VOGONS


First post, by Predator99

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Hi, I am trying to get this board running again. I got it in the condition as shown on the picture with some ICs missing. Will care about BIOS, KBC and cache later. I think critical are the two which are labeled
FCT240
F521
For the F521 I have the exact replacement.
All these ICs need indeed to be populated, I have found several pictures of complete boards.

For the "FCT240" I have a "SN74HCT240N" as spare.

When I insert these 2 ICs I observe that the Reset-light on the POST card is "on" all the time.
It gets off after removing the SN74HCT240N.

So my question is if the SN74HCT240N is an incompatible replacement? Does it make sense to order a FCT240? Or do I have to look somewhere else for the cause..?

Thank you!

https://stason.org/TULARC/pc/motherboards/S/S … 6A-SY-019B.html

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Reply 2 of 9, by Predator99

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Yes sure
https://en.wikipedia.org/wiki/7400-series_int … grated_circuits

74FCT – Fast CMOS TTL-compatible, 74FC technology with TTL-compatible logic levels.
74HCT – High speed CMOS TTL-compatible, 74HC technology with compatible logic levels to bipolar TTL parts.

For me that sounds compatible and the HCT is the faster one so it should work..?

Reply 3 of 9, by Deunan

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FCT should be quite faster than HCT (2ns vs some 5-8ns). But it really depends on the chips and how it's used. There is also ACT which is faster than HCT but somewhat slower than F, but that depends on the manufacturer. Personally I'd look for ACT first and then try HCT.

Reply 4 of 9, by Cyrix200+

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I had a similar board with a similar problem. This is my board's story: Looking for an ID/manual/jumpers and more info on this 386 AMD 40MHz board But you probably remember, you and Deunan helped me in that thread 😀

1982 - 2001

Reply 5 of 9, by keropi

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I would use the F variant - as Deunan stated is is the faster of the lot
if you notice on the board there are also LS variants in non-critical places, back then because F ones were more expensive they only used them in critical places and thus it's not a good idea to use a slower one in it's place IMHO - you might get away with it you might not and get some weird behavior now and then or something...

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Reply 6 of 9, by Predator99

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Thanks for your replies!

I just ordered a 74FCT240AP. It makes sense...why should they use a expensive one and put it - different to most other ICs - on a socket if its not required.

I dont expect too much however...I will report.

@Cyrix200+: You are right, almost the same problem. I didnt rember that and you see I am also no expert 😁

Reply 8 of 9, by Predator99

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That was a quick "repair". 1st try worked.
The 486 "AMI BIOS for J-Bond A433C-C_A450C-C.zip" has the identical ETEQ-Chipset: ET82C491, ET82C493
Picture here:
http://minuszerodegrees.net/at_clone_bios/J-B … ersion%2002.jpg

In my board it detects a 386 and seems to work...

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Used a Keyboard-ROM from a 286 and no Cache.