
data be printed out separately.

Obviously, I don't tend to think like the military....

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

While you've got a legitimate point, you've got to realize the function
of the part number. If you're a technician servicing a piece of military
gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other
capacitor, regardless of its value. To order a replacement, you put in a
requisition for a 20035942. Now, it's vital to you that the capacitors
in the stock bin or coming in from the supply system have 20035942
printed on them, but it's not important that the value is. The
technician can find the value in the parts list in the manual and likely
on the schematic. The stark fact is that the military supply system
wasn't created and isn't maintained for the convenience of the ham who's
working on surplus gear.

You'll actually find this is true throughout the industry, with many
ICs, for example, having only the customer's part numbers on them. Go to
a flea market anywhere around here where I live, and you'll find lots of
components with only Tektronix part numbers on them. You'll also find
lots of folks locally who can tell you what they are, at least
generically. I'm sure the same thing is true for HP and Palo Alto,
Motorola and Phoenix, and so forth.

It's not that you don't think like the military -- it's just that when
they developed their stock system they didn't take into consideration
the inconvenience it would cause you, me, and other hobbyists.

Roy Lewallen, W7EL

 

[Tim Williams]

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:104tf192ht5u305@corp.supernews.com...

My Moto Manual says the 1N485B has a PRV of 180V, a Vf of 1.0V max at
100 mA, and a Ir of 25 nA. This is a bit heftier than the usual 1N4148
signal diode. What's a more current up-to-date substitute for this?

Two 914's in series? ;o)

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - --+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms

 

[Phil Allison]

"Watson A.Name - "Watt Sun, the Dark Remover"" <

My Moto Manual says the 1N485B has a PRV of 180V, a Vf of 1.0V max at
100 mA, and a Ir of 25 nA. This is a bit heftier than the usual 1N4148
signal diode. What's a more current up-to-date substitute for this?

** The BAV20 and BAV 21 are 200 and 250 volt respectively, 250 mA high
speed diodes - otherwise similar to the 1N4148.




............ Phil

 

[DarkMatter]

On Mon, 08 Mar 2004 23:05:13 -0600, Jon Elson <elson@pico-systems.com>
Gave us:

ope, I think they are from 1956-1957, if you read the date code
differently. Was CBS making transistors in 1975? I seriously
doubt it. These were probably used in ICBM guidance systems or
support equipment. Only the exotic military projects could afford
transistors in 1956.

Isn't "CBS" a mil semi maker, and not the broadcaster though?

In 1956, the hot secret project was the IC chip, and in 1960,
fairchild semi made the first one. For the mil boys, and it was ten
transistor elements on one die.

 

[Roger]

On 09 Mar 2004 23:19:50 GMT mmclarenf199@aol.com (Mmclarenf199) wrote in
Message id: <20040309181950.08983.00001091@mb-m13.aol.com>:

I am a retired attorney.

Good. Now suck off a shotgun, you parasite.

 

[Watson A.Name - \"Watt Su]

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:404ebfb7$0$20658$afc38c87@news.optusnet.com.au...

"Watson A.Name - "Watt Sun, the Dark Remover""


My Moto Manual says the 1N485B has a PRV of 180V, a Vf of 1.0V max
at
100 mA, and a Ir of 25 nA. This is a bit heftier than the usual
1N4148
signal diode. What's a more current up-to-date substitute for this?



** The BAV20 and BAV 21 are 200 and 250 volt respectively, 250 mA
high
speed diodes - otherwise similar to the 1N4148.

Google sent me to Fairchild's website where I found that they have them
at Mouser for $3 a hundred. I also found that Fairchild still makes the
1N485B, which is the same price at Mouser. Cool. Thanks for the info.

One problem when dealing with the HP parts list is that, after the HP
part no., many of the parts say something like "2N458A (selected)".
They have selected that part for some parameter, and they don't say what
param, obviously. It might be beta, in which case if an unselected part
is subbed, it might not be good enough, with substandard performance.
If it was selected for breakdown voltage, then an unselected part might
fail. Not nice!

