Topics

REPAIRED : Tektronix 2465B with auto test stopped on "ADD" led lit

Joseph
 

My problem :
On power, the auto test start but stop when arrive at the "ADD" led lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them near 0v .. it was not normal
2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
bingo!! .. I discovered, under a little oxydation bubble on the track near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit

Start state :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159787.jpg[/img]

Track break discover :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-44-58.jpg[/img]

Repair :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg[/img]

]Fix schema and verified voltages :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-38-29.jpg[/img]

Result :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159789.jpg[/img]

Siggi
 

On Fri, Jan 10, 2020, 1:59 AM Joseph <@jo6466> wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led
lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them
near 0v .. it was not normal
Beg to differ, this IS normal. Pins 14/15 are the inputs of an opamp in
negative feedback. They should both be at zero volts, or very near. What's
important is the current into the DAC, which can't be directly measured.


2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
bingo!! .. I discovered, under a little oxydation bubble on the track
near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit
Congrats on your fix. Your image links seem to be mangled, I get 404s all
round.

Did you check and replace the electrolytic capacitors on the A5 board and
clean it? The most usual cause for this problem is electrolyte spillage
causing PCB and component corrosion.



Colin Herbert
 

Siggi,
I think that joseph has tried to insert the images into the message, unsuccessfully. If you remove the final [/img] that is after the .jpg, you will locate the photos.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Siggi
Sent: 10 January 2020 13:04
To: TekScopes@groups.io
Subject: Re: [TekScopes] REPAIRED : Tektronix 2465B with auto test stopped on "ADD" led lit

On Fri, Jan 10, 2020, 1:59 AM Joseph <@jo6466> wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led
lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them
near 0v .. it was not normal
Beg to differ, this IS normal. Pins 14/15 are the inputs of an opamp in
negative feedback. They should both be at zero volts, or very near. What's
important is the current into the DAC, which can't be directly measured.


2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
bingo!! .. I discovered, under a little oxydation bubble on the track
near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit
Congrats on your fix. Your image links seem to be mangled, I get 404s all
round.

Did you check and replace the electrolytic capacitors on the A5 board and
clean it? The most usual cause for this problem is electrolyte spillage
causing PCB and component corrosion.



Dwayne Reid
 

Hi there.

All of your links are "404".

dwayne

At 08:17 AM 1/9/2020, Joseph wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them near 0v .. it was not normal
2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
bingo!! .. I discovered, under a little oxydation bubble on the track near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit

Start state :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159787.jpg[/img]

Track break discover :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-44-58.jpg[/img]

Repair :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg[/img]

]Fix schema and verified voltages :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-38-29.jpg[/img]

Result :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159789.jpg[/img]
--
Dwayne Reid <dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

Siggi
 

On Fri, Jan 10, 2020 at 7:25 PM Dwayne Reid <dwayner@...> wrote:

Hi there.

All of your links are "404".

dwayne


At 08:17 AM 1/9/2020, Joseph wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led
lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find
them near 0v .. it was not normal
2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
bingo!! .. I discovered, under a little oxydation bubble on the
track near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit

Start state :

[img]
https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159787.jpg[/img]

Track break discover :
[img]
https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-44-58.jpg[/img]

Repair :
[img]
https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg[/img]

]Fix schema and verified voltages :
[img]
https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-38-29.jpg[/img]

Result :
[img]
https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159789.jpg[/img]


--
Dwayne Reid <dwayner@...>
Trinity Electronics Systems Ltd Edmonton, AB, CANADA
780-489-3199 voice 780-487-6397 fax 888-489-3199 Toll Free
www.trinity-electronics.com
Custom Electronics Design and Manufacturing




Renée
 

work fine here both the first time and from what you included....leave off the [img] both of them.
Renée

On 2020-01-10 4:25 p.m., Dwayne Reid wrote:
Hi there.

All of your links are "404".

dwayne


At 08:17 AM 1/9/2020, Joseph wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them near 0v .. it was not normal
2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
    bingo!! .. I discovered, under a little oxydation bubble on the track near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit

Start state :

[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159787.jpg[/img]

Track break discover :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-44-58.jpg[/img]

Repair :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg[/img]

]Fix schema and verified voltages :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-38-29.jpg[/img]

Result :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159789.jpg[/img]

 

Joseph,
Nice summary of your repair.  This is a common problem with the 24x5B scopes with serial numbers greater than 05xxxx.  Some or all of C2011, C2331, C2113 rupture with age and spew electrolyte on their neighbors, especially on the traces and resistors.  Nearly all of todays 2445B and 2465B scopes have had this problem at some time.  Your picture: https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg shows evidence of this.  The dull looking solder on the upper components in the picture are the result of acid etch from the electrolyte.  Compare them with the shiny solder on the lower components, away from the offending capacitors.  I suggest you check your scope to verify the offending capacitors have been replaced and are not still damaging their neighbors.  Also, capacitors C2890 and C2895 are likley to do this and should be checked.  Some versions of these board had solid tantalum capacitors in these positions and are much less likely to have the problem but you should check to see what you have.
Mac

On Friday, January 10, 2020, 12:59:58 AM CST, Joseph <@jo6466> wrote:

My problem :
On power, the auto test start but stop when arrive at the "ADD" led lighting ... Screen remain totally black

Fixing:
1) I measured the voltage on pins 14 and 15 of U2101 (DAC) and find them near 0v .. it was not normal
2) I tested the R2010 to R2016 resistors value .. all was been ok
3) I tested the CONTINUITY of the tracks between them
    bingo!! .. I discovered, under a little oxydation bubble on the track near R2016, a break on it
4) after fixing it, the auto test gone until end and the screen lit

Start state :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159787.jpg[/img]

Track break discover :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-44-58.jpg[/img]

Repair :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159788.jpg[/img]

]Fix schema and verified voltages :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575799-capture-2020-01-09-a-13-38-29.jpg[/img]

Result :
[img]https://image.noelshack.com/fichiers/2020/02/4/1578575821-r0159789.jpg[/img]