Author Topic: Just got a Tek 2465A, couple questions (how I screwed the calibration data)!!  (Read 6786 times)

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Offline alpher

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Hi, just got the 2465A CT in rackmount adapter quite cheaply . :)
Unit works, I;m reluctant to do much with it before changing the battery backup for the RAM chip, affraid to lose the calibration data.
I;m I right though? The dreadded test 4 fail on 2465B does it applies to 2465A as well?
Looking breiefly through service manual looks like the auto calibration procedure may
"populate" the RAM with the correct values somehow?
Anyway as I said so far there are no startup errors displayed, I measured the battery voltage to be a healthy 3.5+ V on cr2770.
Should I be worried and replace the battery first (date code from 87) ?
Also since it came in rackmount adapter I'm missing the handle, looks though that to get the handle I may have to get a donor scope, hoped that maybe handle from my TDS340 will somehow fit, but 2465 is ~2" narrower :(
So any one knows if other series (beside 24xx) will fit?
Maybe 22xx?

Thanks.
« Last Edit: March 27, 2018, 05:18:44 pm by alpher »
 

Offline z01z

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Re: Just got a 2465A, couple questions
« Reply #1 on: February 26, 2018, 11:10:10 am »
The battery backs up the SRAM holding the calibration constants, so yes, you can get those errors if the battery is depleted.
The tricky part with this kind of battery is that you cannot really know how much juice is left, according to the datasheet the output voltage is flat then it drops suddenly.
 
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Offline alpher

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Re: Just got a 2465A, couple questions
« Reply #2 on: February 27, 2018, 03:50:51 am »
So you're sayi'n that the RAM data is "unrecovearable", so to speak ?
Also, I removed the cooling fan to lubricate the bearing as it was pretty noisy.
 Just to make sure, the fan should suck the air out of the case?
Thanks.

 

Offline linux-works

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Re: Just got a 2465A, couple questions
« Reply #3 on: March 26, 2018, 05:33:38 pm »
using this thread to ask about my own 2465a, as well (hope its ok).

I bought a new battery for the cal data ram board; I have not opened the scope yet and the scope seems to work right now, so I assume the cal data is still intact.

just checking before I start, to make sure I understand fully: is it true that I don't need to keep the scope plugged in, power on, while doing the work on this board for the battery swap?

I've read about avoiding grounded soldering irons and all that - but my plan is to remove the board from the powered-down scope, have the board sit on my workbench, tack wire some temp connections to a holding battery of some kind, clip out the old battery and solder the new one in its place.

if the board is NOT grounded at all, just floating - and sitting on my bench - there's no need to worry about having a grounded soldering iron, right?  I can't see any reason to worry as long as I don't short the battery while I'm doing the work.

I've also read about people using a small series R on the new battery so that it will limit how much current it might push out (if the old one is low-z; but I'm not sure an old battery would be low-z anymore!).  is this being overly cautious?  same about a series anti-backfeed diode.  so I really need to worry about such things, given that the swap will take a minute or less, with the other battery in parallel?

before I start, wanted to be fully sure so that I don't make any mistakes.
 

Online tautech

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Re: Just got a 2465A, couple questions
« Reply #4 on: March 26, 2018, 07:05:38 pm »
I don't get it.  :-//

What's wrong with this thread:
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

You'll each get a wider audience that can assist you with these great scopes.
Is the A really that much different ?
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Offline alpher

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Re: Just got a 2465A, couple questions
« Reply #5 on: March 27, 2018, 12:41:26 am »
Unfortunately as far as memory backup goes A it's a very different animal than B or plain 2465.
I don't have good advice at this point, preparing a longer post about it.
Long story short, I did lose the calibration constants data!!!!
Even though I thought I have a foolprof method of changing a battery, sheet did happen  >:( >:(
If you're willing to wait a day or so I will post a longer post with pictures of what and how I did it.
Maybe i't will help you avoid the disaster.
« Last Edit: March 27, 2018, 12:43:48 am by alpher »
 

Offline MarkL

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Re: Just got a 2465A, couple questions
« Reply #6 on: March 27, 2018, 02:20:42 am »
I don't get it.  :-//

What's wrong with this thread:
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

You'll each get a wider audience that can assist you with these great scopes.
Is the A really that much different ?
Unfortunately as far as memory backup goes A it's a very different animal than B or plain 2465.
...
That thread started as a tear down, but it seems to have become a catch-all for many of the 2445, 2465 (plain/A/B), and 2467 discussions.  The models share many of the same problems and approaches for fixing.

