HP 4145B Semiconductor Parameter Analyser - Display shuts off

[fourierpwn]

Hi all,

I have a 4145B (3 1/2" floppy version) that is somewhat working. Boots up, passes self tests yet after a short period of time the whole front display goes dead. No display, no lights on front panel but you can still hear that the unit is powered up. This has tended to happen midway through a measurement, however I haven't exactly tried leaving the unit on in the menu screen to see if it happens.

Does anyone have any experience with this unit and know of possible causes/fixes for this? Even some schematics?

Any help is appreciated. 

[IRFP460]

By "No display, no lights" I assume you checked if the  LCD and the backlight fails or if it's just the backlight.
If so: Check the input voltages to the display, maybe it's just an old voltage regulator dropping out.
If not: Hold a torch to the display and see, if it still shows something, that's just your backlight failing, in that case you'd haver to replace the CCFL-Tubes, the inverter or the whole display assembly, depending on what's broken and what parts you can get for cheap.

Good luck with your repair!

[fourierpwn]

4145B is way before LCD days!

Classic green phosphorous CRT 

[MosherIV]

I know nothing but my searchfoo found this :
http://manualzz.com/doc/11813434/hp-4145b-operation-service-manual--higher-resolution-scan-

Sound like PSU is shutting down, at least to the CRT

[alm]

If it turns out to be the display,  then NewScope make an (expensive) suitable LCD replacement, if it is just the CRT that has failed (though it does not sound like that). I would start with the basics like power supply voltages. Compare before and after the front panel goes dead. Check if there is still signal on the external CRT connections (connecting a scope in X-Y mode to the X and Y outputs should give you something that looks like the display, without Z axis obviously). I am not aware of any usable service documentation beyond self tests, but that does not mean it does not exist.

[fourierpwn]

I know nothing but my searchfoo found this :
http://manualzz.com/doc/11813434/hp-4145b-operation-service-manual--higher-resolution-scan-

Sound like PSU is shutting down, at least to the CRT

Thanks, I had already found this. Even though it claims operation AND service manual, the service manual is missing from it :sigh:

Thou shall check voltages... Yep, just need to find the time to do so! Luckily I have a 4145A on hand as well (not sure that it works, it has a sticker on it saying "not to be used after April '94" LOL)

Thanks for the replies.

[alm]

Dave at Artek Manuals appears to sell a 4145B service manual with schematics.

[tec5c]

Dave at Artek Manuals appears to sell a 4145B service manual with schematics.

Thanks! I think I may just buy this just purchased this 

[tec5c]

Not sure if this is the cause but it may be helpful to any future persons attempting to repair a 4145B which has no display.

If the symptom is "No display, but the fan is turning" the A11 board may have shut off because it detected an excessive current... *Reference to A11-1 flow diagram test procedure which is in the service manual* ...Perform the following trouble isolation procedure.

1) Turn off the instrument

2) Disconnect A11J2

3) Wait at least two minutes

4) If "Busy" and "Error A01" are successively displayed, the failure is not on the A11 board, go to Flow Diagram A15-1. If "Busy" and "Error A01" are not successively displayed, proceed with A11-1 Flow Diagram

The referenced flow diagrams simply get you to disconnect some cables and check some voltages, resistances, etc.