Date   

Re: Tek 7854 Doesn't Come On After EPROM ROM Replacement

 

I thought the extra switch on the late 7854 disconnected the internal memory
backup power but you are right; it acts through the keyboard interface and
directs the firmware at POST to either erase or keep the memory contents so that
is certainly one firmware difference. Changing the switch position after POST
does nothing; I tested it.

Was there a third version with a button instead of a switch?

I wonder what other firmware differences there are.

On Mon, 13 Jan 2014 10:23:07 -0000, you wrote:

There are differences between the early an late firmware, as there's a
button on the rear panel that connects to somewhere(TM) that clears the
saved traces and programs (which weren't retained in the early models of
7854 as they used rear panel connectors on provide 2V to maintain the RAM
contents - 12v at 0.5A and all of it was needed - those early RAMs were
greedy).

I don't have a late model 7854 or documentation so can't be more explicit.

Dave
-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf
Of David
Sent: 12 January 2014 21:39
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] RE: Tek 7854 Doesn't Come On After EPROM ROM
Replacement

I am not aware of any differences in the firmware versions.


Re: Problem after recaping LV power supply on 2445A

amit s
 

Hi David, I am going to get isolation transformer that i found on craigslist locally for safety as you suggested.I just don't want to give up on this and would like to fix it.

Do you guys still think that problem could be in the regulator board.Please suggest me.Thanks.


Re: Tek 7854 Doesn't Come On After EPROM ROM Replacement

bogroca
 

Hi all,


On this topic, one can also check:

http://groups.yahoo.com/neo/groups/TekScopes/conversations/topics/87338

http://groups.yahoo.com/neo/groups/TekScopes/conversations/topics/86351


One can also look into converting the TMS9900 to a soft core on an FPGA, and replacing the MPU board accordingly.


Just saying...


Best regards,


Bogdan


Re: Soldering Thermocouple Wires

petertech99h
 

Hi,

Are you sure you 'soldered' rather then 'brazed' the thermocouple junctions?
Anything near the 'hot section' of a turbine runs way over 900 F, solder melts for sure.

I ran into this in the '80s on a series of jobs. I folded one thermocouple wire
over the other in a small, tight mechanical joint, then brazed it. Making
a mechanical connection where the wires are in tight contact was key for
accuracy, a loose junction that relies on solder or brazing rod winds up
with a 3rd metal 'in circuit' skewing any prospect of an accurate reading.

If you have a long wire run greater then the length of the thermo wire you have, you need to use thermocouple junction blocks specific to that type
(ie J or K type, etc)  and countine the to run to the gauge with identical thermocouple wire. Inside the gauge there will be 'cold junction compensation' so the indicate temp will be accurate no matter the ambient temp at the gauge.

For CSA / UL lab tests we needed bang on temps, any ambient errors due to workmanship in making and connecting thermocouples resulted
in lots of re-tests.

In aircraft applications, accurate temps are key, since the tolerance on turbines for hot starts, etc is just ~200 F over operating temp, easy to blow over in a bad 'hot start'.

Very cool that you got away with series connections on a racing boat!

Cheers,

Pete


On Monday, January 13, 2014 12:57:38 AM, Dennis Tillman wrote:
 
The recent threads regarding soldering to difficult metals reminded me of a product I came across a few years ago while helping a Hydroplane boat racing friend. This is a very serious sport during the summers in Seattle (see http://www.seafair.com/ for more info). My friend wanted me to wire up (in series) the ten thermocouples placed around the body of the turboshaft engine in the unlimited class boat he was modifying. At first I told him this couldn’t be done because the thermocouple metals couldn’t be soldered, bla, bla, bla. But when he pointed out that this was the way all the boat drivers monitored the temperature of their turbine engines I started looking for a flux I could use. I finally found one called AQUA-FLUX which is made by Rectorseal in Houston, TX (USA). I contacted them with my needs and they sent out a small jar of it at no charge for me to use.
 
Aqua-Flux did the trick. I soldered all the thermocouples in series without a problem and the resultant signal was large enough to drive an analog temperature meter mounted in the boat without any amplification whatsoever. I was pretty amazed that it was that simple. I never should have doubted my friend in the first place since he has been racing ‘hydros’ since the late 1960s.
 
