Date   

Re: Homemade tunnel diodes

Ed Breya
 

Jose said:
"Not many people seem to have made DIY NLTL, let alone samplers based on it."

This is probably true, because NLTLs usually have lots of stages, so can get very big and complicated before you get remarkable compression. For simplicity and effectiveness, a single SRD/varactor of the right type, in the right circuit environment, is pretty hard to beat for straight up impulse generation or frequency multiplication. A whole bunch of them cascaded can form a NLTL, with its edge-enhancement and wide BW. As always, it depends on the particulars of the application.

I don't think there's a need for a "modern" replacement for the SRD/varactor. It's a common RF part - not at all an obsolete technology. Nowadays there are alternatives for many applications, by using fast active devices capable of appropriate edge speeds.

Ed


2215A LVPS repair

satbeginner
 

Hi all,

a cheap and broken 2215A found it's way to my home :-), so now I am in the process of getting it repaired.

I used this document from Håkan that helped me a lot: http://www.hakanh.com/dl/docs/troubleshooting_tips_on_2200_ps.pdf

The fuse would blow instantly, so I separated the main PS from the rest by removing Q9070.
An inspection by the eye learned that there were several low voltage elco's leaking,
C960/C962 (+8,6V) were leaking;
C961/C963 (-8,6V) were leaking;
C968/C970 (+5,2V) were bad;
C956 (+30V) was leaking;

Fortunately no real damage to the PCB.

Also the Q9070 and CR907 were toast.
According to the document the FET is a IRF730 (400V 5,5A 0,75Ohm 12ns) and the diode a BYD73G (400V 1A 50ns)

I replaced all the capacitors first, and now the scope has trace(s) when applying 43VDC to TP940 (Pos) and TP950 (neg).

Being the optimist, I replaced Q9070 with a FQPF4N90C (900V 4A 3,5Ohm 50ns) and CR907 with a PR1507 (1000V 1,5A 300ns) I harvested from a switching PS,
but.... They last about 2 seconds...

Based on Håkan's document I applied a test voltage to C925, and the signals at the chip U930 check out, and since I tested all surrounding components Q908, CR908, R909, CR920, I come to think it must be the speed of the Q9070 and CR907 that causes the sudden death of these replacement components.

My question is: does anybody (recently) repaired a 2215A LVPS and replaced these 2 comonents?
If so, what replacements were used ?

The documents suggest a MTP6N55 for the FET and a BYD73G for the diode, but I would love to hear if there are other successful candidates.

Pictures can be found in this album: https://groups.io/g/TekScopes/album?id=64919

un saludo,

Leo


Re: Tektronix DM5010 NiCa 2.4V battery replacement

Harvey White
 

On Tue, 24 Jul 2018 00:26:58 -0700, you wrote:

Hi everyone,

Please keep in mind that this DMM has been available since the very beginning of the eighties, if not late seventies.
It has been designed about ten or less years after man walked on moon.
We should now be able to replace the entire CPU board with a single $2-3 micro-controller.

You can, within limits. The 488 bus is a difficulty, and may be more
happily replaced with a chip or an FPGA, your choice, although there
are 488 simulators. The front panel had a separate chip that did LED
output scanning and keypad decoding. That can be replaced with a CPLD
if you want. The rest of it is custom interface to the remainder of
the boards and the EEPROM (the CMOS battery backed up RAM being the
main source of the problems).

I would design with an ARM processor (yes, overkill), and an FPGA (I'd
prefer a Xilinx Spartan 6 in a 144 pin TQFP package, which can be done
at home). Then you'd have to have a number of level converters, some
to the 5 volt front panel, and the rest to the 5 volt system boards.

I'd rather overengineer and have capability left over than to get 3/4
of the way through and not have the capability left.

You'd probably do well with a MEGA 64 (64K flash, and I think 8K RAM,
2K EEPROM) which would do for the 5 volt processor (if you wanted),
then you'd need an interface to the 3.3 volt FPGA. Alternative is the
XMEGA series (runs on 3.3 volts) replacing the ARM processor. I ran
out of capability in the MEGA/XMEGA lines a while back and switched to
ARM.


The main problem is not the circuit design, but the replication of the
original program in C. Mostly you want to know what the interface to
the existing hardware happens to be (program wise). The 488 stuff is
better defined.

Harvey


Best regards,



Re: 7603 specifically and general refurbishment procedures of older oscilloscopes

 

IMHO only replace electrolytic caps that have failed, those big Sprague caps are normally OK except when they go open-circuit.

