1. TekScopes@groups.io
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Re: Please help with TDS340A

James
 

...Also what do you recommend to glue the electrolytics to each other and/or the board. They currently are mostly stuck; do I use hot glue or silicone and if so which grade is suitable?
Re: Please help with TDS340A

James
 

Thanks again Harvey.
I took the scope apart and pulled out the display module. Praise be, it's through hole components! It also appears that the HV section and horizontal deflection parts are all on this module. Following on I have a couple of further dumb questions:
The CRT has a white connector at the end, I presume it works like a valve base and I just gently pull it away from the CRT pins? Any advice/tips on doing this?
The service manual is full of obsolete part numbers for the electrolytics, with no datasheets easily obtainable. The caps are a mixture of 35-160V types from Nichicon and similar and all look fine but as yet unmeasured. It's probably easier to just pull them out and replace them, there's only a handful. Do I need particular spec capacitors or am I likely to be ok if replacing 105C +50-20% types with others that meet this spec (and obviously the same or higher working voltage)?
The parts list distinguishes CAP;FXD;ALUM from CAP;FXD;ELECTLT. Are these all aluminium electrolytics or is there some other difference I am unaware of? They all look like electrolytics!
Many thanks as ever in advance.
Re: Which programmer to use to read/write dallas DS1486?

Raymond Domp Frank
 

On Mon, Sep 21, 2020 at 08:31 AM, tgerbic wrote:


The info in the datasheet is probably not clear because "you should not need
to know this". Based on looking at this and other family datasheets it seems
as if the difference between the W and non-W version is the power fail voltage
level. Both chips seem to be ok with 6V on any pin so I suspect they both work
on 5V but the W version should not be used in a 5V environment because of the
power fail level being so low. This is just a guess from looking at the
datasheets so it is your choice to try it. I would probably pop it into my
Xeltek or Unisite and program it that way but if I did not have either, I
would try programming as a 5V part.
Alternately, if you are worried, you could try the Arduino driving SRAM method
I mentioned to Rogerio on this thread. In that case you could drive it at
3.3V.

I ran into a similar won't work problem with one of my HP 16xx logic analyzers
and its LAN interface. Turns out if the MAC address is not programmed in Flash
(battery died in a timekeeping device), the LAN interface will not come up at
all. I just programmed in a typical value for an HP device (random MAC) and it
came right up. Guess this is the same as your problem.
Hi Tony,
Thanks for your comments. 5 V seemed to be OK for the DS1742W because the data sheet made no distinction between the 3.3 V and 5 V version re. Vcc max. and the idea that the difference in Vpf did not indicate any other differences in the chip.
That was until I saw the data sheet of newer devices, where a Vcc max of 4.6 V is specified for the 3.3 V part. Could all be the reason you mentioned but I have no spare DS1742W in case it dies and can't easily get one, although alternatives exist. That's the main reason for being so careful and hesitant.
I decided to connect/cloak my DS1742W as a DS1750W, although the latter is much larger but it's supported in my programmer (TL866II Plus). Connecting the DS1742W seems quite easy, with most pins straight through and just two wiring changes.
I'll keep your hint re. an Arduino in mind.

ISTR a similar problem with HP's 16702A/B LA's.

Raymond
Re: TDS6604 Acquisition Board Replacement

guy_ellis_1964
 

Hi Charlie,

I tried running SPC but it looks like the Acquisition board I have purchased is faulty. SPC fails and channels 3 and 4 are unstable beyond 2.5GS/s.

I might re-visit the original Acq. board - it has one faulty trigger chip which only affects channels 3 and 4.
Apparently the Tek # 156-8278-00 chips are unobtainium.

Regards,
- Guy
Re: Which programmer to use to read/write dallas DS1486?

tgerbic
 

Raymond,

The info in the datasheet is probably not clear because "you should not need to know this". Based on looking at this and other family datasheets it seems as if the difference between the W and non-W version is the power fail voltage level. Both chips seem to be ok with 6V on any pin so I suspect they both work on 5V but the W version should not be used in a 5V environment because of the power fail level being so low. This is just a guess from looking at the datasheets so it is your choice to try it. I would probably pop it into my Xeltek or Unisite and program it that way but if I did not have either, I would try programming as a 5V part.
Alternately, if you are worried, you could try the Arduino driving SRAM method I mentioned to Rogerio on this thread. In that case you could drive it at 3.3V.

