2 Jun
2001
2 Jun
'01
11:22 a.m.
Anybody know the voltage tolerances for S-100 bus computers, or where
such info. can be found? I am preparing to run a 1981 vintage, 19-slot
S-100 system.
After pulling all but one of the cards out I powered up the system.
Fans run fine, but the motherboard voltage supplies are rather high. For
+8V I measure 10.7V; for +16V I get -19.3V; and for -16V I get -19.3V. Is
this some careless engineering, bad components, or is the board really NOT
supposed to receive the nominal voltage?
Many of the S-100 boards are discoloured brown-green on the solder
side opposite these large transistor-like things with heat sinks. Is that
something to worry about?
I also measured the DC voltages of the pins of one of the slots. This
is what I got (assuming that pins 1|51 is at the power supply end):
volts pin# volts | volts pin# volts | volts pin# volts | volts pin# volts
----- ----- ----- | ----- ----- ----- | ----- ----- ----- | ----- ----- -----
10.7 1 51 10.7 | ? 13 63 ? | ? 26 76 ? | 1.4 38 88 1.4
? 2 52 -19.5 | 5 14 64 ? | ? 27 77 ? | 1.3 39 89 1.3
5 3 53 0 | ? 15 65 ? | ? 28 78 1.3 | 1.3 40 90 1.3
5 4 54 5 | ? 16 66 ? | 1.6 29 79 1.3 | 0.1 41 91 0.1
5 5 55 5 | ? 17 67 5 | 1.3 30 80 1.3 | 0.1 42 92 0.1
5 6 56 5 | 5 18 68 ? | 1.3 31 81 1.3 | 0.1 43 93 0.1
5 7 57 5 | 5 19 69 ? | ? 32 82 1.3 | 1.3 44 94 0.1
5 8 58 ? | 0 20 70 0 | ? 33 83 1.3 | 1.3 45 95 0.1
5 9 59 ? | ? 21 71 ? | ? 34 84 0 | 1.3 46 96 1.3
5 10 60 5 | 5 22 72 5 | 1.4 35 85 0 | AC? 47 97 AC?
5 11 61 ? | 5 23 73 5 | 1.4 36 86 0 | ? 48 48 5
5 12 62 ? | 1.3 24 74 5 | ? 37 87 0 | 1.3 49 99 5
| ? 25 75 ? | | 0 50 100 0
Does that look safe enough to put the boards back and see how this system
runs?
A fair amount of current runs through these slots. I nearly welded my
probe to the slot when I accidently shorted two pins!
Any help, encouragement is much appreciated!
Edwin
2 Jun
2 Jun
11:49 a.m.
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 1395 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/20010603/cd91b212/at…
3:08 p.m.
On Sat, 02 Jun 2001 16:22:58 -0700, Edwin P. Groot wrote:
# A fair amount of current runs through these slots. I nearly
welded my
#probe to the slot when I accidently shorted two pins!
#
Yes, I have done that. Another good trick when creating shorts is to
cause a tantalum capacitor to burst into flames. Maybe we should start
a thread on what kind of fire extinguishers people recommend.
Louis
3:59 p.m.
On Sat, 02 Jun 2001 16:22:58 -0700, Edwin P. Groot
wrote:
# A fair amount of current runs through these slots. I nearly
welded my
#probe to the slot when I accidently shorted two pins!
#
Yes, I have done that. Another good trick when creating shorts is to
cause a tantalum capacitor to burst into flames. Maybe we should start
a thread on what kind of fire extinguishers people recommend.
I used to work in a test house. One of the testers was a
Schlumberger S90 memory tester. The test head contained
several boards in parallel, very close together. The
boards had several tantalum capacitors. Once one of the
tantalum capacitors blew a hole in the board about 1"
around, smallers holes on the boards to each side, and
badly melted areas on the next board on each side, for
a total of five destroyed boards. These boards weren't
cheap, but we had a maintenance contract, so we didn't
have to pay for them.
--
Eric Dittman
dittman(a)dittman.net
3 Jun
3 Jun
1:27 a.m.
At 10:59 PM 6/2/01 -0500, Eric Dittman wrote:
The boards had several tantalum capacitors.
I thought I'd recently heard a news story that
claimed that 80% of the world's supply comes from
a single mine in the Australian outback, but that
may only be a slight exaggeration:
http://www.cellular.co.za/technologies/phones/tantalum.htm
which leads to tantalum ore poaching:
http://www.ebnews.com/digest/story/OEG20010427S0086
Perhaps a richer source of ore is old computers.
- John
2:41 a.m.
Actually, modern ceramic caps are very close to tantalums
in terms of performance, and are approaching the size of
tantalums. Those of you who are engineers (or am I the
only one?) should investigate ceramics before plopping
a half dozen tantalums onto a board...
