AMIGA 500 - SWITCHLESS BOOT SELECTOR (3 RESET BOOT DRIVE SELECTOR)

Hi Markus Wenzel, can you please send photos of the circuit from different angles to c64istanbul@gmail.com? And, have you tried programming different .HEX files to the PIC16F628? Thank you for asking.

Email sent
I've tried hex file with and without buzzer. I have soldered 2 different ones now (4066N from different vendor), but no change.

Did you set the FUSE BITS as shown in the picture when programming the PIC16F628?

Yes, all fuse settings are the same. When I'm loading the hex file, the fuse settings are already set correctly, but I still checked them to ensure.
I have no more ideas why this won't work!

I tried another Amiga 500 (Rev 6A, original Drive, no extensions) - effect is the same. Disk/Drive sounds like if it would start to read, but returns to the Workbench "Disk" screen. Just like if you would insert en empty disk and nothing is found. Without the switch everything works fine.

Have you tried to swap two CIA chips (8520) with each other? And I replied to your email, please read it. Thank you.

1- https://www.aliexpress.com/item/1005006733563575.html

2- The buzzer should be soldered to the edge of the board, as in the photo that Federico Salis shared in the comments.

Hello, thanks for your confirmation. For the buzzer, the pin spacing of the buzzer in the Aliexpress link you provided is 5.0mm, but the pin spacing on the board is 7.62mm. If we buy the buzzer in the link you provided, can it be normally installed on the board?

https://www.aliexpress.com/item/1005005790491951.html

I corrected the link, it should be 7.6mm. Thank you

M74HC4066B1 is a DIP 16 package, but 74HC4066 on the board is a DIP 14 package, please check

http://bg-electronics.de/shop/product_info.php/products_id/10343/language/en

https://www.ebay.co.uk/itm/152256662883

https://www.heisener.com/ProductDetail/M74HC4066B1R

All DIP package M74HC4066B1 should be 14 pin. It is standart.

https://dir.heisener.com/DatasheetDownload/M74HC4066TTR.pdf

https://eu.mouser.com/datasheet/2/389/stmicroelectronics_cd00000319-1204246.pdf

https://www.ebay.com/itm/163685681620

Sorry, I see 16 pins in the picture, but that picture is just an example.

No problem. Thank you for asking.

Hi, The reason is; The electrical properties of CD4066 and 74HC4066 are different, while CD4066 does not work stably, 74HC4066 works stably. You can compare the datasheets. I haven't tried it with LS4066 because LS4066 is hard to find. Thank you for asking.

Thank you Federico Salis ;)

Hello Federico Salis, This problem can occur with some external mechanical floppy disk drives. Can you send photos of your external disk to c64istanbul@gmail.com ? Thank you.

Ps. Retro version 3-Reset Boot Selector works 99 percent in this case.

https://www.pcbway.com/project/shareproject/_DIY_AMIGA_500_SWITCHLESS_BOOT_SELECTOR_Rev_3_RETRO_VERSION_of_3_RESET_BOOT_2056c6f8.html

I wrote to you, thanks

Hello, If you are using HD disks with a 1.44MB PC floppy then you must close the HD hole of the disk with a sticker or Scotch-tape from both sides. I tried different 1.44MB floppy drives most of them worked. It should not be forgotten that; Many old disks become unusable over time because they lose their magnetic properties.

this is what happens... I have the external mechanical floppy and internal Gotek... without the pcb switch card booting from the floppy works... when I connect the card the floppies no longer start... the floppy screen remains... but the switching system works because if I reset the gotek starts...at this point I can do a further test, I saw Sven's problem on the 74HC4066, I ordered these original Philips chips...let's see if I change anything...I'll update you ..in the meantime I'll also try changing the buzzer...thanks

Resolved! I ordered the 74HC4066 chip from another seller... everything works! 😀

Thank you Federico Salis.

Hello Sven. Did you try to program the other .HEX file?

