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Old 10-11-2007, 10:13 PM
Architect Architect is offline
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Default Netherlands + IC99

Meanwhile the kit arrived in the Netherlands. It really looks great. A job well done, Grant. [Actually, it was there already last Tuesday but it had to fight its way through Customs.]

I studied the LOGIC SCHEMATICS in detail and found that IC99 is not used anywhere. The diagrams I downloaded before (sheet 01) said "CORRECTED 9-20-72". IC99 is also not attached to anything at all on the PCB. I assume it was there in an earlier design but John changed it.

Could that be the reason it runs hot (190 F) as Grant noticed (page 28)? I think it is possible to take out IC99 without changing anything whatsoever. Of course I will try that once I assembled everything, but perhaps you guys can already check that.
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Old 10-12-2007, 02:34 AM
Geoff Harrison Geoff Harrison is offline
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Quote:
Originally Posted by Architect View Post
I studied the LOGIC SCHEMATICS in detail and found that IC99 is not used anywhere.
You're absolutely right. You have good eyes.

Quote:
Could that be the reason it runs hot (190 F) as Grant noticed (page 28)?
My Kenbak has been running continuously for 4 days now with the top on and IC99 is not particularly hot. It is warm, as are all of them, but I can keep my finger on it with no discomfort.
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Old 10-12-2007, 07:19 AM
Grant Stockly Grant Stockly is offline
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That heat might have been due to a marginal part.

My incandescent bulb Kenbak has the 190F chip.

My LED Kenbak is just regular warmth.

I don't see any connections (other than power) to the chip either. That's weird.

It doesn't get much more clear than this:

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Old 10-13-2007, 04:52 AM
Architect Architect is offline
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Default IC Cross Reference

The reason I found out about IC99 is that I made a cross reference table for the ICs because I found myself continuously scanning through 24 diagrams to look for a particular IC. See the attachment.
Attached Files
File Type: txt ic-xref-html.txt (11.1 KB, 382 views)
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  #5  
Old 10-13-2007, 06:39 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by Architect View Post
Could that be the reason it runs hot (190 F) as Grant noticed (page 28)? I think it is possible to take out IC99 without changing anything whatsoever. Of course I will try that once I assembled everything, but perhaps you guys can already check that.

I've been thinking about this more and I can't find a good reason. I can guarantee one thing, it IS hot. Maybe the probe was reading wrong, but I couldn't keep my finger on it.

I thought maybe it was because the inputs were floating and maybe the chip was oscillating. But I am pretty sure the inputs are stable when left unconnected.

When I get a chance I will swap the chip out (on the board that gets hot) and see if it also gets hot.

When do you plan to start construction of your Kenbak?
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  #6  
Old 10-13-2007, 06:41 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by Architect View Post
The reason I found out about IC99 is that I made a cross reference table for the ICs because I found myself continuously scanning through 24 diagrams to look for a particular IC. See the attachment.
Thanks for that list! If there is anything I can do to help you let me know.

I know I promised earlier, but I will have the searchable PDF files uploaded soon.
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