Date   
Logic families

KB6NAX
 

Re: Trying to bring back a AA501

KB6NAX
 

Meh, I said "Hz" when I meant MHz. Oh, also, high speed logic designs require much more rigorous power and ground rail decoupling because the faster the logic the noisier the environment. But still you may be OK with the 74HC part.

Arden

-----Original Message-----
From: KB6NAX
Sent: Saturday, January 04, 2020 6:32 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

Eric, the 74C157 and 74HC157 are the same logic functions but are members of
two distinctly different semiconductor processes. The 74C157 belongs to the
metal gate family, the first of the CMOS families. It's maximum toggle
speed is in the neighborhood of 5 - 10 Hz and it's operating voltage ranges
from 3 - 15V. The 74HC157 belongs to the later silicon gate high speed CMOS
family. It toggles at up to around 35MHz. It’s operating voltage maxes at
6 volts. So the rub is knowing what the rail voltage is in the 501. If
it's 5 volts the "HC" part may work OK, but it's not guaranteed if the logic
in the 501 is susceptible to timing issues with much faster through gate
transmission times.

Arden

-----Original Message-----
From: Eric
Sent: Saturday, January 04, 2020 6:03 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I have found a bad IC in the 501 it is the MM74C175N from On
semiconductor. It also seems this part is obsolete. Would I be safe in
subbing a 74HC175N from Texas Instruments. I am not sure if the
difference in C and HC logic will matter?

On 12/31/2019 9:33 PM, Eric via Groups.Io wrote:
OK a little more digging and something I can dig in to at least not sure if this is the only issue but it is a start. I was looking around U1410 on the main board and ran through the truth table. It turns out Pin15 on U1410 has a constant output of about 5VDc. The others go to 14.5V when they should be high. Also when pin 15 should be high the distortion levels look in the ball park when Pin 15 should be low the distortion goes to +100% distortion and the function output from the aa501 is a sign wave as opposed to the distortion elements. The frequency it can’t get past is 959 Hz which is when Pin 15 should go low.

On 12/31/2019 9:35 AM, Eric via Groups.Io wrote:
Well it looks like the AA501 is not as bad off as I though. I got a service manual still need to go over it in detail however it looks like the fault is isolated to “higher frequency”, anything ~1Khz it looks like I am getting numbers that are at least in the realm of sanity. Anything over that and I get 100%+ distortion. I am starting to suspect ½ and opamp has gone out.



Re: Trying to bring back a AA501

KB6NAX
 

Both operate at TTL levels ....
Sorry, Michael, but you are wrong. The input true and false thresholds are different for CMOS and TTL. Only a 74HCT (notice "HCT" for TTL interface compatibility) part may be used with TTL parts only because its input thresholds are offset to meet TTL output levels.

Arden

-----Original Message-----
From: Mlynch001
Sent: Saturday, January 04, 2020 6:33 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

It appears to me that the MM74C175N has a VCC (max. operating) of 15V and the 74HC175N VCC operating range is -.5V - 7.0V. Otherwise they appear to be similar. Both operate at TTL levels. Quad Flip Flops with common clock and clear to all 4. As long as your operating VCC was compatible, it looks like the 74HC175N could sub in.

--
Michael Lynch
Dardanelle, AR

Re: Trying to bring back a AA501

KB6NAX
 

Eric, the 74C157 and 74HC157 are the same logic functions but are members of two distinctly different semiconductor processes. The 74C157 belongs to the metal gate family, the first of the CMOS families. It's maximum toggle speed is in the neighborhood of 5 - 10 Hz and it's operating voltage ranges from 3 - 15V. The 74HC157 belongs to the later silicon gate high speed CMOS family. It toggles at up to around 35MHz. It’s operating voltage maxes at 6 volts. So the rub is knowing what the rail voltage is in the 501. If it's 5 volts the "HC" part may work OK, but it's not guaranteed if the logic in the 501 is susceptible to timing issues with much faster through gate transmission times.

Arden

-----Original Message-----
From: Eric
Sent: Saturday, January 04, 2020 6:03 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Trying to bring back a AA501

I have found a bad IC in the 501 it is the MM74C175N from On
semiconductor. It also seems this part is obsolete. Would I be safe in
subbing a 74HC175N from Texas Instruments. I am not sure if the
difference in C and HC logic will matter?

