[Solved]HP 33120A Function Generator Power On Problem

[coldframe]

Hello, Forum

When I power up the 33120A turns on/off  all display segments then  beep once Apart from anything else, Shift Key Work.
Edit
Of course, Checked a Display Panel Power Rail, Ribbon cable on the basis of the Scmematic (P.141)

 -13V Supply,   -13.4V  (Include two 1uF Tantal Caps OK But Replaced New)
  +6V Supply,      6.1V
+18V Supply,    18.1V
 -18V Supply,   -18.3V
 2.5V Supply,       2.5V

This clip shows a Problem
https://www.flickr.com/photos/boricha/30438162192/in/datetaken/

Here is what Relevant Beeps  says on Service manual

Self-Test Procedures
Power-On Self-Test
Each time the function generator is powered on, a small set of self-tests
are performed. These tests check that the minimum set of logic and
measurement hardware are functioning properly. The power-on self-test
performs checks 601, 625, and 626.

Error 625,  I/O processor does not respond
This test checks that communications can be established between U102 and U903 through the optically isolated (U101 and U901) serial data link.
Failure to establish communication in either direction will generate an error.
If this condition is detected at power-on self-test, the function generator will beep and the error annunciator will be on.

Agilent 33120A 15 MHz Function / Arbitrary Waveform Generator Service Guide (33120-90017)
http://cp.literature.agilent.com/litweb/pdf/33120-90017.pdf

I Guess the probable reason for the "Error 625,  I/O processor does not respond "
Does anyone has an idea what is wrong , or where should i start?

Best regards, coldframe.

[singapol]

Try reseating the connectors in the display panel, that is pull them out and insert back in that it will sort of scrape off whatever contaminants on the pin, other than this as what the manual says check the relevant ICs and components as described.

[coldframe]

Hello singapol.

Try reseating the connectors in the display panel, that is pull them out and insert back in that it will sort of scrape off whatever contaminants on the pin

Well, I appreciate you, and sharing.
Sadly,  still the same 
I should stop for today.

coldframe.

[TheSteve]

This is a tough one as it fails before it can gives any true error codes.
Have you tried communicating with the unit via GPIB?
Do any components get unusually warm/hot?
I know ram failures aren't uncommon in the 33120A so if you decide to just try replacing parts you might want to start there. It would be much more ideal to have a second unit so you can swap parts to narrow the failure down between the front display and the main board.

[coldframe]

Hello TheSteve.

This is a tough one as it fails before it can gives any true error codes.
Have you tried communicating with the unit via GPIB?
Do any components get unusually warm/hot?
I know ram failures aren't uncommon in the 33120A so if you decide to just try replacing parts you might want to start there. It would be much more ideal to have a second unit so you can swap parts to narrow the failure down between the front display and the main board.

GPIB Card, not here right now  the week next, the week after next I could do 
Close by FAN LM2940CT(U1004 ) is Hot but OK(Temeprature Sensor is My finger)

There are four SRAM,
U105(256K-BIT SRAM 70ns)  Floating Logic
U205(256K-BIT SRAM 25ns)  Digital Waveform Data Synthesis
U404,405(256K-BIT SRAM 15ns)  Waveform DAC

if RAM failure, It's U105(256K-BIT SRAM 70-NS) because U105 Control by SCX6206AK0(U103) IC-Gate Ary ASIC(Agilent Part# 1820-8907), What do you think?
I use  33120A a long intervals. Second Unit, humm,  It's too hard to me 
Anyway, It hasn't been long since Reading Schematic
I still want more time to consider opinions.

Thanx TheSteve.
coldframe.

[Jwalling]

Hello, Forum

When I power up the 33120A turns on/off  all display segments then  beep once Apart from anything else, Shift Key Work.
Edit
Of course, Checked a Display Panel Power Rail, Ribbon cable on the basis of the Scmematic (P.141)

 -13V Supply,   -13.4V  (Include two 1uF Tantal Caps OK But Replaced New)
  +6V Supply,      6.1V
+18V Supply,    18.1V
 -18V Supply,   -18.3V
 2.5V Supply,       2.5V

What about the +5V?
I've seen a 34970A with that same error and it was due to the power on reset circuitry, which is very similar to the circuitry on the 33120A.
Check U102 pin 16. IS the micro being held in reset?

[TiN]

My unit has bad U103. Fixed after swap from donor board... 

[coldframe]

Hello Jwalling

What about the +5V?
I've seen a 34970A with that same error and it was due to the power on reset circuitry, which is very similar to the circuitry on the 33120A.
Check U102 pin 16. IS the micro being held in reset?

