|
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
Not looking at the schematic, but tek scopes of that era
are littered with filters for the power entering the boards,
that are made from 10 ohm resistors with a tantalum capacitor
to ground.
Use your eyes and look for the capacitor, or remains of the
capacitor, that is near the resistor. It will usually be of
the tantalum drop variety, with color bands.
Sometimes, they blow up, leaving just two leads sticking out
of the board where the capacitor used to be.
Other times, you will see what looks like a three leaded
capacitor..
And still other times, the capacitor will look normal, but
be a dead (0 ohms) short.
When you replace it, pick a tantalum value that is at least
twice the operating voltage of the power it is filtering.
If it is on the 15V supply, use a 30V tantalum capacitor.
-Chuck Harris
James R. Bartlett wrote:
toggle quoted message
Show quoted text
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
Jim,
Gotta Love that magic smoke! I don't think that is a filter resistor as described in Chuck's last reply, as I do not see a Tantalum cap adjacent to the resistor in that part of the circuit. R956 is the current limiting resistor for the base of Q956 which appears to be part of the sweep generator circuitry. In the schematic, R956 is specified as a 10K, 1/4W 5% resistor, NOT 10 ohms, so if you are seeing only 10 ohms, that is a problem. What I would also suggest is to check Q956, plus CR952,CR955, CR956 and VR956 and verify that these components are all good. Chuck's advice about Tantalum Caps is spot on and you should check the entire machine for blown or otherwise defective caps. My brother calls them "devil caps", they are prone to failure at any moment.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...
toggle quoted message
Show quoted text
On Thursday, August 29, 2019, 6:55:39 AM CDT, James R. Bartlett <james.r.bart@...> wrote:
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
Hi Michael, Thanks for the reply. My query was not about R956 but the one to the left of it and is situated in the middle between VR956 and R956, on my PCB component layout most components are identified but not this resistorThat is the one that measures 10 ohms.Seems to go back to C1448 a 10uf Tant Measuring across C1448 I also get 10 ohms.So need to find out where it goes and its component number. I am a patient man and wil keep trying. Thanks again Regards Jim On Thu, 29 Aug 2019 at 15:40, Michael W. Lynch via Groups.Io <mlynch003= yahoo.com@groups.io> wrote: Jim,
Gotta Love that magic smoke! I don't think that is a filter resistor as
described in Chuck's last reply, as I do not see a Tantalum cap adjacent to
the resistor in that part of the circuit. R956 is the current limiting
resistor for the base of Q956 which appears to be part of the sweep
generator circuitry. In the schematic, R956 is specified as a 10K, 1/4W
5% resistor, NOT 10 ohms, so if you are seeing only 10 ohms, that is a
problem. What I would also suggest is to check Q956, plus CR952,CR955,
CR956 and VR956 and verify that these components are all good. Chuck's
advice about Tantalum Caps is spot on and you should check the entire
machine for blown or otherwise defective caps. My brother calls them
"devil caps", they are prone to failure at any moment.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 6:55:39 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
All of this will be spelled out on the power distribution
schematic for the A9 board... it's somewhere in the manual.
In the meantime, take out the 10 ohm 1/4W resistor (AKA: fuse)
and replace it with a new one, and take out the 10uf Tantalum
cap and replace it with a new one of higher voltage.
You can use an aluminum electrolytic of at least 2x the capacitance,
if you want, but the scope's low temperature operation will be
compromised... it is not at all certain that you care.
I bet the scope works if you do that.
-Chuck Harris
James R. Bartlett wrote:
toggle quoted message
Show quoted text
Hi Michael,
Thanks for the reply.
My query was not about R956 but the one to the left of it and is situated
in the middle
between VR956 and R956, on my PCB component layout most components are
identified
but not this resistorThat is the one that measures 10 ohms.Seems to go back
to C1448 a 10uf Tant
Measuring across C1448 I also get 10 ohms.So need to find out where it
goes and its component number.
I am a patient man and wil keep trying.
Thanks again
Regards
Jim
|
Jim,
I guess I need to go back to reading comprehension school! I see that now. FYI, I have a 475A manual and in that model schematic, that resistor as R963, Indeed it is a 10Ohm 1/4W 1/2% Carbon Comp resistor. As Chuck stated EXACTLY, this appears to be a Filter in conjunction with C963 on +15V (DCPL2). At least this is what the 475A schematic indicates. I did not find this in the 475 schematic. I will sit down quietly at the back of the class, speak when spoken to and try to learn from the teachers!