On 12/31/2019 9:33 PM, Eric via Groups.Io wrote:
OK a little more digging and something I can dig in to at least not sure if this is the only issue but it is a start. I was looking around U1410 on the main board and ran through the truth table. It turns out Pin15 on U1410 has a constant output of about 5VDc. The others go to 14.5V when they should be high. Also when pin 15 should be high the distortion levels look in the ball park when Pin 15 should be low the distortion goes to +100% distortion and the function output from the aa501 is a sign wave as opposed to the distortion elements. The frequency it can’t get past is 959 Hz which is when Pin 15 should go low.

On 12/31/2019 9:35 AM, Eric via Groups.Io wrote:
Well it looks like the AA501 is not as bad off as I though. I got a service manual still need to go over it in detail however it looks like the fault is isolated to “higher frequency”, anything ~1Khz it looks like I am getting numbers that are at least in the realm of sanity. Anything over that and I get 100%+ distortion. I am starting to suspect ½ and opamp has gone out.



Re: Trying to bring back a AA501

Mlynch001
 

It appears to me that the MM74C175N has a VCC (max. operating) of 15V and the 74HC175N VCC operating range is -.5V - 7.0V. Otherwise they appear to be similar. Both operate at TTL levels. Quad Flip Flops with common clock and clear to all 4. As long as your operating VCC was compatible, it looks like the 74HC175N could sub in.

--
Michael Lynch
Dardanelle, AR

Re: Trying to bring back a AA501

Eric
 

I have found a bad IC in the 501 it is the MM74C175N from On semiconductor. It also seems this part is obsolete. Would I be safe in subbing a 74HC175N from Texas Instruments. I am not sure if the difference in C and HC logic will matter?

On 12/31/2019 9:33 PM, Eric via Groups.Io wrote:
OK a little more digging and something I can dig in to at least not sure if this is the only issue but it is a start. I was looking around U1410 on the main board and ran through the truth table. It turns out Pin15 on U1410 has a constant output of about 5VDc. The others go to 14.5V when they should be high. Also when pin 15 should be high the distortion levels look in the ball park when Pin 15 should be low the distortion goes to +100% distortion and the function output from the aa501 is a sign wave as opposed to the distortion elements. The frequency it can’t get past is 959 Hz which is when Pin 15 should go low.

On 12/31/2019 9:35 AM, Eric via Groups.Io wrote:
Well it looks like the AA501 is not as bad off as I though. I got a service manual still need to go over it in detail however it looks like the fault is isolated to “higher frequency”, anything ~1Khz it looks like I am getting numbers that are at least in the realm of sanity. Anything over that and I get 100%+ distortion. I am starting to suspect ½ and opamp has gone out.


Re: Tektronix 2245a Flickering Trace

Siggi
 

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

465M Restoration Completion

KB6NAX
 

It seems my junker 465M has pulled through four days of surgery and hopefully will become useful help for someone (disclaimer - I'm not offering it for sale here). The only thing I need now is a top cover for Junker. If anyone has a top cover for a 465M that is missing a purpose I would like to buy it. If interested send me your coded e-mail address. Thanks.

Arden

Re: Tektronix 2245a Flickering Trace

William Schuler
 

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

On Sat, Jan 4, 2020 at 2:29 PM Panos <sadosp@...> 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.



Re: Tek514D Blows Fuse

KB6NAX
 

That is an apt description of a 5U4 rectifier tube, Steve. But you did two no-no's with your dad's 514D. Putting in a much larger size fuse is a way to do serious damage to a power transformer. If you didn't smell anything like burning shoe leather you're probably OK. Don???t do it again. The other no-no is powering up electronics with 50+ year old power supply electrolytic capacitors that haven't seen voltage in many years. They deform over time, i.e., the aluminum oxide insulating film deposited on the anode (+) plate breaks down resulting in increased current flow between plates. If the current is high enough a hot spot will form that destroys the oxide film and causes a dead short between plates. That is most possibly what happened.