Dave

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of johnasolecki@...
Sent: 24 July 2018 12:40
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7603 specifically and general refurbishment procedures of older oscilloscopes

Thanks for the suggestions. I'm pretty certain I had all the buttons pressed correctly but I'll recheck that (wouldn't be the first time...!) and I'll try to check the unblanking circuitry.
What about capacitors and other aging components? As needed or change them all?

John


Re: Homemade tunnel diodes

Jose Luu
 

I did not know about NLTLs, thanks Bruce for the heads up.

For those in my case, I have found a few references on the net:
https://www.reddit.com/r/rfelectronics/comments/1dkfsx/nltl_low_phase_noise_comb_generators_any/
https://etd.auburn.edu/xmlui/bitstream/handle/10415/2564/HaiLu%27s%20Thesis.pdf?sequence=2&isAllowed=y
https://deepblue.lib.umich.edu/bitstream/handle/2027.42/84461/dmfrench_1.pdf?sequence=1&isAllowed=y

All documents refer to simulations made using Spice/LTSPice/ADS

Not many people seem to have made DIY NLTL, let alone samplers based on it.

On Mon, Jul 23, 2018 at 10:26 PM Bruce Griffiths <bruce.griffiths@...>
wrote:

For the purposes of harmonic generation NLTLs have much lower PN than SRDs.
Bruce

On 24 July 2018 at 05:37 thespin@... wrote:


Modern mixer diodes are great but I have yet to find a good replacement
for step recovery diodes.





Tek 485

Steve Lindberg
 

Hi all,

Looking for a volt/div knob for 485. It works fine and would like to use it more.

Steve
KG7HYG


Re: 465B - Power Switch Mounting Nut Question

n4buq
 

René Rajesh,

Thanks for the replies and pics. I thought that was correct but just wanted to make sure.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Barry" <n4buq@...>
To: TekScopes@groups.io
Sent: Monday, July 23, 2018 9:28:03 PM
Subject: 465B - Power Switch Mounting Nut Question

A few months ago, I removed the trigger board from my 465B to work on the
power supply caps. I started reassembling it and was left with a small
nylon(?) block with a hex nut holder and a small slot in it. See the album
below for pictures of it.

https://groups.io/g/TekScopes/album?id=64907

If I'm not mistaken, I think this is used behind the nut that holds the power
switch in place and I used it that way (last picture); however, I'm
wondering if I have it turned 180-degrees and the small slot is supposed to
align with the main board.

Is that where that part goes and, if so, is it supposed to align with the
other PC board? I've found one picture on the web that shows it and I think
that's correct but would like to know whether I have that right.

Thanks,
Barry - N4BUQ


Re: Tek bits

Colin Herbert
 

Hi Guys,
If there is too much for Craig, I would be interested to do a sharing-type
deal. I live in London, UK. Both Craig and I wouldn't have any import
problems, I think.
This is only if Craig can't take everything, he has first shout.
It would be useful to know in a bit more detail what is being offered, here.
I am guessing that these originally came from Tektronix, Guernsey as did my
7623A?
Regards, Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Craig
Sawyers
Sent: 24 July 2018 11:59
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek bits

Hi Andre

I'm near Oxford UK and would be very pleased to have these.

Regards

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Andre
de guerin via
Groups.Io
Sent: 24 July 2018 10:57
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek bits

Tiny island near France, called Guernsey.

www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered.
$Deity knows what
happened."

On Monday, 23 July 2018, 09:04:47 GMT+1, Craig Sawyers
<c.sawyers@...> wrote:

> Hi, in my shed I have a lot of Tek bits including very hard-to-find
long pots.have a few flybacks
but not
sure what state they are in.
Anyone have a use and want to pay postage only?
_A
Where on planet earth are you?

Craig








Re: 7603 specifically and general refurbishment procedures of older oscilloscopes

johnasolecki@...
 

Thanks for the suggestions. I'm pretty certain I had all the buttons pressed correctly but I'll recheck that (wouldn't be the first time...!) and I'll try to check the unblanking circuitry.
What about capacitors and other aging components? As needed or change them all?

John


TEK 455

ANAND K. PARAMESHWARAN
 

Hi Folks

I am working on a tek 455 scope. managed get the trace up.
facing a trig problem. doesnt trig in auto/normal/single sweep.
trig view signal ok. suspect trig ic 155-0122-00
is this ic used in any other tek scope so that i can try to cannibalise and get this going

Thanks in advance

regards

Anand


Re: Tek bits

Craig Sawyers <c.sawyers@...>
 

Hi Andre

I'm near Oxford UK and would be very pleased to have these.

Regards

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Andre de guerin via
Groups.Io
Sent: 24 July 2018 10:57
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tek bits

Tiny island near France, called Guernsey.

www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what
happened."

