VOGONS


First post, by Baoran

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I have a socket 7 baby AT motherboard that needs a new battery before it could be used. I was considering replacing the dallas battery with a socket and a DS12C887+ from digikey. Does anyone has any experience of how hard removing the battery from a multi layer PCB will be without damaging the motherboard?

Looking at the side of the PCB I can count it having 5 or 6 layers. Am I going to need some kind of special equipment for doing it and what kind of temperatures I should use?
I have replaced caps before but they have been older motherboards and I dont think they have been multi layer PCBs.

Reply 2 of 31, by Baoran

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maxtherabbit wrote on 2022-09-18, 02:26:

I was looking for more specific information related to my case though. Things like how much harder multi layer PCB makes it and how it is related to wattage needed when it comes to soldering iron or if hot air still would work with 5 or 6 layer pcb. Basically if I also need to order new tools in addition to just ordering new battery and socket for it. I currently have 48W soldering iron station and hot air desolderer that goes up to 480C air temperature.

Reply 3 of 31, by Sphere478

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Multi layer doesn’t really matter.

They can be very hard to get out without the right equipment/experience.

Sphere's PCB projects.
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Sphere’s socket 5/7 cpu collection.
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SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod
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Tyan S1564S to S1564D single to dual processor conversion (also s1563 and s1562)

Reply 4 of 31, by maxtherabbit

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Baoran wrote on 2022-09-18, 03:11:
maxtherabbit wrote on 2022-09-18, 02:26:

I was looking for more specific information related to my case though. Things like how much harder multi layer PCB makes it and how it is related to wattage needed when it comes to soldering iron or if hot air still would work with 5 or 6 layer pcb. Basically if I also need to order new tools in addition to just ordering new battery and socket for it. I currently have 48W soldering iron station and hot air desolderer that goes up to 480C air temperature.

if you try to remove a DIP-28 without a ZD-915 or better vac desoldering pump, you are going to regret it

Reply 5 of 31, by Baoran

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Sphere478 wrote on 2022-09-18, 03:17:

Multi layer doesn’t really matter.

They can be very hard to get out without the right equipment/experience.

Did I understand this correctly that it is the dallas battery itself that makes it harder to be remove than removing caps and motherboard being multi layer does not matter that much?

Reply 6 of 31, by TheMobRules

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Removing a DIP-28 from a board with more than one layer is difficult because of the through-hole vias, which means that during assembly the solder flows all the way from the pad on the bottom to the one on the top. In order to desolder each leg properly, you must make sure that you've removed all the solder from both sides of the board, which is easier said than done. Otherwise, you will likely rip the vias when trying to remove the component. The battery has nothing to do with it, but the Dallas RTCs make it more difficult because you can't see how much solder there is on the top side of the legs unlike a regular DIP chip.

Trying to do it with a manual pump is possible, but you need lots of experience, and it's difficult even in that case as you must make sure that ALL of the solder is molten before you use the pump. And if you're thinking about using solder wick: just don't.

As suggested above, with a vaccum desoldering pump you can set an appropriate temperature and wiggle each leg until it moves freely, and then you press the button to suck the solder out. But even this technique needs some experience to get the right "feel".

Reply 8 of 31, by Baoran

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I have been thinking of buying Hakko fr-301. It is sold locally here but it is a bit expensive. Maybe this is a good time to consider that. Might allow me to do more repairing than just recapping boards.

Reply 9 of 31, by majestyk

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With a Hakko fr-301 or a ZD-915 desoldering a DALLAS RTC will be easy peasy and done in no time. Temperature should not exceed 350°C.
In fact there are only 3 - 4 pins of the DIL28 pins that refuse to be desoldered easily. Care has to be taken of tiny traces around the pins so never press the tip against the PCB.

Reply 10 of 31, by Baoran

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majestyk wrote on 2022-09-18, 16:03:

With a Hakko fr-301 or a ZD-915 desoldering a DALLAS RTC will be easy peasy and done in no time. Temperature should not exceed 350°C.
In fact there are only 3 - 4 pins of the DIL28 pins that refuse to be desoldered easily. Care has to be taken of tiny traces around the pins so never press the tip against the PCB.

By the way. I thought dallas batteries only have 24 and not 28?
Like in digikey they have been marked as:
DS12C887+
Analog Devices Inc./Maxim Integrated
IC RTC CLK/CALENDAR PAR 24-EDIP

Reply 11 of 31, by majestyk

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DIL24! - Haven´t counted the pins for ages, I just grab a new socket out of my drawer and solder it in the place of the removed RTC 😉
It´s also true these are not just batteries, but complete standalone realtime clock circuits (with a battery inside).

