Elka Rhythm Machine Repair

[smilan]

Hi,
I have an Elka Rhythm Machine for repair.
The unit turns on, but doesn't make any sounds.
The voltages seems to be right.
I'm suspecting that IC 37 is faulty since it's getting too hot.
The schematic asking for a SN29722 / SN3947.
The IC that connected to the board is a SNB748F.
While looking over the internet for  a SN29722 / SN3947 I found that  SN29722 comes in DIP24, not DIP16 as the schematic and the physical socket are. I couldn't find any info about SN3947.
Do you think that SNB748F is the right IC for this application?
Here's a link to the schematic:
https://drive.google.com/file/d/1Oe7l06FaVub06Pxz2GPAR7AHIBloNcCW/view?usp=sharing

 

[smilan]

I'm start to wondering if the "SN29722" is actually a typo and the right IC is a SN29772. Does it make any sense?

 

[analogguru]

Probably not, but from the schematic IC37 is a dual 3-bit binary counter which are cascaded to form a 6-stage binary counter which could be replaced with an adapterboard by a 74HC4040 (CD4040).  The output of this counter is feeded to IC38.

IC 38 appears to be a ROM containing the rhythm patterns.  If you know the patterns, it should be possible to replace it with an EPROM 2708, 2716, 2732 (or above) with an adapterborad if necessary.

 

[smilan]

Thanks Analogguru,
I have no experience with repairing drum machines.
When I received this machine IC 38 was shorted (and got extremely hot while the unit turned on) so I replaced it with a NOS IC I found on Ebay.
Now I'm understanding that the IC itself doesn't contain the rhythm patterns...
Let's say I would like to program the new IC, who it can be done?