> ........... Phil

 

[Henry Kolesnik]

I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises
(war games) we had to find and fix a fault so the incoming aircraft
wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad
or loose tube, but some seargents had subchassis with cold solder joints,
shorted black beauty capacitors or fried resistors. Time was critcal as the
weather was closing fast and the aircraft was low on fuel. Sometimes the
excercise left us without many parts, partially functional test equpt, and
only partial manuals. To better simulate battle conditions, one end of the
hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF
400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried
22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite
useful in many cases. The objective was to save the aircraft using limited
resources. Today I don't think we see component level repair in the field
but in battle anything may be necessary for survival. I'd much rather have
something with component values rather than a bunch of codes that required
decifering. I still contend this is a result of "military intelligence."
And the codes make it tough on us hobbyists but we not under a critical time
crunch and with the Internet it's usually a piece of cake.
73
Hank WD5JFR
"Roy Lewallen" <w7el@eznec.com> wrote in message
news:104t4knnb23vi14@corp.supernews.com...

Jim Adney wrote:
. . .
So I still don't think it's too much to ask that the most important
data be printed out separately.

Obviously, I don't tend to think like the military....

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

While you've got a legitimate point, you've got to realize the function
of the part number. If you're a technician servicing a piece of military
gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other
capacitor, regardless of its value. To order a replacement, you put in a
requisition for a 20035942. Now, it's vital to you that the capacitors
in the stock bin or coming in from the supply system have 20035942
printed on them, but it's not important that the value is. The
technician can find the value in the parts list in the manual and likely
on the schematic. The stark fact is that the military supply system
wasn't created and isn't maintained for the convenience of the ham who's
working on surplus gear.

You'll actually find this is true throughout the industry, with many
ICs, for example, having only the customer's part numbers on them. Go to
a flea market anywhere around here where I live, and you'll find lots of
components with only Tektronix part numbers on them. You'll also find
lots of folks locally who can tell you what they are, at least
generically. I'm sure the same thing is true for HP and Palo Alto,
Motorola and Phoenix, and so forth.

It's not that you don't think like the military -- it's just that when
they developed their stock system they didn't take into consideration
the inconvenience it would cause you, me, and other hobbyists.

Roy Lewallen, W7EL

 

[Watson A.Name \"Watt Sun]

Tim Williams wrote:

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:104tf192ht5u305@corp.supernews.com...

My Moto Manual says the 1N485B has a PRV of 180V, a Vf of 1.0V max at
100 mA, and a Ir of 25 nA. This is a bit heftier than the usual 1N4148
signal diode. What's a more current up-to-date substitute for this?


Two 914's in series? ;o)

Tim

Actually, coming from you, I'd've expected 6AL5.

 

[Al]

In article <rmF3c.1385$6a3.403587231@newssvr11.news.prodigy.com>,
"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote:

I was a GCA radar tech in the RCAF in the 1960s and in one of the excercises
(war games) we had to find and fix a fault so the incoming aircraft
wouldn't crash, it was zero visibility . Sometimes it was as easy as a bad
or loose tube, but some seargents had subchassis with cold solder joints,
shorted black beauty capacitors or fried resistors. Time was critcal as the
weather was closing fast and the aircraft was low on fuel. Sometimes the
excercise left us without many parts, partially functional test equpt, and
only partial manuals. To better simulate battle conditions, one end of the
hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01 uF
400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a fried
22K 1/2 watt with a 22K 2 watt or something close. Color codes were quite
useful in many cases. The objective was to save the aircraft using limited
resources. Today I don't think we see component level repair in the field
but in battle anything may be necessary for survival. I'd much rather have
something with component values rather than a bunch of codes that required
decifering. I still contend this is a result of "military intelligence."
And the codes make it tough on us hobbyists but we not under a critical time
crunch and with the Internet it's usually a piece of cake.

In the sixties that was possible. But now you can't really fly by the
seat of your pants. Repair is by replacing LRUs (Least Replaceable
Units). Even if the LRU makes it back to the depot for failure
confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be
readily repaired. And would you trust one that was repaired if it did
not go through a burn-in cycle afterward? Would you depend on a
fail-safe circuit to prevent a nuclear launch if it had a component
replaced in it that was "close enough?" Maybe in your cars brake system,
but not on my missile!

Al

--
There's never enough time to do it right the first time.......

 

[Roger Hamlett]

"Al" <no.spam@here.com> wrote in message
news:no.spam-99E7B0.11474610032004@news.verizon.net...