I have no affiliation with Rectorseal, other than as an engineer that learned long ago it couldn’t be done.
 
Dennis Tillman W7PF



Re: Soldering and epoxying aluminium

Tim Phillips <tim@...>
 

from Tim P (UK)
There is another product called 'Anu-Sol'
It is vital that the two are not confused !! 
 

----- Original Message -----
Sent: Monday, January 13, 2014 10:22 AM
Subject: RE: [TekScopes] Soldering and epoxying aluminium

 

> For the benefit of people searching the archives, this message is partly to
> signal that some recent messages in the thread: "Re: About the cable used in
> oscilloscope probes" concerned techniques for soldering aluminium

There is a multicore product called Alu-sol, which is for soldering aluminium, and "most other metals"

Available from Farnell and Newark.

Craig


Re: 7Bxx MOD515C [1 Attachment]

 


On 12 Jan 2014 18:56, "Rens Tel" <rensetel@...> wrote:
>
> [Attachment(s) from Rens Tel included below]
>
> I have tried to make a picture as close as possible to show the connectors, see attachment
> Rens

Thanks. Those look like nothing I know. I wonder if they even follow a standard of some sort.

Cheers,
D.


Re: Tek 7854 Doesn't Come On After EPROM ROM Replacement [3 Attachments]

Mark Wendt <mark.wendt@...>
 

On 01/12/2014 03:46 PM, David wrote:
Hmm, I included a picture of the board itself and the layout and schematic from
the service manual in my post as attachments but apparently Yahoo neither
forwarded nor saved them. I wish Yahoo would at least be consistently broken or
working.

I will try this again.

On 12 Jan 2014 12:35:46 -0800, you wrote:

David,

I'd love to see the RAM board, layout, and schematic!

P.
Neat stuff.

A question about circuit board design. I've not done much circuit board design and making other than the old FeCl etching with tape or laser printer masking. Looking at the picture that David put up of the circuit board, some of the traces between the chips look to be quite skinny, while others are wider. What are the determinants on the width of the trace? In other words, why are some skinnier than others? I can understand wider traces for carrying power, but what about the skinny traces?

Mark


Re: Soldering and epoxying aluminium

Craig Sawyers <c.sawyers@...>
 

For the benefit of people searching the archives, this message is partly to
signal that some recent messages in the thread: "Re: About the cable used in
oscilloscope probes"
There is also a Multicore solder called Arax, which solders just about anything including resistance wires http://www.farnell.com/datasheets/69550.pdf

Again either Farnell or Newark sell the stuff. These solders (Alusol and Arax) are not cheap by the way.

Craig


Re: Tek 7854 Doesn't Come On After EPROM ROM Replacement

 

There are differences between the early an late firmware, as there's a
button on the rear panel that connects to somewhere(TM) that clears the
saved traces and programs (which weren't retained in the early models of
7854 as they used rear panel connectors on provide 2V to maintain the RAM
contents - 12v at 0.5A and all of it was needed - those early RAMs were
greedy).

I don't have a late model 7854 or documentation so can't be more explicit.

Dave

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com] On Behalf
Of David
Sent: 12 January 2014 21:39
To: TekScopes@yahoogroups.com
Subject: Re: [TekScopes] RE: Tek 7854 Doesn't Come On After EPROM ROM
Replacement

I am not aware of any differences in the firmware versions.


Re: Soldering and epoxying aluminium

Craig Sawyers <c.sawyers@...>
 

For the benefit of people searching the archives, this message is partly to
signal that some recent messages in the thread: "Re: About the cable used in
oscilloscope probes" concerned techniques for soldering aluminium
There is a multicore product called Alu-sol, which is for soldering aluminium, and "most other metals"

Available from Farnell and Newark.

Craig


Re: About the cable used in oscilloscope probes

EricJ
 

Actually if you miss anywhere with your cleaning it's pretty immediately obvious - the solder doesn't stick there. I would agree that the ultrasonic procedure is probably accomplishing the same exact thing though, and certainly the better, faster procedure for any sort of production work.

