Search found 173 matches

by Sniffer
Wed Apr 17, 2019 8:07 pm
Forum: 8-bit acorn hardware
Topic: Colured text all modes (Yellow)
Replies: 4
Views: 421

Colured text all modes (Yellow)

Is there a prime suspect for an Issue 3 board that produces yellow text, instead of white?
by Sniffer
Sat Apr 13, 2019 2:26 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

Success.

I socketed IC55 and replacing the 4564 did the trick. Cheers guys.
by Sniffer
Sat Apr 13, 2019 9:15 am
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

I agree with Kazzie that this is most probably caused by a faulty IC55. Sometimes the first bit (bit 0) is high when it should be low and vice versa. The way it behaves it could well work if you piggyback a working memory chip on it (but you can never really tell). Piggy backing didn't have any eff...
by Sniffer
Fri Apr 12, 2019 11:05 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

Actually, just a photo of the first (mode 7) screen may be sufficient. Does the sound and the caps lock/shift lock toggling work with Tricky’s rom installed?
Sorry, missed this post. Yes, the sound works at the start and the caps lock/shift lock toggle.
by Sniffer
Fri Apr 12, 2019 11:01 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

Here's a gif of the start of the test rom but I doubt it's of any help. It is too big to upload here so I've made it available at;

https://www.ictprovision.com:80/pics/TEST2.gif
by Sniffer
Fri Apr 12, 2019 10:28 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

Ok. On power on with long beeeeeeeep; Pon.jpg After CTRL-BREAK without long beeeeep; ctrl-break.jpg Typing MODE 6; goto-mode6.jpg In MODE6; mode6.jpg and MODE0; mode0.jpg After a memory check, which I assume from previous info means nothing; memchk.jpg Test ROM pic to follow. Hope this helps.
by Sniffer
Fri Apr 12, 2019 9:58 pm
Forum: wanted
Topic: Acorn Electron board in 100% working order
Replies: 1
Views: 373

Re: Acorn Electron board in 100% working order

I have a Elk that I _think_ was just waiting for me to fix the internal power pcb. Can't be sure, it's been a while (for while read years), so if you still want one, I can fix the pcb and test the board. It won't be in the next day or two but I will get back to you as soon as I can. Ping me if I don...
by Sniffer
Fri Apr 12, 2019 9:42 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

Re: BBC B+ fault

Thank you for the comments Kazzie. Firstly (with all the B+-related posts recently I've got them all mixed up in my head) are we talking about a 64k or a 128k model? 64K If you see screen corruption (possibly of a different nature) in other MODEs, then that would suggest that it isn't IC54. Narrowin...
by Sniffer
Fri Apr 12, 2019 8:49 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ fault
Replies: 12
Views: 703

BBC B+ fault

Maybe I should start a new thread on this, if so just say. The reason I asked initially about the B+ memory mapping was that having just sorted my B, due the help received here, I powered up a B+ and got a long beeeeep. Another machine out of the loft. Pressing CTRL BREAK gets rid of the long beeeee...
by Sniffer
Thu Apr 11, 2019 9:54 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

No. Pin 3 on IC49 which is RD5 is only connected to Din / Dout of IC65. However, I think I understand the point you were trying to make. IC49 pins 2 thru 9 do not translate directly to RD0 thru RD7 as is stated in that other topic. Pin assignment for IC49 is as you have stated. Ok, cool. The owner ...
by Sniffer
Thu Apr 11, 2019 9:25 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

IC49 is not a RAM chip. It's a 74LS245 tri-state octal bus transceiver. This transceiver buffers the 8 data lines, and each one of these data lines connects to the data in / out pins of each dram chip. Well yes, I know it's not a ram chip, what is confusing me is it's links to the ram chips. From t...
by Sniffer
Thu Apr 11, 2019 8:36 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

Ok, getting confused now (easily done some might say), Kazzie stated D0= IC55 D1= IC56 D2= IC60 D3= IC61 D4= IC64 D5= IC65 D6= IC66 D7= IC66 and over in the pointed to thread of the B+ ram problem at https://stardot.org.uk/forums/viewtopic.php?t=15961 stated this; Voltmeter measurements on page 1 ga...
by Sniffer
Tue Apr 09, 2019 12:48 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

Thank you Kazzie for the detailed explanation. every RAM chip is used to provide the byte of memory at every address location So, each memory location, say &3000 for example, comprises of one bit from each dram chip? Therefore, any apparent fault at any location could be caused by any one or more of...
by Sniffer
Tue Apr 09, 2019 10:40 am
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

Gah, that's what I get for posting so early in the morning. For a B+, let's try: For a B+ 64k Code: Select all D0= IC55 D1= IC56 D2= IC60 D3= IC61 D4= IC64 D5= IC65 D6= IC66 D7= IC66 The early bird catches the worm :D So, for a mere mortal like myself, how does this equate to memory locations/addre...
by Sniffer
Tue Apr 09, 2019 10:32 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non booting BBC/B Issue 7 - Continuous beep

Well done :D
viewtopic.php?f=3&t=6383&p=61457 may help you with your noisy beeb...
Is that topic pertinent to Bs as well as the Master?
by Sniffer
Mon Apr 08, 2019 11:28 pm
Forum: 8-bit acorn hardware
Topic: BBC B+ 128K: Fault after warming up.
Replies: 84
Views: 4223

Re: BBC B+ 128K: Fault after warming up.