In article <rmF3c.1385$6a3.403587231@newssvr11.news.prodigy.com>,
"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote:

I was a GCA radar tech in the RCAF in the 1960s and in one of the
excercises
(war games) we had to find and fix a fault so the incoming aircraft
wouldn't crash, it was zero visibility . Sometimes it was as easy as a
bad
or loose tube, but some seargents had subchassis with cold solder
joints,
shorted black beauty capacitors or fried resistors. Time was critcal as
the
weather was closing fast and the aircraft was low on fuel. Sometimes
the
excercise left us without many parts, partially functional test equpt,
and
only partial manuals. To better simulate battle conditions, one end of
the
hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01
uF
400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a
fried
22K 1/2 watt with a 22K 2 watt or something close. Color codes were
quite
useful in many cases. The objective was to save the aircraft using
limited
resources. Today I don't think we see component level repair in the
field
but in battle anything may be necessary for survival. I'd much rather
have
something with component values rather than a bunch of codes that
required
decifering. I still contend this is a result of "military
intelligence."
And the codes make it tough on us hobbyists but we not under a critical
time
crunch and with the Internet it's usually a piece of cake.

In the sixties that was possible. But now you can't really fly by the
seat of your pants. Repair is by replacing LRUs (Least Replaceable
Units). Even if the LRU makes it back to the depot for failure
confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be
readily repaired. And would you trust one that was repaired if it did
not go through a burn-in cycle afterward? Would you depend on a
fail-safe circuit to prevent a nuclear launch if it had a component
replaced in it that was "close enough?" Maybe in your cars brake system,
but not on my missile!
True, in the 'close enough' stakes, but it is well worth reflecting that 90%

of simple systems use a relatively small 'subset' of parts from the avilable
world pool. An engineer, with one each of the IC's for a range of boards,
and a few dozen resistors and capacitors, can potentially repair most faults
on such boards 'on site', especially if the board is designed with this in
mind (possibly with some form of self diagnostics for many parts). However
if the same units are built with SM parts in quantity, using custom IC's,
the solution becomes to carry a complete replacement board. Doing this for a
few dozen products is often not practical. The problem here is that the
custom IC/SM solution is cheaper once production reaches a reasonable level,
but is not the best solution where the units are going to be a long way from
'spares'.
I designed a range of units used on sites across many third-world countries,
and it became necessary to deliberately design the units with both
redundancy, and repairability in mind. Given that the service engineer may
have to travel 1000miles to get to a unit, having it so that repair is
likely to be possible, was a vital design criterion. The parts list was
deliberately 'shrunk', retaining as far as was practical a limited range of
parts used in all. Unfortunately the relative costs of truly 'mass'
production, combined with robot construction/assembly, make such designs a
'dying art'...

Best Wishes

 

[Peter Bennett]

On 9 Mar 2004 16:32:29 -0800, larsson.elias@telia.com (Elias) wrote:

Thank you - all of you - for your help!
However, I still don't have much of an idea what an adjustable
transformer actually looks like.

http://img-europe.electrocomponents.com/largeimages/C278816-01.jpg
I did find this, but I suspect this is an adjustable _inductor_ with
only one coil.
A Farnell/RS Components order code, or even a picture would be highly
appreciated!

I curse myself for not taking those courses in electronics when I was
young(er).

\\Elias

Many adjustable IF transformers will look very much like the inductor
in the picture you referred to above.

These things are generally "set and forget" - they are adjusted during
the initial testing and alignment of the receiver, and rarely touched
again.

A radio receiver will usually have several IF transformers, and they
must all be tuned to the correct frequency for the radio to work.






--
Peter Bennett VE7CEI
email: peterbb (at) interchange.ubc.ca
GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html
Newsgroup new user info: http://vancouver-webpages.com/nnq

 

[Al]

In article <2HI3c.3458$re1.1290@newsfe1-win>,
"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk> wrote:

"Al" <no.spam@here.com> wrote in message
news:no.spam-99E7B0.11474610032004@news.verizon.net...
In article <rmF3c.1385$6a3.403587231@newssvr11.news.prodigy.com>,
"Henry Kolesnik" <kolesnik@sbcglobal.net> wrote:

I was a GCA radar tech in the RCAF in the 1960s and in one of the
excercises
(war games) we had to find and fix a fault so the incoming aircraft
wouldn't crash, it was zero visibility . Sometimes it was as easy as a
bad
or loose tube, but some seargents had subchassis with cold solder
joints,
shorted black beauty capacitors or fried resistors. Time was critcal as
the
weather was closing fast and the aircraft was low on fuel. Sometimes
the
excercise left us without many parts, partially functional test equpt,
and
only partial manuals. To better simulate battle conditions, one end of
the
hut could be on fire and CO2 smoke to hinder visibilty! A shorted .01
uF
400VDC black beauty was easliy replaced with a .01 uF 600VDC or .02 a
fried
22K 1/2 watt with a 22K 2 watt or something close. Color codes were
quite
useful in many cases. The objective was to save the aircraft using
limited
resources. Today I don't think we see component level repair in the
field
but in battle anything may be necessary for survival. I'd much rather
have
something with component values rather than a bunch of codes that
required
decifering. I still contend this is a result of "military
intelligence."
And the codes make it tough on us hobbyists but we not under a critical
time
crunch and with the Internet it's usually a piece of cake.