Clint
On Sun, 3 Jun 2001, John Foust wrote:
At 10:59 PM 6/2/01 -0500, Eric Dittman wrote:
The boards had several tantalum capacitors.
I thought I'd recently heard a news story that
claimed that 80% of the world's supply comes from
a single mine in the Australian outback, but that
may only be a slight exaggeration:
http://www.cellular.co.za/technologies/phones/tantalum.htm
which leads to tantalum ore poaching:
http://www.ebnews.com/digest/story/OEG20010427S0086
Perhaps a richer source of ore is old computers.
- John
5:27 a.m.
I'm not sure what you mean by "performance" with respect to these cap's,
but the
reason we used to justify the somewhat more costly tantalum cap's back in the
'80's was that their frequency response was much better than electrolytics,
going pretty far into the range normally associated with ceramic cap's, yet they
would perform as well as the comparable values of electrolytics at lower
frequencies. That meant one didn't have to put a small ceramic in parallel with
a larger electrolytic in dense structures like DRAM arrays, which, with 3
supplies, and lots of noise, along with pretty significant currents, switching
at relatively high speeds, required both high-frequency response compatible with
the sequences of control strobes at least the three major ones, (nRAS, nCAS,
nWE) not considering the addresses and their associated muxes, all switching
within a tyipically 40-60 ns window. The electrolytic's function was to hold
the supply up so the power-to-ground surge didn't cause problems as devices were
suddenly selected, while the ceramic's function was to pick up the slack while
the electrolytic figured out what to do. I remember supply fluctuations over a
volt in magnitude in some memory circuits. That didn't make for high
reliability.
As for the S-100 supply spec, the 8-volt spec is a minimum because the forward
voltage of the regulators typical in the '80's was over 2 volts. Likewise, the
+/- 16 volt spec called out in the standard is a minimum for the same reason,
and, in fact, because some circuits used Zener regulators or the like, with
fairly low dropout, to supply ananlog circuits requiring bipolar 15 volt
supplies. It's not unusual to see the no-load voltages on these supplies to
look like 10 volts for the +8 and 21-22 volts for the bipolar 16 volt supplies.
I always preferred to stay close to the lower limits, but since then-current
design practice was to design transformers such that they produced a 10% voltage
drop from no-load to full load, and since many vendors pushed that to 15 or even
20%, the >20 volt values were not uncommon. Even my own designs tended to look
closer to 10 volts on the +8 in order to save on cost and size. Of course my
stuff was not with custom designed transformers, and COTS products tended to
have 18VCT and 36VCT secondaries.
BTW, the cardcage protects you from stupidly plugging a board in backward, which
I recently did on motherboard that was on the benchtop with no cage. That can
lead to real problems (smoke!), so be careful. I did that once before, back in
the '70's and a piece of an IC hit me right between the eyes when the thing
burst. That was with a regulated supply to the bus, (not S-100) so there was no
regulator to protect the circuits.
It is, by the way, a good idea to solder a hefty diode conducting from regulator
output to regulator input on S-100 boards, to protect the regulators against the
occasional situation during power-down, when stored charge in the load holds the
voltage up while loads elsewhere in the system pull the regulator's input down.
When that happens, next time you power the system up, you may no longer have a
regulator. These diodes would not have cost much to include on the PCB, but the
combination of cost and space made folks leave them out.
Dick
----- Original Message -----
From: "Clint Wolff (VAX collector)" <vaxman(a)qwest.net>
To: <classiccmp(a)classiccmp.org>
Sent: Sunday, June 03, 2001 8:41 AM
Subject: Re: S-100 Bus Voltages
Actually, modern ceramic caps are very close to tantalums
in terms of performance, and are approaching the size of
tantalums. Those of you who are engineers (or am I the
only one?) should investigate ceramics before plopping
a half dozen tantalums onto a board...
Clint
On Sun, 3 Jun 2001, John Foust wrote:
At 10:59 PM 6/2/01 -0500, Eric Dittman wrote:
The boards had several tantalum capacitors.
I thought I'd recently heard a news story that
claimed that 80% of the world's supply comes from
a single mine in the Australian outback, but that
may only be a slight exaggeration:
http://www.cellular.co.za/technologies/phones/tantalum.htm
which leads to tantalum ore poaching:
http://www.ebnews.com/digest/story/OEG20010427S0086
Perhaps a richer source of ore is old computers.
- John
4 Jun
4 Jun
5:34 a.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
Well, I plugged in the boards and powered up the computer, and
promptly powered it down after a few loud pops - D'Oh! Nothing was
displayed on my teminal connected to the console serial line. The affected
boards are the CPU board and a serial board - some tantalum capacitors
blew. I'm assuming they're tantalum caps- they're not electrolytic
can-style, or ceramic disc-style, but look like a gob of shiny blue acrylic
paint on two leads. The board marks which lead is +.