Dp you mean U1002(MC78L05ACD)?  Yes It's ok
I'm out of town Now,  I'll check U102 pin 16 later. 
How did you manage the Your problem?

Hello TiN

My unit has bad U103. Fixed after swap from donor board... 

How did you know U103  dead?
If it's a question of U103 Maybe I can find a Second Hand chip.

U103 IC GATE-ARY CMOS  Mfr. Part#  SCX6206AK0, Agilent Part# "1820-8907"
34401A  U501 also "1820-8907"

Thanks
coldframe.

[TiN]

Output on my ARB was garbled, giving random signals, so I replaced bunch of ICs around, SRAMs, checked DAC, checked firmware ROM, margined with power, but all was for nothing. Then I bought second 33120A board, swapped U103 it got fixed right on. I still has that spare board without chips

[Jwalling]

Dp you mean U1002(MC78L05ACD)?  Yes It's ok

No, I mean VCC which comes from U1004, a LM2940.

I'm out of town Now,  I'll check U102 pin 16 later. 
How did you manage the Your problem?

I've seen the problem on more than one 34970A. In one case it was a bad 34064 undervoltage sensor chip. That would be U1052 on the 33120A in the power supply schematic.

Other error 625s from my 34970A repair logs - maybe you can correlate to the 33120A using a 34970A schematic:
1. U302 74HCT132-1 (schematic page 3 of 4) pin shorted internally.

2. Fan not running unless I PRESS DOWN ON THE pcb. U303-5 (GND for one of the optos; signal = ER_OPDO ) had a fractured solder joint.

[coldframe]

Hello Forum
I'm sorry that my Feedback is so late, I have made a business trip.

TheSteve, Jwalling,

This is a tough one as it fails before it can gives any true error codes.
Have you tried communicating with the unit via GPIB?
Do any components get unusually warm/hot?

No, I mean VCC which comes from U1004, a LM2940.

The above image>  The GPIB isn't working.


The above image> measured U1004(LM2940)  Voltage, Current, Temperature
Voltage :  In:9.9V, Out:4.9V, Current :  900mA, Temperature : Almost 80C  (Fan Not Connected)
Voltage is Looking Good but  Current & Temperature That seems to be the problem.
LM2940x 1-A Low Dropout Regulator
http://www.ti.com/lit/ds/symlink/lm2940-n.pdf



Tin,

My unit has bad U103. Fixed after swap from donor board... 

I switched U103 to where good 34401A(U501) was and vice versa.  no change in the patient’s condition 

I need to do more investigation.  I welcome any comments you may have.

coldframe.

P.S
I'm  Information Technology Engineer
BUT, collecting firewood  better than  My job 


Safety  First.

[Jwalling]

You haven't checked to see whether the micro is being held in reset yet?

[EE-digger]

Late arrival to this thread but it just brought life to my "new" 33120A.

It exhibited the all segments on, then off, then one or two beeps, then only the shift key responds, indicating that the display processor is running.

There was no clock or data activity on the display cable.

Thanks to JWalling's posts, I targeted the power on reset chip, U1006, and found 2.3V at its output.  In a lazy attempt to force the pin, I shorted it to the adjacent pin at 5.0V with my scope probe tip.  After doing this a few times, the unit started to power=up properly.

My assumption at this point is that one of the two caps sitting on the reset line were bad, pulling the line down.  My application of 5V may have "opened up" the damaged cap.

If the problem resurfaces, I'll replace those caps and maybe U1006 itself.

[mzzj]

Had somewhat similar adventure that started 6 years ago https://www.eevblog.com/forum/repair/help-anyone-have-hp-33120a-function-gen-rom-firmware/ 

one beep on power up and only shift key/announciator works on front panel.

U102 main mCU PONRST (reset) was low, checked voltage supervisor U1006, output high so something else is pulling the PONRST low.
on oscilloscope PONRST is sawtooth-looking signal approx from 1...2 volts
Reset on 80C196 MCU is bi-directional so pull PONRST pin from U102 mCU --> PONRST no longer pulled down -->Suspect U102 not happy about  memory content, clone and flash U104 EPROM and U106 Flash chips from working unit --> no improvement 
Replace U102 80C196 mCU --> no improvement.
Replace U103 ASIC --> no improvement 
Swap U105 SRAM from working unit to UUR(unit under repair)
working unit now dead (turns out I soldered U105 upside down) 
previously non-functioning unit turns on and works but I get error 625 
turns out OP_RXD* to U103 ASIC is not properly soldered, resolder the pin to board and UUR is working   

Would have been lot easier to replace the U105 SRAM right away 


 

 

[free_electron]

i've seen multiple reports of the rams failing.

[coldframe]

Yes!

In My case U105 SRAM Fault.