There are some tests you can do with a partially working scope, but you
are going to be very limited.

1) assuming horizontal sweep problems, you use an external ramp or the
"other" sweep if you have a dual sweep model.

2) if you have a horizontal amplifier problem, using the scope in XY
mode, even with the calibrator, can give you some idea of whether or not
it's the sweep or the amplifier.

3) if you have a dual channel scope, you can use a working channel to
debug the separate part of the vertical amplifier

These generally end up being go/no-go tests and are somewhat crude.

Function generators can make a very crude horizontal sweep. If they're
gated, then a gated ramp might work as a sweep.

Very crude, but better than nothing.

Generally, unless you have a scope specifically designed for self
diagnosis, you're better off with another, completely working, scope.

Even then, a scope designed for self diagnosis makes certain assumptions
about what's working, especially once you get past the "is the CPU
working...."

Harvey


On 1/4/2020 4:29 PM, Panos wrote:

I have read enough service manuals for the oscilloscopes, and till today

I didn't find any of them to mention, that someone can use the same faulty
scope (partially or totally) to repair his self.

But as always we can hope for something like that. After all, don't

they say that hope dies always last? :-)

In my opinion if you have time to play then do it by that way. But if

you want really to repair it, then proceed it with another oscilloscope.

from Tim P (UK)
The posts re '465M junker' remind me of a post I sent a couple of years
ago. I had a 1S1 plug-in that was intermittent, sometimes OK, sometimes
just would not sample.
Did the usual things, re-seat transistors, clean switches, check sampling
bridge etc. Finally, I lifted the PCBs, thinking maybe a wire-clipping or
solder blob had got between the PCB and the chassis. Close examination
with
a jewellers loupe and bright light showed a  bad joint, where the solder
seemed to have parted from a transistor socket - there was a visible gap
between the solder fillet and the pin, not broken but as if the solder had

'shrunk'. Found a few other cases also. I guess solder ages like most
things, or sort-of-crystallises.
Tim

I received a verified-working Tek 454 scope from eBay, and it seems to now,
after shipping, have an issue where the CRT is incredibly bright, like
we're talking burn-a-hole-in-your-vision bright. Naturally I immediately
powered it off, fearing damage to the CRT, and upon turning it back on to
test it, dialing the trace way off the screen, there is still a sizeable,
though not dangerous, glow from electron splash. The grid appears to be at
-150 to -190 volts depending on the brightness setting, and the grid bias
trimmer does essentially nothing, moving the grid bias by around 8 volts
only (not sure if this is a fault or just the design). I checked for a G-K
short, but its about 25 megaohm between (in-circuit), so looks good. I'm
wondering if maybe the grid assembly was knocked loose during shipping
maybe? I'm not intimately familiar with the CRT construction, so maybe
someone more well-acquainted with Tek's CRTs could give me some idea of
what may be going on...

HI Albert,
Groups.io changed my real email address without my knowing it so non-members could not search our posts and harvest our email addresses. I didn't know this is what groups.io did. The only wat I can tell you what the correct email address is if I spell it out like this:
dennis at ridesoft dot com.
You can figure out from this what my email address really is.
Dennis

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Albert Otten
Sent: Wednesday, January 01, 2020 3:29 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] My email address was changed by Groups.io my request for contributions

There is one more issue Dennis. I use the website. There @Dennis... is a link which points to https://groups.io/profile/Dennis_Tillman_W7PF . This is not your profile at Tekscopes since /g/Tekscopes is missing from the path. I can read your Tekscopes profile, but I get a "404 not found" error on that link.

Albert

This one did fail the truth table check when it was in the device. VCC is about 15V which means a HIGH is 15V. Output 3 has a 5V output and does not move from there. When it should be high it is at 5V when it should be low it is at 5V. In the 501 the truth table is frequency dependent on the input. As you roll through the frequency the outputs should do their thing. 1 2 and 4 seem to function as expected.

On 1/5/2020 3:30 PM, KB6NAX wrote:

Watch out! The CD and 74 pinouts are different.  You don't what to hack up your circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the device gives understanding of how inputs and outputs work.  For example a tri-state output could be "off" and not "open."   A CMOS input is high impedance so you don't know if the input stage is blown unless a clamp diode is shorted.  The ultimate is to try the truth table, a lot of work on complex parts.  Parts substitution can't be beat for getting results.  I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:

  My GOTO place has it: http://www.utsource.net/sch/MM74C175N
     On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001 <mlynch002@gmail.com> wrote:
  OK, learned something.  LSTTL and TTL are different animals? SN74HC175N Will drive 10 outputs of LSTTL.    Just trying to learn how logic works, I will likely encounter a similar issue in the future.

Thanks!

This one did fail the truth table check when it was in the device. VCC is about 15V
which means a HIGH is 15V. Output 3 has a 5V output and does not move from there.
When it should be high it is at 5V when it should be low it is at 5V. In the 501 the
truth table is frequency dependent on the input. As you roll through the frequency
the outputs should do their thing. 1 2 and 4 seem to function as expected.