On Monday, 23 July 2018, 09:04:47 GMT+1, Craig Sawyers <c.sawyers@...> wrote:

> Hi, in my shed I have a lot of Tek bits including very hard-to-find long pots.have a few flybacks
but not
sure what state they are in.
Anyone have a use and want to pay postage only?
_A
Where on planet earth are you?

Craig








Re: Tek bits

Andre de guerin
 

Tiny island near France, called Guernsey.

www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."

On Monday, 23 July 2018, 09:04:47 GMT+1, Craig Sawyers <c.sawyers@...> wrote:

> Hi, in my shed I have a lot of Tek bits including very hard-to-find long pots.have a few flybacks
but not
sure what state they are in.
Anyone have a use and want to pay postage only?
_A
Where on planet earth are you?

Craig


Re: 465B - Power Switch Mounting Nut Question

Rajesh VS
 

Hey Barry,


Ive added two pics from my 465 to your album, the Slit needs to align in to
the PCB.


https://groups.io/g/TekScopes/album?id=64907

hope it helps,

regards
Rajesh

On Mon, Jul 23, 2018 at 7:28 PM, n4buq <n4buq@...> wrote:

A few months ago, I removed the trigger board from my 465B to work on the
power supply caps. I started reassembling it and was left with a small
nylon(?) block with a hex nut holder and a small slot in it. See the album
below for pictures of it.

https://groups.io/g/TekScopes/album?id=64907

If I'm not mistaken, I think this is used behind the nut that holds the
power switch in place and I used it that way (last picture); however, I'm
wondering if I have it turned 180-degrees and the small slot is supposed to
align with the main board.

Is that where that part goes and, if so, is it supposed to align with the
other PC board? I've found one picture on the web that shows it and I
think that's correct but would like to know whether I have that right.

Thanks,
Barry - N4BUQ



--
/Rajesh


Bringing up a Tek 555 dual-beam scope

Michael Leslie Squires
 

Just bought a Tek 555 scope with cart and power supply. The scope appeared to have been used until replaced by a couple of 4xx series scopes but just shunted aside when replaced.

I owned and used a 555 40 years ago (warmed my basement quite well) but that scope, a Frankenstein monster created by plugging the CRT unit from one into the power supply from another, not only worked but was calibrated when turned on. As a result I never had to do any work on the unit.

Are there any precautions I should take when powering up this unit? One suggestion is to plug it in and turn it on; if the magic smoke escapes find where it came from and fix it. I do have a Variac and am thinking about building one of the devices which has a large incandescent in series with the DUT.

I do note that the contacts on some of the plug-ins are quite dirty, so I'm going to give the unit a good cleaning before firing it up. I will also check the big electrolytics for signs of failure and possibly for high ESR.

My first scope was a Tek 511; I had to rebuild the HV supply as the diodes had failed. I currently have a 465B which is working well.

Mike Squires
wwww.siralan.org or www.smithgreensound.com
UN*X at home since 1986


Re: Tektronix DM5010 NiCa 2.4V battery replacement

Ke-Fong Lin
 

Hi everyone,

Please keep in mind that this DMM has been available since the very beginning of the eighties, if not late seventies.
It has been designed about ten or less years after man walked on moon.
We should now be able to replace the entire CPU board with a single $2-3 micro-controller.

Best regards,


Re: Weird serial number on 7L14

Artekmedia <manuals@...>
 

Bruce

The list doesn't accept attachments. You will have to upload it to the photos section or host it somewhere and then post a link

Dave
manuals@...

On 7/24/2018 1:44 AM, Bruce Lane wrote:
Fellow Tekkies,

I picked up a 7L14 from an estate sale this last weekend. One of the
things which struck me is the bizarre serial number the thing has -- See
the attached photo.

My best guess is -- Prototype? Something which was never officially in
production? I've never seen the middle symbol (small circle with a
vertical slash through it) used on any Tek instrument I've ever owned.

The other oddity with it is it seems to be missing its red filter
window over the LED display on the input module side (see other photo).
Is this something which can be replaced easily? Perhaps scavenged from,
say, a dead 7A13? They look like they're about the same dimensions.

Thanks much!
--
Dave
Manuals@...
www.ArtekManuals.com


Re: 465B - Power Switch Mounting Nut Question

tek_547
 
Edited

Hi Barry, a few weeks ago I had to do the same (horrible) job of replacing the power supply caps in my 475A, same construction. And I also wondered why Tek used such a "distance" holder for the PCB to lock the nut. I mount it exactly as yours in the first picture and it´s sitting sturdy and fine.
So if you mount it as picture 1 and it´s alligned with the other board it is OK.
René


Weird serial number on 7L14

Bruce Lane
 

Fellow Tekkies,

I picked up a 7L14 from an estate sale this last weekend. One of the
things which struck me is the bizarre serial number the thing has -- See
the attached photo.

