Ok in case anyone is still interested I found the issue. The unit has a bad A&B Trigger chip - 155-0239-02
Hi everyone,
very good thread about the 2465B Scope. I got mine some years ago from ebay, a 2465BDV, which hat some options included (01, 05, 06, 09, 10), TV triggering, CTT, Word Recognizer Probe, DVM, GPIB). It came frome a production site, a lot of opreation hours, very few on/off cycles.
Just replaced all caps in the power supply, and the Dallas chip and the already leaking electrilytics on the A5 boards. Without this thread, I would never have noticed that, thanks!
I bought a Dallas chip from china, which was an old one with reprinted date code. And then one from a local distributor, which was fresh.
Because there were no pics of a BDV in this thread ( I think), I will post some:
Next post will be about my new scope, a 2445B.
Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany. I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).
But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.
I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.
Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany. I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).
But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.
I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.
Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Attached is a partial schematic of the 2465 focus/astig circuit. The 2445 should be similar. The first thing I would check is that -300V to Q1851 and Q1852. With the scope "cold" and power off hang your probe on that supply and see what it does as the scope powers up and warms up. Of course be VERY CAREFUL working around the high voltage supply. It can really hurt.
Now to my new scope, a 2445B (same as a 2465B except bandwith), Serial below 050000, so it has the old-style A5 board without SMD and without the leaking caps.
It looks almost like new, has below 900h of operation, came from a broadcasting station (sfb, Sender Freies Berlin) here in Germany. I did the bandwith "hack" on the A1 board (seems to work very close to my 2465B).
But it has a focus problem: When cold, it is extremely out of focus (and astig as well), it takes 5 to 10 minutes to get a sharp image. My other 2465BDV is perfect from the first second.
I did replace all caps in the power supply. But I am not sure if this problem was there before the re-cap, because this was one of the first things to do after getting the scope.
Any suggestions? I did check the supply voltages (J119 on Board A1), all stable from the beginning.
Attached is a partial schematic of the 2465 focus/astig circuit. The 2445 should be similar. The first thing I would check is that -300V to Q1851 and Q1852. With the scope "cold" and power off hang your probe on that supply and see what it does as the scope powers up and warms up. Of course be VERY CAREFUL working around the high voltage supply. It can really hurt.
I checked all voltages around Q1851 and Q1852, all very stable from the beginning. -300V is stable. Focus can also be bad if other voltages of the tube are wrong, so I have to look elsewhere.
There is a test point "74" with a warm-up voltage raising from zero to 15V (around U1890), I will try to understand what is done with this circuit.
Yep, that circuit is the grid bias to the CRT. If that's not correct it will affect the focus. Section 5-4 of the Service Manual describes the adjustments. If you have a slowly rising voltage at the output of that Op-amp concurrent with better focus I would check for leaky capacitors in that area.
Thinking out loud....try swapping the HV supplies between the 2 scopes. I believe they are the same part number. I've never pulled the supply in a 24XX so I don't know how difficult it would be.
If that doesn't fix it you basically only have one thing left. The CRT itself. If it were "gassy" (loosing it's vacuum) or has low emission it could cause an extended warm up time.
Thinking out loud....try swapping the HV supplies between the 2 scopes. I believe they are the same part number. I've never pulled the supply in a 24XX so I don't know how difficult it would be.
If that doesn't fix it you basically only have one thing left. The CRT itself. If it were "gassy" (loosing it's vacuum) or has low emission it could cause an extended warm up time.
Swapping the A9 (HV) boards did not change anything. 2465B sharp as ever, 2445B sharp 10 minutes from start. And it takes about one hour switched-off to get it fully out of focus again.
I have never heart of a bad 2465 CRT up to now. And it is bright from the first moment.
I will check the power supply again, because I think it was not having this problem before i replaced the caps in it, or at least not so bad. I think I would have noticed that.
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I will check the power supply again, because I think it was not having this problem before i replaced the caps in it, or at least not so bad. I think I would have noticed that.
Since there is no way to remove the RAM to read the contents, without losing the data, there must be a method for the scope to "restore" itself from a dead battery.
This might be possible through the GPIB interface; I do not remember. One of the 2465 series experts will know.I don't know about the 2565A/2467, but the EAROM in the 2456 can dumped via GPIB. By examining the EPROMs on the GPIB board I was able to figure out the following. It may be extensible to other models.
First, you have to enable the "special" commands:
key 0
Then you can dump the EAROM with the following command:
earom? <address to dump>[,<address to dump>,<...>]
This allows reading out of multiple locations in one command. For example, to dump the first 10 addresses:
earom? 0,1,2,3,4,5,6,7,8,9
Then the next 10:
earom? 10,11,12,13,14,15,16,17,18,19
And so on, until address 199. The first 100 locations are the EAROM on the main board, and the second 100 is the EAROM on the buffer board. This is the same as in the exerciser. The values should match.
The above commands return a line in the form (from the above example 0 to 9):
EAR 0:84,1:1993,2:10102,3:1893,4:10091,5:1798,6:1494,7:1420,8:9608,9:1431;
The return format is <address>:<value> and everything is in decimal. You can set an EAROM value by using the same format:
earom <address>:<value>
Trying to write multiple values in one line didn't work for me and crashed my scope. YMMV.
It would be interesting if someone could try this on a model other than a 2465(plain).
WARNING!! If you want to play with any of this, be careful not to overwrite overwrite the EAROM values until you've saved them with a screen capture! On my 2465 it DOES NOT MATTER if you have the the cal jumper set to off. These commands are surely hidden for a reason!
If you're even braver, there's another hidden query I've discovered called "BYTE?". It takes one argument and dumps that number of bytes from somewhere. I can't figure out what it's dumping, and I can't make it repeat itself except after a reboot. Eventually after several hundred bytes it causes my 2465 to reboot. I'm mentioning it because maybe that command will be useful on other models without EAROMs.
If anyone decides to try anything, please post your results. Obviously this needs a GPIB interface. I haven't found any equivalent method to write EAROM/NVRAM values from the screen, although now that I found it via GPIB it makes me suspect it's possible.
First thanks for your help here a small Video
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the next days i will test the scope