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HP 33120A test failures and schematics

Question asked by arekmx on Dec 18, 2013
Latest reply on Dec 23, 2013 by arekmx

I'm trying to fix old HP 33120A. Test reports few errors:
- "603 Waveform RAM readback failed"
- "604 Modulation RAM readback failed"  (this one seems to be fixed by replacing 32k x 8 SRAM memory)
- "606 Waveform ASIC failed"
- "608 SYNC signal detection failure, Elliptical filter path"

My guess is that "606 Waveform ASIC failed" is due to more failed SRAM memory. Unfortunately this old revision/model uses ancient TC55417J-15H (SOJ24 package) 16k x 4 type of SRAM. These kinds look no longer produced.

- looking for HP 33120A schematic (not Agilent 33120A since Agilent variant uses moden memory while my HP 33120A uses some ancient, no-one-sells-now type of ram)

- anyone having TC55417J-15H pinout, so I could replace it with something modern? I found that this is:

"Memory Category SRAM Chip
Density 66 kbits
Number of Words 16 k
Bits per Word   4 bits
Package Type    SOJ, 0.300 INCH, PLASTIC, SOJ-24
Pins    24
Logic Family    CMOS
Power Characteristics
Supply Voltage  5V
Access Time     15 ns
Operating Temperature   0 to 70 C (32 to 158 F)
so looks like a weird one.