Are these tantalum caps common enough to buy at the local electronics
shop? We've got Radio Shack, but I heard they are overpriced. The caps to
be replaced were in the uF range.
BTW this is a complete system and the cards are arranged (from low
slot # to high slot #): CPU, RAM, FD controller, Serial/Parallel,
Terminator. Will check with documentation that RAM and ROM banks, and I/O
is configured right once I get the boards fixed.
Thanks,
Edwin
At 11:08 PM 6/2/2001 -0400, you wrote:
Yes, I have done that. Another good trick when
creating shorts is to
cause a tantalum capacitor to burst into flames. Maybe we should start
a thread on what kind of fire extinguishers people recommend.
Louis
6:11 a.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 1203 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/20010604/38326e7e/at…
7:55 a.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
On Mon, 4 Jun 2001, Edwin P. Groot wrote:
Well, I plugged in the boards and powered up the
computer, and
promptly powered it down after a few loud pops - D'Oh! Nothing was
displayed on my teminal connected to the console serial line. The affected
boards are the CPU board and a serial board - some tantalum capacitors
blew. I'm assuming they're tantalum caps- they're not electrolytic
can-style, or ceramic disc-style, but look like a gob of shiny blue acrylic
paint on two leads. The board marks which lead is +.
Are these tantalum caps common enough to buy at the local electronics
shop? We've got Radio Shack, but I heard they are overpriced. The caps to
be replaced were in the uF range.
BTW this is a complete system and the cards are arranged (from low
slot # to high slot #): CPU, RAM, FD controller, Serial/Parallel,
Terminator. Will check with documentation that RAM and ROM banks, and I/O
is configured right once I get the boards fixed.
I had this experience before with a Sol-20. Aside from being loud and
smelly, the tantalum caps exploding really shouldn't hinder the operation
of the system. Tantalum caps on older systems like S-100's that haven't
been powered up in some time are prone to exploding.
If you have a problem it's most likely related to some other failure.
Perhaps you should check to make sure you have matching settings on
your serial port and terminal. Also, make sure your cable is the right
kind (straight through...NOT a "null-modem" cable).
Also, maybe your system is expecting a boot disk to do anything useful.
Did you notice if your drives are spinning when you fire it up?
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
9:07 a.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
--- Sellam Ismail <foo(a)siconic.com> wrote:
That all depends. I saw a COMBOARD come back from a customer site that
had a tantalum cap blow - there was a 5mm ragged hole in the 6-layer board
and I was told that the DEC boards on either side were damaged badly enough
to need replacement.
Glad I wasn't looking inside the BA-11 when it went off!
-ethan
=====
Visit "The Seventh Continent"
http://penguincentral.com/penguincentral.html
__________________________________________________
Do You Yahoo!?
Get personalized email addresses from Yahoo! Mail - only $35
a year! http://personal.mail.yahoo.com/
On Mon, 4 Jun 2001, Edwin P. Groot wrote:
> Well, I plugged in the boards and powered up the computer, and
> promptly powered it down after a few loud pops - D'Oh!
Wahoo!
...some
tantalum capacitors blew.
I had this experience before with a Sol-20. Aside from being loud and
smelly, the tantalum caps exploding really shouldn't hinder the operation
of the system.
10:28 a.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
While the generalized observation that when something pops, there's a good
reason, in the case of tantalum cap's it's often simply the age of the cap.
They don't age gracefully and it's not at all unusual for the only thing wrong
with a board that bursts into flame to be the cap's that were engaged in the
conflagration.
If you replace the tantalum cap's it's likely the problem will be gone.
However, if you leave one of the old ones on the board, it will "go" later, for
you to clean up later.
Not all such aged cap's will catch fire, though the tantalum ones tend to do so.
Some will just short, causing your power supply to act funny, since they're
quite a large load. That's what makes 'em catch fire when they do.
Dick
----- Original Message -----
From: "Sellam Ismail" <foo(a)siconic.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, June 04, 2001 1:55 PM
Subject: Re: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
On Mon, 4 Jun 2001, Edwin P. Groot wrote:
Well, I plugged in the boards and powered up
the computer, and
promptly powered it down after a few loud pops - D'Oh! Nothing was
displayed on my teminal connected to the console serial line. The affected
boards are the CPU board and a serial board - some tantalum capacitors
blew. I'm assuming they're tantalum caps- they're not electrolytic
can-style, or ceramic disc-style, but look like a gob of shiny blue acrylic
paint on two leads. The board marks which lead is +.
Are these tantalum caps common enough to buy at the local electronics
shop? We've got Radio Shack, but I heard they are overpriced. The caps to
be replaced were in the uF range.
