HP 4145B Semiconductor Parameter Analyser - Display shuts off - Page 1
Forum section: electronics / repair

author: fourierpwn
author_rank: Regular Contributor
timestamp: June 27, 2017, 08:33:25 am
content: 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.

author: IRFP460
author_rank: Contributor
timestamp: June 27, 2017, 09:04:47 am
content: 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!

author: fourierpwn
author_rank: Regular Contributor
timestamp: June 27, 2017, 02:18:24 pm
content: 4145B is way before LCD days!Classic green phosphorous CRT

author: MosherIV
author_rank: Super Contributor
timestamp: June 27, 2017, 02:31:57 pm
content: 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

author: alm
author_rank: Super Contributor
timestamp: June 27, 2017, 02:48:15 pm
content: 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.

author: fourierpwn
author_rank: Regular Contributor
timestamp: June 27, 2017, 03:48:02 pm
content: Quote from: MosherIV on June 27, 2017, 02:31:57 pmThanks, 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.

author: alm
author_rank: Super Contributor
timestamp: June 27, 2017, 04:20:49 pm
content: Dave at Artek Manuals appears tosell a 4145B service manual with schematics.

author: tec5c
author_rank: Frequent Contributor
timestamp: June 27, 2017, 04:36:59 pm
content: Quote from: alm on June 27, 2017, 04:20:49 pmThanks! Ithink I may just buy thisjust purchased this

author: tec5c
author_rank: Frequent Contributor
timestamp: June 27, 2017, 11:41:52 pm
content: 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 instrument2) Disconnect A11J23) Wait at least two minutes4) 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 DiagramThe referenced flow diagrams simply get you to disconnect some cables and check some voltages, resistances, etc.