My best guess is -- Prototype? Something which was never officially in
production? I've never seen the middle symbol (small circle with a
vertical slash through it) used on any Tek instrument I've ever owned.

The other oddity with it is it seems to be missing its red filter
window over the LED display on the input module side (see other photo).
Is this something which can be replaced easily? Perhaps scavenged from,
say, a dead 7A13? They look like they're about the same dimensions.

Thanks much!

--
---
Bruce Lane, ARS KC7GR
http://www.bluefeathertech.com
kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)


Re: Tektronix DM5010 NiCa 2.4V battery replacement

Reed Dickinson
 

Hi Russ:

You have a very valid point concerning corrosion due to batteries leaking.  It is probably a matter of economics that makes the manufacturer
continue to provide super thin casings.  Also, the casing cannot encompass the entire battery, there must be electrical isolation between the
terminals which is a natural source of leaking.  If the manufacturer were to encompass the battery in a leak proof shell the weight, cost and
size would go up dramatically.  It all boils down to the almighty buck!

Reed Dickinson

On 7/23/2018 9:45 PM, musicamex wrote:
Half a century after men walked on the moon, can anyone please explain why
batteries still leak? Or why engineers capable of designing incredible
electronics can't at least protect the circuits from leak caused damage?
I'm sure that I'm not the only one who has lost often irreplaceable
electronics to this pitfall.

Russ

On Monday, July 23, 2018, Kevin Oconnor <@KO3Y> wrote:

You can certainly trickle charge some NiMH cells depending on the mfgr.
I’ve used Panasonic cells that have a trickle charge spec. The trick is
that the trickle charge level can’t generate more evolved oxygen than can
be absorbed at operating temps. That is the upper bound on trickle
charging.
There is also a lower bound on trickle charging that is often overlooked.
You have about 15-20 hrs max to recharge to full capacity. The reasoning by
mfgrs is vague but true and likely related to temp rise and gas evolution.
If you trickle charge at a rate less than that which will fully recharge in
15-20 hrs you will never fully restore full capacity.

Kjo

Sent from kjo iPhone




Re: Tektronix DM5010 NiCa 2.4V battery replacement

Harvey White
 

On Mon, 23 Jul 2018 23:45:15 -0500, you wrote:

Half a century after men walked on the moon, can anyone please explain why
batteries still leak?
Because the batteries don't cost $20,000 each. They're made (for
primary cells) as throwaways. For secondary cells, it's the cost.


Or why engineers capable of designing incredible
electronics can't at least protect the circuits from leak caused damage?
They've all been laid off because they are too old, those that did not
retire.

You could protect the circuits, just put the battery in a hermeticly
sealed enclosure.

Look at the original post, though. The DM5010 had a VERY leaky
battery (don't ask how I know) and as such, the battery was to be
replaced every two to three years. This was well within the point
where the battery would leak, so no problem.

What the equipment was NOT designed to do was to sit idle on a shelf
for five to fifteen years, not being used, not being charged, while
the innards of the 5 dollar battery merrily ate away at the seals, or
the shell, way after the point at which the battery would have been
replaced.

Lithium primary cells don't seem to be so badly behaved, although if
you charge the secondary cells wrongly, or short either one; well,
overheating as well as realize that lithium IS very fond of oxygen.

We don't have a good cell chemistry yet, not one that can be charged
thousands of times, has a good power to weight ratio, and so on. Still
looking at the electron valence voltages between something
electropositive and electronegative, and hoping that it's stable,
light weight, and hopefully part of a reversible chemical action.

How to store charge/power WELL is something we don't really know yet.

Harvey


I'm sure that I'm not the only one who has lost often irreplaceable
electronics to this pitfall.

Russ

On Monday, July 23, 2018, Kevin Oconnor <@KO3Y> wrote:

You can certainly trickle charge some NiMH cells depending on the mfgr.
I’ve used Panasonic cells that have a trickle charge spec. The trick is
that the trickle charge level can’t generate more evolved oxygen than can
be absorbed at operating temps. That is the upper bound on trickle
charging.
There is also a lower bound on trickle charging that is often overlooked.
You have about 15-20 hrs max to recharge to full capacity. The reasoning by
mfgrs is vague but true and likely related to temp rise and gas evolution.
If you trickle charge at a rate less than that which will fully recharge in
15-20 hrs you will never fully restore full capacity.

Kjo

Sent from kjo iPhone