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Electronics => Repair => Topic started by: usagi on April 18, 2017, 08:47:51 am

Title: [FIXED] Agilent 34401a repair - dead GPIB
Post by: usagi on April 18, 2017, 08:47:51 am
Picked up a used 34401a off ebay. The unit passes self test without errors.

RS232 works but GPIB does not.

Is there a common cause of failure for 34401a GPIB ports?

I'm guessing either U703 (75ALS162) or U702 (75ALS160) is bad. Is there any way to tell which one?
Title: Re: Agilent 34401a repair - dead GPIB
Post by: Dr. Frank on April 18, 2017, 09:56:49 am
Hello usagi,

see manual p. 92: 'Only one interface can be enabled at a time'.

So I assume, that you have to enable 'HP-IB / 488' first, in the I/O menu, see p. 162, and then it should work.

Frank
Title: Re: Agilent 34401a repair - dead GPIB
Post by: usagi on April 18, 2017, 05:11:57 pm
Quote from: Dr. Frank on April 18, 2017, 09:56:49 am
Hello usagi,

see manual p. 92: 'Only one interface can be enabled at a time'.

So I assume, that you have to enable 'HP-IB / 488' first, in the I/O menu, see p. 162, and then it should work.

Frank

i know this already  :) i had to go into those menus to enable RS232 in the first place, since it came with GPIB interface enabled by default.

so I can confirm GPIB is 100% busted.  :scared:  GPIB works on my other devices - keithley 2015 and R&S cmu200.

so do you know which exact 34401a IC to verify for GPIB troubleshooting?
Title: Re: Agilent 34401a repair - dead GPIB
Post by: Tony_G on April 19, 2017, 08:38:01 pm
I just repaired an 11713A that didn't work with GPIB by resoldering the GPIB connector - Might be worth giving it a try if the connector is soldered direct to the board in those devices.
Title: Re: Agilent 34401a repair - dead GPIB
Post by: usagi on April 20, 2017, 07:24:27 am
100% confirmed the connector is perfect.

100% confirmed an IC is blown. waiting on mouser order to arrive now.
Title: Re: Agilent 34401a repair - dead GPIB
Post by: HighVoltage on April 20, 2017, 07:39:32 am
Once you exchange the GPIB controller it should work perfect again.

Title: Re: Agilent 34401a repair - dead GPIB
Post by: usagi on April 20, 2017, 08:25:08 am
Quote from: HighVoltage on April 20, 2017, 07:39:32 am
Once you exchange the GPIB controller it should work perfect again.

U701 is fine.
Title: Re: Agilent 34401a repair - dead GPIB
Post by: HighVoltage on April 20, 2017, 08:44:40 am
Quote from: usagi on April 20, 2017, 08:25:08 am

U701 is fine.
Ahh, which IC do you think is blown?
Title: Re: Agilent 34401a repair - dead GPIB
Post by: usagi on April 23, 2017, 03:16:40 am
replaced blown IC, GPIB now works. again :-DMM

Title: Re: [FIXED] Agilent 34401a repair - dead GPIB
Post by: TheSteve on April 23, 2017, 03:39:30 am
Excellent!!!

Please do post which IC you actually changed to make it work though.