I ran into a similar won't work problem with one of my HP 16xx logic analyzers and its LAN interface. Turns out if the MAC address is not programmed in Flash (battery died in a timekeeping device), the LAN interface will not come up at all. I just programmed in a typical value for an HP device (random MAC) and it came right up. Guess this is the same as your problem.

Regards
Tony
Re: Is my Tek 468 beyond repair? Trap and Kernel test procedure

Heitor Lima
 

Hi Tony
Thank you very much for your guidance.
I have been looking for an image of SERVICE ROM for about 5 years without success. It is unbelievable that nobody in the group has this file. After all, TEK 468 was very popular in the world. I have the image files for the 2 ROM's but unfortunately I don't have the image file for the SERVICE ROM.
All power supply are OK with voltages according to the specifications in the manual. The ripples are also OK.
I'll start with where you suggested.

Regards

Heitor

On Monday, September 21, 2020, 02:02:39 AM GMT-3, tgerbic <tgerbic@gmail.com> wrote:

Heitor,
POST 3000 indicates that the acquisition RAM has failures.  The fact that the testing took place indicates the processor, address bus, data bus and ROM should be ok.  The next step would be to use the Service ROM to run some tests, especially on the acquisition RAM. No one seems to be able to product a copy of the service RAM so using the manual's troubleshooting by Service ROM is not going to work.  Additionally the manual is focused on using a signature analyzer for much of the testing.  Most people don't have one, and I assume you don't either.  They were popular back in the 80s but you don't see them today. So, I think the way forward is to use a more general troubleshooting process.

Acquisition RAM is on the A18 board so I suggest you start on the "Partial A18 Memory Board Schematic" ACQUISITION MEMORY<14>. The upper right shows the RAM and the address/data decoders. I would start looking there. Perhaps focus your logic analyzer on one of the chips and see where the test stops when the POST 3000 comes up.  Could be a bad RAM chip(s).  Since both scopes show a POST 3000 error, it could be the RAMs going bad.  I would find it hard to believe you would have identical logic failures on both scopes.

I assume you have checked the digital supply voltages, especially for high ripple voltage.  There are two +5V power supply systems, one for the microprocessor section at the back of the scope and a second one on the A15 board which powers digital logic in the rest of the scope.  Make sure you rock any ICs that are in sockets to make sure they are making contact in the crummy TI sockets.  I would avoid touching the A/D converter chip as it is big and if you break it, it might be very hard to find a replacement.

In any case this should get you started.

Regards
Tony
Re: Which programmer to use to read/write dallas DS1486?

tgerbic
 

Rogerio,

The Xeltek 610P will also program these. I suspect any programmer that can program a 128K battery backed RAM chip, and can be set to start at 0E hex, should be able to program the chip.

You could take a different out-of-the-box approach and attach the chip to an Arduino, wire it as a 128K static RAM chip and write to it skipping the first 14 bytes (0D hex) used by the timekeeping circuit. Might be faster and cheaper than buying a programmer just to burn a flash. Just remember to skip the first 14 bytes as they are used by the timekeeping circuit. 0E hex and higher is RAM. I suspect the data you need to program in is much less than the 128K. You only need to wire up as much RAM address as needed to cover the data you need to program. Pull the rest of the address lines down. Take a look at the data and see how much there is and if there is a serial number or MAC address at the start of the data file. You might just need to add a serial number to get the scope back up.

Regards
Tony
Re: Is my Tek 468 beyond repair? Trap and Kernel test procedure

tgerbic
 

Heitor,
POST 3000 indicates that the acquisition RAM has failures. The fact that the testing took place indicates the processor, address bus, data bus and ROM should be ok. The next step would be to use the Service ROM to run some tests, especially on the acquisition RAM. No one seems to be able to product a copy of the service RAM so using the manual's troubleshooting by Service ROM is not going to work. Additionally the manual is focused on using a signature analyzer for much of the testing. Most people don't have one, and I assume you don't either. They were popular back in the 80s but you don't see them today. So, I think the way forward is to use a more general troubleshooting process.