On 1/5/2020 3:30 PM, KB6NAX wrote:

Watch out! The CD and 74 pinouts are different. You don't what to hack up your
circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the
device gives understanding of how inputs and outputs work. For example a tri-state
output could be "off" and not "open." A CMOS input is high impedance so you don't
know if the input stage is blown unless a clamp diode is shorted. The ultimate is
to try the truth table, a lot of work on complex parts. Parts substitution can't
be beat for getting results. I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:

My GOTO place has it: http://www.utsource.net/sch/MM74C175N
On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001
<mlynch002@gmail.com> wrote:
OK, learned something. LSTTL and TTL are different animals? SN74HC175N Will
drive 10 outputs of LSTTL. Just trying to learn how logic works, I will likely
encounter a similar issue in the future.

Thanks!

There are some tests you can do with a partially working scope, but you
are going to be very limited.

1) assuming horizontal sweep problems, you use an external ramp or the
"other" sweep if you have a dual sweep model.

2) if you have a horizontal amplifier problem, using the scope in XY
mode, even with the calibrator, can give you some idea of whether or not
it's the sweep or the amplifier.

3) if you have a dual channel scope, you can use a working channel to
debug the separate part of the vertical amplifier

These generally end up being go/no-go tests and are somewhat crude.

Function generators can make a very crude horizontal sweep. If they're
gated, then a gated ramp might work as a sweep.

Very crude, but better than nothing.

Generally, unless you have a scope specifically designed for self
diagnosis, you're better off with another, completely working, scope.

Even then, a scope designed for self diagnosis makes certain assumptions
about what's working, especially once you get past the "is the CPU
working...."

Harvey


On 1/4/2020 4:29 PM, Panos wrote:

I have read enough service manuals for the oscilloscopes, and till today

I didn't find any of them to mention, that someone can use the same faulty
scope (partially or totally) to repair his self.

But as always we can hope for something like that. After all, don't

they say that hope dies always last? :-)

In my opinion if you have time to play then do it by that way. But if

you want really to repair it, then proceed it with another oscilloscope.

On Sat, Jan 4, 2020 at 8:13 PM William Schuler <guitardad1967@gmail.com>
wrote:

I am in no hurry, so I will give it a try just for fun. It would be
interesting to compare results with my buddy’s functional scope.

Hmmm, you already see the output of the horizontal amplifier - that's what
your CRT shows.
The only thing is that your horizontal output (
https://youtu.be/8dzxGlcErUo?t=10) is differential. By comparing both
sides, you'd be able to see whether this is due to one side pulling or both
- it's a data point at least. I'd bet that you'll find your problem
elsewhere than in the horizontal amp, though. I'm betting on power
supplies, as that's where ~90% of all trouble happens. Is the fan working
OK?
In any case, while I often^Wsometimes miss the most direct way to figure
out what's up, I find the detours are more than worth their while for the
learnin'.

Now to
figure out exactly where that horizontal amplifier is....

You have the service manual (

http://www.ko4bb.com/manuals/download.php?file=Tektronix/Tektronix_-_2245A/Tektronix_2245A_Oscilloscope_Service_Manual.pdf
)?

Have fun!
Siggi

I have read enough service manuals for the oscilloscopes, and till today I didn't find any of them to mention, that someone can use the same faulty scope (partially or totally) to repair his self.
But as always we can hope for something like that. After all, don't they say that hope dies always last? :-)

In my opinion if you have time to play then do it by that way. But if you want really to repair it, then proceed it with another oscilloscope.

Watch out! The CD and 74 pinouts are different.  You don't what to hack up your circuit board.

Also, be advised, when troubleshooting IC's in general having the schematic of the device gives understanding of how inputs and outputs work.  For example a tri-state output could be "off" and not "open."   A CMOS input is high impedance so you don't know if the input stage is blown unless a clamp diode is shorted.  The ultimate is to try the truth table, a lot of work on complex parts.  Parts substitution can't be beat for getting results.  I always buy two or more when in that situation.

eBay to the rescue - Item #372418190226

Arden

-----Original Message----- From: Eric
Sent: Sunday, January 05, 2020 6:51 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I did find out that the AA501 does need the VCC of 15V so the HC series
logic is out for sure. I am going to order some of the direct
replacement parts as there is a supply house that has then mouser and
digikey were out. Texas Instrument cross reference says a CD40175BE is a
comparable part as well. I have also confirmed the fault as with this IC
out of circuit the 501 says 100+% distortion on all frequencies also one
of the outputs is open when i check it with my small curve tracer. On
this one pin 14 is dead.


On 1/5/2020 1:08 AM, KeepIt SimpleStupid via Groups.Io wrote:

  My GOTO place has it: http://www.utsource.net/sch/MM74C175N
     On Saturday, January 4, 2020, 10:31:47 PM EST, Mlynch001 <mlynch002@gmail.com> wrote:
  OK, learned something.  LSTTL and TTL are different animals? SN74HC175N Will drive 10 outputs of LSTTL.    Just trying to learn how logic works, I will likely encounter a similar issue in the future.

Thanks!

I have a couple working 2465s i don't use, but I am not in Continental
USA...so I could maybe scrap out a m'board from 1