Old electrolytic capacitors that have not been operated to the end of their life can be reformed but it is a delicate operation to gradually increase applied voltage so as not to cause overheating until oxide reformation is adequate to stand off the normal operating voltage. The line voltage applied to the scope is gradually raised in successive steps utilizing a variac while line current is monitored at each step for 20 minutes or more. If current appears to be rising after several minutes decrease the voltage and observe if line current decreases and continues to decrease over hours before raising the voltage more. If you are unable to get to 120 volts without the current running away there's no chance of saving a failing capacitor. It has to be replaced. On the subject of electrolytic capacitors in general have a read: <https://en.wikipedia.org/wiki/Electrolytic_capacitor#Charge_principle>

If you are in luck only one of the gang of electrolytic capacitors is shorted. Making sure that all of the electrolytic capacitors are fully discharged before probing them with an ohmmeter will keep you from being badly bitten. Pull the power cord out of the wall and go shopping or watch the ball game on TV before looking for a shorted capacitor. While you are in the power supply you will also want to look for open electrolytic capacitors. That takes applying a high frequency signal, say 50-100 KHz, across capacitor terminals while observing with an oscilloscope or AC voltmeter that has sufficient bandwidth. Open capacitors will not act as an AC short circuit. The better the capacitor the lower the AC voltage across terminals.

Replacing failed electrolytic capacitors is a subject I'm not going to impart here. The subject gets involved with many competing opinions as to how to make a quick and reliable job of it. You could say it's the price you pay for a moment of misappreciation. Some studies of YouTube videos will give you some ideas. Good luck.

Arden

-----Original Message-----
From: Steve Hendrix
Sent: Saturday, January 04, 2020 5:38 AM
To: TekScopes@groups.io
Subject: [TekScopes] Tek514D Blows Fuse

My dad is a long-retired EE, and no longer able
to do a lot of electronics. But we are enjoying a
chance to work together, where I can be his eyes
and hands while he shares his knowledge of
ancient (to me) history. I'm a practicing EE
today, but my knowledge of tubes is mostly
theoretical. I live about an hour away from him,
so need to be sure I take along everything I need
when I visit. So there's the picture.

Yesterday I attended a funeral for a high school
classmate of mine, and took the opportunity
afterwards to visit Mom & Dad to tinker some more
with another instrument (to be discussed on the
HP group). I didn't have my scope along and found
that we needed one, so fired up his Tek514D. Not
so much, this first try - no line fuse installed.
We couldn't find any reference for the correct
fuse (I've since found it, a 5A slo-blo) and the
only one we had handy was a 20A - the house
circuit breaker will protect that! But we tried
it anyway. Power switch on, pilot light lights,
fans run.....maybe 20 or 30 seconds, then all
dark. Yup, the fuse is more than clearly blown.

Based on discussions here and on the HP group,
I'm suspecting deteriorated electrolytic caps in
the power supply. I found a schematic on the Bama
site. It appears that Tek liked to just stock one
size (20 ??F) and use them in parallel where more
capacitance was needed. I assume that those
probably need at least a 630V rating. We didn't
have time to open up the scope, as I had to
attend to several household repairs while there.
Can anyone guide me as to what physical size is
going to fit, and even get so specific as to what
to order from DK? I have a large stock of
capacitors of all sizes, but very limited on
high-voltage types as I mostly work at 24VDC and
below these days. Any other tips as to how to tackle this?

One other question as well. I recognize the
schematic symbols for triodes, tetrodes, and
pentodes. But they use an unfamiliar symbol
several times in the schematic of the power
supply. Sometimes two plates on opposite sides of
a circle, with a little hook entering 90?? from
the plates (similar to the cathode symbol in the
tubes). Sometimes the two plates are
side-by-side, with the hook directly opposite
them. What is that? Based on the way they're used
in the schematic, I'm speculating that they're diodes. (?)