Acquisition RAM is on the A18 board so I suggest you start on the "Partial A18 Memory Board Schematic" ACQUISITION MEMORY<14>. The upper right shows the RAM and the address/data decoders. I would start looking there. Perhaps focus your logic analyzer on one of the chips and see where the test stops when the POST 3000 comes up. Could be a bad RAM chip(s). Since both scopes show a POST 3000 error, it could be the RAMs going bad. I would find it hard to believe you would have identical logic failures on both scopes.

I assume you have checked the digital supply voltages, especially for high ripple voltage. There are two +5V power supply systems, one for the microprocessor section at the back of the scope and a second one on the A15 board which powers digital logic in the rest of the scope. Make sure you rock any ICs that are in sockets to make sure they are making contact in the crummy TI sockets. I would avoid touching the A/D converter chip as it is big and if you break it, it might be very hard to find a replacement.

In any case this should get you started.

Regards
Tony
Re: Looking for TM503B manual

Gregor Lasser
 

Hi Jared,

To change the line voltage on the TM503B simply pop out the bright grey plastic piece that is part of the line selector/power switch/power connector assembly on the back. (The piece that shows 240 (V) in the little window on the left side)
http://w140.com/tekwiki/wiki/TM503#/media/File:Tek_tm503b_pwr_supply_rear.jpg

Greetings,
Gregor

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jared Cabot via groups.io
Sent: Sunday, September 20, 2020 3:50 AM
To: TekScopes@groups.io
Subject: [TekScopes] Looking for TM503B manual

I'm poking away at my TM503B and wondering if anyone has a manual for this mainframe?
I've found the TM503 manual, but no B version yet.

Failing that, does anyone know how to set the line voltage, and what Option 2 is?


Thanks!
Re: 585A -- time base A linearity

Sean Turner
 

Did some poking around today. Deoxit didn't change anything. I noted, however, that the linearity issue is definitely temp related. It starts out in spec, then drifts out as the instrument warms up. I reckon this probably points right at the timing capacitors (which appear to be hidden behind the adjustable trimmers). No idea how to get to them short of considerable disassembly. Any suggestions on a modern replacement cap?

Sean
Re: Is my Tek 468 beyond repair?

Ray
 

Yep done similar repairs just from the top of the board when the need arose.


-Ray

On 09/20/2020 4:43 PM tgerbic <tgerbic@gmail.com> wrote:


Roger,

The PDF schematic is a bit hard to read but you are right they are S types which, based on a 74S112 datasheet, four Clock inputs could pull 4ma each worst case for 16ma total. I think the oscillator can drive up to about 20ma. Good suggestion to move to HCT.

Ray,
I have a couple of old electrical cutters (1970s era) that have a fine point and great for cutting IC pins. I also use this method of rework from the top of the board on chips and axial leaded components. Some products are a nightmare to get a board out to desolder/rework from the bottom. Sometimes you can cause a lot more problems with the device by trying to take everything apart. Can be hard to install sockets unless you install something like a machined single row WW-pin type connector with the leads shortened but it can be done.

Regards
Re: Which programmer to use to read/write dallas DS1486?

J. L. Trantham
 

Roger,

I agree, probably too much hassle.

I looked at the Advin website but the earliest programmer I see that specifically supports these two chips is the SpeedPro 280A. It is USB connected but does not work with Win 7 or later. Needs WinXP or VISTA.

Happy to help if I can.

Good luck.

Joe

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Rogerio O
Sent: Sunday, September 20, 2020 9:11 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Which programmer to use to read/write dallas DS1486?

Hi Joe,
Thank you for your kind offer, but I am located in Brasil.
I think it would be too complicated to ship the Nvrams to you to have them read and programmed.
Regards,
Roger
Re: Looking for TM503B manual

Raymond Domp Frank
 

On Sun, Sep 20, 2020 at 11:52 PM, Jim Ford wrote:


I find it interesting that the first version of a Tek model had no letter
after it, while the first version of an HP model always had an "A"
Model numbers with a letter following the model make life a lot easier when looking up an instrument on the Internet. Take 465 vs 465B, 2265 vs 2465A.

