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| Keithley 2306 Dual Battery Simulator Repair (maybe) |
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| Smokey:
Update..... Not out of the woods yet. The supply only successfully powers up intermittently. Especially if it's been sitting for a while and is cold, it will just hang at the "initializing" part of the remote display routine (as mentioned in the other repair thread, the display has it's own processor and is responsible for that "initializing" text). The remote display actually doesn't show the word "initializing", it just shows two flashing boxes in the middle, but I think it's the same thing. Power cycling sometimes results in the supply powering up successfully, and once it does it seems to power up consistently until I let it sit again. I confirmed the output is good when it's working and I can talk to it over GPIB. There is also one more piece to the puzzle, which is while the unit is working, sometimes the front panel display will actually come alive for a few seconds and show "Initializing", then die again. It never actually displays anything else even when I unplug the remote display while it's running, still just "Initializing" randomly flashing on the front. I had the thought that maybe something on the front panel display is shorting a supply rail or something, but having it completely unplugged has no apparent effect on the intermittent power up issue. I can also confirm that the issue looks like it's in the bottom processor/supply board (not the top output board). Even with the top board off, it still only powers up intermittently with the remote display showing the flashing boxes when it fails, and an error code when it does power up without the top board. A few people replaced the SRAM (R1LP0408CSB-5SC) in the other thread, but they are presently out of stock unless I want to buy a minimum of like 20 pieces at $15-$20 each. I'm still unsure why that would be causing an issue like this though. |
| picburner:
The two vertical flashing boxes you noticed on the display are normal and are shown just before the final splash screen appears. It should do this when everything is working normally. I had to replace the SRAM because the VFD display was stuck on 'initializing', this is not necessarily your case because at least sometimes your instrument starts up. .....Unless this is a symptom of an upcoming demise. |
| Smokey:
When the unit fails to power up, the two vertical boxes on the remote screen never go away. They just keep flashing until I power cycle. When it does power up, they are only there for a second or two before it kicks into operational mode. |
| Smokey:
Ok. New update. First a confession... The unit I'm working on is actually a 2308, which is the updated version of the 2306: https://forum.tek.com/viewtopic.php?t=94760#p153847 But... The bottom board that is giving me trouble is shared with the 2306, just with a different firmware build (it actually has the 2306 check mark on the silk screen for the board model). I haven't seen anyone here with a 2308 and I didn't want to scare everyone off since the board that's having issues appears to be the same. Update: I hooked a logic analyzer up to the serial lines on the display connector and captured the messages on Pin4 and Pin5: [UART decoding at 9600 8n1]. Pin4 is coming from the main processor because it gets traffic even when the cable to the display is unplugged. During successful power up without the top board installed: Pin4 has the following messages: \x0C\x01\x06\0 2308 ADDR 6 A01 00000 60HZ \x05\xFF\x06\0 start response model INVALID \x05\xFF\x06\0 start response rev INVALID \x05\xFF\x06\0 start response key INVALID \05\0\06\0 0.000 V #1 OFFOVERFLOW \05\0\06\0 0.000 V #1 OFFOVERFLOW ...[repeating] Pin5 has the following messages: 2304 B02 \x80 The overflow message is because the top board isn't installed. That doesn't happen when the top board is installed. When the unit doesn't power up correctly I get these messages, then nothing... Pin4 has the following messages: \x07 \t\x17 \x07 \x0C\x01\x06\0\x20 Pin5 has the following messages: 2304 B02 \x80 2304 B02 \x80 With the remote display plugged in, I get the following message on Pin4: \x0C\x01\x03 REMOTE PANEL ENABLED Does any of that set off any alarms for anyone? Any more ideas on ways to troubleshoot this? I haven't see any other diagnostic interfaces. |
| Smokey:
I'm not sure if this is relevant, but it is interesting. I took the front panel off of the unit and powered the unreliable internal VFD display from a 5.00V bench supply. When I power up the display this way, it pulls about 230mA and powers up every time. Right into "INITIALIZING". Nice and bright. This is very different from the random intermittent flashing that happens when it's being powered while connected to the unit. So I figured I would see what minimum voltage would turn on the display. And... It starts to operate unreliably at about... 4.95V. It won't turn on under 4.94. Well when I measure the +5VD rail at the display cable, it measures..... +4.95V. So that appears to be the (an?) issue with the display. Is this a design flaw where they used some parts in the display board without sufficient minimum voltage margin? Or has something aged to where it's unreliable now? Is this related to the system not powering up somehow (like whatever components won't power up in the display are also refusing to consistently power up on the rest of the digital section?). ::Update 7-24:: See msg bellow: https://www.eevblog.com/forum/testgear/keithley-2306-dual-battery-simulator-repair-(maybe)/msg4319182/#msg4319182 It looks like the undervoltage monitor IC on the display board is not working correctly.... |
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