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| | Previous Messages | Posted By
MikeZ
on 2009-06-05
18:28:07
 |  Re: Why is the TED chip so vulnerable to frying?
TLC proposes a better solution to finding fan voltage. It looks like soldering on the ckt board is required.
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Posted By
MMS
on 2009-06-05
17:21:49
 | Re: Why is the TED chip so vulnerable to frying?
Sunon: we used Sunons some years ago in our products, most of them had premature noise after few months usage. We chaged to Delta since 3 years.
Sorry, if I was not precise enough: when the board are connected, and has a proper connection to gound and housing, you cannot damage the ICs with ESD.
BUT during production (till the board is alone with it's ICs) you can damage several ICs on the board, just by touching it, like imagine the people assembling the board intot the housing, and charged. As there is nothing which is connected -may dissipate the electrons- they stay and damage the IC. That1s why double ESD protection is needed on all employees working on the line: ESD shoes + ESD bracelet.
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Posted By
TLC
on 2009-06-05
16:34:58
| Re: Why is the TED chip so vulnerable to frying?
ESD is not that problematic, as speaking of the TED (or any other C= chips). First, these chips are manufactured in NMOS... NMOS is not as prone to ESD as CMOS chips of the time have all been. Second, ESD can be a source of problems only if you expose the chips to it somehow (say, in order to give it an ESD shock, you somehow have to touch the pins of the chip first) -- this is rarely the case here, the only possiblitity being crude ways of connecting/disconnecting peripherals, touching the pins of the user port or things like that, unless you had disassembled the computer first... In reality, as long as you don't do something nasty, you don't really have much to worry about ESD.
Periodic dilatation of the silicon chip (because of heat-up and cool-down) is usually the problem (...not especially dilatation, but hairline cracks on the chip, that start up from defects in the crystalline structure, and develop by each heat-up / cool-down cycles... these hairline cracks would reach vital traces or FETs sooner or later). I remember reading some articles about that... this is a very old one:
http://www.zimmers.net/anonftp/pub/cbm/documents/repair/heatsink.txt
As for using a PC fan or something like that...
You can usually feed such fans from some volts below their nominal supply voltage. But that takes some experimenting. For example, it's been a well known trick to use "large" (8 cm) fans and operate them from 7v instead of 12v amongst PC modders (back then, when today's regulated fans were unavailable), to replace noisy high-rev fans of CPU heatsinks. This trick might be applicable here (not the large fan, but underpowering an otherwise high-rev 12v PC fan). ...You also need much smaller air flow here than PC fans are originally designed for... the heat dissipation of these chips is in the order of below 1 Watt(s). If you take a look at the schematics of the Plus/4 power supply, you can notice that _everything_ (excluding the datasette and the 9v AC supply of the User Port, but including everything else) is powered off from a 7805 voltage regulator... whose current is (by definition) limited to 1 Amps. Multiple 5 Volts by 1 Amps -- you'll find that the _whole computer_, including cartridges, must (by definition) dissipate _below_ 5 Watts. ...Have a compare of that value to todays PC components... 
Also, keep in mind that fans operating above something like 1000-1500 rpms "are" noisy... especially if you have to listen to it directly (which seems to be the case here). At least it won't be absolutely quiet anymore.
If needed, small fans could be operated from the unregulated rectified voltage (+9v unreg), which is about 9-10v. You can draw this from some point at C7, C8, C9 (+9v unreg, as seen at the bottom of this page: http://zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/plus4-310164-2of4.gif ). I'd probably go for that option first anyway, as this is a separate power circuit from the main one, and is only used for the datassette and the 9v AC output of the User Port. (Including a variable series resistor to the pack, with which one could set a reasonable speed, would be the best).
It's interesting to read that most of you met dying TEDs instead of CPUs... my experience has so far been the opposite (...say, usually the CPU would give it up first).
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Posted By
MikeZ
on 2009-06-05
12:42:13
| Re: Why is the TED chip so vulnerable to frying?
