Battery pack inside 520 ST?

[rcgldr]

I have an old 520 ST, and inside there is a battery holder for 2 AA sized batteries that hooks up to what looks like a 9 volt connector with wires that lead to a circuit board on the bottom of the keyboard. I used a pair of NIMH batteries since I don't know if there is any charging done to the batteries when the ST is on. If not, I could switch to alkaline batteries which have slightly higher voltage.

 

I assume the battery pack is used to keep the clock going when the ST is turned off, but it seems I have to leave the power brick on. I'll need to do more testing to see if this is true.

 

[ParanoidLittleMan]

Yeah, it is possible to make part of IKBD chip - clock to work from battery power. I made it back in time, around 1992, if remember correct. Voltage was about 3.6 V, and it went on specific pin. When ST was on, batteries were charged.  I can dig out exact connection, circuit.

It could work max couple days without turning on ST power - IKBD clock consumes much more current than special RTC chips.

 

[rcgldr]

17 minutes ago, ParanoidLittleMan said:

When ST was on, batteries were charged.

In that case, I'll stick with the NIMH batteries. They're Duracell Duralock NIMH, 2400 mah. I'm not aware of a rechargeable battery with 1.8 volts that was available back in 1986 or 1987 when I got the 520 ST (developer kit, upgraded to 1MB ram, had the battery pack inside. 

[ParanoidLittleMan]

I think that it was 3x 1.2 V. Nickel-Cadmium ?

[rcgldr]

7 hours ago, ParanoidLittleMan said:

I think that it was 3x 1.2 V. Nickel-Cadmium ?

Probably. I checked the voltage to an empty battery holder with power on and it was 4.2 volts. The old battery pack was broken, so I replaced it with a 3 x  AA battery holder using Futaba radio control type connectors, which are easy to plug and unplug. I charged the pack to 4.15 volts so that it wouldn't be excessive voltage. 

 

The circuit board with the 6301 chip that plugs into the 40 pin socket on the bottom of the keyboard is labeled "time saver", and already had the batter pack wires on it. It came with the "developer" version of the Atari 520 ST (which also has 1MB ram upgrade). I'll have to leave it off for a while to verify if it works.

Edited March 17, 2020 by rcgldr

[rcgldr]

Looks like the 3 x AA nimh battery pack is working. (I used a 4 cell back with one of the cells short circuited to make it a 3 cell pack.) Here is an image of the circuit board, which plugs into the 40 pin socket on the bottom of the keyboard, and in turn has it's own 40 pin socket for the 6301. This board was included on my 1986 520 ST.

 

 

Edited March 17, 2020 by rcgldr

[Cyprian]

never seen that before.

what is between those boards? just 6301 socket?

[rcgldr]

2 hours ago, Cyprian_K said:

what is between those boards? just 6301 socket?

Yes, just the socket. There are no components on the bottom of that board (just the pins to plug into the 6301 socket). The board replaces the 6301, then the 6301 is plugged into the board. The black and red wires go to the rechargeable battery pack. I did a web search but couldn't find it. This was on a 1986 Atari 520 ST as part of a developer kit. I don't if the "time-saver" board was made by Atari or by a third party. I did a web search for "atari st" battery clock, and found a description of the components that could be used, but no luck in finding the board.

[ParanoidLittleMan]

Here is schematic of circuit I made around 1991 :  http://atari.8bitchip.info/ikbdbatt.html

 

 

[rcgldr]

Then again, I'm wondering if that 6301 chip would still be running today if a battery pack had been used to keep it running for what is about 35 years now. It's easy to disconnect now with the Futaba plug (the original one used a 9 volt battery type connector, not as convenient). 

 

Edited March 20, 2020 by rcgldr

[Zogging Hell]

On 3/17/2020 at 2:06 PM, rcgldr said:

I did a web search for "atari st" battery clock, and found a description of the components that could be used, but no luck in finding the board.

If I remember right, one of the 'serious' Atari mags did a round up of clock battery options for the ST that included a number of the keyboard clock battery units (ST Review perhaps), a trawl of some magazine archives might find your model. I have one and for a short while it was fitted, unfortunately it ate battery power at an alarming rate, and the unit would run out of juice after a few days if the ST wasn't used, which kind of made it pretty useless unless your ST was on 24/7. I was also fearful of the inevitible battery leak scenario and the ST I did use it in also had a TOS and memory upgrades and I couldn't find a way to make it fit with those in there as well. It's been in my ST parts bin since then.