Steve Hendrix

Re: TDS694C 50 Ohm Overload

George Langston
 

Reg, Eric,
I looked high and low for a burned 50 ohm resistor - everything was perfect compared to the other channels. The termination measures a perfect 50 ohms *until* the bad channel is activated. Then the signal is routed (through 2 relays) to one of two inputs to the 156-8127-00 input attenuator/preamp device, and I believe termination then takes place within this device, and this is where it became damaged. The only tds scopes that I know of that utilize this input attenuator/preamp device are the 694c and the 794d. It sort of provides the same function as the hybrid attenuators in all the other tds 500/600/700 scopes. Since this is a 3GHz, 50-ohm only scope with dc coupling only and a 10mV/div to 1.0mV/div range, it requires a different custom input device.

The "50-ohm overload" error message shows up when SPC is run - both in the error log and in the onscreen comments after SPC fails. The signal is clean going into the device (ruling out the relays). Everything points to the attenuator/preamp (unobtainable) device.

-George

Re: Tektronix 2465 for sale ...

Chuck Harris
 

I'm not sure why you think this error has anything to do with the
horizontal sweep. It is specified on page 6-11 in the service manual
with this cryptic phrase:

Positive level too positive

This is a test of the triggering system, the CPU's DAC and MUX circuitry,
and the line trigger transformer.

The scope has a transformer that goes to the power line, and its output
winding is routed to the trigger hybrid as a test signal. The CPU attempts
to adjust the trigger point to where the hybrid just triggers, sequentially
to trigger on the positive peak of the sine wave, and then the negative peak
of the sine wave. It knows approximately what voltage that should be.

If the voltage necessary to trigger the trigger hybrid is above the highest
expected value for the positive peak of the sine wave, it will fail with:

Test 05, Error 4X

If the voltage necessary to trigger the trigger hybrid is below the lowest
expected value for the negative peak of the sine wave, it will fail with:

Test 05, Error X2

If both of these fault conditions exist it will display:

Test 05, Error 42, which is the logical sum of both error conditions.

It has nothing to do with the horizontal.

Usually this is caused by a problem with the trigger hybrid, or perhaps
the circuitry that drives it.

-Chuck Harris



rskrishnan@... wrote:

Hello All,
The new year has pushed me to realize that I am _never_ going to find time to poke around with my Tektronix 2465 :(
I'm happy to sell it to someone who might actually restore and _use_ it.
Details:
Tektronix 2465 oscilloscope. 4 channels, 300 MHz.
Reference info - http://w140.com/tekwiki/wiki/2465
The scope powers up fine, but POST shows that Test 05 fails with condition 42.
I think this is related to the horizontal sweep.
Most likely needs caps replaced - which is a typical problem with these scopes with age.
Scope is in good condition, display is fine, focuses well.
This could be a great scope if you are willing to spend time and replace caps.

I bought this for around $250 a few years back. Happy to sell this for something reasonable.
Please ping me for pics if you want to see it power up or the POST message.



Re: TDS694C 50 Ohm Overload

Stephen Hanselman
 

I think, underline think, that a good number of those fails are due to bad relay contacts but cannot prove that yet.

Regards,

Stephen Hanselman
Datagate Systems, LLC

On Jan 4, 2020, at 14:01, Reginald Beardsley via Groups.Io <pulaskite=yahoo.com@groups.io> wrote:

If it works on the higher setting, the problem is in the input section ahead of the ADC. I'd look for a burned 50 ohm resistor. Or perhaps a cracked solder joint.

I saw several of these on ebay with the SPC fail, but had been unable to find any information about what might be wrong with such a unit. How did you get the input damage information?

Reg


Re: TDS694C 50 Ohm Overload

EricJ
 

A lot of SPC fails on TDS scopes seem to be related to contact resistance in the switching relays on the hybrid acquisition boards. I have a TDS754D that had that problem. Changing the relays solved it.

--Eric

On Jan 4, 2020 4:00 PM, "Reginald Beardsley via Groups.Io" <pulaskite=yahoo.com@groups.io> wrote:




If it works on the higher setting, the problem is in the input section
ahead of the ADC.  I'd look for a burned 50 ohm resistor. Or perhaps a
cracked solder joint.

I saw several of these on ebay with the SPC fail, but had been unable to
find any information about what might be wrong with such a unit.  How did
you get the input damage information?

Reg





Re: Tektronix 2245a Flickering Trace

William Schuler
 

Exactly!