Raymond
Re: Looking for TM503B manual

Jim Ford
 

I find it interesting that the first version of a Tek model had no letter after it, while the first version of an HP model always had an "A", which would be the second version of a Tek scope or other piece.  Makes things confusing for those of us with large quantities of both Tek and HP gear. Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Dennis Tillman W7pF <dennis@ridesoft.com> Date: 9/20/20 2:24 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Looking for TM503B manual Hi Jared,Congratulations on finding a TM503B. "B" versions of a product are uncommon for Tek to make. They are an indication that the product sold very well. Tek was also convinced it would continue to sell well. There were two main reasons to create a "B" version of a product. 1) To update it to meet current market requirements such as new electrical standards, safety standards, international environmental standards (such as being free of lead or mercury), energy efficiency goals, etc.2) To reduce manufacturing costs, reduce parts count, reduce assembly time, improve product performance, improve product reliability, reduce the total cost of ownership for the customer, etc.I have seen enough different TM503s that I am certain Tek made many versions of the TM503. I posted a 4 page paper on a TM503 that I came across that had every indication of being a very late model TM503 judging from how simplified Tek's production engineers redesigned it for quick assembly and low manufacturing cost. This particular TM503 was unusual for many reasons: * There were no markings on indicating what it was but you could tell immediately that it was a TM503 by looking at it. * It had GPIB connectors for each slot like a TM5003 would have.* The power supply was a conventional transformer and filter caps analog design, and not a switching power supply like the TM5003 has.* It produced higher TM5xx DC voltages than the TM5003 and TM5006.  TM500x voltages are lower than the TM5xx unregulated voltages because TM500x voltages are regulated by the switching supply they use.You may find something that applies to your TM503B in the unusual TM503 I found and modified. It is at: https://groups.io/g/TekScopes/files/Modification%20of%20an%20Unusual%20Three%20Wide%20TM%20Mainframe%20into%20an%20ordinary%20TM503/Unusual%20Three%20Wide%20TM%20Mainframe.pdf.You may have to paste that link back together to use it. Alternatively you can simply do a search for Unusual TM503in the TekScopes files section and find it that way.Dennis Tillman W7pF-----Original Message-----From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jared Cabot via groups.ioSent: Sunday, September 20, 2020 5:07 AMTo: TekScopes@groups.ioSubject: Re: [TekScopes] Looking for TM503B manualAh ha, I guess I'm going blind, I was looking inside for jumpers and completely missed the selector on the rear power switch. :DRe. Option 2, my unit has the sticker, but no signs at all of any option ever being installed besides one BNC blanking plug missing, but that doesn't necessarily mean much...Maybe I'll go get a few plugs and jacks and install the option myself one day when I get bored.Thanks!Jared.On Sun, Sep 20, 2020 at 07:26 PM, JoeKoch wrote:>> Hi,> Voltage selector is on the back site above the power switch. Pull it > out and rotate it to the correct voltage.> Option 2 is the rear interface, 3 BNC Connectors, 50 pin Sub D > connector on the back site and internal pins.> > Joe> > > > -----Ursprüngliche Nachricht-----> Von: TekScopes@groups.io [mailto:TekScopes@groups.io] Im Auftrag von > Jared Cabot via groups.io> Gesendet: Sonntag, 20. September 2020 11:50> An: TekScopes@groups.io> Betreff: [TekScopes] Looking for TM503B manual> > I'm poking away at my TM503B and wondering if anyone has a manual for > this mainframe?> I've found the TM503 manual, but no B version yet.> > Failing that, does anyone know how to set the line voltage, and what > Option 2 is?> > > Thanks!-- Dennis Tillman W7pFTekScopes Moderator
Re: Is my Tek 468 beyond repair?

tgerbic
 

Roger,

The PDF schematic is a bit hard to read but you are right they are S types which, based on a 74S112 datasheet, four Clock inputs could pull 4ma each worst case for 16ma total. I think the oscillator can drive up to about 20ma. Good suggestion to move to HCT.

