GS Type 1 Replacement Parts Found!

[chris96]

Hey everyone. After researching online, I've been able to identify some of the actual chips used on the GS Type 1 soundboard, with all the components I found still in production! Starting with the DAC (Digital to Analog Converter), the Type 1 uses a AD9652 chip from Analog Devices Inc. Here's an overview of the product on their website:
https://www.analog.com/en/products/ad96 ... t-overview

From my background in audio, it was quite surprising to see such an advanced chip used in a device that just makes the same sound over and over again. Analog Devices DACs are commonly used in things like CD players and game consoles to drive their audio (even some phones use them too I believe), so it's funny to see it used in basic railroad crossing equipment like this.

The other component I was able to identify was the LM384N 5W Power Amplifier chip from National Semiconductor. This device receives the low level audio signal from the DAC and boosts it up to a level that the speaker can use to produce sound (the same way a car or home stereo amp would). Here's some more information about this chip:
https://www.wiltronics.com.au/product/3 ... power-amp/

I'm not sure what the two Motorola chips are (U1, U2 and U6 on the board) as I have been unable to locate the exact model so far. However, they are most likely related to controlling the pitch, speed and volume of playback.

The only other major component on the board is the ROM chip that would contain the bell's sound file and program software. Unfortunately, GS's sticker being in the way makes it impossible to tell what brand/model the chip is. However, any ROM chip with the correct amount of pins and capacity should work in this situation when the original software from the old chip is copied and loaded onto it.

The rest of the board is just diodes and capacitors which are fairly standard.

Here's an image of a Type 1's circuit board with all of the identified parts labeled. I hope you guys find it interesting!

[ZachL]

Nice find!

[McK&H.Aust]

That's some cool research you've done

I've often wondered if the change in sound between the different bell types was because maybe GS originally had a certain amount of circuit boards made and components obtained for the type 1's (probably in the thousands) and once they were used up, had to source more in another bulk purchase which used different components at the time?

I'm guessing the ability to adjust the tone on the type 1's was removed from the type 2's to reduce the number of components (lower the cost) and simplify the circuit arrangement, also that feature probably wasn't in demand from the railroads so was likely overkill in most situations.