--Eric

On Jan 13, 2014 2:21 AM, Don Black <donald_black@...> wrote:
 

I think that's the same type of process as the ultrasonic tinning in that it lifts off the oxide layer. The ultrasonic cleaning probably cleans the entire surface better whereas the rubbing may miss spots. One's better for production, the other fine for one off's. I think any flux would have to be carefully selected to ensure no long term corrosion. The Wharfedale speakers are still going strong after 40+ years. With mechanical cleaning in the molten solder it shouldn't need any flux.

Don Black.

On 13-Jan-14 11:48 AM, wyzkydd2358@... wrote:
 

Aluminum can be easily soldered using regular old leaded solder using the right trick. You don't even need any special flux. Take your soldering iron and dab some fresh solder on so there's a ball of molten solder hanging from the tip and apply it to the aluminum to be soldered. Using the iron's tip lightly abrade the aluminum surface with a scraping motion, and the oxide layer will be wiped right off, allowing the solder to properly adhere.

On Jan 12, 2014 6:08 PM, David <davidwhess@...> wrote:
 

I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

>I don't know what is used now but in his sixties books GA Briggs of
>Wharfedale speaker fame mentions they tinned the aluminium voice coil
>wire using an ultrasonic solder pot. The ultrasonic energy causes
>cavitation that strips off the surface oxidation under the solder
>surface, excluding the air.
>I think it would likely work with nichrome too.
>
>Don Black.
>
>On 13-Jan-14 4:16 AM, David wrote:
>>
>> Difficult to solder metals can often be handled by cleaning and
>> etching with
>> hydrochloric acid and then depositing copper via electrolysis and an
>> easily
>> acquired solution of copper sulphate or copper nitrate. I would worry
>> about
>> strain relief of the wire at the edge of the solder joint though.
>>
>> 12 Jan 2014 09:01:51 -0800, you wrote:
>>
>> > . . .
>> >
>> > BTW, as the center conductor is nichrome, you can't solder it. The
>> connections at the terminations are usually crimped on the wire.
>> >
>> > - Steve





This email is free from viruses and malware because avast! Antivirus protection is active.



Re: Soldering and epoxying aluminium

Geoffrey Thomas
 

I've seen this stuff advertised over here (uk) anyone know how good it is?

http://www.laco.com/aluminum-flux-paste/

Geoff.

On 13/01/2014 05:20, Michael Noone wrote:


OK if we're talking about soldering to aluminum - I should mention my
experience. I've used Indium flux number 3. It is designed for aluminum.
It works great, but you absolutely have to wash it off afterwards as it
is very corrosive. You can get it as a core inside of normal solders and
it works very well for aluminum.

I would love to find a non-clean aluminum flux - but I don't think such
a thing exists.

-Michael


Re: CRTs on Ebay

Don Black <donald_black@...>
 

Ah! You're a hard man to please. Must have been a B movie ;)

Don Black.

On 13-Jan-14 4:56 PM, Michael A. Terrell wrote:
 

Don Black wrote:
>
> Hello Michael,
> I agree with all you say, I'm aware that NTSC is
> the standards committee rather than the colour standard but NTSC is
> what the colour standard has become known as (at least outside the US).
> I take your point about the US colour standard being capable of good
> results if all is well, however if you haven't experienced the two
> systems in operation you don't know just how much "hardier" and more
> stable the PAL system is. It takes truly awful reception to notice hue
> changes with PAL.
> As I said, I have great respect for the development of the NTSC colour
> system , the fact it remained in use for so long speaks volumes.
I've seen PAL TV with PAL video tape. I wasn't impressed.





This email is free from viruses and malware because avast! Antivirus protection is active.



Re: About the cable used in oscilloscope probes

Don Black <donald_black@...>
 

I think that's the same type of process as the ultrasonic tinning in that it lifts off the oxide layer. The ultrasonic cleaning probably cleans the entire surface better whereas the rubbing may miss spots. One's better for production, the other fine for one off's. I think any flux would have to be carefully selected to ensure no long term corrosion. The Wharfedale speakers are still going strong after 40+ years. With mechanical cleaning in the molten solder it shouldn't need any flux.