Good to see you were successful.

Does anybody know which ram ICs map to which addresses?
by Sniffer
Mon Apr 08, 2019 3:51 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non booting BBC/B Issue 7 - Continuous beep

Glad to hear that your Beeb's looking more and more healthy! Thank you. With regard to the memory test, memory chips can fail in all sorts of unusual ways, not all of which will be picked up by any particular type-in test. I guess you're right on that. As well as using the likes of Mode 0 to test t...
by Sniffer
Mon Apr 08, 2019 1:25 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

So, I still have some noise through the speaker. Very faint background noise on key press and a louder hissing noise in tandem with floppy drive usage. Anyway, I ran the memory tester (listing at https://stardot.org.uk/forums/viewtopic.php?f=3&t=14809 ) with and without the LS04 inverter and in both...
by Sniffer
Mon Apr 08, 2019 11:32 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

I replaced IC32 this morning and had a bit of weirdness then some success. Having replaced the ic, switching on left me in a worse position. I had the continuous beeeeeep and no display. Powered off and then back on, same situation! Did the same for a third time and hey presto, beep, beep and a 16K ...
by Sniffer
Mon Apr 08, 2019 8:18 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

About the tuneful keypresses: is the tone always the same for each key, and does it differ between keys? Are there groups of keys which give the same tone? I can't see any real pattern other than as well as making a sound of it's own, each key press further distorts the continuous tone that's ongoi...
by Sniffer
Sun Apr 07, 2019 11:05 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

Could you confirm for me how the Caps and Shift LEDs behave when you turn the machine on, and then after pressing break? Also, is there any difference if you press Control+break instead of break? Sure. On initial power on, no key press response, 'CAPS LOCK', 'SHIFT LOCK' on. On pressing break, no c...
by Sniffer
Sun Apr 07, 2019 9:39 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

You said pin 8 is now high: that's surprising, as pin 8 should be ground! Did you make an error, perhaps? (Are you sure of the other pin numbers?) Great info, thank you very much. I need to read over it a few times I think, but I just want to correct myself. You were obviously correct about pin 8 a...
by Sniffer
Sat Apr 06, 2019 2:32 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

Apologies for bombarding you with all this info but it helps me remember what I've done :) Anyway, with a good system, testing IC32 I get; 1->High, 2->High, 3->Low, 4->High, 5->High, 6->High, 7->High, 8->Low, 9->Low, 10->High, 11->Low, 12->High, 13->High, 14->Pulsing, 15->High, 16->High Which is mar...
by Sniffer
Sat Apr 06, 2019 1:50 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

A little more info. As mentioned, on startup, the keyboard is unresponsive until break is pressed. It was in this condition that the readings with the logic probe in my previous post were taken. If I press break and get a responsive keyboard, the readings change slightly. Here are the differences wi...
by Sniffer
Sat Apr 06, 2019 11:39 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

The sound chip (IC18, 76489) is connected to the ‘slow bus’ from the system VIA (IC3) and controlled by the /WE signal (pin 5 on IC18). This control signal also comes from IC3, but via IC32 (74LS259). Ok, got IC 33 back in, still the same situation. So, in an attempt to check sound, got my (cheapo)...
by Sniffer
Fri Apr 05, 2019 10:05 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

Yay! :D

Some hints and links to guides on using an oscilloscope are here and here ;-)

You can either use your logic probe or your ‘scope to trace signals.
Ok, thanks for the info. If tomorrow I get the bits I'm waiting for I'll start having a play with the probe.
by Sniffer
Fri Apr 05, 2019 7:32 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

By the way, what test gear do you have / have available/ can borrow or pinch?
Well I have a Fluke (179) and a logic probe which I can use confidently, I have a Siglent SDS 1052DL which I'm not so proficient with. In fact, I'm not proficient at all with it, but I would like to be :D
by Sniffer
Fri Apr 05, 2019 4:59 pm
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

Default start-up is in MODE 7, the teletext mode. So if there is one or more defective RAM chips, the resulting bit errors will result in the wrong character being displayed. If you know what should be shown (compare to a normal start-up screen), you can use the table of teletext characters in the ...
by Sniffer
Fri Apr 05, 2019 9:49 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

More info: So, with the inverter fitted I pressed BREAK, typed MODE 6 and typed in the simple memory test prog, as below. Typed characters appear correctly in mode 6. 5 MODE 0 10 ?&4000=0 20 A=?&4000 30 IF A=0 THEN GOTO 20 40 PRINT A This produced nothing but the cursor at the top of the screen. The...
by Sniffer
Fri Apr 05, 2019 9:22 am
Forum: 8-bit acorn hardware
Topic: Non booting BBC/B Issue 7 - Continuous beep
Replies: 60
Views: 2579

Re: Non bootong BBC/B Issue 7 - Continuous beep

With the inverter fitted the symptoms are similar to those with S25 south. Cannot type until break is pressed . Then th 32k message disappears and typing is possible, albeit with musical tones. The beeeeeeeep continues. Typing in the startup MODE (cant remember what mode that is) produces random cha...

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