Oscilloscope YOKOGAWA LD1640

[GGMM]

Good morning,
I recovered a YOGAWA LD1640 oscilloscope. It looks very nice on its design and has 4* 200MHZ channels and a 6.4 inch tft screen.
I just got it, it looks a bit worn, but I’ll clean it.
I’m quite capable of completely demonizing it and exposing it.
Of course, there is a problem  because it would be too simple.
It presents a calibration error when starting and also if we try the procedure. (NB: It automatically calibrates at regular intervals)
You have a lot of tests
Memory test gives this error; ACQ_12 Med WA:0 RA:0 WD:1 RD:0
I read on forums that calibration problems on other oscilloscope type tektronic that it could come from the capacitors leakage  on the acquisition board on the 12v  or  5v ?
Your opinion
If you had this problem, give me a lead. Anyway, we’ll have to show for inspection.
cdt

[GGMM]

I add:
The lithium batterry is good. 3.6V

[GGMM]

I found this post very interesting
https://www.eevblog.com/forum/testgear/yokogawa-dl1740-oscilloscope-repair-teardown/

i think there is here some interresting ideas to read.

Maybe there’s a channel or something. I have to dig.

I’ll read all this, but I have to translate
cdt

[shakalnokturn]

Is that the bashed-up one that was selling on Leboncoin not so long ago?

If so, I hesitated on buying, it was just too expensive considering the state of the case.

I'd assume your error message concerns channels 1 and 2, I seem to remember reading somewhere that the RAM multiplexers failed on some Yokogawa DSO's.
Of course the usual advice applies: Check power (then check again at the IC's), find another oscilloscope, look for reset, clocks, stuck buses...

[GGMM]

Hello,
I need to dig into the testing.
With the test we can test each channel one at a time. (I think)
But strangely it is in systematic error for the 4. Amazing because in the posts it is often 1 or 2 HS channels.
It is also strange that the rear outlet tests indicate "not connected".
I need to see if the exit card is present and well connected.
Maybe all this is coming from an HS voltage? Maybe the self-test should tell?
Frankly, yesterday after the carcass was dismantled, I spent only half an hour on it. I see this afternoon.
NB: On the post, it says that this would be a chronic failure of the channel amps. A power surge at disassembly and/or heating.
he preconise to put zeners 5.1v on the 5v and -5v, but do we simply cable them in// on the power supply or provide a resisistance. I need a schematic.
In case I go see if we can put an internal fan or something. I read that some holes are drilled to evacuate heat at the preamp level.
But before I have to make the mistake

I was also wondering, if we shouldn’t do a general reset of the memory stored with the battery.
Do a short circuit of the battery with a small resistance a few seconds (?)  I have not seen for the moment of general reset in the menu
If you have a solution do do that

cdt

[GGMM]

Hello,

I found in the documentation a way to reinit all parameters

All settings will be initialized. ---->>>Power up with the RESET key depressed

to try ....
cdt

[GGMM]

Hello,

This day I completely dismantled the oscillo.
I did a practically microscopic inspection of the components, there is nothing abnormal and no smell of burning. No component "burned"
As the error is on channels 1-2, tomorrow I will reverse modules 1-2 and 3-4 to see if the error is reversed.
But since everything seems normal at first glance, I could investigate a little more.
I will spare myself if it is not necessary to heat a little the CI's  that do not have apparent connections, a little is done on the PS console, because no trace of destruction or deformation. I also tested all capacitors no problem

cdt

[nctnico]

If the self test throws an acquisition memory error, then it is of very little use to swap the channels. The problem is in the acquisition memory. If this is on a seperate board then cleaning the connectors with alcohol and re-assembling the oscilloscope may do the trick.

BTW: don't run the analog front-ends without the heatsinks attached. These can overheat very easely and then you have more trouble instead of less.

[GGMM]

Hello Nctnico,

I will still try because the error indicates a scan bp on channels 1-2 (1module PCB for 2 channels)
If the error is reversed, it will be a pb on this PCB module.  To be seen.
As for the thermal protection, I added the thermal pate on the IC’s and the conductive bearings. This can only be beneficial. After as indicated on another post one can imagine improving the ventilation. Besides the rear fan is too noisy for my taste, in case of success I will look at a silent model.

