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Robotrontechnik-Forum » Technische Diskussionen » Robotron 1715 first power-on » Themenansicht

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000
01.11.2020, 21:57 Uhr
milan



 Hi,
I'm from former Czechoslovakia (now Slovakia part) and Robotron 1715 was first computer I ever saw and as a kid I played on it Wurmi many many times at that time. Now, after 32 years I was lucky to purchase one survivor with keyboard and without the monitor. According to http://www.sax.de/~zander/index2h.html I have variante mit KR565RU6 memory (+5V only) with A302 floppy disc controller (TEAC FDDs). I disassembled it and visually inspected, nothing strange there no bulging or leaking capacitors caught my attention.

But I wonder, how to test computer before I first turn it on, probably especially power supply. Should I just measure -5+5-12+12V on connection plate (connector) from power supply to the motherboard without the load, in other words when motherboard is disconnected? As you see I'm not too skilled electrotechnician to answer this, but I think it is not good idea to test power supply without its usual load.

Also is there anything on Robotron 1715, I should be aware of, something which is usual cause of problems after so many years...

P.S. Sorry to use English but I can't speak German and I can find nearly no info about Robotron's in my homeland. Thanks...
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001
01.11.2020, 22:27 Uhr
schlaub_01



 Hello milan,
the idea to test the power supply separately at first is perfect, but you need a small load resistance for the 5V and 12V supply rails. Without the load on the 5V rail, the -12V and -5V will not appear. But at first I would check the fuses and fuse holders. Inside of the power supply you can find an additional 4A fuse, which is very often corroded. If you have checked these things, we can proceed.

Best regards,
Sven.
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002
01.11.2020, 23:06 Uhr
Rüdiger
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If you have a K7222 monitor it makes sense to remove the secondary coil of the flyback transformer first and to bake it some hours at low temperatures. Otherwise this component could die quickly.

If you have a Reikotronic screen it it not necessary to do this.
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003
01.11.2020, 23:09 Uhr
milan



 Yes, there is a patina on fuse rails and on fuse caps itself - kind of blue corrosion, but overall checking conductivity (by beeping with multimeter) through fuse rails worked OK. So I consider fuse to be fine. I just don't know resistor values (ohms) we should use as a load. (I have two 10W resistors one (3.3ohm and second is showing me 32ohm hmmm). I disconnected FDDs and FDC from motherboardboard. But how should I unplug power supply cable from motherboard. Should I just pull up? I tried but it seems to be stuck on the motherboard. Maybe I should use more force, but I hesitate to do so .
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004
01.11.2020, 23:13 Uhr
milan



 Rüdiger, no I do not have any monitor, I would like to test booting over V.24 and also later to create connection to the composite monitor or TV over SCART, like is depicted here: http://xepb.org/robotron/gifs/1715_tft.pdf (scheme taken from: http://xepb.org/robotron/docs.html).
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005
01.11.2020, 23:24 Uhr
milan



 ... also I forgot to mention, bot F1 and F2 fuses and their holders on the back of PSU are OK.
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006
01.11.2020, 23:30 Uhr
Rüdiger
Administrator
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I would plug a current limitation into the net cable: a 500W heater or a similar device.
Then I would switch on.
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007
01.11.2020, 23:30 Uhr
milan



 ... and fan is of the following brand: "Style Electronic co., ltd". Made in Japan. Model UP12D22-T of 15/16Watt. Interestingly Style brand is still in the bussiness today with those fans too.
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008
01.11.2020, 23:32 Uhr
schlaub_01



 Okay, your 10W resistors are okay for testing the power supply for a short moment. You can use the 3,3 Ohm for the 5V and the 32 Ohm for the 12V rail. The 12v rail switches on after few seconds after the 5V rail - this is normal. Yes, the connector is very hard to remove, but if you press down the pcb next to the connector by pulling the connector should work. If you wiggle a little bit the connector, can also help after the long storage time.

Best regards,
Sven.
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009
02.11.2020, 00:37 Uhr
milan



 OK, I have been successful pulling PSU onnector out, thanks for the guidance, pushing mobo down did the trick plus a bit of wiggling of course.
Now I placed first 3.3 Ohm 10W resistor between 0V and 5P and second 32 Ohm 10W resistor between 0V and 12P on the PSU's plug end (FDD and FDC are disconected). Now my understanding is that I should measure voltage on the first resistor and then on the second, if it gives me +5V and +12V respectively.
Can I measure without removing aforementioned resistors also voltage between 0V and 5N and then 0V and 12N to get -5V and -12V?

Probably I should later use oscilloscope (instead of multimeter) to measure how stable voltage level is (ripple)?

Also Rüdiger idea seems to me wise, I think it should limit the intake current in series to the PSU (so the current is the same on both devices PSU and for example 100W Edison's bulb), probably mainly in case of electric short in PSU, but I don't know why to use 500W, should not be 100W bulb enough? I found that PSU is 120W according this http://www.sax.de/~zander/pc1715/doku/pc_manu.pdf on Page 35: Leistungsaufnahme: 120 W
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010
02.11.2020, 00:48 Uhr
milan



 ... and it's late hour, so just rephrase myself to be clear, I did unplug not only FDD with FDC but also whole motherboard, of course .
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011
02.11.2020, 09:10 Uhr
Rüdiger
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Zitat:
milan schrieb
but I don't know why to use 500W, should not be 100W bulb enough?



If you run the power supply with a load (board or resistors), 100W is not enough, because
you want to get nearly 230V behind the current limitation, not 115V.

For the power supply without load 100W maybe enough.
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