Sincerely,
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...
toggle quoted message
Show quoted text
On Thursday, August 29, 2019, 10:22:59 AM CDT, James R. Bartlett <james.r.bart@...> wrote: Hi Michael, Thanks for the reply. My query was not about R956 but the one to the left of it and is situated in the middle between VR956 and R956, on my PCB component layout most components are identified but not this resistorThat is the one that measures 10 ohms.Seems to go back to C1448 a 10uf Tant Measuring across C1448 I also get 10 ohms.So need to find out where it goes and its component number. I am a patient man and wil keep trying. Thanks again Regards Jim On Thu, 29 Aug 2019 at 15:40, Michael W. Lynch via Groups.Io <mlynch003= yahoo.com@groups.io> wrote: Jim,
Gotta Love that magic smoke! I don't think that is a filter resistor as
described in Chuck's last reply, as I do not see a Tantalum cap adjacent to
the resistor in that part of the circuit. R956 is the current limiting
resistor for the base of Q956 which appears to be part of the sweep
generator circuitry. In the schematic, R956 is specified as a 10K, 1/4W
5% resistor, NOT 10 ohms, so if you are seeing only 10 ohms, that is a
problem. What I would also suggest is to check Q956, plus CR952,CR955,
CR956 and VR956 and verify that these components are all good. Chuck's
advice about Tantalum Caps is spot on and you should check the entire
machine for blown or otherwise defective caps. My brother calls them
"devil caps", they are prone to failure at any moment.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 6:55:39 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
Chuck,
My money is on your suggestion. I am sorry that I misread the OP message. I found that on my 475A schematic and it is EXACTLY as you stated, a filter on that +15V supply. Shorted Cap is almost certainly the issue.
I appreciate all the wisdom that you bring to the table. I just wish I would read more carefully!
Sincerely,
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...
toggle quoted message
Show quoted text
On Thursday, August 29, 2019, 10:36:14 AM CDT, Chuck Harris <cfharris@...> wrote: All of this will be spelled out on the power distribution schematic for the A9 board... it's somewhere in the manual. In the meantime, take out the 10 ohm 1/4W resistor (AKA: fuse) and replace it with a new one, and take out the 10uf Tantalum cap and replace it with a new one of higher voltage. You can use an aluminum electrolytic of at least 2x the capacitance, if you want, but the scope's low temperature operation will be compromised... it is not at all certain that you care. I bet the scope works if you do that. -Chuck Harris James R. Bartlett wrote: Hi Michael,
Thanks for the reply.
My query was not about R956 but the one to the left of it and is situated
in the middle
between VR956 and R956, on my PCB component layout most components are
identified
but not this resistorThat is the one that measures 10 ohms.Seems to go back
to C1448 a 10uf Tant
Measuring across C1448 I also get 10 ohms.So need to find out where it
goes and its component number.
I am a patient man and wil keep trying.
Thanks again
Regards
Jim
|
No Michael, I hope you will continue to do what you
did, helping to keep the information honest.
I make as many mistakes as you do... maybe more.
-Chuck Harris
Michael W. Lynch via Groups.Io wrote:
toggle quoted message
Show quoted text
Jim,
I guess I need to go back to reading comprehension school! I see that now. FYI, I have a 475A manual and in that model schematic, that resistor as R963, Indeed it is a 10Ohm 1/4W 1/2% Carbon Comp resistor. As Chuck stated EXACTLY, this appears to be a Filter in conjunction with C963 on +15V (DCPL2). At least this is what the 475A schematic indicates. I did not find this in the 475 schematic. I will sit down quietly at the back of the class, speak when spoken to and try to learn from the teachers!
Sincerely,
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
|
Chuck,
I will continue to learn and contribute when I am able. I do learn from my mistakes. You would make more mistakes than I, only because you work on a lot more equipment than I do. I tend to concentrate my many mistakes into one or two pieces of gear. I am trying to absorb these lessons as quickly and completely as I am able. You teach me a lot, just from your comments!
Many thanks!
