Search found 19 matches

by rh74
Tue Jun 08, 2021 10:01 am
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Another easy option can be GF's nail polish :). Or wife's... Once I've seen a marker style technique. You were able to cover tracks just following them with a marker. An easy way indeed. I have little doubt this Oric will be revived in the end! I'm not yet defeated... I would be tempted to give up,...
by rh74
Mon Jun 07, 2021 11:02 am
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

...and left the beer as table-water replacement :D Good idea... So here a quick update about the quest for Oric 1. I removed both IC20 and IC8 and measured PIN 39 of ULA. The signal is there. As soon as I inserted the IC20 back the signal gone IMG_20210606_110757.jpg I'm still wondering how I didn'...
by rh74
Thu Jun 03, 2021 5:15 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Ah forgot to mention... The noising signal from PIN 39 is combined to the output of PIN 16 (6502) in pin 13 and 14 of IC20. The combined signal is then addressed to PIN 9 (A7) of RAM. Is where I initially found the missing square wave. Now afaik both are combined in two logical AND port and then in ...
by rh74
Thu Jun 03, 2021 2:21 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Hey there! Here some news to talk about. Finally I had some time to sit and do some oscilloscope measures. I found the PIN 39 on ULA is emitting garbage. I measured it a few times but the result is always the same: just noise instead of a square wave. I've tested the Atmos for comparison, signals ar...
by rh74
Fri May 28, 2021 10:34 am
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

You may want to check the main signals in the CPU. A stuck IRQ or RESET, bad clock in or clock out... Just in case... Yes I've checked that, but now I am a little more aware about what to check exactly... Noel's C64 provided some hints and I'm going through some 6502 literature to have a clear idea...
by rh74
Thu May 27, 2021 5:14 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Uhm... I just realized I didn't tested Address bus from the ULA and CPU... ok another test to add to the list...
by rh74
Thu May 27, 2021 4:42 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

So here I am... No damaged tracks between RAM chips. Awww. Let's start with the oscilloscope. I hope I'll find something. Keep going. :)
by rh74
Mon May 24, 2021 1:59 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

HI there, my friends. Unfortunately I had no spare time during the weekend, so no news for the moment. I checked the other two Oric (the early 1 and the Atmos) which still have original RAM soldered and I can confirm they are both HM4864P-2 equipped as Vyper68 wrote. So RAM access time should not be...
by rh74
Fri May 21, 2021 4:39 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Guys it's me again... Is there a minimum and safe number of RAM ICs to start testing? I mean, I know at least a couple of ICs must be inserted to allow ROM find space to load, but the IC numeration is puzzling me (e.g. IC13 is not numbered and it falls between IC18 and IC20). Is the IC20 the first b...
by rh74
Fri May 21, 2021 1:35 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Sorry Chema just realized you are talking about RAS/CAS and address/data buses. Using a RAM IC datasheet should give me the right wave to observe. Definitively a job for the weekend. I hope it will rain... :D
by rh74
Fri May 21, 2021 1:33 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

HI there, so I tested the Oric with i ss ROM. As soon as I power the mainboard I've got no "busy" signal. After a reset button push the tone is present. No RAM inserted. So at this point I guess I have a problem during the ROM bootstrap and definitively with RAM communication. I can't explain myself...
by rh74
Thu May 20, 2021 5:43 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

It seems an hard case... But not yet a desperate one. :D
by rh74
Thu May 20, 2021 5:42 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

The main suspect remains RAM chips :( and broken tracks. I know... :( One easy thing: check/replace the capacitor C21. You can short quickly its pins to "emulate" reset. Already changed. The previous one was already changed, but once I removed and measured it, it showed a smaller capacitance than t...
by rh74
Thu May 20, 2021 2:10 pm
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

Well known apart (IC8, IC20 and IC21), are there other crucial ICs I should check? As you can see in photos just the 8, 20, 21 and 24 are socketed. I was going to remove the remaining ones, but if I can start from the culprit one it would be great.
by rh74
Thu May 20, 2021 11:28 am
Forum: Technical questions
Topic: A problematic Oric 1
Replies: 37
Views: 2187

Re: A problematic Oric 1

For a working board the readings should be roughly ~250 Ohms. I gave it a really super quick try yesterday but not over the pins you are suggesting (took a +5v and a pin 14 of a RAM IC). It said 170 Ohm... This evening I'll try taking measure on ROM IC. Is there a reason TR1 was removed? Yes there ...