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Old 26th June 2006, 02:02 AM   #1
Voltaic is offline Voltaic  United Kingdom
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Default HP 8116A Pulse Function generator

A few years ago I had an HP 8116A Pulse Function generator given to me, which is nice seeing as how they still go (even at 15 years old or so) for over $2,000. Unfortunately for me theres a problem with it, when it comes on and does a P.O.S.T. it returns E21, and I get nothing from the output. Recently I dug it out of the closet because I thought maybe I should try to get it working, so I did some searching online and found that E21 means "Fault in the internal repetition rate generator" I'm no expert but I would think the repetition rate generator has to do with controlling the pulse waveform portion of this unit, and wouldn't effect the sine/square/etc. Maybe (more like probably) I'm wrong. I guess what I'm getting at is: does anyone out there have any experience repairing function generators, or know a lot about them that might be able to help me get this thing working.

cheers,
Daniel
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Old 26th June 2006, 02:42 AM   #2
poobah is offline poobah  United States
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Crack it open and look for a lithium battery (if it has one)... these things die and then the programming is lost... good luck fixing it in that event.

Otherwise, look for bad electrolytics first.

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Old 26th June 2006, 03:02 AM   #3
Voltaic is offline Voltaic  United Kingdom
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hmmm, you might be on to something here I opened her up and looked around, I didnt see any caps that were obviously blown or oozing yummy yellow snot, but I did find a battery, I through a DMM on it, and it reads 1.05V, I googled some numbers printed on the battery and found out that the battery is a 2.5V NiCd battery, do you think that this much of a power loss could be causing problems? Check out this picture here (if the link doesnt work let me know, its the first time I've tried to link to picasa) notice the corrosion on the terminals. 8116A Battery

thanks for the response,
Daniel
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Old 26th June 2006, 03:18 AM   #4
Voltaic is offline Voltaic  United Kingdom
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new information; I managed to find an excerpt of the service manual online regarding battery failure it reads: "If the instrument RAM becomes corrupted due to battery failure, the Standard Paramater Set will be selected when the instrument is first turned on, in order to give an error free display"

After reading this I dont think my problem could be caused by battery failure, as it seems to mantain programming, even if the battery fails, it just wont mantain the same settings if the power is disconnected. Thats what I get from that passage anyway, what are your ideas?
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Old 26th June 2006, 03:29 AM   #5
poobah is offline poobah  United States
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Before flash memory was invented, batteries were a popular way of providing continous power for a RAM memory. What was in the RAM? Likely it held calibration coefficients. So the microproceesor goes there and the numbers are gone, then flags an error. The rate generator probably needs numbers to correct the oscillator

How do you fix it? Send it to HP. More than likely... it is a paperweight now.

You could try replacing the battery... don't get your hopes up. If you do decide to... its complicated.


1) Get a new battery.

2) Measure the old battery's voltage in circuit.

3) Set a DC supply to this exact voltage.

4) Connect the supply to the circuit... there might be a place to plug in for this... otherwise you'll have to tack some wires on the board.

5) With power in place... remove the old battery.

6) Increase the supply voltage to equal the voltage of the new battery.

7) Install the new battery.

8) Remove the power supply.

The idea behind all of this is to keep power to the RAM chips at all times. And, also not to set the lithiums on fire by mismatching a parallel supply.

Before you spend the $10 on the battery... find the RAM chips and look up the spec for minimum voltage to ensure data retention. Sorry but 1.05 volts sounds way low... you are probably hosed.

Check HP's site (Agilent) and see if they still support it and how much a service costs.

Been here, done this...

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Old 26th June 2006, 03:32 AM   #6
poobah is offline poobah  United States
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It could be that it still won't work until the battery is made right.

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Old 27th June 2006, 06:42 AM   #7
clem_o is offline clem_o  Philippines
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Howdy - I have an 8116A, which had an intermittent signal problem. Managed to trace this to one of the small-signal transistors. Never did find an exact replacement, but the unit works, with perhaps a degradation in speed.

Anyway, the manual from the Agilent website unfortunately doesn't include any information on how to service the "E" code errors. It's supposed to be in Chapter 10.1, but the downloadable manual ends at chapter 9.

The manual does say that the battery is only used to "remember" the last operating parameters, but I guess taking out the battery, letting the unit sit idle for some time and turning it back on should reset the RAM to uninitialized state - if the error code persists it's time to ask Agilent for the rest of the chapters!!

Cheers

Clem
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Old 27th June 2006, 01:38 PM   #8
Voltaic is offline Voltaic  United Kingdom
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Quote:
Originally posted by clem_o
Howdy - I have an 8116A, which had an intermittent signal problem. Managed to trace this to one of the small-signal transistors. Never did find an exact replacement, but the unit works, with perhaps a degradation in speed.

Anyway, the manual from the Agilent website unfortunately doesn't include any information on how to service the "E" code errors. It's supposed to be in Chapter 10.1, but the downloadable manual ends at chapter 9.

The manual does say that the battery is only used to "remember" the last operating parameters, but I guess taking out the battery, letting the unit sit idle for some time and turning it back on should reset the RAM to uninitialized state - if the error code persists it's time to ask Agilent for the rest of the chapters!!

Cheers

Clem
I think I'll make this my next course of action, I'm not thrilled with the idea of removing the battery as it's soldered in, but I suppose to reinstall it I could solder leads to the PCB and use a battery holder, might be an idea there. on a side note, the +5V lead that goes to the PCB next to the battery broke off lastnight, that was a fun one to solder

I'll give Agilent a call, and I'll keep you posted on the progress

cheers,
Daniel

PS If I manage to get a manual (including chapter 10) from Agilent I'll send you a copy.
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Old 27th June 2006, 02:45 PM   #9
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there are quite a few former HP engineers who are ham radio operators and lurk on the rec.radio.amateur.homebrew newsgroup
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Old 27th June 2006, 02:46 PM   #10
Voltaic is offline Voltaic  United Kingdom
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Quote:
Originally posted by jackinnj
there are quite a few former HP engineers who are ham radio operators and lurk on the rec.radio.amateur.homebrew newsgroup

great suggestion! maybe I can exploit them for their knowledge of my machine
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