--
Michael Lynch
Dardanelle, AR
|
Not to worry Michael, I know the feeling only too well, having used up my 3 score and ten years, everything else is a bonus😇 Interesting it is shown in the 475A but not the 475. Who knows what other errors might be there, but the resistor IS there !!!! and SMOKED but obviously not destroyed., glad to have it confirmed as 10 ohms. Might try disconnecting C 1448 the 10uf Tant and see what happens Don't like those things and modern electrolyic types are very smaall now All good fun and a nice way to meet new friends Thanks for your help. Regards Jim On Thu, 29 Aug 2019 at 16:48, Michael W. Lynch via Groups.Io <mlynch003= yahoo.com@groups.io> wrote: Jim,
I guess I need to go back to reading comprehension school! I see that
now. FYI, I have a 475A manual and in that model schematic, that resistor
as R963, Indeed it is a 10Ohm 1/4W 1/2% Carbon Comp resistor. As Chuck
stated EXACTLY, this appears to be a Filter in conjunction with C963 on
+15V (DCPL2). At least this is what the 475A schematic indicates. I did
not find this in the 475 schematic. I will sit down quietly at the back of
the class, speak when spoken to and try to learn from the teachers!
Sincerely,
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 10:22:59 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hi Michael,
Thanks for the reply.
My query was not about R956 but the one to the left of it and is situated
in the middle
between VR956 and R956, on my PCB component layout most components are
identified
but not this resistorThat is the one that measures 10 ohms.Seems to go back
to C1448 a 10uf Tant
Measuring across C1448 I also get 10 ohms.So need to find out where it
goes and its component number.
I am a patient man and wil keep trying.
Thanks again
Regards
Jim
On Thu, 29 Aug 2019 at 15:40, Michael W. Lynch via Groups.Io <mlynch003=
yahoo.com@groups.io> wrote:
Jim,
Gotta Love that magic smoke! I don't think that is a filter resistor as
described in Chuck's last reply, as I do not see a Tantalum cap adjacent to
the resistor in that part of the circuit. R956 is the current limiting
resistor for the base of Q956 which appears to be part of the sweep
generator circuitry. In the schematic, R956 is specified as a 10K, 1/4W
5% resistor, NOT 10 ohms, so if you are seeing only 10 ohms, that is a
problem. What I would also suggest is to check Q956, plus CR952,CR955,
CR956 and VR956 and verify that these components are all good. Chuck's
advice about Tantalum Caps is spot on and you should check the entire
machine for blown or otherwise defective caps. My brother calls them
"devil caps", they are prone to failure at any moment.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 6:55:39 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
I have no great objection to replacing a tantalum filter
with a low impedance aluminum electrolytic, but be sure
that you understand that aluminum electrolytic capacitors
loose about 1/2 their value when they hit 0C, and all of
it by the time they get to around -20C. They will not work
well if the scope is left in the car trunk in the winter,
and then brought into the lab and turned on.
Tantalum capacitors have no such loss of capacitance.
If you select the tantalum's ratings correctly, they will
outlast us all by easily 3 score and 10 years. All you
have to do is set the rating to be double the voltage they
will operate at.
-Chuck Harris
James R. Bartlett wrote:
toggle quoted message
Show quoted text
Not to worry Michael,
I know the feeling only too well, having used up my 3 score and ten years,
everything else is a bonus😇 Interesting it is shown in the 475A but not
the 475. Who knows what other errors
might be there, but the resistor IS there !!!! and SMOKED but obviously
not destroyed., glad to have it confirmed as 10 ohms. Might try
disconnecting C 1448 the 10uf Tant and see what happens
Don't like those things and modern electrolyic types are very smaall now
All good fun and a nice way to meet new friends
Thanks for your help.
Regards
Jim
|
Hi Jim,
I would be 99% certain that changing the cap will fix it. I've seen identical symptoms and faults in a 7912AD. Browned off 10 ohm resistors and bead tants all over the thing.
I actually watched one fail, I found two shorted ones, fired it up with the side covers off and it ran fine for about 15 minutes then I thought I noticed a wisp of smoke out of the corner of my eye by the time I saw which resistor was hot the screen blanked!
I've actually replaced them with 35V tants on the grounds that, as someone else who's running in 'bonus time', in another 50 years if they fail a second time my 121st birthday present to myself will be to pay someone else to change them!
Adrian
toggle quoted message
Show quoted text
On 8/29/2019 5:44 PM, James R. Bartlett wrote: Not to worry Michael,
I know the feeling only too well, having used up my 3 score and ten years,
everything else is a bonus😇 Interesting it is shown in the 475A but not
the 475. Who knows what other errors
might be there, but the resistor IS there !!!! and SMOKED but obviously
not destroyed., glad to have it confirmed as 10 ohms. Might try
disconnecting C 1448 the 10uf Tant and see what happens
Don't like those things and modern electrolyic types are very smaall now
All good fun and a nice way to meet new friends
Thanks for your help.
