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Please Help with the Identification of this Part

jw0752

While cleaning out the backroom of an Electronics Store we came across about 100 of these chips. I took them to the shop but I have not been able to determine what they are. Resistance readings are very high and capacitance readings are negligible. Hamlin is now owned by Littlefuse. The 8235 on each appears to be a date code which makes sense as all the other chips that were with this lot all came from the 1970s. Anyone have any ideas. I have tried to Google the image also with no results.

 

image

 

Thanks John

  • in reply to jc2048

    Hi Jon,

    I tested your hypothesis by charging a large capacitor to 50 volts and discharging it into three of the 130 ohm links to pins 10 and 12. The resistive links were opened in all cases with almost no discharge of the cap. Residual resistance was slightly less than 100 K. there was no outward evidence of the damage to the resistors. This method is simple and effective and likely the way the chip were programmed.

    John

  • in reply to jw0752

    I was wondering if these resistors were to form a part of a DAC/ADC chain. Also resistors of this size are like 50v breakdown in SMD parts (all a bit approximate!!) so you may of damaged them at 100v or at least have to allow for an amount of breakdown in your values!

     

    John A

  • in reply to Problemchild
    Also resistors of this size are like 50v breakdown in SMD parts

    I was thinking that many of the circuits these would have been used in would be 5v or at worst 12v.

    Personally I would have used 15-20v to prove the function.

     

    They are an interesting device.

     

    Mark

  • in reply to Problemchild

    Hi John,

    Anything is possible. The reason my analysis went the way it did was that the resistors all have a common lead and each of the several chips that I tested had the same branches damaged so that their resistances were anywhere from 300K to OL. The 2 resistors on each chip that are still intact have poor consistency from chip to chip with resistances of 130 to 150 ohms typical. It seemed to me that the only think important to the application must have been either a very high resistance or a relatively low one and this sound a lot like digital. I didn't try the 100 volt megger until I had taken lots of measurements with the fluke meter. The instability of the high readings I was getting made me want to verify and so I tried the megger. I would get resistance readings on the Fluke that would wander 1 meg in either direction on some of the resistors. Now I suspect that this was just residual unstable material left over from the resistor being fused.

    John

  • in reply to mcb1

    Hi Mark,

     

    I did start at a more modest level but voltages up to 25 volts did not fuse the resistors but rather just made them hot until a burn mark could be seen on the outside of the chip. Once I got about 40 volts the chip fused quickly enough so no heat damage was noted.

     

    John