Part values

[Marco-Both]

Hello,

could you please provide the values for the EMI filters and ferrites?

Thanks

[Marco-Both]

The 1581 service manual says 100pF. I have now used these for the test setup.

[sjgray]

Good catch. I completely missed that.

[Marco-Both]

Hi,
I received the last components today and assembled the PCB (Proto 2). With a 12 V power supply, the 5 V 7805 linear regulator immediately becomes very hot. After a few seconds, you burn your fingers, and a little later, even the PCB becomes very hot.
The circuit board draws approx. 500mA at 5V. The regulator converts the rest into heat. That seems too much to me. Therefore, I cannot recommend it. I think a switching regulator such as the TRACO switching regulator TSR 1-2450 would be a better alternative.

[AtomicRPM]

Found a floating 5V on R5. See here for fix.

https://imgur.com/a/KatH6Lv

[sjgray]

Thanks. I was sure I had done a DRC so not sure how I missed that. Will update.

[sjgray]

@Marco-Both Did you try a "TSR 1-2450 "? If so, how does it work? I ordered a few to try. Other than that, is everything working as expected?

[Marco-Both]

@sjgray I haven't ordered one yet. I first need to find out why the drive isn't working. When loading the directory, the mechanism starts to turn. But then it stops with an error (27, read error). I know that the cable and mechanism are OK. They come from my original 1581.

[AtomicRPM]

@sjgray I haven't ordered one yet. I first need to find out why the drive isn't working. When loading the directory, the mechanism starts to turn. But then it stops with an error (27, read error). I know that the cable and mechanism are OK. They come from my original 1581.

This sounds like something is going on with the /ATN signal which is pin 3 on the serial port.

[Marco-Both]

In the meantime, I have built a Rev 2 of the enhanced version. I inserted the fix with R5 into the circuit board before.

Here I get a comparable result. The directory addresses the drive and it starts spinning. Unfortunately, I then get a 74 drive not ready error. Before that, I can read the error channel with @. I get either CBM or JiffyDOS, depending on the ROM jumper. This tells me that at least the CPU, ROM, and 74 logic should be working. Instead of the 1772, I also tested a 1770 and close the jumper, but without success.
I have one suspect: the RAM. I am using a W24257AK-20 PC cache IC. According to the data sheet, this is a 32k x8 CMOS SRAM. But even replacing it with another one of this type did not make any difference.

[sjgray]

I verified /ATN is connected to resistor pack 11D (pin 5) on both Enhanced and Internal versions. If internal version have you jumpered the enable header? I realize this is labelled as "DISABLE" on the board but it must be jumpered.

[Marco-Both]

Hi, yes i set the jumper J6. And i set J1 & J2 to 1581 to use an Amiga/1581 mechanic. I also use an 1770 and a 1772 IC (i set JP1). This applies to both the internal and extended versions. Device ID, Drive Select, and the alternative ROM work as expected.