Regards
Jim
On Thu, 29 Aug 2019 at 16:48, Michael W. Lynch via Groups.Io <mlynch003=
yahoo.com@groups.io> wrote:
Jim,
I guess I need to go back to reading comprehension school! I see that
now. FYI, I have a 475A manual and in that model schematic, that resistor
as R963, Indeed it is a 10Ohm 1/4W 1/2% Carbon Comp resistor. As Chuck
stated EXACTLY, this appears to be a Filter in conjunction with C963 on
+15V (DCPL2). At least this is what the 475A schematic indicates. I did
not find this in the 475 schematic. I will sit down quietly at the back of
the class, speak when spoken to and try to learn from the teachers!
Sincerely,
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 10:22:59 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hi Michael,
Thanks for the reply.
My query was not about R956 but the one to the left of it and is situated
in the middle
between VR956 and R956, on my PCB component layout most components are
identified
but not this resistorThat is the one that measures 10 ohms.Seems to go back
to C1448 a 10uf Tant
Measuring across C1448 I also get 10 ohms.So need to find out where it
goes and its component number.
I am a patient man and wil keep trying.
Thanks again
Regards
Jim
On Thu, 29 Aug 2019 at 15:40, Michael W. Lynch via Groups.Io <mlynch003=
yahoo.com@groups.io> wrote:
Jim,
Gotta Love that magic smoke! I don't think that is a filter resistor as
described in Chuck's last reply, as I do not see a Tantalum cap adjacent to
the resistor in that part of the circuit. R956 is the current limiting
resistor for the base of Q956 which appears to be part of the sweep
generator circuitry. In the schematic, R956 is specified as a 10K, 1/4W
5% resistor, NOT 10 ohms, so if you are seeing only 10 ohms, that is a
problem. What I would also suggest is to check Q956, plus CR952,CR955,
CR956 and VR956 and verify that these components are all good. Chuck's
advice about Tantalum Caps is spot on and you should check the entire
machine for blown or otherwise defective caps. My brother calls them
"devil caps", they are prone to failure at any moment.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell
Phonemlynch001@...@gmail.commlynch003@...
On Thursday, August 29, 2019, 6:55:39 AM CDT, James R. Bartlett <
james.r.bart@...> wrote:
Hello to the group.
I find that I am in need of your assistance. Firsty repairing scopes is not
my forte but I
want to do and learn.
I have a Tek 475, which was working.
However I went to use it the other day and
got the magic smoke. Problem seems to be related to the +15 supply/
Scope switches on,
The smoke came fro a resistor on the A9 board.
However it does not appear to be numbered on the PCB layout as shown on the
downloaded
service manual.
It is located to the left and between VR956 and R956 it meters out at 10
ohms
Is this the correct value ? and what is its circuit number ?
I checked C1448 and that meters out also at 10 ohms.
+ 15 volt supply is 0 Volt
Any thoughts suggestions appreciated .
Many thanks
Jim
|
Jim,
I found it in the 475 manual as well. Just in a different location on the schematics. It just took a bit of searching. I have a 475A that I was able to bring back from oblivion and I was more familiar with that instrument, manual and the schematics. The two machines are very likely identical in that area. I have a Type 576 CT that had about 15 “bad” axial Tantalum caps when I first received it, these things were quitting every time I turned it on, after the 2nd or 3rd failure, I decided to replace them all, with modern equivalents.
--
Michael Lynch
Dardanelle, AR
|
Jim,
FYI, found this on Page 216 of 293 in the version of the 475 manual that I am looking at. The LV supplies are populated with many of these filters. So a good chance that others are on the verge of failure.
Hope this helps.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...
toggle quoted message
Show quoted text
On Thursday, August 29, 2019, 1:57:41 PM CDT, Mlynch001 <mlynch002@...> wrote:
Jim,
I found it in the 475 manual as well. Just in a different location on the schematics. It just took a bit of searching. I have a 475A that I was able to bring back from oblivion and I was more familiar with that instrument, manual and the schematics. The two machines are very likely identical in that area. I have a Type 576 CT that had about 15 “bad” axial Tantalum caps when I first received it, these things were quitting every time I turned it on, after the 2nd or 3rd failure, I decided to replace them all, with modern equivalents.
--
Michael Lynch
Dardanelle, AR
|
Thanks Michael,
I have a few higher voltage Tants so will use a 35 or 50 volt one.
Can you point me in the direction on the schematic where I can see that
resistor.
Will replace it as well.
