MK3870 replacement based on Arduino Nano

FM, AM, voor ieder wat wils. Tuners zijn nog steeds hot en Philips heeft een hoop mooie gemaakt.

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Lid geworden op: zo dec 10, 2017 7:58 pm

MK3870 replacement based on Arduino Nano

Berichtdoor 1gcarlo » zo dec 10, 2017 8:44 pm

Hello, I would like to share with you this my little design, done to build a replacement for the MK3870 processor of the tuner 22AH106 / 22AH107, and the 22AH799 receiver.

It's based on an Arduino Nano board, available for few Euro, and a little bit of manual work. It emulates as closely as possible the functions of the original part, but it's possible to enable some extended functions (like the direct frequency input for example).

20171210_135951_HDRcr.jpg (41.5 KiB) 900 keer bekeken

I've used a 20x7 board with holes and 40 round pins to build the base. The resistors used are 0603 size and the wire used is a 0.2 mm diameter type, enameled, but any other should be ok. Wire length is about 7 centimeters.

The Arduino Nano board has been fixed to the base by two copper wires on one side, so to permit to spread the two for testing and changes. Before to put it in the equipment the other side can be fixed too, by two more wires.

I've removed the upper plastic part of the socket to insert the replacement.

Attached there are the schematics and the firmware listing (use the Arduino development system to program the board)

To enable the extended functions keep the “STORE” button pressed when turning on the equipment. To turn them off push the “STORE” button during the turn off of the tuner/receiver

The extended functions are:
- display of year, month name, day and “Philips” when in stand by, plus seconds in bynary code
- set of minutes, day, month and year with increment and decrement (push the “TIME” button to cycle through functions, use “SET”+”MIN” to increment and “SET”+”HOURS” to decrement)
- display of the intermediate frequencies and firmware release (pushing “TIME” more times, they are after the clock and calendar settings)
- direct frequency input using the memory buttons (STORE for 0). Push the current frequency range (FM or MW or LW) and keeping it down press and release “STORE”. Four horizontal lines will appear, then you can type the frequency
- display of the the string “tape” and “Phon” when the Tape A or Pick Up are selected

Enjoy it !
Check out my instagram @1gcarlo to see some photo of my little collection of vintage Philips equipments

(7.54 KiB) 34 keer gedownload
Laatst gewijzigd door 1gcarlo op za dec 16, 2017 9:37 am, 1 keer totaal gewijzigd.

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Re: MK3870 replacement based on Arduino Nano

Berichtdoor David » zo dec 10, 2017 9:21 pm

Hi Giancarlo,

Nice design, thank you for sharing the details. Where do the +5V and +3V3 go?

Does the MK3870 tend to break, is that why you made this? Just curious.

Best regards,
MFB Collectie: Aanwezig...
Overige hobby's: flipperkasten, auto's, watersport, aquaria, zendamateur

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Re: MK3870 replacement based on Arduino Nano

Berichtdoor movieman » zo dec 10, 2017 9:33 pm

Nice indeed. :handgestures-thumbup:

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Lid geworden op: zo dec 10, 2017 7:58 pm

Re: MK3870 replacement based on Arduino Nano

Berichtdoor 1gcarlo » zo dec 10, 2017 9:50 pm

Hello David, those arrows comes from the design prototype in Kicad, they go nowhere, sorry for the confusion it was better to delete them. The Arduino just needs the +5V supply coming from the pin 40 of the MK3870.

I've done this design because one of the 106 tuners I've bought on ebay was without the microcontroller, it was sold as defective at a very low price. But I had the idea of this design from a very long time, at least from the eighties, when I've bought the 22AH107 as new, for about 400000 lire (about 200 Euro) of that time, because there are enough keys to do the direct frequency input, but it was available only in the AH180, much more expensive.

Still haven't found a defective MK3870 up to now, just the supply's capacitors.

Hope to do an extension to the AH798, but need to buy one before. The hardware should be compatible because I've left the related pins free and kept the one for the interrupt reserved for this task
20171210_140358_HDRcr.jpg (58.42 KiB) 885 keer bekeken
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