Multimeter Solartron Schlumberger 7150 reboots constantly - but not in I-Mode - Page 1
Forum section: electronics / repair

author: zaphod_beeblebrox
author_rank: Newbie
timestamp: May 04, 2025, 09:07:38 am
content: Dear forum,I have a Solartron 7150 multimeter. In 2015, I replaced the power line filter and the LEDs. Since then, I have moved, and the device was stored away for several years. I have now set up my new home lab and wanted to bring the multimeter back into use. Unfortunately, it is now experiencing a problem…It automatically reboots/restarts/resets approximately every 2 seconds. The display test runs through, the relays click, and it restarts again.I have already conducted several tests and observed the following:- The optocouplers are fine. I temporarily desoldered one and then received a FAIL 1 error. Although I have installed new ones now, the old one was definitely not defective.- If I press the current measurement ("I") button during the reboot, the meter starts up and does not reboot. Resistance and voltage measurements cause an immediate reboot.- UART communication takes place between the analog and digital boards. I can clearly see it with the oscilloscope, likely at 9600 baud. The data bursts correspond to the display update (only detectable in current mode; in voltage and resistance modes it immediately reboots).- In my opinion, the reset is triggered by IC108. At pin 12, I see either one or two signals dropping to 0 V. I cannot say why sometimes one and sometimes two signals appear; I have not yet been able to reproduce this consistently. I estimate about 80% of the time it’s two signals in quick succession and 20% of the time just one.- Pin 1 of IC108 receives the signal from the optocouplers on the digital board.The fault seems to lie somewhere in the analog section. I do not understand where the reset originates because, as I understand it, IC108 should only reset when:a) Power is applied (reset circuit via resistor in IC104 and C103)b) No signal is present from the digital board at pin 1Both the digital and analog boards have many test points. Unfortunately, I can find no documentation specifying which signals should be measured at these. Does anyone have any information on this?I have read the threadhttps://www.eevblog.com/forum/projects/schlumberger-7150/.Unfortunately, many responses from the original questioner are missing (for whatever reason).So far, I have replaced:- C103 (a tantalum capacitor)- Power supply electrolytics on the digital board (though these were still 100% fine, as I found out only after removal)All voltage regulators provide clean voltages well within tolerance; no oscillations detected.I would really appreciate any help. This multimeter has always served me very well.Here is the maintenance manual incl. schematics:http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Solartron/Solartron_7150_Maintenance_Manual.pdfThank you!

author: coromonadalix
author_rank: Super Contributor
timestamp: May 04, 2025, 10:48:37 am
content: if the supply voltages seems stables and no noises on themhave you checked the watchdog operation ?you have 2 similar reset circuits, one at page 2.17 near IC510 and the other at p 2.16 since reset is driven low,i would have removed the 2x ls197 chips (IC508 and IC517) to stop the reset from happening and try to find where it does come from, if the watchdog triggers or the anti lock feature does kick inaround ic 103 you have asterisk notes about some parts and link #3 do you have theses parts or just the link #3

author: zaphod_beeblebrox
author_rank: Newbie
timestamp: May 04, 2025, 11:31:05 am
content: Yes, I've tested the Watchdogs:- Digital doesn't fire- Analog fires (IC108, 74LS197) on QD, Pin 12. Sometimes once, some times twice.What do you mean with Anti-Lock-Feature?The parts with an asterisk are all populated.I've desoldered R104 but the the IC103 (Analog CPU) doesnt boot and the Logical CPU will send FAIL 1 to the Display (same as removed communication link over UART between digitgal and analog CPU).I'll try do desolder IC108, 74LS197.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 04, 2025, 12:33:35 pm
content: they say in the manual you have something to avoid cpu lock section 2.8 and goes down to the watchdog ...if you say the meter was okay before storage and now, if nothing else happened and it is now resetting ... i would not be surprised of any capacitor going bad ...as you know, check all psu's voltages and noises in them, to be absolutelty sure the main mcu is not affected bay any ripple, checking the watchdog and reset as you knowthe manual gives explanations about many things, witch is rare nowadaysi dont know if this meter can work without the analog part, just to be sure all is okay on the digital side .. no eeprom eprom degradationyeah you do get some fail warnings damn ... you need to get the reset line high on each mcu ... the 100 ohms is normally a very strong pull up ?? unless tr101 is weak in some ways ?ic104 6.8k resistors are good ? with the tantalum 22uf you changed it should provide a small timed charge to the CLR pin, should be wrote in the manual ? and ic107 not sure where its reset line goes ? seems grounded ? it passes the CLK line thru ic102 to the ic108 ls197...'oh old thread about same symptoms no end results ?https://www.eevblog.com/forum/projects/schlumberger-7150/other threadshttps://www.eevblog.com/forum/repair/glitchy-enertec-7150-(-solartron-schlumberger-)/msg1287379/#msg1287379https://www.eevblog.com/forum/repair/solartronschlumberger-7150-plus-_fail-1_/you have a manual with more pages at:https://dn720404.ca.archive.org/0/items/manualsplus_01010/manualsplus_01010.pdf