Don Black.

On 13-Jan-14 11:48 AM, wyzkydd2358@... wrote:
 

Aluminum can be easily soldered using regular old leaded solder using the right trick. You don't even need any special flux. Take your soldering iron and dab some fresh solder on so there's a ball of molten solder hanging from the tip and apply it to the aluminum to be soldered. Using the iron's tip lightly abrade the aluminum surface with a scraping motion, and the oxide layer will be wiped right off, allowing the solder to properly adhere.

On Jan 12, 2014 6:08 PM, David wrote:
 

I assume then that the aluminum tabs on can capacitors are tinned in this way. I
always wondered how they did that.

I have also seen copper plated aluminum wire.

On Mon, 13 Jan 2014 10:34:38 +1100, you wrote:

>I don't know what is used now but in his sixties books GA Briggs of
>Wharfedale speaker fame mentions they tinned the aluminium voice coil
>wire using an ultrasonic solder pot. The ultrasonic energy causes
>cavitation that strips off the surface oxidation under the solder
>surface, excluding the air.
>I think it would likely work with nichrome too.
>
>Don Black.
>
>On 13-Jan-14 4:16 AM, David wrote:
>>
>> Difficult to solder metals can often be handled by cleaning and
>> etching with
>> hydrochloric acid and then depositing copper via electrolysis and an
>> easily
>> acquired solution of copper sulphate or copper nitrate. I would worry
>> about
>> strain relief of the wire at the edge of the solder joint though.
>>
>> 12 Jan 2014 09:01:51 -0800, you wrote:
>>
>> > . . .
>> >
>> > BTW, as the center conductor is nichrome, you can't solder it. The
>> connections at the terminations are usually crimped on the wire.
>> >
>> > - Steve





This email is free from viruses and malware because avast! Antivirus protection is active.



Re: Soldering and epoxying aluminium

 

I have used Miller Stephenson epoxy 907 to attach to aluminum for heat sinks and
such with good results:

http://www.miller-stephenson.com/products/detail.aspx?ItemId=60

I believe this is the same thing:

http://gokimco.com/hysol-epoxy-907-2-2oz-epk-kit-qty-10.html?gclid=CLOSkL3Q-rsCFaHm7Aod3W8Aaw

I wonder if enough carbon black could be mixed in to make it conductive enough
to be useful. It would be a lot less expensive then the conductive silver
epoxies they have.

On Mon, 13 Jan 2014 15:28:49 +1100, you wrote:

Here is a technique I have used a few times. I mix up some "24 hour
Araldite" - two part retail epoxy which takes about 24 hours at room
temperature to set.

I abrade both surfaces with emery paper ("wet and dry"), apply some
epoxy and then abrade some more. This removes the oxide layer and lets
fresh epoxy bond to the metal. At this point the formerly clear,
somewhat yellow, epoxy becomes opaque and grey.

Then the two surfaces can be brought together. Popping the item in a
not too hot oven for half an hour or so will harden the epoxy without
having to wait a day.

Perhaps this would work with silver-loaded conductive epoxy to make an
electrically conductive joint.


Re: Soldering and epoxying aluminium

 

On Mon, 13 Jan 2014 02:43:18 -0430, you wrote:

Actually about 14 yrs back I had reason to make an in tank electric fuel
(gasoline) pump become mounted externally. Was on a 1986 Mazda 626 GT.
I did eventually electroplate copper onto the cast pump manifold and
solder on copper tubing. Did it overnight with about a 250mA (per sq
inch of surface) current I believe.
The car is still running.

I think if the plated nichrome is for heating purposes....you can't use
regular low temp solder. But u might be able to get by with a braze.
I have used silver brazing solder to attach to nichrome and stainless steel but
because of the temperature required, like 1300F, I would not consider this
viable for the thin wire used in probe cable.


