Questions regarding Minimig build

[Viserion]

Got a chance to get a Minimig rev 1.1 MB, that I couldn't let pass.

I've spent some hours finding out what parts are needed, more on that later.

I have started asembling, and has come as far as the test phase under building order.

It basically is the power supply part of the MB, so you can test it before soldering on the expensive parts.

Was a bit nervous when powering it up for the first time, but the blue led was shining, and it didn't blow in my face.

I take that as a good sign

My multimeter is a Fluke 12, but I don't know much on how to use it.

I use it with a symbol on the display that looks like a 'V' with a '-' on top, and three dots under the '-' .

The 4 first ones are OK, as far as I can work out. I measure by holding the red wire behind the DC socket, and the black one the given pin. Again not sure witch is pin 7/4, but by counting on different ways, I do get a reading a ltlle above the correct 5V.

On IC 1,3 and 4 there is a different story. I got 1.x -2.X on IC1 that should be 3.2 - 3.4, and got high voltage, up to 5V on IC 3 and 4, that should be 1.2 - 1.26V and 2.4 to 2.6 respectively.

No idea if I measure wrong, so a little guide to the correct way would be appreciated.


Now to the second part of this post which is parts.

I used this as a guide to what I need.

I started with another list with parts from Digikey an Farnell.

Farnell I couldn't order from as they do not accept orders from private persons, but only companies.

I found an alternative in Reichelt where I got the parts I couldn't get at digikey.


The alternatives don't match exactly, so I need someone with more clue than me to decide if they are usable or not.

I only lists the alternatives, as the rest can be found in the first link.

Maybe Reichelt can supply everything, but I haven't checked.

They also charge EUR 28 as a minimum to Norway, so shipping costs are quite high.

Reichelt.de

Description list part no. ordered part no.


crystal 20MHz SER3438-ND 20,0000-HC49U-S

Crystal 4.433619MHz SE3406-ND 4,4336-HC49U-S

CONN VGA D-SUB HD 15 POS A35120-ND HD 15FW

CONN Multimedia push/pull FPS009-2305 CONNECTOR MMC 12

Digikey
sot23 diode – bav99sot23 diode – bav99 BAV99FSCT-ND sot 2 types ordered both

Led red 160-1196-1-ND LTST-C170KRKT
crystal 20MHz 535-9046-ND SER3438-ND
crystal 4.33.... 300-8473-ND SE3406-ND

As you probably noticed I ordered an alternative from both places regarding crystals. The ones from Digikey looked so different, that when I had to order from Reichelt anyway I ordered from them as well, since they looked closer to the one in the first list. So I will try those first.

Neither of them is 100% the same specs as on the list.

[prowler]

Moved from News to the support.Hardware forum where it is more appropriate.

[Viserion]

Sorry, have more than one window open in the browser at one time, and happened to post in the wrong one.

[robinsonb5]

Originally Posted by Viserion

I use it with a symbol on the display that looks like a 'V' with a '-' on top, and three dots under the '-' .

OK - that symbol means it's measuring DC voltage.

The 4 first ones are OK, as far as I can work out. I measure by holding the red wire behind the DC socket, and the black one the given pin. Again not sure witch is pin 7/4, but by counting on different ways, I do get a reading a ltlle above the correct 5V.

Are you sure you're seeing 5, and not -5? Normally you'd put the black probe on something that's at ground, and use the red probe to measure the voltage with respect to ground at the test point.

On IC 1,3 and 4 there is a different story. I got 1.x -2.X on IC1 that should be 3.2 - 3.4, and got high voltage, up to 5V on IC 3 and 4, that should be 1.2 - 1.26V and 2.4 to 2.6 respectively.

If you're holding the red probe on the +5v pin of the DC socket and putting the black probe on the test point, you will get readings of 5v minus the value you expect, so at the tab of regulator 1 you'd see roughly 1.8v instead of 3.2v, and so on.

Good luck with the build!