Again thanks for help much appreciated,
Regards
Jim
toggle quoted message
Show quoted text
On Thu, 29 Aug 2019 at 19:57, Mlynch001 <mlynch002@...> wrote: Jim,
I found it in the 475 manual as well. Just in a different location on the
schematics. It just took a bit of searching. I have a 475A that I was
able to bring back from oblivion and I was more familiar with that
instrument, manual and the schematics. The two machines are very likely
identical in that area. I have a Type 576 CT that had about 15 “bad” axial
Tantalum caps when I first received it, these things were quitting every
time I turned it on, after the 2nd or 3rd failure, I decided to replace
them all, with modern equivalents.
--
Michael Lynch
Dardanelle, AR
|
|
|
Good morning Michael.
Many thanks for the info/link.
I downloaded it and it is slightly different to mine.
I found the 3, 10 ohm resistors in the +15 volt supply on page 216.
However none of them appear in the component list for that circuit.!!!!!
I have searched but cannot find R961,R963 and R965 and associated 2.2uf
capacitors anywhere except in the main component list.
Can you help and point me as to where they might be.
Sorry to be a pain but this has me puzzled.
Many thanks
Regards
Jim
toggle quoted message
Show quoted text
On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote: Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
http://w140.com/Tektronix_475_Oscilloscope_Service_Manual.pdf< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
|
Hi Jim,
Tektronix has always been terrible about identifying
these little power filter circuits. I rarely can find
them on any part's layout in the manuals.
The schematic where the filters are located is on page
216 of my copy of the 475 manual... But I think you
already know that.
The schematic shows them to be in the Sweep Generator
area, which is schematic <8>,,, Then everything goes
to heck...
However, they can usually be found near the source of
the noise. In the case of power coming onto a circuit
board, that is where the filter will be. In the case
of a noise source like a EHT supply, that's where the
filter will be.
The resistor will always be pointing at the noise source.
-Chuck Harris
James R. Bartlett wrote:
toggle quoted message
Show quoted text
Good morning Michael.
Many thanks for the info/link.
I downloaded it and it is slightly different to mine.
I found the 3, 10 ohm resistors in the +15 volt supply on page 216.
However none of them appear in the component list for that circuit.!!!!!
I have searched but cannot find R961,R963 and R965 and associated 2.2uf
capacitors anywhere except in the main component list.
Can you help and point me as to where they might be.
Sorry to be a pain but this has me puzzled.
Many thanks
Regards
Jim
On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote:
Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
http://w140.com/Tektronix_475_Oscilloscope_Service_Manual.pdf< TEKWiki is a great resource.
Best of luck on your repair.
--
Michael Lynch
Dardanelle, AR
|
Jim,
Been there, done that and have the Tee Shirt. As chuck stated, TEK is not always the best about these locations. Not sure how this comes about, but even the best have shortcomings. I gave up on that 475 manual and went back to my old 475A manual and this is what I found.
This is the LOWER front corner of the board on the 475A and this board LOOKS like the same part as the 475.
I hope this is of some assistance.
Michael Lynch 479-226-0126 Home Phone479-477-1115 Cell Phonemlynch001@...@gmail.commlynch003@...
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On Friday, August 30, 2019, 3:53:51 AM CDT, James R. Bartlett <james.r.bart@...> wrote: Good morning Michael. Many thanks for the info/link. I downloaded it and it is slightly different to mine. I found the 3, 10 ohm resistors in the +15 volt supply on page 216. However none of them appear in the component list for that circuit.!!!!! I have searched but cannot find R961,R963 and R965 and associated 2.2uf capacitors anywhere except in the main component list. Can you help and point me as to where they might be. Sorry to be a pain but this has me puzzled. Many thanks Regards Jim On Thu, 29 Aug 2019 at 23:11, Mlynch001 <mlynch002@...> wrote: Jim,
Page 216 of 293 in the version of the 475 manual that I am looking at.
TEKWiki has a couple of versions for that instrument.
here is the link:
http://w140.com/Tektronix_475_Oscilloscope_Service_Manual.pdf< TEKWiki is a great resource.
Best of luck on your repair.
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Michael Lynch
Dardanelle, AR
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Jim,
Evidently the photo I attempted to attach will not post here directly? Contact me off list at this e-mail and I can send the picture to you.
If there is a way to insert pictures in a post, I do not know how to make it happen.
All 3 filters are on the A9 board near the J6 and J4 connectors. The 475A manual is much more detailed. Maybe TEK felt they had to step up their game?
mlynch002@...
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Michael Lynch
Dardanelle, AR
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Michael W. Lynch
Mlynch001