Searching for "ancient" A/D-converter IC

[Reinhard Zwirner]

Attention: FUP2 sci.electronics.repair

Dear Experts

Maybe somebody here can help me. I'm searching for a certain 3 digit
ADC-IC (18 pin DIL) for a Kamoden DM-200 DVM. Unfortunately the IC
I'm searching for was already missing when I got the DVM for repair.

The IC seems to be part of a two chip converter solution. On one hand,
it controls the 3 switching transistors for the 3 digit LED display
(common cathode). On the other hand it generates the BCD word for the
decoder IC MM 74C48. Additionally it may (partly?) contain a dual slope
ADC. I've found out the following pin functions:

Pin 1: Vss/ground
3: Gate JFET (E 204)
4: Source JFET; foil cap A (100 nF)
6: Vss/ground
7: Base transistor digit 3
8: Base transistor digit 2
9: Base transistor digit 1

10: BCD "A"
11: BCD "C"
12: BCD "B"
13: BCD "D"
14: via capacitor 1 nF to ground
15: Vdd (?)
16: Drain JFET; foil cap B (100 nF)
18: foil cap A (100 nF); foil cap B (100 nF)

Okay, I've already done a lot of research. I found out that none
of the following IC's will fit:

Siliconix LD 120/121
LD 122/121

RCA CA 3162E

TI TL 50x

Ferranti ZNA 116E

AD AD 2020

Any suggestions?

Full of hope

Reinhard

 

[Reinhard Zwirner]

Reinhard Zwirner schrieb:

Dear Experts

Maybe somebody here can help me. I'm searching for a certain 3 digit
ADC-IC (18 pin DIL) for a Kamoden DM-200 DVM. Unfortunately the IC
I'm searching for was already missing when I got the DVM for repair.

The IC seems to be part of a two chip converter solution. On one hand,
it controls the 3 switching transistors for the 3 digit LED display
(common cathode). On the other hand it generates the BCD word for the
decoder IC MM 74C48. Additionally it may (partly?) contain a dual slope
ADC. I've found out the following pin functions:

Pin 1: Vss/ground
3: Gate JFET (E 204)
4: Source JFET; foil cap A (100 nF)
6: Vss/ground
7: Base transistor digit 3
8: Base transistor digit 2
9: Base transistor digit 1

10: BCD "A"
11: BCD "C"
12: BCD "B"
13: BCD "D"
14: via capacitor 1 nF to ground
15: Vdd (?)
16: Drain JFET; foil cap B (100 nF)
18: foil cap A (100 nF); foil cap B (100 nF)

Okay, I've already done a lot of research. I found out that none
of the following IC's will fit:

Siliconix LD 120/121
LD 122/121

RCA CA 3162E

TI TL 50x

Ferranti ZNA 116E

AD AD 2020

Hi

Yesterday I got the answer to my question (and the datasheet):
my searched for A/D converter is a Siliconix LD 130.
Unfortunately I'll have to pay 50.- Euros for a new one :-( ....
But perhaps someone here might know a less expensive source.

CU

Reinhard