Tecmar Jr2ndMate Clock circuit: address latch IC?

Hardware questions and modifications

Tecmar Jr2ndMate Clock circuit: address latch IC?

Postby Firebottle » Thu Mar 24, 2016 8:24 am

I have a Tecmar Jr2ndMate card that never had it's clock circuitry installed.

I got this as part of a large lot of old IBM stuff a while back. Today I finally dug out the original manual and addendum...

In the Addendum it states: "Your version of the Tecmar Jr2ndMATE does not include the clock/calendar"

It then tells me to disregard pages 20-21, 22, 27-33 of the user manual.

However, in Appendix B of the user manual it states:

"the real time clock is made up of an address latch, the clock itself (MM58167) and the battery for standby power."

As it turns out, when opened up, the *sockets* for the clock circuit are installed but empty, including the coin battery holder.

There is an empty socket on the board marked U14 (largest chip on the board, probably the MM58167),

directly above it another empty socket marked U13 (address latch?)

and to the right... in what I'm thinking is the parallel port circuitry area, an empty socket marked "RN2" (resistor network?)

Also, on page 22 of the manual, it describes jumper 2 which is used to select the interrupt line for the time of day chip.

Strangely enough those jumper pins are present with a jumper installed (!) in the low position (IRQ1).

Anyone have a Jr2ndMate with a clock that could tell me what the IC in U13 is? And maybe even what model # of coin battery is being used?

And also is RN2 present?

Thanks in advance for any info... :D
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Re: Tecmar Jr2ndMate Clock circuit: address latch IC?

Postby Brutman » Thu Mar 24, 2016 6:59 pm

U14 = MM58167AN
U13 = DM74LS174N
RN2 is empty on my board
Coin cell is a BR2325 (3 volts)

Pictures can be found at:

Entire board: https://goo.gl/photos/mVrYHpsdfc2m4pbo9
Closeup of the clock chip: https://goo.gl/photos/pvkP2PbKeSRMARM7A
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Re: Tecmar Jr2ndMate Clock circuit: address latch IC?

Postby Firebottle » Fri Mar 25, 2016 8:04 am

Great! Thank you! :D
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Re: Tecmar Jr2ndMate Clock circuit: address latch IC?

Postby Firebottle » Mon May 09, 2016 12:26 pm

Finally got the necessary parts, and using Tecmar's software, the time circuit works great. DOS 5 even recognizes that the chip is set to the year 2016.
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Re: Tecmar Jr2ndMate Clock circuit: address latch IC?

Postby Meknapp » Mon Jul 04, 2016 9:44 am

That's really cool!!
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