Ray,
I have a couple of old electrical cutters (1970s era) that have a fine point and great for cutting IC pins. I also use this method of rework from the top of the board on chips and axial leaded components. Some products are a nightmare to get a board out to desolder/rework from the bottom. Sometimes you can cause a lot more problems with the device by trying to take everything apart. Can be hard to install sockets unless you install something like a machined single row WW-pin type connector with the leads shortened but it can be done.

Regards
Re: Looking for TM503B manual

Dennis Tillman W7pF
 

Hi Jared,
Congratulations on finding a TM503B. "B" versions of a product are uncommon for Tek to make. They are an indication that the product sold very well. Tek was also convinced it would continue to sell well. There were two main reasons to create a "B" version of a product.
1) To update it to meet current market requirements such as new electrical standards, safety standards, international environmental standards (such as being free of lead or mercury), energy efficiency goals, etc.
2) To reduce manufacturing costs, reduce parts count, reduce assembly time, improve product performance, improve product reliability, reduce the total cost of ownership for the customer, etc.

I have seen enough different TM503s that I am certain Tek made many versions of the TM503. I posted a 4 page paper on a TM503 that I came across that had every indication of being a very late model TM503 judging from how simplified Tek's production engineers redesigned it for quick assembly and low manufacturing cost.

This particular TM503 was unusual for many reasons:
* There were no markings on indicating what it was but you could tell immediately that it was a TM503 by looking at it.
* It had GPIB connectors for each slot like a TM5003 would have.
* The power supply was a conventional transformer and filter caps analog design, and not a switching power supply like the TM5003 has.
* It produced higher TM5xx DC voltages than the TM5003 and TM5006. TM500x voltages are lower than the TM5xx unregulated voltages because TM500x voltages are regulated by the switching supply they use.

You may find something that applies to your TM503B in the unusual TM503 I found and modified. It is at:
https://groups.io/g/TekScopes/files/Modification%20of%20an%20Unusual%20Three%20Wide%20TM%20Mainframe%20into%20an%20ordinary%20TM503/Unusual%20Three%20Wide%20TM%20Mainframe.pdf.
You may have to paste that link back together to use it.
Alternatively you can simply do a search for
Unusual TM503
in the TekScopes files section and find it that way.
Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Jared Cabot via groups.io
Sent: Sunday, September 20, 2020 5:07 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Looking for TM503B manual

Ah ha, I guess I'm going blind, I was looking inside for jumpers and completely missed the selector on the rear power switch. :D

Re. Option 2, my unit has the sticker, but no signs at all of any option ever being installed besides one BNC blanking plug missing, but that doesn't necessarily mean much...
Maybe I'll go get a few plugs and jacks and install the option myself one day when I get bored.


Thanks!
Jared.


On Sun, Sep 20, 2020 at 07:26 PM, JoeKoch wrote:


Hi,
Voltage selector is on the back site above the power switch. Pull it
out and rotate it to the correct voltage.
Option 2 is the rear interface, 3 BNC Connectors, 50 pin Sub D
connector on the back site and internal pins.

Joe



-----Ursprüngliche Nachricht-----
Von: TekScopes@groups.io [mailto:TekScopes@groups.io] Im Auftrag von
Jared Cabot via groups.io
Gesendet: Sonntag, 20. September 2020 11:50
An: TekScopes@groups.io
Betreff: [TekScopes] Looking for TM503B manual

I'm poking away at my TM503B and wondering if anyone has a manual for
this mainframe?
I've found the TM503 manual, but no B version yet.

Failing that, does anyone know how to set the line voltage, and what
Option 2 is?


Thanks!






--
Dennis Tillman W7pF
TekScopes Moderator
Re: Is my Tek 468 beyond repair?

Ray
 

So there is a very easy albeit brutal sounding way of dealing with removing DIL type chips:

Take same slim side cutters and snip through every single leg as close as you can to the body.

Then you heat each leg with the solder iron and pull from the other side. Suck out the hole with a solder sucker. Works all the time.
Off course the chip is done for.

I use a crescent brand cutter from home depot, found in the electrical tools section right nex to the zip ties, for which it was probably designed.

You could call it the divide and concur method ;)
-Ray

On 09/20/2020 5:42 AM John <subs@qcontinuum.plus.com> wrote:


He was trying to tell you that until you have a working CPU,
all of your other tests are wasted.

Fair point.

