Date   

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

 

Earlier today, I did as I described earlier and successfully "programmed" the DS1742W, cloaking it as a DS1750W, at 3.3 V on a TL866II Plus.

The TDS 3014B's ethernet connection is working fine now!

Raymond


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

 

On Mon, Sep 21, 2020 at 11:14 AM, Raymond Domp Frank wrote:


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.
Earlier today, I did as I described above and "programmed" the DS1742W successfully at 3.3 V on a TL866II Plus.

Raymond


Re: Is my Tek 468 beyond repair?

Brian Cockburn
 

Hi,

When I look at the Nexperia 74HCT112 data sheet I would guess that it will be fast enough. You may have to buy a few and hand select. But, and it's a big but, they look to only be available in surface mount. No DIP part. :-( Going for a 74S112 from a NOS vendor would be the best solution I reckon. And. just in case a reminder is needed. eBay and various Chinese vendors sometimes end up delivering re-marked parts (whether this is deliberate or inadvertent is a discussion for another day), so testing/validating the part on the bench is essential IMHO. You don't want to be installing a re-marked LS part that will fade out as the temperature goes up, if it even managed it at the start.

Cheers, Brian.


Auction for 7K scopemobile

Dave Seiter
 

Just spotted a scopemobile for 7K gear at an auction in Paso Robles, Ca (south west of the bay area).  Lot 131:
https://precisionwarehouse.hibid.com/catalog/233676/monthly-auction-september-26th/?cpage=3

They say it would be great for a welder...
Dave


Re: Is my Tek 468 beyond repair?

Ray
 

hmmm...

Looked at the TI datasheet: fmax for the 74HCT112 is typically 60 Mhz. So it is worth trying.

I somehow got the price wrong by a few cents, at mouser it is actually 68 cents in single quantities and they still have 788 ea in stock.

Ray

On 09/21/2020 3:19 PM tgerbic <tgerbic@gmail.com> wrote:


On Mon, Sep 21, 2020 at 10:54 AM, ron roetzer wrote:


The 74HCT112 is only guaranteed for 24MHz clock. The 74S112 is rated for 80MHz minimum. The 74F112 is rated for 100MHz min.
Makes sense to look at the rated speeds. Tek picked the S type for a reason, and it is clock speed. If the oscillator is replaced, the original part numbers would work as designed, as they did for the last 30+ years. Pick F if you cannot find S. Digikey and Mouser have both types in stock. I did not see them at Allied, RS or Farnell.


There are only 4 actual pins, but their positions are mapped onto a 14 pin DIL package?
Yes oscillators often come in 8 or 14 pin footprints, so the pins are referred to by DIP numbering.

Regards
Tony




Re: Is my Tek 468 beyond repair?

Chuck Harris
 

Sounds to me like the crystal oscillator is feeding a
shorted input.

-Chuck Harris

John wrote:

I managed to remove the crystal without any damage to the board using the SMD heat gun. I tested is as suggested with a 470Ω load resistor. The output was around 3.5V and stable for several minutes. Without the load resistor the amplitude was over 4V. Frequency is just a smidgen under 50MHz (49.999xxx) on the FC. I hooked it back up to the board using jump leads, powered up the 5V rail but there was no output. I hooked up the sig gen again and got output from both 74S112s. Could it simply be that the sig gen is handling the sink current better than the crystal? Or does the almost 0.8V voltage drop under load suggest that the output from the oscillator is weak? I'm still uncertain whether to replace both ICs and the crystal for good measure?






Re: Is my Tek 468 beyond repair?

John
 

The 74LS112 spec sheet quotes maximum clock frequencies of 25MHz or 30MHz depending on the loading of the outputs. It is going to be decidedly marginal at 50MHz.
The 74HCT112 is only guaranteed for 24MHz clock. The 74S112 is rated for 80MHz minimum. The 74F112 is rated for 100MHz min.
Agreed and thank you for pointing that out. I will not be using the "LS" variant as replacements then. However, the 74HCT112 seems to be rated at 66MHz at a Vcc of 5V?

https://assets.nexperia.com/documents/data-sheet/74HC_HCT112.pdf

The "F" variant looks interesting and plenty available from China, but the 74S112 seems to be the available as genuine NOS parts and perhaps the cheapest option on eBay at present.