BTW this is a complete system and the cards are arranged (from low
slot # to high slot #): CPU, RAM, FD controller, Serial/Parallel,
Terminator. Will check with documentation that RAM and ROM banks, and I/O
is configured right once I get the boards fixed.
I had this experience before with a Sol-20. Aside from being loud and
smelly, the tantalum caps exploding really shouldn't hinder the operation
of the system. Tantalum caps on older systems like S-100's that haven't
been powered up in some time are prone to exploding.
If you have a problem it's most likely related to some other failure.
Perhaps you should check to make sure you have matching settings on
your serial port and terminal. Also, make sure your cable is the right
kind (straight through...NOT a "null-modem" cable).
Also, maybe your system is expecting a boot disk to do anything useful.
Did you notice if your drives are spinning when you fire it up?
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
12:06 p.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
Luckily I had no flames or holey boards! After checking my terminal
settings, cabling, etc., should I power up with those burnt caps in place,
or should I desolder them and leave their contacts on the boards open?
Didn't connect the floppies yet. Just wanted to see if I was going to
get messages on the terminal from the ROMs first.
Edwin
At 12:55 PM 6/4/2001 -0700, you wrote:
I had this experience before with a Sol-20. Aside from being loud and
smelly, the tantalum caps exploding really shouldn't hinder the operation
of the system. Tantalum caps on older systems like S-100's that haven't
been powered up in some time are prone to exploding.
If you have a problem it's most likely related to some other failure.
Perhaps you should check to make sure you have matching settings on
your serial port and terminal. Also, make sure your cable is the right
kind (straight through...NOT a "null-modem" cable).
Also, maybe your system is expecting a boot disk to do anything useful.
Did you notice if your drives are spinning when you fire it up?
Sellam Ismail Vintage Computer
Festival
---------------------------------------------------------------------------
---
International Man of Intrigue and Danger
http://www.vintage.org
12:11 p.m.
New subject: Tantalum Popcorn - What to do (Was S-100 Bus Voltages)
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 394 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/20010605/f04c12c3/at…
12:44 p.m.
New subject: Tantalum Popcorn - What to do (Was
On Mon, 4 Jun 2001, Edwin P. Groot wrote:
Luckily I had no flames or holey boards! After
checking my terminal
To get flames here, you need to post about discarding old equipment, or
advocate using e-bay, or advocate a Microsoft product newer than the
green-eyed mouse.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
2:48 p.m.
New subject: Tantalum Popcorn - What to do (Was
Not so! All you have to do is power up a board on which there are a few shorted
but small tantalum cap's. That involves no tossing of old gear, auctioning on
eBay, or advocacy of Microsoft.
Dick
----- Original Message -----
From: "Fred Cisin (XenoSoft)" <cisin(a)xenosoft.com>
To: <classiccmp(a)classiccmp.org>
Sent: Monday, June 04, 2001 6:44 PM
Subject: Re: Tantalum Popcorn - What to do (Was
On Mon, 4 Jun 2001, Edwin P. Groot wrote:
Luckily I had no flames or holey boards!
After checking my terminal
To get flames here, you need to post about discarding old equipment, or
advocate using e-bay, or advocate a Microsoft product newer than the
green-eyed mouse.
--
Grumpy Ol' Fred cisin(a)xenosoft.com
5 Jun
5 Jun
6:40 a.m.
New subject: Tantalum Popcorn - What to do (Was
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 368 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/20010605/d784cc1f/at…
1:56 p.m.
New subject: Flaming DECpacks (was Re: Tantalum Popcorn - What to do (Was)
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
The fans in DEC RK05 drives are also quite good at
starting flames when
the insulation starts to break down (as has happened to at least one of
mine)....
I have heard of such things - that fan can really feed the flames. Are
there any tips for precheckout of an RK05 drive?
-ethan
=====
Visit "The Seventh Continent"
http://penguincentral.com/penguincentral.html
__________________________________________________
Do You Yahoo!?
Get personalized email addresses from Yahoo! Mail - only $35
a year! http://personal.mail.yahoo.com/
6 Jun
6 Jun
5:56 a.m.
New subject: Flaming DECpacks (was Re: Tantalum Popcorn - What to do (Was)
A non-text attachment was scrubbed...
Name: not available
Type: text
Size: 1889 bytes
Desc: not available
Url :
http://www.classiccmp.org/pipermail/cctalk/attachments/20010606/e24666ec/at…
8600
days inactive
8604
days old
18 comments
10 participants
participants (10)
-
ard＠p850ug1.demon.co.uk -
cisin＠xenosoft.com -
dittman＠dittman.net -
edick＠idcomm.com -
epgroot＠ucdavis.edu -
ethan_dicks＠yahoo.com -
foo＠siconic.com -
jfoust＠threedee.com -
louiss＠gate.net -
vaxman＠qwest.net