I see you helped out a 1740, but the components looked pretty damaged.
Do you have the schematic?
You also said that we need 5.1v zeners on +5v and -5v power supplies.
I don’t know if the main power supply provided these voltages, or if small regulators are on the channel board.
If you have the information, I’m a taker.
and to finish how connect the diodes? Simply in // on the  + - 5.1v??

cdt

[GGMM]

hello,
i  got it all back together thinking I could reverse 1-2 and 3-4, but in fact the card is not scalable on this model.
I did a visual check, but I didn’t see that.
I’ve tried to heat the circuit in question, but I’m at the same point.
If the fault is in a component, difficult to see. Also impossible to find the diagram.

cdt

[TomKatt]

Memory test gives this error; ACQ_12 Med WA:0 RA:0 WD:1 RD:0

Memory Test
This test checks the internal ROM. The ROM is functioning correctly, if Pass is
displayed. If Failed is displayed, contact your nearest YOKOGAWA dealer as listed on
the back cover of this manual.

No experience with this equipment, but if I had to guess based on the symbols I'd interpret this as
ACQ_12 - Channels 1+2
Med ?
WA: Write Address
RA: Read Address
WD: Write Data
RD: Read Data

Now, obviously you can't write to ROM so either the memory test checks more than just the ROM or I'm completely off base.  If everything else seems to work correctly and you don't see any kind of pcb issues, it's unfortunately quite possible a memory IC has failed.

[GGMM]

Hello,


I did a visual review of the PCB's again.
nothing special
The error in choosing the memory test is:
Memory test gives this error; ACQ_12 Med WA:0 RA:0 WD:1 RD:0

I think that for channels 1 and 2 this must correspond to the RAMs D45128163G5 (128M Dram 4 bank LVTTL). (if we still follow the logic of the implementation).
For the converter if we always follow the logic of the implantation of the components it must correspond to the one in red.
My question is how to determine the failed component? A ram or a circuit that handles all this.
It’s impossible because the cpu is on top.

I read somewhere that you can fool the converter with a triangular signal. Basically if we can display the triangle but if there are hatches, it would prove that it works, but ram problem. Not easy without a diagram.
Your opinion.

NB: I think Tomkatt was talking about RAM and not ROM

Also one idea,  Do you think there may be an anomaly in the NVRam powered by the lithium battery. 
I was wondering, if it would be useful to cut the + wire of the battery and reset the card by putting a ground wire to empty the capacitors. (?)
Then get back together.
Unless there is a trick (??) with NVRam

 

[GGMM]

I wanted it to be impossible to look at the signals on the oscilloscope, because the CPU board is plugged on top!

[GGMM]

Hello,
I thought I’d find a defectous regulator, but it’s actually good. it would be too easy!! Lol
I repeated memory tests, this gives at least 4 different results. I can not see anything on this card because covered by the cpu.
So, I wonder if a failed memory chipset can give this result (random or not??).
This is where we regret that it is not on supports.
the question of how to identify the component. I can’t rely on the heat, the time I show...

cdt

[GGMM]

Hello,

This afternoon I trained myself to desolder circuits of the same type (54 legs). I took an old memory stick and this is the first time I tried with a hot air gun.
I put 450°C. At the stiffness no matter if the component is still good after. It worked relatively well, but in the environment of the circuit there must be no componsant smd, because it will leave too.
Now, the question is, do we need to change all four or one at a time?
Knowing that already in the lottery I am not too lucky!! LOL.
Too bad no one has the knowledge of this material to guide me.
NB: The chipsets are located.

I hope I’m not wrong, the CI's to change for me are surrounded in red in a previous answer.
Your opinion please.

cdt

[max.wwwang]

Hello,

This afternoon I trained myself to desolder circuits of the same type (54 legs). I took an old memory stick and this is the first time I tried with a hot air gun.
I put 450°C. At the stiffness no matter if the component is still good after. It worked relatively well, but in the environment of the circuit there must be no componsant smd, because it will leave too.
Now, the question is, do we need to change all four or one at a time?
Knowing that already in the lottery I am not too lucky!! LOL.
Too bad no one has the knowledge of this material to guide me.
NB: The chipsets are located.

I hope I’m not wrong, the CI's to change for me are surrounded in red in a previous answer.
Your opinion please.

cdt

The quality of the photos has room for improvement, for gurus (not me) to be able to comment on. 

[GGMM]

Hello,

Yes, the quality of the desoldering pictures is not perfect. The goal was to prove that i can desolder components memory similar to 54 legs.
I watched this video before testing.
 

I managed on an old memory of PC to desolden, so it should be okay.
I made very precise pictures of the environment around each memory in case a component would unsolden.
In addition I ordered the same type of memory and manufacturer and also kapton to protect around.
After the question is: Change all 4 components at once or change one at a time and have a little luck to fall on the first one down.
cdt

[jonpaul]

My experience: The old Yokogawa  scopes 1970s..1990s  are poorly documented (schem in Japan and not public) and any digital Yokogawa scope  has many hard to get IC and proprietary FW.

My take: Reading the OP notes I   doubt if this OP can fix the scope. Even a very skilled tech or eng ma be in similar situation.