I checked the fan URL. It will draw 80 - 92 ma. This should be OK if nothing else is connected to the user port or expansion port and the plus4 is otherwise operating properly. I must also repeat that you will get the most out of the fan IF the heat conducting grease on the TED chip is in good condition. Also, you will have to be sure that the fan blows air across the metal box containing the TED chip. Sorry if I overstate the obvious.
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Posted By
MikeZ
on 2009-06-05
10:46:57
| Re: Why is the TED chip so vulnerable to frying?
Just 5VDC and limited to 100 ma MAX.
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Posted By
MMS
on 2009-06-05
09:40:37
| Re: Why is the TED chip so vulnerable to frying?
In fact, there is an other potential source. ESD.
I am working on consumer Electronics products, and is any electrostatic issue appears >200V (touching, or even just walking around with poly coat), then it may harm the IC.
It will not die soon,sometimes it take 1-3 years to show the effect, the more often you yuse the faster you will see it. It has a specific pattern, how such an IC looks under microscope, but for that you need a lab, we do not have.
So, the circumstances of production (how strictly they managed it) could be one impact, but this one was really not in focus in the 80s (to be honest, now even at the mid of 90s), and I do not know, if those TED ICs (MOS / CMOS?) are sensitive to ESD, or just to overvoltage (which should come to the environment, not from the IC itself).
Please forgive me for the mistakes I potentially made, I am not an expert, my degree is from a different area. So feel free to correct me.
(active cooling: nice idea, in fact NOT all fans need regulated 12V, some of them is work from 6V DC also, like Delta Fan DSB0612MA-6Q78). Do we have 6V? Or just 5?
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Posted By
Chronos
on 2009-06-04
15:46:01
 | Re: Why is the TED chip so vulnerable to frying?
and what about the sizzling plusi power adaptors? tlc told me once (or my father i cannot remember - don't laugh my father is a power magician too) its about the ageing crackling stuff in the adaptor. i have one that works but makes a sizzling noise what makes me nervous  and back to the topic yes, the TED's are dying  i have 3 plusis and ONE working TED chip...
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Posted By
MikeZ
on 2009-06-04
15:32:13
| Re: Why is the TED chip so vulnerable to frying?
You cannot get 12vdc from the plus4. You have to use a small transformer that plugs into the electricity in your house and provides the correct DC volts and current for a fan.The TED sits in a metal box and there is heat conducting grease connecting the TED to this box. It's possible after all these years that the grease is dry or cracked.
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Posted By
Chronos
on 2009-06-04
10:41:39
| Re: Why is the TED chip so vulnerable to frying?
Where can we get 12v for the active cooler on the plusi mobo?
There is Many Iny Miny Miney Moe cheap cooler on the market for our shitty pc's
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Posted By
MikeZ
on 2009-06-04
10:31:47
| Re: Why is the TED chip so vulnerable to frying?
I bought 4 plus4s in 1985 thinking I had a lifetime supply of spare parts. Three of them lost the TED chip after 2-3 years. A TED chip alive today is almost 25 years old and way past the initial burn out at the beginning of its life. The cooling ideas are all good. But, you have to ask yourself what else is causing the overheat. After all, that TED chip has been well behaved for many years with no problems, unless in storage all this time.
It's time to get out the schematic and look for bad capacitors and resistors. These other things go bad as well. I recently repaired a plus4 where one of the inverter/buffers for the serial bus was fried.
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Posted By
MMS
on 2009-06-04
01:42:34
| Re: Why is the TED chip so vulnerable to frying?
Yeah, I alro read several places, that TED is prone to die rather soon.
I do not know, if it is due to heat, or something else.
Based on your feedback, it is the overheat.
Maybe -as a preventive action- it would worth to apply a heatsink (eg. PC Memory) on the head of the TED IC.
But maybe a set of PC Memory heatsink is more expensive than a Plus/4 (just kidding )
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Posted By
Dunric
on 2009-06-03
22:09:04
| Why is the TED chip so vulnerable to frying?
I've had some Plus/4's just up and fry on me. The TED gets too hot and so it causes damage to the entire computer.
Paul
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