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E4438c display problem, controler memory location please

 

Re Agilent E4438C Display
Problem finding any info on the processor card not even block diagram (4400-60500). Unit has a display prob, thin vertical line and pixels missing hear and there. Plus what I would describe as mouse droppings, black blobs hear and there. Otherwise working and usable,? not the display itself as I have swaped for known good one but no different. Slightly different every time powered up. This unit is different from the circuit posted on here, display controller is not on motherboard and appears to be on processor card (from tracing tracks back). I suspect the display ram but can't find any info on which chip it is. U20 hm6285128blfp-7 or U21 kr1016v10-v10 look possible but as they are soldered in don't want to do too much trial and error. Suspect controller is in one of the many fpga's. Any help please.
John g8bxh
 

If there is evidence of rodent infestation, I would start by thoroughly cleaning every circuit board with soap and water. It could be that vermin piss or crap is causing conduction to places it shouldn't be.?
 

 

I am not sure this covers the 4438B specifically, but the CLIP for the 4400 family shows that they use the 66510 LCD controller, at U607.? This controller uses a dedicated 514260 256k x 16 DRAM, at U610-A.
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Hope this helps,
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-mark
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Thank you Mark
I have seen that part of the clip. Mine is a different release, not sure if newer or older but made in 2005 or 6. All lcd drive circuits appear to be on cpu card. Can't find a lcd controler chip so assume is been put in fpga. Have ordered both ram chips, will start with the 4Mb one.
John
 

On a more general note, I would strongly recommend that you check/replace the main bulk capacitor in the main switched mode PSU module if it hasn't already been done. This is a known weak point once the E4438C sig gen has seen a lot of use. It failed in mine but luckily the previous owner immediately stopped trying to use it once it failed.
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Keysight looked at it and claimed that they couldn't repair it (they said the PSU module is obsolete) so I was able to??acquire the E4438C sig gen as BER.?Once it was mine, I replaced the cap and it has been fine ever since. There are plenty of pictures online of failed PSUs in these sig gens. If the bulk cap fully fails with low capacitance and high ESR then other components in the PSU are likely to fail in a big way. So it is worth replacing this cap.
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I think I used this 220uF 400V cap from Mouser with Mouser part number?661-ETXH401N221MR35S. It is a higher spec version of what was already in the PSU with a longer lifetime and it only costs about ?4. Same manufacturer, same dimensions. However, the voltage rating is the same at only 400V. It might be worth trying to find one rated to 450V.?
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The other thing to be aware of is that these sig gens consume a lot of power when running. Mine has lots of hardware options fitted and it can exceed 200W power consumption when I measure it under certain operating modes. The datasheet says <300W. It isn't really suited as a general purpose sig gen because of this. I only use it when I need the special features or the high performance it offers.
 

I'll? sure check out the psu caps. This gen has about 40000 hours on the clock. Original seal's intact. When I opened it up found it's like new inside. No dust or dirt anywhere, my guess is it must have spent it's working life in a clean room. Has all board's fitted and a number of options. I didn't make a proper note but think it was drawing over 200W.
Many thanks John
 

In case it helps others, it's not U20 or U21. U21 Dose not affect opperation of sig gen (work's and passes all self tests even when removed) mabe user storage? Closer look at screen shows a coloum of 2 (when black pixels) wide is deleted and appears 64 pixels to left. Not a memory problem in the usual sens as this would have to happen after decode (or a very weird internal fault). All points to screen, but swapping out screen with another gen makes no difference. A diagram would be really usefull...

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