One suggestion in there is to use Exerciser 02 to flip through all the calibration entries that are in the cal NVRAM and take a video of it.  Getting the numbers back in the RAM is a different problem, but at least you have them should the NVRAM replacement go wrong.

Sounds like it's too late in your case, alpher, but maybe not for linux-works.

If you have the GPIB interface, user korlatos recently reported in that thread you can dump the cal values via GPIB.  They didn't say, but you can probably put them back via GPIB too.
 

Offline MarkL

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Re: Just got a 2465A, couple questions
« Reply #7 on: March 27, 2018, 02:28:59 am »
So you're sayi'n that the RAM data is "unrecovearable", so to speak ?
Also, I removed the cooling fan to lubricate the bearing as it was pretty noisy.
 Just to make sure, the fan should suck the air out of the case?
Thanks.
If the NVRAM data is gone the scope will need a calibration.  I have seen posts of people using NVRAM contents from other scopes of the same model, but I can't agree it's a good approach.

Yes, the fan sucks air out of the case and blows it out the back.
 

Offline alpher

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Re: Just got a 2465A, couple questions
« Reply #8 on: March 27, 2018, 02:30:30 am »
Again, thread in question(is  it somehow a sacred thread ?), doesn't do much for the 2465A users.
I guess it's all in the numbers, thre were simply many more B's made, even plain 2465's.

 

Offline MarkL

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Re: Just got a 2465A, couple questions
« Reply #9 on: March 27, 2018, 02:46:05 am »
No, not a sacred thread at all.  (Is any thread?)  Just information and various repairs on different models of that series piled in one place.  It just grew that way.
 
The title is misleading, so sometimes it helps to point people to it.  Might help, or might not.
 

Offline linux-works

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Re: Just got a 2465A, couple questions
« Reply #10 on: March 27, 2018, 04:14:53 am »
I have a 2465b and I went thru the dallas chip copy and replace exercise.  it was not under stress since you can easily read the data, and then just copy it to a new chip that was $25 or less.  so, yeah, I'm familiar with the 'b' thread but I don't see a lot of 'a' talk and the 'a' is quite diff on that battery stuff.

its also WAY too long and unpractical to read thru, so its not worth more posts there (unless its very clearly a 'b' post).

anyway, I can wait a few more days.  I have a battery that came from mouser but have not touched it yet.  the stuff I read is scary, about it wanting to explode if your short the terms and that its for military use only, these days, and almost never civilian.  really makes me feel comfortable handling such a thing, lol..

I'll wait for your post on your method and what I should avoid.  thx.
 

Offline linux-works

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Re: Just got a 2465A, couple questions
« Reply #11 on: March 27, 2018, 04:18:01 am »
oh, and while I'm at it, anyone have the part # from mouser/digikey/etc for a proper 'a' replacement fan?  I think it will take the same as a 'b' and I remember ordering one from either of those 2 places, but it was several years ago.  if you have the part # handy, that would be appreciated.  might as well do the fan while I do the battery, at least on first look.
 

Online tautech

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Re: Just got a 2465A, couple questions
« Reply #12 on: March 27, 2018, 08:13:12 am »
I don't get it.  :-//

What's wrong with this thread:
https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/

You'll each get a wider audience that can assist you with these great scopes.
Is the A really that much different ?
Unfortunately as far as memory backup goes A it's a very different animal than B or plain 2465.
...
That thread started as a tear down, but it seems to have become a catch-all for many of the 2445, 2465 (plain/A/B), and 2467 discussions.  The models share many of the same problems and approaches for fixing.
Exactly.

IMHO posters here are doing a disservice by not keeping all the info about these great scopes together and not scattered and lost deep in forum archives.

its also WAY too long and unpractical to read thru, so its not worth more posts there (unless its very clearly a 'b' post).
:o
What's up with you guys ?  :-//

Shit, I've read it and studied it a couple of times over the years just for interests sake and have never even owned one.

This and that thread should be merged by the moderators to keep all the good info in one place IHMO.  :horse:
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Online tggzzz

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Re: Just got a 2465A, couple questions
« Reply #13 on: March 27, 2018, 08:34:44 am »
its also WAY too long and unpractical to read thru, so its not worth more posts there (unless its very clearly a 'b' post).

Translation: my time[1] is more valuable than your time[2].

