Crown FM1 tuner in Europe

[KlaasBaas]

A friend of mine bought a Crown FM1 tuner in good shape.
A US tuner thus 115 volt.

No issue for me to convert it to 240 volt EU (Netherlands that is).

De-emphasis converted to 50 us, there was a switch on the board for this.

But now.. US and EU frequencies differ in steps and base number. (FM)
We (EU) make steps of 100 Khz whereas US 200 Khz.
We (EU) tune in most cases on even numbers, 94,6 94,8 Mhz etc.

Is there a way to change this on a Crown FM1 ?
There is a microcontroller in the FM1 called AY-3-8115, but I can't find relevant info on this IC.

I could place a trimmer of 22 pF in series with the crystal to tune it closer to say 96,8 Mhz.
The display will stay state 96,7 or 96,9, I know.
And the steps will remain 200 Khz for sure.

Any ideas or help ?

 

[KentTeffeteller]

I don't think you can change frequency steps! Ask someone at AE Techron in Elkhart, Indiana if you can.

 

[rcs16]

Not too sure myself, with no datasheet available. I do see pin 36 (FDI) tied to ground, not sure what that pin does.
I have a FM1 with a dead AY-3-8115, so I temporarily disabled the VCO PLL control voltage and ran it off a mult-turn heli-trim pot connected to the 30VDC varactor control voltage. i used a old center tuning meter connected to the AFC ckt on the CA3189.
I have since found a replacement AY-3-8115 from Little Diode and have yet to try it out to see if it fixed my problem.

 

[KlaasBaas]

Thnx both.

PIN 36 is FDI, and no idea what it is for. If I google I find references to FDIV (Frequency DIVider ?) Could be.
A replacement for your AY-3-8115, most interesting.
But... since this is a micro controller it needs to be programmed, I presume there is 2 or 4 kbyte flash space for it.
An assumption I know.
I might give it a try to lift pin 36 from ground or give it 5 volt.

 

[rcs16]

FDI could be the freq divider selection for the FM VCO input depending on the pre-scaler divide ratio.
The AY-3-8115 is a ROM based ckt, there is no means to program it.

 

[fordon]

Hi @KlaasBaas (and everyone here in this topic!), have you managed to find a solution to change the frequency steps to 100 kHz? Here in Romania most radio stations transmit also on even frequency numbers... And thank you @rcs16 for your information regarding Little Diode as AY-3-8115 supplier, I have already ordered a replacement for this controller as mine has instantly fried after my wife accidentally connected the FM-1 (purchased from U.S.) to the 230/240V EU mains voltage before I've had the time to make that minor internal power supply change... It's my second Crown FM-1 tuner and I really like its sound (btw, I'm a vintage Crown collector, proudly owning about 15 fully restored vintage '60-'80's devices...).

 

[rcs16]

I can say I used the Littlediode part and it worked just fine. I still do not know if you can get the AY-3-8115 to step in 100KHz increments. We need to find a datasheet or and old GI manual.
I have a FM2 too, I do not like it as much as the FM1. The FM2 seems to overload the mixer much easier, it is jfet mixer whereas the FM1 is a dual gate MOSFET..
Lets hope that the AY-3-8115 was the only part fried with the over voltage condition. At least you have another one to compare against.