You mean "Primary External"? Yes, I did

Really strange behaviour, at my Rev5. board the internal drive is booting, despite the fact there is no "normal drive clicking" when showing Kickstart Logo (V1.2); when resetting 3 times, no external drive is booting, after resetting again 3 times, the internal drive starts booting again. So at least the "Switching" seems to work. regardless which .Hex file I was using... On my Rev.6 Board, nothing happens at all, none of the drives are booting no matter how often I reset. Important: Both Amiga500 Rev.5 & Rev.6 are working perfectly fine when 8520 is in the socket insted of the Boot Selector. Btw. Many thanks for your swift response :)

Basically what all the boot drive selector circuits do; It is to ensure that the legs 13 and 14 of the CIA2 8520 IC are interchanged. If legs 13 and 14 are swapped, the Amiga500 will boot from the external floppy disk drive. This is basically what this circuit does.

Thanks, I will check / measure the legs 13 and 14 and get back to you.

Just wanted to come back and tell the rootcause of my issues. It was the 74HC4066 purchased from Reichelt which let me down (all 12 pcs.) They have shown as good testing with the IC Tester. Using a different one from a different supplier is working like a charm 👍 So important: The circuit is 100% working! It was a component making me trouble!

Good to hear the issue has been resolved, thank you for your kind feedback.

I am glad you like it. Many thanks to Douglas Kier.

Hi Bradley Tate, I am sorry there is no way to adjust settings of the pic controller so that the selected boot setting is remembered after power off, but you can select first boot internal or external by changing Pic .HEX code (in the .zip file). Most users, who prefer to use external GOTEK drive more than internal FDD use this solution. Thank you.

Hello Peter Dimitriovskii, you should programm the "PRIMERY INTERNAL.hex" file in to PIC16F628(A). I do not know all kind of programmers software. you should choose your IC model (PIC16F628(A)), choose HEX file wile loading "PRIMERY INTERNAL.hex" , and choose the right fuse setings shown on this page. You should build the circuit with right components. CD4066 is Not good you have to use 74LS4066. This is not a very complex circuit. Please check all the solder points for short circuit. Thank you.

Thanks for the quick reply. I have used 74HC4066 as i thought this was the required part. Will this not work? I checked the logic chip and it passed the test from the programmer. Perhaps i stuffed up with the soldering so i will try again over the weekend.

I am the biggest idiot of the day. For the past few hours ive been using the wrong CIA. I should have checked it should have been the EVEN one. All works now! I even checked to see if the CIA's were broken and all is fine.

74HC4066 should work. thank you Peter.

Hello Sven Pook. You are right, but you can enable internal DF:1 useable by software, for example; if you select "DRIVES ON" from X-COPY then you can use internal DF:1. This circuit acts like all other Amiga 500 disk swappers. Thank you for asking.

There is no fuse settings required, I use TL866 programmer and program the HEX file directly. You should use 74HC4066 (Do NOT use CD4066).

Hello, thanks for response. Yes i use SN74HC4066N. well there are some fuse settings loaded into the TL866 when i load the files, should i uncheck all? what does the fuse settings say on your programmer?

Hello, I added fuse settings in the instructions. Please look at the images. Thank you.

I may miss the comments. If there is a problem then you can e-mail me. c64istanbul@bikom.com

No. I did NOT mentioned that "after 30 seconds it reverts back to DF0". I wrote "30 seconds after last reset, counter sets itself to zero." That means; If you want to toggle drives, you can not wait too much between 3 resets, Drives stay in their last position if you do not press reset 3 times in short time . Of course, drives do NOT change position (toggle), if you do not press reset 3 times, themselves automatically. Thank you for asking. You can see the answer for your second question in the zip file, There is 2 different firmware you can use in the zip file.

Ok, thanks. Looks like what i need. I will make an order later this week along with perhaps some of your other stuff. I checked my email and there is no "zip" file but rather an explanation of one. I trust that after my order i will receive the hex files? Sorry to ask heaps of questions but im doing a lot of this for the first time.

Thank you. You can download HEX files from "source code" link.

There is a rom switcher by a SukkoPera that seems to use the same keys to switch roms. Can this adaptor change the they keys you use to switch between DF0 and DF1?

I am sorry, I do not know SukkoPera's rom switcher. This is not an adaptor, This Electronic Circuit does a regular switched boot selectors job without using any mechanical switch. that is all. nothing more or less.

Rom switchers have different working principles. This circuit toggles 2 pins of 8520.

For further questions and answers please e-mail me: c64istanbul@bikom.com