That's not a way to get people to help you, nor a way for you to learn (unless, I suppose, you think stackexchange's "which button should I press" ethos is good).

[1] reading and researching
[2] writing and repeating
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
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Offline alpher

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Re: Just got a 2465A, couple questions
« Reply #14 on: March 27, 2018, 01:09:44 pm »

[/quote]
That thread started as a tear down, but it seems to have become a catch-all for many of the 2445, 2465 (plain/A/B), and 2467 discussions.  The models share many of the same problems and approaches for fixing.
[/quote]

Unfortunately this is not true in this case, simply put, battery backup of the calibration constants is done very differently in the A model.


In the B, provided that the dallas chip still works you can just pull it of the board, read the data using any cheap eprom reader and voilla!!
On the A it's just a touch more convoluted.
I did read the sram memory, too bad it was only after it went scramble |O |O
Anyway I edited the title of the thread, preparing the pics that I took to post how I did it.

 

Offline linux-works

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some of us disagree that long thread become useless due to their length and chat nature.

if it was pure tech and no chit-chat, that would help, but this is a FORUM and not a wiki site, so its to be expected of course.

still, those that enjoy pouring thru hundreds of pages of chat text to find the gems, more power to you, but I don't have THAT kind of time on my hands, these days; it can take hours to go thru a thread like that.

(on many forums, once a thread reaches a certain size, its locked.)

hey, if that thread could get distilled into a simple FAQ, that would be a true service.  but to blame people for not wanting to spend hours going thru it, seems a bit much.  its not a 10 page thread we're talking about, folks, remember that.  its just too friggin long and unwieldly as a REFERENCE thread.
 

Online tggzzz

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some of us disagree that long thread become useless due to their length and chat nature.

if it was pure tech and no chit-chat, that would help, but this is a FORUM and not a wiki site, so its to be expected of course.

still, those that enjoy pouring thru hundreds of pages of chat text to find the gems, more power to you, but I don't have THAT kind of time on my hands, these days; it can take hours to go thru a thread like that.

(on many forums, once a thread reaches a certain size, its locked.)

hey, if that thread could get distilled into a simple FAQ, that would be a true service.  but to blame people for not wanting to spend hours going thru it, seems a bit much.  its not a 10 page thread we're talking about, folks, remember that.  its just too friggin long and unwieldly as a REFERENCE thread.

That doesn't change the basic point that the "my time is more valuable than your time" attitude is very irritating for many people.

When I was young it was necessary to learn how to glean all the information possible from the meagre available sources.
Nowadays the key skill for young people is how to speedily disregard most of the available "data", thus allowing you to concentrate on the "information".

Hence "speedreading" is a key skill.
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline MarkL

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...
On the A it's just a touch more convoluted.
I did read the sram memory, too bad it was only after it went scramble |O |O
Anyway I edited the title of the thread, preparing the pics that I took to post how I did it.

Well, there were a couple of postings specifically on 2465A NVRAM battery replacement in that thread (Jan 8, 2016).  Using the "Print" format of the thread and then the browser search tools is one way to find stuff.

But it doesn't really matter at this point.  I for one am interested in hearing about your procedure and how you figured out how to read the SRAM.  Thanks for sharing your information and experience.
 

Offline linux-works

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That doesn't change the basic point that the "my time is more valuable than your time" attitude is very irritating for many people.

I just don't see it that way and we'll have to disagree and leave it at that.

I checked to see if I could find the part # for the fan I ordered years ago, maybe still in my email from mouser or something, but could not find it.  but when I read forum posts asking for info, if I happen to have that info handy, I post it and don't give the poster a hard time about it, either...  its how we help each other online, rather than just beat each other with a stick and tell them to RTFM (which is really what you are saying).

if you don't want to help, don't help; but its uncalled for to criticize other members for not wanting to spend hours in a chatty thread.  if you don't want to supply the info or help, don't.  commenting in a thread just adds noise (like this, sad to say) and just makes extracting info even harder for the next guy...