In the sixties that was possible. But now you can't really fly by the
seat of your pants. Repair is by replacing LRUs (Least Replaceable
Units). Even if the LRU makes it back to the depot for failure
confirmation, it may not be repairable. 6, 8 or 12 layer PCBs cannot be
readily repaired. And would you trust one that was repaired if it did
not go through a burn-in cycle afterward? Would you depend on a
fail-safe circuit to prevent a nuclear launch if it had a component
replaced in it that was "close enough?" Maybe in your cars brake system,
but not on my missile!
True, in the 'close enough' stakes, but it is well worth reflecting that 90%
of simple systems use a relatively small 'subset' of parts from the avilable
world pool. An engineer, with one each of the IC's for a range of boards,
and a few dozen resistors and capacitors, can potentially repair most faults
on such boards 'on site', especially if the board is designed with this in
mind (possibly with some form of self diagnostics for many parts). However
if the same units are built with SM parts in quantity, using custom IC's,
the solution becomes to carry a complete replacement board. Doing this for a
few dozen products is often not practical. The problem here is that the
custom IC/SM solution is cheaper once production reaches a reasonable level,
but is not the best solution where the units are going to be a long way from
'spares'.
I designed a range of units used on sites across many third-world countries,
and it became necessary to deliberately design the units with both
redundancy, and repairability in mind. Given that the service engineer may
have to travel 1000miles to get to a unit, having it so that repair is
likely to be possible, was a vital design criterion. The parts list was
deliberately 'shrunk', retaining as far as was practical a limited range of
parts used in all. Unfortunately the relative costs of truly 'mass'
production, combined with robot construction/assembly, make such designs a
'dying art'...

Best Wishes

If your design criterion is that the equipment be field repairable with
readily available parts, then so be it. I have no argument with that!
But in the high-reliability military electronics world in which I worked
in the late 60's, that was not possible. Would you believe that one
printed circuit card, 4 in by 6 in, was needed just to implement 4
flip-flops using descrete components. Each component, yes even a carbon
composition resistor, had a serial number on it. Why? So it could be
traced back to the lot from it which it had been selected if it failed.
And boy, did those components have to be reliable! So that's why the
military specifications with their "strange" component markings were
invented. Expensive? Lordy, lordy! I was very shocked one day when I
requisitioned a capacitor from stock to compare to a rejected one. The
price for that unit, a precision paper mylar cap. was $100 - in 1970's
dollars! I almost fell out of my chair! And now you can buy stuff like
that, surplus, for just pennies on the dollar...and with their strange
markings.

I have a bag full of CSR13G825KR's! Anybody need one?

Al

Al

--
There's never enough time to do it right the first time.......

 

[Tim Williams]

"Watson A.Name "Watt Sun - the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:c2ncdf$69d96$1@hades.csu.net...

Actually, coming from you, I'd've expected 6AL5.

Only rated for some 9mA per section, DC. Although I've had one up to 50mADC
at a nasty duty cycle in a flyback setup with no meltdowns.

Tim

--
"I have misplaced my pants." - Homer Simpson | Electronics,
- - - - - - - - - - - - - - - - - - - - - - --+ Metalcasting
and Games: http://webpages.charter.net/dawill/tmoranwms

 

[Jim Adney]

On Tue, 09 Mar 2004 19:59:19 -0800 Roy Lewallen <w7el@eznec.com>
wrote:

Jim Adney wrote:
. . .
So I still don't think it's too much to ask that the most important
data be printed out separately.

Obviously, I don't tend to think like the military....

While you've got a legitimate point, you've got to realize the function
of the part number. If you're a technician servicing a piece of military
gear, you replace a 20035942 *ONLY* with a 20035942, not *ANY* other
capacitor, regardless of its value. To order a replacement, you put in a
requisition for a 20035942. Now, it's vital to you that the capacitors
in the stock bin or coming in from the supply system have 20035942
printed on them, but it's not important that the value is. The
technician can find the value in the parts list in the manual and likely
on the schematic.