Reply 12 of 31, by Baoran

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majestyk wrote on 2022-09-18, 18:15:

DIL24! - Haven´t counted the pins for ages, I just grab a new socket out of my drawer and solder it in the place of the removed RTC 😉
It´s also true these are not just batteries, but complete standalone realtime clock circuits (with a battery inside).

Yeah. The socket 7 motherboard does not keep any bios settings with bad battery. Even if I go to bios and save settings it loads bios defaults when it boots after I save even if I dont turn off the power.

Reply 13 of 31, by Sphere478

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Aren’t bios settings actually stored on the Dallas rtc?

Btw, this is a good time to mention that these exist:

https://monotech.fwscart.com/DS12887_RTC_Drop … 4_19810725.aspx

Email them and tell them your exact dallas pn and they will make you one that takes a standard sized coin cell.

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Sphere's PCB projects.
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Sphere’s socket 5/7 cpu collection.
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SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod
-
Tyan S1564S to S1564D single to dual processor conversion (also s1563 and s1562)

Reply 14 of 31, by Baoran

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Sphere478 wrote on 2022-09-18, 18:45:
Aren’t bios settings actually stored on the Dallas rtc? […]
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Aren’t bios settings actually stored on the Dallas rtc?

Btw, this is a good time to mention that these exist:

https://monotech.fwscart.com/DS12887_RTC_Drop … 4_19810725.aspx

Email them and tell them your exact dallas pn and they will make you one that takes a standard sized coin cell.

It keeps date and time but gives some kind of cmos mismatch error and says that bios defaults have been loaded.

Unfortunately on my motherboard the isa slot would probably block me from using that.

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Reply 15 of 31, by TrashPanda

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Baoran wrote on 2022-09-18, 19:03:
It keeps date and time but gives some kind of cmos mismatch error and says that bios defaults have been loaded. […]
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Sphere478 wrote on 2022-09-18, 18:45:
Aren’t bios settings actually stored on the Dallas rtc? […]
Show full quote

Aren’t bios settings actually stored on the Dallas rtc?

Btw, this is a good time to mention that these exist:

https://monotech.fwscart.com/DS12887_RTC_Drop … 4_19810725.aspx

Email them and tell them your exact dallas pn and they will make you one that takes a standard sized coin cell.

It keeps date and time but gives some kind of cmos mismatch error and says that bios defaults have been loaded.

Unfortunately on my motherboard the isa slot would probably block me from using that.

socket7-mb.jpg

You might have to get creative with a dremel on that ISA slot, you should be able to shave enough plastic off the side to fit a RTC replacement and not affect the slot.

That’s said the replacement should fit just fine in the space there.

Oh noes, the cap let the shmooo out 😁

Reply 16 of 31, by Sphere478

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Solder the socket in at an angle? For isa slot clearance.

Tangent:
ugh, another socket 5 motherboard pretending to be a socket 7.

This board looks to be a single plane voltage board.

Without a interposer, your top upgrades are overdrive mmx 200
Pentium 200 non mmx
K6 233
Cyrix 166?
Winchip 266?

With a interposer and a bios update you can probably do k6-3+ 400-500mhz

Sphere's PCB projects.
-
Sphere’s socket 5/7 cpu collection.
-
SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod
-
Tyan S1564S to S1564D single to dual processor conversion (also s1563 and s1562)

Reply 18 of 31, by Baoran

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Sphere478 wrote on 2022-09-18, 19:34:
Solder the socket in at an angle? For isa slot clearance. […]
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Solder the socket in at an angle? For isa slot clearance.

Tangent:
ugh, another socket 5 motherboard pretending to be a socket 7.

This board looks to be a single plane voltage board.

Without a interposer, your top upgrades are overdrive mmx 200
Pentium 200 non mmx
K6 233
Cyrix 166?
Winchip 266?

With a interposer and a bios update you can probably do k6-3+ 400-500mhz

That is fine for me. I dont think I have anything faster than 100Mhz pentium cpu to install on it anyway right now.

I have had this cache module for quite long time that I was planning to try with this motherboard if I get it fully working and if I find a case where the hard drive cage does not block the module sticking up from the motherboard though.
Not sure if it will make it any faster but I can try benchmarking it with and without it to see.

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Reply 19 of 31, by Sphere478

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Be very sure that that module works with your mobo before installing. Some of them are destructively incompatible.

Sphere's PCB projects.
-
Sphere’s socket 5/7 cpu collection.
-
SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod
-
Tyan S1564S to S1564D single to dual processor conversion (also s1563 and s1562)