Digikey and Mouser have both types in stock.
True and thanks for pointing that out, but the drawback for us in the UK is that both Mouser and Digikey have a £12 shipping cost. Not unreasonable given they ship from the USA, but nevertheless dis-proportionally high for a small order under £30.

I managed to remove the crystal without any damage to the board using the SMD heat gun. I tested is as suggested with a 470Ω load resistor. The output was around 3.5V and stable for several minutes. Without the load resistor the amplitude was over 4V. Frequency is just a smidgen under 50MHz (49.999xxx) on the FC. I hooked it back up to the board using jump leads, powered up the 5V rail but there was no output. I hooked up the sig gen again and got output from both 74S112s. Could it simply be that the sig gen is handling the sink current better than the crystal? Or does the almost 0.8V voltage drop under load suggest that the output from the oscillator is weak? I'm still uncertain whether to replace both ICs and the crystal for good measure?


Re: Is my Tek 468 beyond repair?

tgerbic
 

On Mon, Sep 21, 2020 at 10:54 AM, ron roetzer wrote:


The 74HCT112 is only guaranteed for 24MHz clock. The 74S112 is rated for 80MHz minimum. The 74F112 is rated for 100MHz min.
Makes sense to look at the rated speeds. Tek picked the S type for a reason, and it is clock speed. If the oscillator is replaced, the original part numbers would work as designed, as they did for the last 30+ years. Pick F if you cannot find S. Digikey and Mouser have both types in stock. I did not see them at Allied, RS or Farnell.


There are only 4 actual pins, but their positions are mapped onto a 14 pin DIL package?
Yes oscillators often come in 8 or 14 pin footprints, so the pins are referred to by DIP numbering.

Regards
Tony


Re: 2235 Repair having no power

satbeginner
 

Raymond,

Contacted you through MP.

Leo


Re: Is my Tek 468 beyond repair?

Ray
 

Mouser has 788 in stock at 41 cents each.RaySent from my T-Mobile 4G LTE device------ Original message------From: Roger Evans via groups.ioDate: Mon, Sep 21, 2020 12:48To: TekScopes@groups.io;Cc: Subject:Re: [TekScopes] Is my Tek 468 beyond repair?John,

540uF and 390uF sound like 'preferred values' as in resistor values. As far as I know there is no reason for any great precision on the values of reservoir and smoothing capacitors, too small and they don't do the job, too large and they are expensive, take up more space and stress the rectifier diodes on switch on. Quite commonly large value electrolytics will be toleranced at -20% +50%. (or at least they were in my younger days).

The 74LS112 spec sheet quotes maximum clock frequencies of 25MHz or 30MHz depending on the loading of the outputs. It is going to be decidedly marginal at 50MHz.

Regards,

Roger


Re: Is my Tek 468 beyond repair?

ron roetzer
 

The 74HCT112 is only guaranteed for 24MHz clock. The 74S112 is rated for 80MHz minimum. The 74F112 is rated for 100MHz min.

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of John
Sent: Monday, September 21, 2020 11:30 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Is my Tek 468 beyond repair?

To test, connect pin 14 to +5, pin-7 to ground and pin 8 is the output. Pin 1 is no connect.
tgerbic, ok, I think I get this now. There are only 4 actual pins, but their positions are mapped onto a 14 pin DIL package? So far corners would be 1, 7, 8 and 14 as indicated? You are correct that pin 7 is connected to ground. It isn't very visible but a continuity test confirms it.

So there is a very easy albeit brutal sounding way of dealing with removing DIL type chips:
I tried the de-soldering gun and solder sucker but this only removed solder from the top of the joint leaving the hole clogged. Similar problem with the IC pins. From one side the hole looked clean but the other side was still firmly soldered in place. Basically there is no chance of removing any DIL device from this board without a specialised DIL de-soldering tool or snipping pins so removal is going to be destructive and any replacement will have to go into a socket. With the crystal, the problem is that there is no access to the pins so the only way I could test was in situ by cutting the output pin track and soldering 3 short wires to the pins in question. Unfortunately this resulted in no output from the crystal.

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.
Roger is quite correct. The ICs are 74S112. Earlier I had mistakenly stated 74LS112 but I had mis-read the diagram. Using 74HCT112's sounds like a good idea

Incidentally, why are the two caps on the 5V rail such specific values? They are marked Sprague 637D 540μF 25VDC and 672D 390μF 0-15VDC but no indication of tolerence. I couldn't find any data on these, but would 680μF and 470μF 105deg be suitable replacements?

