93XX Series RTC Battery

Step 2 – CPU Board Removal Disconnect the ribbon cables from the CPU board. There is a large one in the rear, and two in the front. These cables conne...

0 downloads 80 Views 838KB Size
Replacing the ML2430-HS1 MnLiO2 Rechargeable Lithium RTC battery in the LeCroy Series 93XX Digital Storage Oscilloscopes Note: Under no circumstances should a non-rechargeable battery be installed in the CPU board as the circuitry on the board trickle charges the battery. Charging a non-rechargeable (primary) Lithium battery can cause the battery to overheat and explode. Best case it would make a mess of the insides of your scope. Worst case you would rather not know. There are only so many perfect scopes in this world and it would be a shame to ruin yours. (Paraphrased with great liberty from the movie “The Princess Bride”) Just like in school read this entire document before doing anything. Take your time. Now for the standard disclaimer: NOTE: USE ONLY THE CELL SPECIFIED BELOW. THE INFORMATION IN THIS DOCUMENT IS BELIEVED TO BE CORRECT, HOWEVER, AS YOU MIGHT GUESS THE AUTHOR CANNOT ASSUME RESPOSIBILITY FOR YOUR WORK. IF YOU HAVE DOUBTS IN YOUR ABILITY TO DO ANY OF THE WORK REQUIRED, PLEASE FIND A COMPETENT ELECTRONICS TECHNICIAN WHO KNOWS HOW TO USE A SOLDERING IRON AND HOW TO WORK AROUND CRTS! Step 1: Turn the scopes’ power off and disconnect the power plug. It is best to remove the CPU card from the instrument to replace the battery. This will greatly reduce the risk of solder balls or solder splashes from falling into the instrument. Believe me, it can happen, and you may not even notice it until you turn on the power! The section of the 9314 series maintenance manual dealing with disassembly of the instrument is duplicated below for reference. Warnings: FIRST OF ALL WEAR SAFETY GLASSES WHEN WORKING WITH CRT’S AND HOT SOLDER •

• •

Take note of all cables that you disconnect so that you know exactly how they were connected. A digital camera is great for this purpose! Take special care with ribbon cables that run along the backside of circuit boards to prevent scraping or puncturing the cable insulation. Troubleshooting intermittent shorts is never fun. Do not place too much sideways pressure on any of the control knobs as the shafts of the encoders are plastic and can be sheared off easier than you might think. Before removing the CRT/Front Panel Assembly, discharge the second anode (HV) connector to the frame ground (metal rear panel chassis) of the scope. Disconnect all of the connectors before removing the CRT. When removing, support the CRT by the bell, never the neck. Take extra care that you do not bump the neck or move the deflection yoke when removing the assembly. If you are lucky enough to have a front panel cover use it to cover the CRT/Front Panel Assembly after you remove it. If you do not have the front cover, get some 2 inch soft polyurethane foam (the type used for upholstery) to set the assembly upon. Put the CRT/Front Panel assembly aside. For added protection, find a strong cardboard box that is taller than the CRT/Front Panel Assembly and large enough to cover the entire assembly. Place the box over the assembly, inverted bottom side up. Keep pets and children of all ages away from the work and parts staging area until the scope is fully reassembled.

Step 2 – CPU Board Removal Disconnect the ribbon cables from the CPU board. There is a large one in the rear, and two in the front. These cables connect to the CRT driver board and the front panel board. You probably disconnected them when you separated the CRT/Front Panel Assembly. Pull the CPU board straight up. You may have to gently rock the board back and forth to free it from the connector. If should take very little force to free the board. Measure the new battery voltage with a DMM. Note the reading. Chances are that the battery will arrive to you partially if not fully charged. Remove the old battery and solder the new one in place noting the position of the tab. The correct position is positive side up. After soldering the battery in place, measure the voltage by placing the positive probe on the top of the battery, and the negative probe on one of the large square ground pads near the gray connector at the bottom of the board. See the picture of a typical CPU2 PCB below for details. The voltage that you measure should be fairly close to the voltage that you measured above. If your measured voltage is drastically different, then you may have a short or leakage in the battery circuit or the battery has a weak surface charge. Time to get out the CPU schematics and do some troubleshooting. This exercise is left up to the reader as they say… Re-install the CPU board and reassemble the scope in reverse order. Refer to the manual reprint section below for details. Take care around the CRT (don’t bump it) and the knobs/encoder shafts as stated earlier. When re-installing the CRT/Front Panel Assembly, the hardest part of the re-assembly process is locating the position of the MC01 front slot that guides the PCMCIA card insertion Step 3 – Check Out Power up the scope and go to the utilities menu and set the time and date. You might want to check the battery voltage between the positive terminal and any convenient ground and make note of the reading. After being powered on for several hours, you can recheck the battery and confirm that it is being charged. When measured with the instrument power off, the voltage should be greater than the voltage noted when the battery was measured as received. You will also notice that on the system status screen, the last digits of the serial number are all zeros. To fix this you need a GPIB card and a PC running LeCroy ScopeExplorer. Use the terminal mode to send commands and refer to the “Scopes Tips and Tricks” Excel spreadsheet (located in the files section of the LeCroy_Owners_Group) under the GPIB tab to reset the serial number.