 

Offline alpher

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OK, here's the scoop:
Allways wanted to have a good analog Tek scope, was looking for a 2465B but they are a little pricey for my taste.
So I bought an A instead and quite cheaply I may add, took a gamble really because of blurry pic and the usual description "removed from a working environment"  ;).
To my pleasant surprise when it arrived not only it worked just fine (it did  |O ) but looked really clean both outside and inside, I mean not a speck of dust ! Here's a pic of the A5 control board before removal:


I did not clean it in any way, cause it looks mint to me.
I meassured the battery voltage and it was very healthy 3.6V despite battery date code from 1987 !
Decided to change that damn battery anyway  >:( , ordered one from Allied and waited.
When I got it I just removed the A5 board from the scope, carefully not to short the battery or sram pins to the standoffs. I had this 18650 laying arround charged, prfect voltage 3.6V so I used it as a temporary backup during battery replacement. Here you can see it attached by soldered ! leads to one of the standoff grounds and cathode of CR2770 . There is also an 1N4007 in series with the positive lead ( just in case) .



Measured voltage, everything was fine so desoldered the original battery using my hakko 808, checked voltage again, and again no problems at all. Soldered a new battery, check the voltage, desolder temporary leads, check the voltage, everything seemed peachy, here's a pic of the new battery on the A5 board:



Very well, here's what I saw when I turned the machine on:


 :'( :'( :'( :'( :'(
Did I deserve it?

 

Online tggzzz

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That doesn't change the basic point that the "my time is more valuable than your time" attitude is very irritating for many people.

I just don't see it that way and we'll have to disagree and leave it at that.

I doubt we will agree, but others do share my weltanschauung - including some in this thread!

Quote
... and tell them to RTFM (which is really what you are saying).

No, that is not what I am saying.

I am saying that if you know what you could do but can't be bothered to do the legwork, what make you think we can be bothered to do legwork helping you?
There are lies, damned lies, statistics - and ADC/DAC specs.
Glider pilot's aphorism: "there is no substitute for span". Retort: "There is a substitute: skill+imagination. But you can buy span".
Having fun doing more, with less
 

Offline MarkL

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...
Here you can see it attached by soldered ! leads to one of the standoff grounds and cathode of CR2770 . There is also an 1N4007 in series with the positive lead ( just in case) .
...
Are you sure that screw pad you soldered to is connected to the ground of the board?  Some of those pads could be floating.
 

Offline alpher

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When I saw what I've done was quite upset >:(, so much so that I let it sit for a couple of weeks or so.
You must know that this is a purelly hobby for me, and not only I lack the equipment necessary to calibrate such a scope but probably also skills to do it.  :(
Then I came up with an idea that if the sram got scrambled by me momentarily shorteing somehow the vcc pin during the whole procedure it may be scrambled only by a couple of bits or so and by reading it I may be able to figure out what was there originally.
Rigged something like this:




Read the memory no problems at all, actually I read it mor than 10 times switching on/off between the reads changing settings ETC.
Just to have a general feeling what's going on inside. Found out that the las 512 bytes or so never change and probably there the cal constants are stored.
When I figure out how to properly paste HEX data I'll post the listing.
T.B.C.
 

Offline alpher

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OK, here's the last 512 bytes of the SRAM:
Code: [Select]
Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F