[Viserion]

You are correct, I see -5V, and not +5V.


It does say it should be +5V in the guide however, that's why I assumed I had reversed the order when putting black behind the power socket, and red on pin 7/4 on the different test points.

On IC1 I get the following values when using black behind the power socket.

Pin 1(closest to power socket): 0V (this is also ground I assume)
Pin2: -1.74
Pn3: -2.981
Big pin:-1.740


IC3:

Pin1(closes to power socket):0
pin2:-3.805
pin3:-5.05
Big pin:-3.804

IC4:

pin1(closes to power socket):0
pin2:-2.562
pin3:-5.05
Big pin:-2.563

It does not make sense to me, if it's not too much bother could you explain it briefly.

Thanks, regarding the good luck part. I need it.

Doesn't look like I can solder much today, but can hopefully do more tomorrow.

[Viserion]

Have a few other questions.

On list linked to at first post there is 30 311-2.20KCRCT-ND (digikey part no).

However in BOM list. There is 1 2.2K at R54, and 6 2K2 at R7,9,11,28,67 and 68.

As far as I can see these two are not the same.

Unfortunately the BOM list is very sparingly in description of each part.

Anyone knows what the difference of these parts are, as I most likely has soldered on the wrong part, before I discovered this, and need to remove it, and order the correct part.

[robinsonb5]

Firstly, I've never attempted a build anything like as complicated as the Minimig - so this is all general.

The voltages you read should be positive, not negative. Are the probes on your multimeter removable, and if so, have you maybe got them the wrong way round?

2.2K and 2K2 are just two ways of writing the same thing - I should imaging their being written differently and thus ending up separated in the BOM was just an oversight.

[Viserion]

There are removable probes.

There is 2 holes to connect the probes, one is marked red, and has a '+' sign, the other is black as the rest of the case, marked with 'COM'.

Red probe connected to '+', and other to 'COM'.

I have but on other components, so if it's safe, I can try measuring from another point.

On a side note there are also some pins marked with 'JTAG', 'MCU/FPGA' and '31KHz/15KHz'.

Does anyone what those are called in English, so I can search and order some.

[robinsonb5]

Originally Posted by Viserion

On a side note there are also some pins marked with 'JTAG', 'MCU/FPGA' and '31KHz/15KHz'.

Does anyone what those are called in English, so I can search and order some.

Those are "pin headers". The MCU/FPGA header selects whether the RS232 port outputs serial data from the "Amiga" or debugging information from the microcontroller. (Use a jumper cap to select by bridging a pair of pins.) Likewise, the 31KHz/15KHz header enables or disables the scandoubler.

[Viserion]

Thanks robinsonb5.

Often searching for whatever you think it is, usually doesn't get any results when searching.

[Viserion]

One final update.

On Thursday I tried to solder on the Spartan, and bungled it up massively .

On one of the sides I was a bit careless, and got a big bridge between the pins on several places.

Trying to remove the solder, I used a very small wick that snapped when trying to desolder.

In the process of removing the braid I ended up draging loose 2 of the copper wires on the MB.

I don't think it's possible to salvage this any more, at least it's beyond me.

Which is a pity since I think I managed to get parts that I did soldered on right, including the MC68SE processor.

I think maybe the last part was my downfall, as I managed to get that on fairly easy, and I got too cocky with the Spartan.

If I ever manage to find a blank Minimig board again, I might try again, as it was rather fun doing this, at least until the end.

Thanks to all who have helped me, I have at least learned a lot from this.

[Hewitson]

You should be able to trace those two tracks back to a solderable point and run jumper wires to the FPGA. If not, scrape off some of the solder mask and solder the wires to that.

In the future, if you manage to get the wick stuck to the board, heating it up will make it much easier to remove.

[Viserion]

Thanks for the suggestion, but the biggest problem is that I have made the bridging of the pins so bad, and then mixed it with the remnants of the wick.

I'm aware of heating it of will ease removal, but I heated it up , and used too much force when trying loosen it.