[rcgldr]

1 hour ago, Zogging Hell said:

ate battery power at an alarming rate, and the unit would run out of juice after a few days if the ST wasn't used, which kind of made it pretty useless unless your ST was on 24/7. I was also fearful of the inevitable battery leak scenario and the ST I did use it in also had a TOS and memory upgrades and I couldn't find a way to make it fit with those in there as well. It's been in my ST parts bin since then.

On my 520 ST, there's an empty space on the main board between the monitor and midi connectors. I attached an image that shows a white 2 x AA pack holder (it's empty) there with plenty of space left over (3 size A cells could easily fit there). This is what the board originally looked like. Maybe something else went there on later boards.  Recently I switched to a 3 x AA pack once I measured 4.2 volts output from the time saver circuit board. (I don't really use it though, see below).

 

In the 1980's AA nicd had about 600 mah, up to 1000 mah later on. Size A nicd would have been 850 mah, now 1400 mah. Modern nimh AA are 2400+ mah. A prior post mentioned a current draw of 1.3 ma, with 3 x AA at 600 mah, that should be enough for 2 weeks on a full charge. The issue is time on versus time off. If the ST was on 2 hours a day on average, it would need to charge the pack at around 20 ma (taking losses into account), just to break even, and I don't know if the board outputs that much current. A pair of packs could be used, charging one of the packs offline, then swapping packs while the ST is on. 

 

I'm more concerned about the lifespan of a 6301 running 24/7 (my ST is 35 years old), so most of the time, I don't have the pack plugged in. I've occasionally used it, most recently with the nimh batteries, just to confirm it works. Nimh batteries self-discharge even with no load, and I don't know what percentage of time the ST would have to be on for a break even situation. A single cell li-po battery has a working voltage range of 3.85 (low charge) to 4.20 volts (full charge), which should be enough, and no self-discharge, but I'd be concerned about potential failure (heat) with a li-poll battery. 

 

 

 

Edited March 20, 2020 by rcgldr

[ParanoidLittleMan]

Allright, time for some 'anti-Atari' talk, again ?

I have Mega ST, Mega STE, had 520 ST (pardon, still have it as component source) with here discussed IKBD RTC solution ... When - 20-29 years ago.  I just removed all batteries. extra circuits around 2000-2004. Why ? It was no sense to do programming, serious work on those machines, in low resolution, while could do all it much more comfortable on PC, with emulator with supergood debugger. In high res. , lot of colors, monitor at 70 or more Hz (well 71 Hz works on STs, but only B/W).

 

I know, some people considering this way as some kind of blasphemy - to develop Atari ST SW on some other HW. But that existed in early 80-es - Psion used some VAX expensive computers to develop SW for Sinclair Spectrum. And I could do it practically for free - PC was there, and faster than those workstations. Debugger made all it much much faster.

 

My point is that really don't see all this excitement about having RTC solution in some rare, early ST. Especially when all it was done by multiple people at home, in garage.

Will my 6301 die because it's age ? It already happened (without batteries attached), and I replaced it in 5 minutes.  Last thing what I care is will it lose date.

[rcgldr]

5 minutes ago, ParanoidLittleMan said:

don't see all this excitement about having RTC solution in some rare, early ST.  ... serious work ...

Will my 6301 die because it's age ? It already happened (without batteries attached), and I replaced it in 5 minutes.  Last thing what I care is will it lose date.

About a year or so ago, I took my Atari stuff out of storage to see what worked. On the 520 ST, I noticed the empty battery holder, and it wasn't until after I started this thread that I realized it was for the clock (a clue was the board was named "time-saver"). I contacted someone that sold Atari stuff back in the 1980's but he didn't remember that board (and he doesn't have his ST anymore). I'm also using a Sony KV 1311CR tv as a monitor (it can handle 480p), with some special cable made for it.

 

For me it's a novelty system now, and I was surprised it still works (it's 35 years old). I made some utilities for the ST and did some general programming on it until around 1990, when I bought my first PC (486 based). As for serious work with the 68000 family, from 1980 to 1987, I worked at a company that converted from an AMD 2901 based processor to the 68000 family for the multi-tasking, multi-console based systems they sold. The company was a Motorola development site, so they got early releases of the 68020, 68030 (just before I changed jobs) and later 68040 (after I had left the company).