Does anyone have the bin files for the service ROMs, or knows where there is a link to them? I have the bins for the normal ROMs but am looking for the service ROMs to try out on my 468.
I would be interested in the same and a "test ROM" was mentioned in a discussion by Reed Dickson posed by Daveolla posted in message 171596.

https://groups.io/g/TekScopes/message/171596

I was going to go back with a request but only once I got the computer working to a suitable point.

Just my opinion but 100mv of ripple on the digital circuits seems excessive. When I checked my 468 yesterday, I don't think I had more than 20mv of ripple on main PS +5V line.
Agree and must admit to being suprised that 80mVpp was the expected signal. Since I had everything unplugged except the transformer connection from the fuseboard, these indications were without load attached other than the logic chips onboard the A19 board.

Have you tried pulling out pin 1 and connecting it to a 5Mhz clock from a function generator?
I monitored the clock while I was taking the LA trace to make sure that a signal wwas present. Nevertheless, tried an experiment this morning with the CPU board reconnected and a lead clipped to the output of the crystal at pin 1 of U128, and one to pin the output at pin 10 of U120 (couldn't get the clip on pin 5 of U128) to allow me to connect a scope. First thing I observed was that there was no signal at all from the crystal. I set the sig gen for a 10MHz sine, 5V amplitude, 2.0V offset so that the floor was at -0.5V as per the trace at point 151 and injected into the first lead at the crystal output. This gave me almost exactly 2MHz square signal at the output with an amplitude of approximately 4V. I checked pin 1 for the 8085 for the clock signal and it was there. Still no ALE though. I pushed the signal to 20MHz (the max of this particular sig gen), got a 4MHz output, but still no ALE on the CPU.

One thing that puzzles me is that if 50MHz in should give 25MHz out (20ns square = 1/2 cycle = 25MHz) then presumably 10MHz in should give 5MHz out? So although the output using the sig gen seems stable, it is not proportional to the injected frequency.

I am guessing that the 50MHz oscillator is the type in a DIL metal package with just four external pins. The output is driving four Schottky high speed TTL gates which is quite a load (each gate about four times as much load as the usual 74LS devices), but no doubt within the spec of the oscillator package when new. It is possible that one or other 74S112 is moving out of spec and presenting an even larger load which is causing the oscillator to heatup and fail.
Its quite possible as you suggest that one of the 74LS112's is dragging the crystal down. It also seems likely that the CPU is faulty. The logic ICs are not in sockets so I'm not particularly looking forward to trying to remove them from a board with plated through holes. If I go ahead and manage it, then I will probably install sockets.

I assume you will be pulling the crystal and trying it out on the bench before replacing the crystal. The output should be able to drive a 470 ohm load if the crystal is ok.
Yes, I think that will be the next task on the list. Remove the board and extract the crystal + 74LS112s. Might as well rig up a test for the crystal while I'm at it. Not sure how to set it up though. Will need to research.

Is there any possibility of testing the 8085 on a breadboard with minimal hardware? I can hook up a sign gen and power rails. Not sure about memory though.

Looks like the shopping list now consists of an 8085, a crystal, two 74LS112's and IC sockets + parts required for the EEPROM adapters.
Re: Is my Tek 468 beyond repair?

Roger Evans
 

John, Tony,

My copy of the manual has U128 and U230 as 74S122 (not LS122), my memory says that most LS devices are rated to around 40MHz which is why I suggested HCT as a possible alternative. Anyway, until there is some evidence against them there is no reason to replace. The 470R load resistor should be a good test, a quick look at 74S series specs says that you might have to sink 4 x 2mA while keeping the output voltage below 0.8V.

A quick look on ebay (search 50MHz crystal) comes up with a 50MHz crystal oscillator in a 14 pin DIL outline for under £3, you might find a branded one if you look a little harder. I have a similar 50MHz oscillator in an 8 pin DIL package, I will check its performance into 470R tomorrow!

You can, as a temporary measure, add another large electrolytic capacitor across C820 using flying leads to place the (much smaller) new capacitor somewhere convenient. The old capacitors dry out, going low capacitance and high series resistance. They don't do any harm, they just don't do what they are supposed to do. I think the 100mV ripple John measured was with part of the 5V logic circuitry disconnected so it may be much worse with everything connected up.