If I'm that tech, how do I correlate that p/n with this cap on the
schematic? Does the schematic have both the value AND the p/n on it?

I understand your point about using the exact replacement, but I don't
see why a part should not have BOTH sets of data. To me, that seems
like it adds a lot of value to the part.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Mac]

On Tue, 25 Nov 2003 08:32:41 +0000, rishi wrote:

I have a project to log the keypresses from an hall of 60m X 50m area.
There are around 500 switches in this area(actually there r 500 users
sitting in this hall, each table has one toggle switch,reset switch).

Tables are arranged as 10cols X 50 rows.

I was thinking for a simple matrix logic as its extremely simple and
would be cost effective in terms of cabling costs as well as other
hardware required.

I have a requirement of running 60 m cables with ttl signals.Is it
possible with using BUS Buffers/transreceivers?

ON the computer end i will use 60 bit digital I/O board and write the
software which will scan rows and columns continuosly.

Will be feasible or there is any better alternative...

Please , can u suggest me on this.

Thanks alot
Best Regards
Rishi Bhanot

Rishi. If you just need to detect key-presses, I think the cabling is OK.
You can put a pull-up (2.2k) and a capacitor on each line, near where the
logic senses it. Then put a 100-Ohm resistor in series with the wire. The
switches can be normally-open types. (view with courier or similar)

VCC
|
/
\ 2.2k
/
\
|
/| |
/ | | 100 60m wire
< +---+----/\/\/\/-------------------------+
\ | | |
\| = C \
| \ switch
| |
+------------------------------------+
| 60m wire
GND

So when a switch is closed, the logic will detect a low.

There are some things you will have to be careful with. For example, if
the capacitor is not big enough, or too big, the logic may switch more
than once per press. Also, there are a bunch of issues associated with the
scan speed. If you scan fast, (>10 Hz) and they press slow, there should
be no problem.

What I don't understand is how you plan to multiplex your 60 IO lines into
500 (or 1000?) switches. Is that where you would use the bus receivers? I
guess it could work. Logically you have 10 banks of 50-line bus receivers.
In reality, each bank may be more than one chip. The banks are all
connected together, and at any given time, only one bank is active,
and the others are disabled with their drivers in a high impedance state.

The 10 remaining lines on your IO board can be configured as outputs, and
each one can select one of the banks.

It's going to be a pretty large circuit. I hope you can have a board made
for it, because I wouldn't want to prototype it with point to point wires!

The other option is trying to find an IO board with 500 IO's on it.

Mac
--

 

[Roy Lewallen]

Jim Adney wrote:

If I'm that tech, how do I correlate that p/n with this cap on the
schematic? Does the schematic have both the value AND the p/n on it?

I understand your point about using the exact replacement, but I don't
see why a part should not have BOTH sets of data. To me, that seems
like it adds a lot of value to the part.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

Typically, the schematic will identify the part by "circuit number", say
C143 (and might or might not show the value), and it'll be on page A4B3,
which is the schematic for board B3 in larger assembly A4. In the same
manual, there'll be a parts list for A4B3, where you can find the
description of C143, along with its part number. It would certainly
include the value, type, and probably the tolerance, which are important
to know when troubleshooting. Sometimes it'll tell a little more, if
there's something particularly unusual about the part. But the full
description of that part #20035942 only appears on a document that's
typically many pages long and fully describes its specifications. There
might be 100 different part numbers for 4.7 uF, 10%, 50 volt tantalum
capacitors, each with different specifications for reliability testing,
temperature range, ESR, mechanical lead strength, vibration tolerance,
tada, tada, tada. They are *NOT* interchangeable in the military or
commercial environment. Substitution could result in failure at a
critical time or place with incredibly expensive, disastrous, or fatal
consequences.

When replacing the part, the only thing that's important to the
technician is whether the replacement has the right part number. If it
doesn't, the part doesn't go in, regardless of what its capacitance
value might be.

Yep, stamping the value on the capacitor would undoubtedly add value to
the part for you and me. But again, the military just wasn't thinking of
us when it set up its stock system.

Roy Lewallen, W7EL

 

[Udo Piechottka]

Mac schrieb:

In reality, each bank may be more than one chip. The banks are all
connected together, and at any given time, only one bank is active,
and the others are disabled with their drivers in a high impedance state.

Don't forget the decoupling diodes for each switch.

- Udo