My suggestion: Old analog scopes are cheap and easy to find locally (eg Hameg 103 EU5 Hameg 204 EU 25)

The Asian  digital and UB scopes  are low cost,  suggest to drop the repair  project and find a new scope.

Sorry,

Jon

[GGMM]

Hi Jonpaul,

I don’t know what a PO rating is (?PO  = post??)
May  you explain.
Yes, it’s very hard to find technical documentation, but I found everything that is user manual, and also DL1740 technical documentation. No electronic schematic. This can help a little.
 I have also  oscillos  analog PM3055 and a Hameg 312.
Otherwise, I’ll have all the hardware to change the 4 acquisition memories for channels 1 and 2. We’ll just have to test the experiment and see.
If you have more information on diagnostic, you may help.

Ideally, a technical who has worked at the Yokogawa after-sales service should give his resolution diagnosis.
The Korean after sales service  answered me by mail  to invest the card in korea. LOL

cdt

[Haenk]

After the question is: Change all 4 components at once or change one at a time and have a little luck to fall on the first one down.

I'd go with all 4 at once, assembling/disassembling might break additional stuff, so...

(edit: I still have a 1540 around, I found it great as a non-permanently installed scope, the size and weight of a Mac, easily portable and not taking up a lot of space on the bench. It has long been replaced by a LCD scope, but it is really lovely, when it's army of selenoids starts...)

[pcprogrammer]

I don’t know what a PO rating is (?PO  = post??)

He wrote OP which means Original Poster and therefore you GGMM 

[jonpaul]

Rebonjour GGMM, j'habite à Paris 6eme, peut-être sommes-nous voisins ?

Dans et autour de Paris se trouvent des experts en instruments électroniques vintage, qui ont réparé de nombreux scopes, TEK, HP,

1/ PO .......no it is OP = Original Poster, YOU!

2/ Yokogawa: Since 1992  I had good connections to Yokogawa-san , Japan and USA,  we have  WT110, DL1640,  DL7440, DL1740, TA320, TA720.

Despite  connections  we never  obtained any  doc or schema or repair info on these 1990s units besides the operation manuals.

Even replacement of backup battery is a huge hassle.

3/ Fiddling with SMD CPU/RAM/NVRAM is risky and unlikely to fix it.

4/ SMD chip removal and replacement requires the right materials, tools and practice. Easy to damage the PCB or chips.

5/ Only idea is send a note in very basic English to Yokogawa HQ in Japan, ATT TECHNICAL SUPPORT OBSELETE INSTRUMENT

You might  get a schematic or manual of service (in Japanese!)

Amicalement

Jon

[GGMM]

Hello,

Thank you for your answers.
You are right this oscilloscope is very nice and I find that its design is relatively different. Not too heavy and full of features.
I read that we could improve its ventilation by drilling a few holes on the housing and that the fan is quite noisy.
Thanks for your answers on OP, we learn every day.
For disassembly , it’s actually well done and easy to do.
The problem lies in the fact that the cards are superimposed and embossed on the motherboard, this poses a difficulty to see the signals. Surely at the service they must have extension boards for the tests.
You will see on this video that the battery exchange can be done, but indeed there is desassembly.



Don’t worry about disseminating the memory's , I think I can do that by taking a maximum of precautions.

cdt

[GGMM]

Hello,

I got kaptron this day.
I prepared the ACQ card to desolder the 4 memories and also protected the main connector. See picture.
Having never used this product, I did a test on my old Ram bar to see. So I selected the smallest SMD components and put the kaptron on top. See picture
I did a two-minute test at 230°C with full ventilation, then another at 400°C 2 minutes to see.
I’m really surprised, because nothing has changed (that’s the goal)!
Even the bottom of the PCB is no warm, you can put your finger on it without burning.
Well, I’m going to look at the properties of this product, this may come from aerospace origin?
Rest a question: For you the best temperature, duration, and ventilation level (from 1 to 10(max)).  Knowing the chips won’t be recovered.

cdt

[GGMM]

Hello,

https://www.eevblog.com/forum/repair/tds-754d-diagnostic-test-acquisition-fail/

I found this post interesting.
It may be about the same.
For now I don’t know if there is an option to run the test internally in a loop.
For the memory test, a priori, no choice on the "type" of memory to test. It’s all or nothing.
This oscillo also has a USB port, I don’t know if we can write a test program as in this example. (??)
It doesn’t seem obvious to find the failed chip (4 memories for 2 channels)
In short, changing them will take less time, but not yet received.
Track to study can be, see the state of the welds of the 4 rams.
The outage occurred after a long period of non-use.
False contact, oxidation???
But for that you need a hot air station, and no luck, mine is down!! Components ordered. Lol

cdt