Re: Soldering and epoxying aluminium

mosaicmerc
 

Actually about 14 yrs back I had reason to make an in tank electric fuel (gasoline) pump become mounted externally. Was on a 1986 Mazda 626 GT.
I did eventually electroplate copper onto the cast pump manifold and solder on copper tubing. Did it overnight with about a 250mA (per sq inch of surface) current I believe.
The car is still running.

I think if the plated nichrome is for heating purposes....you can't use regular low temp solder. But u might be able to get by with a braze.


Re: About the cable used in oscilloscope probes

stefan_trethan
 

You can solder right to glass with ultrasonic.
Check out the videos on the web, look for ultrasonic soldering iron.

Strange thing to see...

ST


On Mon, Jan 13, 2014 at 12:34 AM, Don Black <donald_black@...> wrote:


I don't know what is used now but in his sixties books GA Briggs of Wharfedale speaker fame mentions they tinned the aluminium voice coil wire using an ultrasonic solder pot. The ultrasonic energy causes cavitation that strips off the surface oxidation under the solder surface, excluding the air.
I think it would likely work with nichrome too.

Don Black.



Re: Introduction and looking for guidance on Tek 2246 troubleshooting

 

On Sun, 12 Jan 2014 23:49:56 -0500, you wrote:

I picked up an untested Tek 2246 on eBay relatively cheaply, and after
letting it warm up, connected my probes on channels 1 & 2 to the
square wave calibrator. For the most part, I believe things are
working as they should on channel 2. After adjusting the probes
themselves, I get a good looking square wave.
They are nice oscilloscopes and one of the last models with full service
documentation. They seem to have fewer problems than the faster 2465 series.

On channel 1, I get a square wave also, but the image intermittently
jumps position on the vertical axis up and down before it settles back
to the original location for awhile, and then repeats. It's the
entire waveform image shifting up and down as a whole. I was looking
for some advice on whether this is a common issue, and suggestions on
additional troubleshooting or fixes for this behavior. I'd like to
keep the scope if possible, especially if there is a relative easy fix
for it.
There might be something mechanically worn with the BNC connector. Channel 1
tends to get used the most so it usually wears out first.

Does the trace jump when you wiggle the BNC connector?

Does the behavior change with different input coupling settings?

The Uncal lights are also lit on the front panel.
The channel 1 and channel 2 volts/div controls and the A and B sec/div control
each have a small inner control marked VAR which varies the volts/div or
seconds/div continuously and has a detent in the fully clockwise position where
the UNCAL (uncalibrated) indicator should extinguish. On the 2246, the vertical
UNCAL indicator is shared between channel 1 and channel 2. The readout also
shows the UNCAL status by displaying a greater than symbol (>) next to the
appropriate displayed scale factor.

Under most conditions, the VAR controls should be fully clockwise and locked
into their detent. The vertical VAR controls are used for adjusting the
vertical gain to make rise and fall time measurements and can also be used to
adjust the DC common mode rejection when making differential measurements in add
and invert mode. I have never found a use for the horizontal VAR control.


Soldering Thermocouple Wires

 

The recent threads regarding soldering to difficult metals reminded me of a product I came across a few years ago while helping a Hydroplane boat racing friend. This is a very serious sport during the summers in Seattle (see http://www.seafair.com/ for more info). My friend wanted me to wire up (in series) the ten thermocouples placed around the body of the turboshaft engine in the unlimited class boat he was modifying. At first I told him this couldn’t be done because the thermocouple metals couldn’t be soldered, bla, bla, bla. But when he pointed out that this was the way all the boat drivers monitored the temperature of their turbine engines I started looking for a flux I could use. I finally found one called AQUA-FLUX which is made by Rectorseal in Houston, TX (USA). I contacted them with my needs and they sent out a small jar of it at no charge for me to use.

 

Aqua-Flux did the trick. I soldered all the thermocouples in series without a problem and the resultant signal was large enough to drive an analog temperature meter mounted in the boat without any amplification whatsoever. I was pretty amazed that it was that simple. I never should have doubted my friend in the first place since he has been racing ‘hydros’ since the late 1960s.

 

I have no affiliation with Rectorseal, other than as an engineer that learned long ago it couldn’t be done.

 

Dennis Tillman W7PF

83521 - 83540 of 186291