Chip Dallas 12887, Prehistoric motherboard, No startup - Page 1
Forum section: electronics / repair

author: GGMM
author_rank: Frequent Contributor
timestamp: August 01, 2024, 02:56:57 pm
content: Hello,I got an Atlas 757 card. The setup was lost, once redone the card started normally.After 2 days, again no more config, new setup. restart OK.I think the battery is dead (more than 20 years). nb: the dallas chip is weldedDespite everything, the map was on the edge, but the situation seems to have gotten worse.Start after several stop/ start, then once in 10, etc., etc and now there nothing more.So I ordered a PC analyzer card but nothing happens. Only dashes.Is it possible that the battery is completely discharged and prevents boot, or other? (corrupted flash?).I found of course some articles to graft a battery, but also one interesting with the connector clear to use.https://arduinoinfo.mywikis.net/wiki/DS12887A-DALLAS-RTC-DEADAnyway, what’s going on for you?your opinioncdt

author: coromonadalix
author_rank: Super Contributor
timestamp: August 01, 2024, 03:03:12 pm
content: once again a new thread about your scope issue reportedhttps://www.eevblog.com/forum/repair/the-early-repair-of-agilent-54810a/msg5585083/#msg5585083https://www.eevblog.com/forum/repair/keyboard-on-oscilloscope-agilent-54810a/msg5549317/#msg5549317https://www.eevblog.com/forum/repair/hp-54810a/msg5539833/#msg5539833https://www.eevblog.com/forum/repair/hpagilent-infinium-548xx-scope-power-supply-schematic-!/msg5508766/#msg5508766is this the way you use to get answers here ?

author: squadchannel
author_rank: Frequent Contributor
timestamp: August 01, 2024, 03:21:11 pm
content: It is a different motherboard, but in my experience it will not boot without the DS12887.I used DS12885 in a battery-less TQFP package as an alternative to DS12887.The DS12887 may be damaged.The BIOSROM also needs to be checked.MOD:Thinking about it, the way you dremel the sides of the DS12887 to install the battery, does not cut the internal battery, does it?If that is the case, you are charging a non-rechargeable battery, which is dangerous i think.

author: GGMM
author_rank: Frequent Contributor
timestamp: August 01, 2024, 03:55:22 pm
content: Coromonadelix,I agree with you that this is in a 54810A issue.It’s full of anomalies.However, this concerns a specific point on the motherboard.This anomaly can also occur on others old motherboards.So I think a specific topic will be more interesting for research.Will you put 54810 or Dallas 12887 in search word if you run into the same problem? the answer is Dallas 12887!!I think the users of this forum we’ll agree.Cdt

author: coromonadalix
author_rank: Super Contributor
timestamp: August 01, 2024, 04:21:37 pm
content: the problem is :you dissect parts of your scope trying to get answers on each part,this is annoying to say the least, and make things difficult IF some members try to follow your threads, you're not helping the others AND not helping YOUyou have no excuses for this kind of behaviour

author: GGMM
author_rank: Frequent Contributor
timestamp: August 07, 2024, 04:12:09 pm
content: Hello,If someone in the EEC (Europe) has this type of adapter, that may interest me. I spent several hours searching, impossible to find even on auction sites or classified ads. This is necessarily for a prehistoric motherboard.with 26 pins flat cable.https://www.pccables.com/Products/07127.htmlIf there is only the sound part, this also goes (no need for the joystick)Otherwise, I only see a solution, to make onecdt

author: GGMM
author_rank: Frequent Contributor
timestamp: August 17, 2024, 04:00:28 pm
content: Hello,Back to this Atlas 757 motherboard and its Dallas circuit.I would like to have a sure confirmation on this famous Dallas 12887A chip.1) "If you have the battery completely discharged does this prevent the motherboard from starting systematically"?I put a PC Analyzer card and there is no variation on the digits (Power ok). Nothing to the screen necessarily.I had 2 starts on at least 50 resets. So very random....Then the Dallas circuit was replaced by a Chinese equivalent.Good much literature on it...(False marking, half-worn pile, etc.)I have the same symptoms. It seems that you can guess the date of manufacture with the marking. Method?2em) Is it possible to measure the battery voltage?What is important to me is whether someone can confirm this point #1 through their experienceTest without the Dallas chip, it's the same...Your opinion. Thank's

author: GGMM
author_rank: Frequent Contributor
timestamp: August 18, 2024, 02:32:57 pm
content: hello,Do you have experience on the Dallas 12887A+?It would seem that them you receive a new, the internal oscillator is disabled to save battery and that you need to make a manipulation to reactivate it.see:https://www.reddit.com/r/vintagecomputing/comments/hkddzu/dallas_chip_issue/?rdt=34002Page 18 it's wrote:When the DS12887, DS12887A, DS12C887, andDS12C887A are shipped from the factory, the internaloscillator is turned off. This prevents the lithium energycell from being used until the device is installed in asystem.A pattern of 010 in bits 4 to 6 of Register A turns theoscillator on and enables the countdown chain. A pattern of 11x (DV2 = 1, DV1 = 1, DV0 = X) turns the oscillator on, but holds the countdown chain of the oscillator in reset. All other combinations of bits 4 to 6 keep theoscillator off.So the block swap dallas would not be enough?your opinioncdt

author: GGMM
author_rank: Frequent Contributor
timestamp: August 18, 2024, 04:18:42 pm
content: I have filed at the Dallas chip’s (original of the motherboard) the pins 16 and 20 to see connections to measure battery voltage.I have 2.6vIt’s a 03xxxx chip, so I guess it’s from 2003.The battery may be too low?Can anyone give the approximative value to have normally.The 2 received from China are 97xxxx, so 1997?Batteries already dead, which would explain that the motherboard does not start too?cdt