00001E00  EF 22 00 FD FE 02 85 FA 7F A0 04 DE EB 80 00 7F  ï".ýþ.…ú. .Þë€..
00001E10  7F 04 41 DF 9F 02 10 BD 15 A0 04 BF D5 88 00 DF  ..Aߟ..½. .¿Õˆ.ß
00001E20  FD 20 00 FD FF 34 13 7B BE 84 48 FB 7D 00 01 FD  ý .ýÿ4.{¾„Hû}..ý
00001E30  F2 C0 40 EF FF 03 40 D9 FB 00 02 BB 7D 00 04 9F  òÀ@ïÿ.@Ùû..»}..Ÿ
00001E40  BE 90 90 F7 FB 08 83 3F 9F 40 0C FF BF 00 88 FF  ¾..÷û.ƒ?Ÿ@.ÿ¿.ˆÿ
00001E50  FF 08 22 EF FF 42 42 AF 5F 01 00 59 FF 0A 40 F6  ÿ."ïÿBB¯_..Yÿ.@ö
00001E60  BF 0A 24 FD 7F 18 28 B7 FE 84 80 FF 7F 00 40 FF  ¿.$ý..(·þ„€ÿ..@ÿ
00001E70  FB 18 00 4F 97 13 02 BF FA 8A 23 FF F7 02 05 F7  û..O—..¿úŠ#ÿ÷..÷
00001E80  D7 00 61 7F DD 01 88 B7 3C 20 21 FE DD 01 A8 FF  ×.a.Ý.ˆ·< !þÝ.¨ÿ
00001E90  BF A1 00 BA FF 40 48 3F FF 04 00 9B DF E1 92 FB  ¿¡.ºÿ@H?ÿ..›ßá’û
00001EA0  FF 00 06 7F FD C4 20 FD FE 26 10 79 FE 32 84 8F  ÿ...ýÄ ýþ&.yþ2„.
00001EB0  EB 00 30 FF EE 00 05 7F DF 80 81 B7 BD CA 40 DF  ë.0ÿî...߀.·½Ê@ß
00001EC0  AE 26 04 D7 F6 06 82 F7 76 10 02 DC F7 E1 10 7F  ®&.×ö.‚÷v..Ü÷á..
00001ED0  DD 31 04 EB D7 2A 41 FB DE 06 20 DD BE 00 20 7F  Ý1.ë×*AûÞ. ݾ. .
00001EE0  FD 01 14 F5 7F 04 60 FF FF 90 0C FF EE 80 8C BF  ý..õ..`ÿÿ..ÿ¿
00001EF0  DB 00 91 57 BF 10 4A FF DF 52 A0 DF 7E 08 40 3E  Û.‘W¿.JÿßR ß~.@>
00001F00  FF 00 00 B7 FF 00 02 FF DF 84 08 FB F7 30 14 FF  ÿ..·ÿ..ÿß„.û÷0.ÿ
00001F10  FF 0A 10 7B FC 0A 00 DF C7 A1 C2 FF EF 20 00 FF  ÿ..{ü..ßÇ¡Âÿï .ÿ
00001F20  FD 62 00 7F 7F 44 20 AF F7 80 80 B5 FF 41 20 DD  ýb...D ¯÷€€µÿA Ý
00001F30  FF 30 00 FF E7 03 10 FB B7 00 10 DF F5 40 61 FF  ÿ0.ÿç..û·..ßõ@aÿ
00001F40  FA 00 21 3F FF 40 50 BF 8F 05 B0 9F CF 00 00 DB  ú.!?ÿ@P¿..°ŸÏ..Û
00001F50  7E 0A B0 37 FE A0 08 7F 7F 90 38 ED FF 49 32 FB  ~.°7þ ....8íÿI2û
00001F60  EF 00 20 EB 3F 03 10 FF 7D 00 31 6F FB 10 1A FF  ï. ë?..ÿ}.1oû..ÿ
00001F70  F7 10 C1 D7 FF 50 11 FD FE 50 02 BD FE 22 00 EF  ÷.Á×ÿP.ýþP.½þ".ï
00001F80  FF 40 08 DF EB 04 00 DF 3F 80 08 AD 9F 01 00 DE  ÿ@.ßë..ß?€..Ÿ..Þ
00001F90  F7 10 89 7E FF E4 40 E3 FC 22 00 FF FF 00 80 5F  ÷.‰~ÿä@ãü".ÿÿ.€_
00001FA0  E3 C2 00 EA DF 40 01 BF 7D 10 18 7D FF 00 80 FE  ãÂ.êß@.¿}..}ÿ.€þ
00001FB0  EF 02 00 BF DF 00 0A FF F7 08 D0 FF FE 80 00 5F  ï..¿ß..ÿ÷.Ðÿþ€._
00001FC0  FB 01 50 5D F7 10 01 7F 3F 00 14 EF D7 00 08 6F  û.P]÷...?..ï×..o
00001FD0  F7 50 02 BD FE 80 08 FF F6 60 14 ED AF A4 06 EF  ÷P.½þ€.ÿö`.í¯¤.ï
00001FE0  7F 02 00 E7 FF 82 08 FF FE 04 21 3F FD 00 44 F7  ...çÿ‚.ÿþ.!?ý.D÷
00001FF0  FF 20 00 7D FF 10 20 FD BE 24 10 F4 BF A0 0A FB  ÿ .}ÿ. ý¾$.ô¿ .û

These are the calibration constants for the scope, I verified it by doing calibration ram exerciser 02 :

https://youtu.be/-Upu0b4jBlA

As you can see it matches, from the service manual I know that the data is 14 bits (including parity), that's a maximum 3FFF in hex !
As you can see lots of it is way higher that that  :-// also parity is all over the place.
I'm at loss how it got scrambled so badly?
Attached a ful 8K image of the memory, maybe someone will be able to figure it out?
 

Offline MarkL

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It looks like you have a diode to power up the SRAM.  Did you read the SRAM while the scope was powered off?

If so, that's interesting that it worked given that the programmer was driving all those off components through their I/O pins.

What are the resistors doing?
 


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