Roger
Re: TDS 3000B-family 'scope (TDS 3014B) has problem with LAN interface

Raymond Domp Frank
 

That may be a very useful hint, John! Simple to check and repair.
I'll check the PSU and its startup behavior, although it seems that the problem with Ethernet connectivity is caused by the NVRAM battery failing, resulting in intermittent running of the clock and loss of the MAC (hardware) address. I found a complete description of my problem, complete with cause and all symptoms, on EEVBlog.

Raymond

On 20-sep.-20 20:55, John Gord via groups.io wrote:
Raymond,
I have seen several TDS30XXB scopes with flaky power supplies. The problem is in the optoisolator used for feedback, which looses gain with age and demands too much current from the TL431 reference, causing the supply to sag and the reference to overheat (and sometimes die).
Check to see if the power supplies are behaving during startup. I am not sure, but you might be able to monitor the supply adequately via the +15V output jack on the back.
--John Gord

On Sat, Sep 19, 2020 at 03:30 PM, Raymond Domp Frank wrote:

I recently acquired a TDS 3014B 'scope.
It looks fine and operates as it should, except for its LAN interface.
In the beginning (first half day since I got the 'scope), it could sometimes
be configured and would be OK for a while, then stop after a few minutes.
Now, after a few days, the LAN interface does not work at all and even hangs
up (blocks) the 'scope when I select the DHCP button in the LAN setup menu:

Immediately after I press the DHCP enabling button, the usual popup telling me
it'll try and acquire an IP address appears. After that, everything stays
frozen and no buttons or knobs respond. The only way to get out of that
situation is power cycling, however after that, the scope shows its normal
background, graticule, numbers etc. but no traces appear and it does not
respond to operating keys or knobs.
The only remedy seems to be power cycling while doing a Reset by keeping the
"B Trig" button depressed during power up.
This to me looks like a hardware/firmware failure. I haven't found a way to
completely disable/enable the LAN interface, thereby possibly resetting the
thing.

I'd very much appreciate any remedies, ideas or info.

Raymond
Re: Is my Tek 468 beyond repair?

tgerbic
 

John,
The oscillator can be replaced by most any other of the same design and frequency. The Motorola K1100A series would be the correct datasheet to look at. There are several other manufactures such as Sunny SCO-010, Valpey-Fisher VF155-T or one from Koyo. To test, connect pin 14 to +5, pin-7 to ground and pin 8 is the output. Pin 1 is no connect. You can see if the amplitude and frequency are as expected. Then connect a 470 ohm resistor across pin 7 and 8 to load it down. It should still produce a good TTL waveform. If so, the oscillator should be ok. If the oscillator is actually bad, I would not touch the LS112s but rather put a 50Mhz (or in your case a 20Mhz) squarewave on the oscillator output trace (oscillator removed), and make sure the flip flops are all working with a clock at pin 1 of the CPU. Got to have a clock to run...

Roger mentioned the loading from the LS112s. If the oscillator spec is 10 TTL loads then it can drive up to 10 devices with 1 standard TTL load each. There are four LS122 pins sitting on the oscillator so the load would be at least 4 TTL loads, assuming the chips are good. If the chips had been replaced with 74S112 then they would greatly exceed the driving capability of the oscillator. Make sure the chips are at least LS chips. If you think you are going to pull and replace the chips anyway, you might leave them in place and carefully cut one input pin at a time to see if the oscillator will stop fading. If you are taking the board out and putting in sockets, and the oscillator checks out ok, I would just start with the old chips out and put them back in the new sockets one at a time. Many different ways to troubleshoot this problem :)

Might as well recap if you can, while the digital cards are out of the way. The back of this scope can get very hot. Make sure you use good quality 60 degree C or higher caps. You may have a bit of trouble finding exact replacements for the multi-pin caps. Newer technology caps are generally much smaller and my have lower ESR. You may need to find a two-pin cap of the same or higher V and C to put in. Also might want to put a dab of high temp silicon (like you find in switching supplies on the capacitors) in place to keep the cap from moving in transit. This is a practical solution but not authentic looking.

Regards
Tony
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