author: zaphod_beeblebrox
author_rank: Newbie
timestamp: May 04, 2025, 07:24:31 pm
content: When I short circuit the Voltage and Resistor inputs to ground (left most sockets), the Multimeter starts up normally, shows 0.000x V or Ohms and will not reboot. When measuring a voltage (I’ve only tried an fully charged Li-Ion cell laying around) the device reboots. There must be an error in the analog part…

author: zaphod_beeblebrox
author_rank: Newbie
timestamp: May 04, 2025, 07:45:24 pm
content: Quote from: coromonadalix on May 04, 2025, 12:33:35 pmQuote from: coromonadalix on May 04, 2025, 12:33:35 pmQuote from: coromonadalix on May 04, 2025, 12:33:35 pmNo it can't. If the analog part is not connected (or not responding via UART over optocoupler the digital part will show "FAIL 1" on the display.Quote from: coromonadalix on May 04, 2025, 12:33:35 pmTR101 is fine. IC107 Pin11(Rest) is tight to 0V, it is "allways running" because the Reset on that IC is active on high. It's just a frequency generator.IC104 is fine. I've got 13.6k (two resistors in series).Quote from: coromonadalix on May 04, 2025, 12:33:35 pmI've red all of them. But no solution to my problem...

author: coromonadalix
author_rank: Super Contributor
timestamp: May 05, 2025, 09:53:21 am
content: Quote from: zaphod_beeblebrox on May 04, 2025, 07:24:31 pmopen ground(s) bad solder you would need to read all the analog part functionality and understand each input section(s) ohms volts etc ... you have current generators and may thingsi'm still doubting if the calibrations / memory settings, something like this has gone bad, corruption .... when it is not resetting, are you able to enter calibration modei had a tek dm5120 in the past, it was not okay until i rewrote the calibrations in the eeprom ... even having eeprom dumps did not work ...

author: unseenninja
author_rank: Regular Contributor
timestamp: May 05, 2025, 07:19:55 pm
content: My guess would be that the firmware on the analogue board (or perhaps even the digital board) is corrupted. I'd suggest getting the EPROMS out of both boards, read them and see if the checksums match those from known good firmware.

author: JuOOLs
author_rank: Contributor
timestamp: May 06, 2025, 08:31:12 pm
content: I've got a unit i bought from ebay that just resets in the same manner; I also have a fully working unit; so I tried the bad unit digital board in the working one and it worked ok; so I know it's the analog board; I swapped the cpu from the bad analog board into the good unit analog board and it worked ok. I suspected maybe bad eeproms so I managed to read some data out from those - not sure if the data is correct or whether the cpu likes it.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 06, 2025, 11:54:25 pm
content: https://www.ko4bb.com/getsimple/index.php?id=download&file=01_ROM_Images_and_Drivers/Solartron-7150_Plus_ROM_Image.ziphttps://www.ko4bb.com/getsimple/index.php?id=download&file=01_ROM_Images_and_Drivers/Solartron_7150_Plus_ROMs.zipmaybe in theses

author: JuOOLs
author_rank: Contributor
timestamp: May 10, 2025, 01:30:21 pm
content: "I've got a unit i bought from ebay that just resets in the same manner; I also have a fully working unit; so I tried the bad unit digital board in the working one and it worked ok; so I know it's the analog board; I swapped the cpu from the bad analog board into the good unit analog board and it worked ok. I suspected maybe bad eeproms so I managed to read some data out from those - not sure if the data is correct or whether the cpu likes it."I've just replaced IC6 with a cheap pin-for-pin opamp and it's stopped the constant resetting; so now it's up and displaying stuff, but there's still more wrong with it.