I am just putting together an order to RS. Seems to work out cheaper than ordering individual bits from eBay. Also the 74LS112 is considerably cheaper than the 74HCT112 which I can only get on eBay.


Re: Looking for TM503B manual

Jared Cabot
 

Thanks for the info!
I've seen a couple versions of the TM503 too, even what looked like a TM5003 of sorts with no markings or real part number, it appeared to be a part of a 'pre-built' unit that was never designed to be used with normal TM modules.
It may have been the same as the one you played with in your link..

Jared.

On Mon, Sep 21, 2020 at 06:24 AM, Dennis Tillman W7pF wrote:


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


Re: Is my Tek 468 beyond repair?

Roger Evans
 

John,

540uF and 390uF sound like 'preferred values' as in resistor values. As far as I know there is no reason for any great precision on the values of reservoir and smoothing capacitors, too small and they don't do the job, too large and they are expensive, take up more space and stress the rectifier diodes on switch on. Quite commonly large value electrolytics will be toleranced at -20% +50%. (or at least they were in my younger days).

The 74LS112 spec sheet quotes maximum clock frequencies of 25MHz or 30MHz depending on the loading of the outputs. It is going to be decidedly marginal at 50MHz.

Regards,

Roger


Re: Is my Tek 468 beyond repair?

John
 

To test, connect pin 14 to +5, pin-7 to ground and pin 8 is the output. Pin 1 is no connect.
tgerbic, ok, I think I get this now. There are only 4 actual pins, but their positions are mapped onto a 14 pin DIL package? So far corners would be 1, 7, 8 and 14 as indicated? You are correct that pin 7 is connected to ground. It isn't very visible but a continuity test confirms it.

So there is a very easy albeit brutal sounding way of dealing with removing DIL type chips:
I tried the de-soldering gun and solder sucker but this only removed solder from the top of the joint leaving the hole clogged. Similar problem with the IC pins. From one side the hole looked clean but the other side was still firmly soldered in place. Basically there is no chance of removing any DIL device from this board without a specialised DIL de-soldering tool or snipping pins so removal is going to be destructive and any replacement will have to go into a socket. With the crystal, the problem is that there is no access to the pins so the only way I could test was in situ by cutting the output pin track and soldering 3 short wires to the pins in question. Unfortunately this resulted in no output from the crystal.

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.
Roger is quite correct. The ICs are 74S112. Earlier I had mistakenly stated 74LS112 but I had mis-read the diagram. Using 74HCT112's sounds like a good idea

Incidentally, why are the two caps on the 5V rail such specific values? They are marked Sprague 637D 540μF 25VDC and 672D 390μF 0-15VDC but no indication of tolerence. I couldn't find any data on these, but would 680μF and 470μF 105deg be suitable replacements?

I am just putting together an order to RS. Seems to work out cheaper than ordering individual bits from eBay. Also the 74LS112 is considerably cheaper than the 74HCT112 which I can only get on eBay.


Re: Please help with TDS340A

Harvey White
 

Comments Interleaved:

On 9/21/2020 7:04 AM, James wrote:
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.
Pretty much have to be.  The monitor is pretty much a standard VGA monitor (I'd think) and needs the usual assortment of HV section, Horizontal and Vertical drivers (for the yoke), and a video driver.


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?
That would be right.  Make sure that you are pulling only on the socket, and not the pin holder/base of the tube as well.  I'd be tempted to try to very gently rock it back and forth in case the pins are somehow stuck.  It should be keyed, either by a keyway in the plastic base or, if like a 7 or 9 pin valve, pin spacing
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.
I'd  do a little probing of the power inputs with another scope (I think you said you had one) to look for that 30 KHz waveform. That might tell you which to replace.  Alternatively, you can (assuming it's a 15 volt line), tack a 100 to 1000 uf 25 volt capacitor across that at the input to the monitor and see what that does or doesn't do.

Another possibility is that if there's a shield around the HV (that's HT for you) transformer, then see if the screws are tight.