On Sat, Jan 4, 2020 at 9:39 AM Panos <sadosp@...> wrote:

On Sat, Jan 4, 2020 at 02:59 PM, William Schuler wrote:

That makes me wonder – can you use a mostly functional scope to diagnose
itself?
I think that already I see the Star Trek to arriving as to save the earth
after this!!!



Re: Does anyone know Ynvge Von Spalden's current email address?

Göran Krusell
 

Perhaps it should be Yngve? That is the way I would spell it. Göran

Den lör 4 jan. 2020 23:29Dennis Tillman W7PF <@Dennis_Tillman_W7PF> skrev:

I'm trying to reach Ynvge von Spalden, a member of TekScopes.

Does anyone know his current email address?
If so contact please contact me off list at dennis at ridesoft dot com.

The email address I have been using as recently as August 2019 just bounced
back to me as an unknown address.
Dennis Tillman W7PF

----
Final-Recipient: rfc822; dvs@... (I deliberately crossed out
most of his email address)
Action: failed
Status: 0.0.0 (Unknown class - no additional status information available)
Diagnostic-Code: smtp; 550 5.1.1 Unknown recipient



--
Dennis Tillman W7PF
TekScopes Moderator



Does anyone know Ynvge Von Spalden's current email address?

 

I'm trying to reach Ynvge von Spalden, a member of TekScopes.

Does anyone know his current email address?
If so contact please contact me off list at dennis at ridesoft dot com.

The email address I have been using as recently as August 2019 just bounced
back to me as an unknown address.
Dennis Tillman W7PF

----
Final-Recipient: rfc822; dvs@... (I deliberately crossed out
most of his email address)
Action: failed
Status: 0.0.0 (Unknown class - no additional status information available)
Diagnostic-Code: smtp; 550 5.1.1 Unknown recipient



--
Dennis Tillman W7PF
TekScopes Moderator

Re: Sony/Tek 318 Logic Analyser - parts needed

 

Hi Gala,
Please provide your contact information so interested members can get in touch with you directly and not through the list.
This will keep unnecessary personal business off TekScopes.
Note that you will have to spell out your email address since groups.io will alter it otherwise.
Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Gala Dragos via Groups.Io
Sent: Saturday, January 04, 2020 8:21 AM
Subject: [TekScopes] Sony/Tek 318 Logic Analyser - parts needed

Hi,
I am looking for an MPU & DISPLAY board for a Sony/Tektronix 318 Logic Analyser, mine is all messed up and difficult repair.
Please quote if you got any. I live in the EU.
Thanks




--
Dennis Tillman W7PF
TekScopes Moderator

Re: SG5030 and SG504 leveling heads

Melvin Gleep
 

I bit the bullet and bought one on Ebay (outch!). I will use your SG504 development as a guideline and see if I can come up with something as a substitute. If successful I might be able to resell it and get some of my money back.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ancel
Sent: Freitag, 3. Januar 2020 17:21
To: TekScopes@groups.io
Subject: [TekScopes] SG5030 and SG504 leveling heads

I've considered doing a head leveling replacement for the SG5030, but without one on hand to develop on it has not happened. The SG504 head I made runs at nearly double the frequency range of the SG5030 so I imagine it is quite possible to develop.

The capital Investment for the SG5030 and the mainframe for it makes the exercise not a sustainable one so far, unless the replacement heads have some guaranteed sales.

My development of a SG504 head occurred because I own a SG504 and found that the David P's groundbreaking head kit was a bit difficult to assemble/use without an OEM head housing on hand (and also required an additional calibration step) . So offering a more compact, complete working head in a custom enclosure negated the need for the DIY calibration. Overall the community supported my efforts and the head I designed/built still sells occasionally (one every 2 months or so) online on EBAY, but I rarely promote it now as I have other products in the pipeline to manufacture.

However, never say never. I may have the opportunity one day to work with the SG5030.

Re: TDS694C 50 Ohm Overload

Reginald Beardsley
 

If it works on the higher setting, the problem is in the input section ahead of the ADC. I'd look for a burned 50 ohm resistor. Or perhaps a cracked solder joint.

I saw several of these on ebay with the SPC fail, but had been unable to find any information about what might be wrong with such a unit. How did you get the input damage information?

Reg