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Netronics Explorer/85

I built an EPROM programmer onto my original Explorer-85. I used a capacitor charge pump circuit with a 555 chip to make the 25V.
At the time I only had an analog voltmeter. And I can remember being very worried about the accuracy of that 25V,
being still a kid, and the datasheet putting a very tight tolerance on it.

Also the programming pulse time. 50ms, or whatever, I cannot remember now.

But it worked!

My college roommate had a summer intern job with Texas Instruments, in Texas, and came
back with oodles of 25xx series EPROMs (probably 2516) that were supposedly testing rejects.
My programmer was for those.

I had more trouble erasing the darn things, than programming them. :)

/Bill
 
wrljet said:
Cool!

My box is ~ 13" x 9-1/2" x 2".
I got my (original) Explorer/85 in 1979, if I remember correctly. So the box wasn't from that.

/Bill
Click to expand...
Mine is 15"x10"x2", so yeah, probably not an Explorer box. I think an ELF II would fit in there though as other's have said.. or any of the other boards they sold (I know they sold a few S100 boards).
 
James0555 said:
Do you have the actual manual for the monitor. I too spent time dissembling the ROM but I now have the manual. I too am interested in the keypad ROM. I did discover a lot came straight from the SDK-85 monitor so I suspect the Keypad ROM does too. Are those the Basic ROMs in your board curious as to what is on the labels?

Link to Monitor listing and Basic user manual.

https://dl.dropboxusercontent.com/u/8496003/Netronics EX-85 manuals.zip
Click to expand...
This file is no longer present. Does anyone have it?

Bill
 
wrljet said:
Any idea what this Netronics AP-1 power supply was for?

www.ebay.com

Vintage Netronics Research AP-1 Power Supply | eBay

Find many great new & used options and get the best deals for Vintage Netronics Research AP-1 Power Supply at the best online prices at eBay! Free shipping for many products!
www.ebay.com
Click to expand...

That was certainly offered as an option for the Explorer/85 (I have a couple). I think it was also positioned as an option for the Netronics Elf II. Note that the voltage meter was added by the owner and not original.
 
Does anyone have the Level C kit with the metal frame, and could possibly provide some decent pictures of what it all looks like?

Bill
 
Nobody has one of these Netronics C-level with the metal framework for the S-100 cards?
 
Hi wrljet, hope these help...
 

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AstronomyGuy said:
Hi Tech Time Traveler (I recognize your logo from your YT channel) -- did you ever get your Explorer 85 going? I have one that I finally got going after a lot of debugging down rabbit holes. (I think I was one of the people who beat you to it on eBay back in 2017). The "ready" LED never lit and it didn't look like it was ever running proper code. It turns out the issue was a completely hosed 8355 ROM. I got a burner for 8755A and made a new terminal version ROM (EPROM), and it booted successfully. If you need an 8755, let me know.

Responding to your other questions -- yes that's a DB25 for serial. Here's the pinout I found in the docs:

View attachment 1247637

BTW I found that the serial timing is way off -- not sure if it's a general bug or just my unit, but anything above 1200 baud won't work (2400 partly works but is flakey) -- using a scope I found out that the timing is too fast -- e.g. when I try 4800 baud and it auto-detects the space bar, it transmits the response at about 5500 baud. It seems like whoever programmed the monitor was assuming a different clock speed (but it has the 6.144MHz crystal in it as specified). Oh well. Maybe the crystal could be replaced with a slower speed that makes it work.

I also burned some EPROMS with BASIC and got that working also.

Now that I got it going, I'm going to sell it on eBay -- probably listing it tomorrow (as an auction). It's a nice unit and fun to play with, but I have plenty of S100 computers.
Click to expand...
Hi AstonomyGuy - I realize that you sold this unit, however I wanted to mention to you and the forum that I encountered this baud rate issue recently while refurbishing my Exp85. After poking around with my scope I found that the capacitor, C104, across R126 in the "RS-232 IN" portion of the Exp85 circuit was affecting the shape of the voltage transitions in the RS-232 signal - throwing off the bit timing of the space character by the time it reached the 8085's SID pin. This cap is present in my Rev B schematic but does not appear in the Rev C-1 schematic I found on line. I can't remember if I had issues at 9600 baud back in the day, but it now works without issue after removing the cap.
 
Hi All, anyone in the group have schematics/assembly instruction for the Netronics Floppy-1A board that they would be willing to share?
Thanks!
 
Hi. I'm trying to understand how the RST 7.5 interrupt circuit works in the Explorer 85 level A, since in the i8085 the address jumped is located in 003CH (for level A there is no memory mapped here), but the monitor handles this interrupt in the address F03CH. Could somebody please explain me which part of the circuit does this?

Thanks!

Federico
 
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