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!
I suspect that they're all standard aluminum electrolytics, since this is mostly consumer level off-the-shelf electronics in the display.  I'd go for 105 degree C capacitors (typically you'd be getting 85 or 105, 105 lasts longer at higher temperatures, and even at lower ones), working voltage equal to or up to 50% more (that's arbitrary, but a slightly larger working voltage is better).  Do not use a 15 volt or 16 volt rated capacitor on a 15 volt line, just not enough headroom.

and for the actual value, most electrolytics are about -20% + 100% in tolerance, so putting a 150 uf capacitor in place of a 100 uf capacitor should be fine.  If you think it's part of a signal chain, as in a filter for a particular frequency, or something doing timing, then go for the same value.


Many thanks as ever in advance.
Not a problem.  Check out some of the other repair threads some time to see some general "what do I put in its place?" advice. Not sure if anyone ever collected this and put it somewhere.

Harvey





Re: 2235 Repair having no power

tekscopegroup@...
 

I don't have a 2235 manual on hand but this sounds very similar to my case with the T948 main inverter transformer (120-1348-03) used in the 2213A that had failed, in my case on a scope I fixed about 10 years ago. Once I replaced that transformer with one taken from a scrap board, everything came back to life. So these sometimes do indeed fail, although apparently not very often. I never did any testing to the failed one, so no idea what really went wrong. Wish I could offer more insight but that's it for now.


Re: 2235 Repair having no power

 

On Mon, Sep 21, 2020 at 02:47 PM, satbeginner wrote:


Now I need to find another transformer for my 2235, preferably in the EU,
120-1601-01 or similar (2213, 2215, 2215A, ...)
Hi Leo,
I have a 2215 wreck (very incomplete) with a transformer, will have to check.
I also have a 2235 with a defective primary switcher. Never tried to repair.

Contact me if interested.

Raymond


Re: Please help with TDS340A

Tony Fleming
 

Harvey is the BEST!!! I need him to download his brain and email me a copy
of it! Thanks Harvey for helping everyone here!!!

On Mon, Sep 21, 2020 at 6:05 AM James <james@firthgardens.co.uk> wrote:

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.






2235 Repair having no power

satbeginner
 

Hi all,

I am fighting with a 2235 PS.
I previously repaired several 2213 and 2215A's, and it "always" was the primary switcher, but this time....

I removed the Power FET to apply a external 43VDC to see if the scope would work, but no, it looked like a full short, the secondary switcher would not work at all.
I disconnected all secondary diodes from transformer 120-1601-01 , still the same.
I disconnected the 2kV wire and disconnected the two filament wires, still full short, no switching in the secondary switcher.

I checked all components in the secondary switcher circuit, all OK.

I removed the transformer 120-1601-01 (PITA!) and temporarily replaced the two primary windings in the secondary switcher circuit with two 24 Ohm 5W resistors, and behold, the secondary switcher is working!

So, is my transformer dead?

The weird thing is, I applied a 400mV 50kHz sine to one of the primary windings, and all secondary windings give a voltage which looks like OK with respect to what is to be expected??
My thoughts were: if the input is roughly 40V switched, I know roughly what to expect, so if I use a similar, but lower voltage from a generator, I could check the individual outputs?

I still do not know if the transformer is dead or not, but when I connect the two primary windings it will not switch at all.

So to test further, I did the following first: I did a "ringing test" on the transformer.
Basically you apply a fast rise and fall square wave to (one of) the primary winding(s) and measure using a scope the output of one of the secondary windings at the moment of the Rising flank.

More info on this "ringing test" can be found here: https://www.flippers.com/fbt-main.html

Here are some pictures I took: https://groups.io/g/TekScopes/album?id=254000

In the mentioned album you see the result of the TekTronix transformer and the result of an other transformer I got from a switched mode power supply.

When there is (hardly) any "ringing" that means there is a shorted winding, or at least a heavily loaded winding.
But since these transformers are now both out-of-circuit, there should be no load.
However, the TekTronix transformer is showing hardly any ringing, so somewhere in there is a short.... :-(

Now I need to find another transformer for my 2235, preferably in the EU, 120-1601-01 or similar (2213, 2215, 2215A, ...)

Saludos, stay safe,

Leo


Re: Please help with TDS340A

 

Personally I'd use neutral cure silicone. Hot glue gun glue is a pain to remove when you need to.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of James
Sent: 21 September 2020 12:07
To: TekScopes@groups.io
Subject: Re: [TekScopes] Please help with TDS340A

...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?

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