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Grayhill makes some DIP switches that are sealed with epoxy on each pin, and I've seen them with a clear layer of tape that is to be removed after a board is cleaned. They are the types with recessed actuators.

I have some old stock of Grayhill 76RSB04. The datasheet specifies adding a 's' suffix to have them shipped with the tape. The RSB part of the stock number is for the recessed rocker.

Microdyne used these, and I never saw any bad ones.


<>

Michael A. Terrell

On Wed, 25 Jul 2018 17:10:29 +0100, you wrote:

Pretty clear you're not helpless!

For what it's worth, I find pulling a SOIC is simple with basic tools, I
use solder wick along all the pins first then 'ping' each pin in turn by
using a scalpel point - No 3 handle with 11 blade - inserted between the
pin and the next and applying a *very* slight twist behind the pin as I
heat it, to lift it clear of the pad and then work my way along. I find
this works and leaves the PCB clean, tidy and ready for the replacement
and the removed part totally reusable in the event that it was ok after
all .....not that that ever happens of course...!

Sometimes a bit of flux before you start is worthwhile, depends on the
solder/solder wick condition.

Yep, have to agree with this opinion, wonder why? <grin>

Also FWIW, I concur with the comments re DIP switches, don't know why
they were so unreliable (PCB washing perhaps?) but I've had to replace a
significant number of the GPIB address selector switches on both TEK and
HP gear, had them failed open and closed but mostly open.

Contaminants from the cleaning process, and that most are not sealed
by any stretch of the imagination. Bet you.

Harvey

Adrian
On 7/25/2018 4:31 PM, Rick Boswell wrote:

I am on a mission to demonstrate that I am not helpless. Ordered the 74LS244 tri-state buffer and Grayhill DIP switches from DigiKey this AM. For less than $10 I got a lifetime supply of both. Will be a bit more complicated than I thought as the buffer is in an SO style surface mount package, not a DIP. We'll see. If I screw it up, I'll send it to you to bail me out!

On Wed, 25 Jul 2018 18:35:50 +0000 (UTC), you wrote:

Help,
Now all my TekScopes email is sent to spam folder. Is this a Yahoo problem?

All email is directed by your email program, not yahoo. It's possible
that the classification of the yahoo email has changed somehow,
causing your email program to put it elsewhere. You might want to
check watch filters (or kill filters), the terminology likely will
change program to program.

Harvey

Carl Hallberg (W9CJH)

On Wed, Jul 25, 2018 at 12:38 AM, satbeginner wrote:

the recommended IRF730 has a input capacity of 620pF
The ordered replacement IPA60R280E6 has a typical input capacity of 950pF.

For what it's worth: the broken FET I found in my scope when I got is was a
IRF710 (400V 200pF...)

I am no expert on driving power FETs, however I think the biggest concern is the gate charge rather than Gate/Source capacitance ?
There is a good deal of correlation between the two of course, but they aren't 1:1 related.

In datasheet, on the first page of any MOSFET, the key parameter they specify to brag about how good their FET is (running cool and going fast), is RDson, and gate charge. BTW I got carried away in a previous post... the RDson of the modern replacement I used is 280mohoms not 28mohoms, of course, so "only" an order of magnitude better than the old part, not 2 orders. Still, quite impressive....

Gate charge tells you exactly just how many electrons/energy you need to shove into the gate to turn the FET on. Up to your gate driver to supply this many electrons in as short a time as it possibly can, to make the transition as fast as possible, to waste as little energy as possible and make the FET run as cool as possible. It's more to do with the "rise time". I feel gate/source capacitance is more of a limiting factor when you are trying to drive the FET as fast as possible. Like in the hundreds of kHz. But in the 22XX Tek scopes, the regulator runs at only 40kHz or so.

So I think we are in the case of slow signal but with fast edges, aren't we.

I looked at the datasheet of all the FETs you mentioned, plus the one I bought to fix my 2215 the other day. One can see that there is no linear relationship between input capacitance, and gate charge.

Here goes :

IRF 730 700pF 38nC
IRF 710 170pF 17nC
IRF 820 400pF 19nC
IPA60R280E6 950pF 43nC
IPP60R280P7 760pF 18nC


So for example take the old IRF820 I pulled from 2215. My replacement IPP60R280P7, has twice the input capacitance (Rated 100V higher than the IRF820), BUT..... the gate charge is virtually the same, even a tad lower if anything, at 18nC versus 19nC.

And if you compare it to the IPA60R280E6, though a very similar FET made by the same manufacturer, in the same vein... has more than double the gate charge (but only a bit more input capacitance).

Waiting to the expert to chime in, but as for me, unless I am demonstrated otherwise, I will continue to worry more about (total) gate charge than input capacitance. At least for the old Tek scopes that are driven very slowly at only a few tens of kHz.

So IOW, Leo... the FET you bought, with more than twice the gate charge of the old FET well.... might "work", kinda, but as for efficiency/power dissipation and long term reliability, that would need more investigation... Depends how much headroom was designed in the driver circuitry. I am not competent enough to analyze/quantify the operation of this circuitry.
At least you in your scope, the FET is mounted a heat sink, with some air around it (might have a fan also ??), so you have some margin there... unlike my 2215 which has no heatsink and zero air around it... :-/

Anyway, keep us posted on you progress ! ^^


Vincent Trouilliez

Same here. Any ideas?

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

Help,
Now all my TekScopes email is sent to spam folder. Is this a Yahoo problem?
Carl Hallberg (W9CJH)

This is interesting! I have a 3L5 with serial number J22. Would that also be a prototype?

Bob Krassa AC?JL

Thanks for the documents. It indeed seems a good subject for tinkering and
having fun building samplers.



On Jul 25, 2018 9:46 AM, "Bruce Griffiths" <bruce.griffiths@...>
wrote:

1N4007's have been used in high voltage discrete NLTLs.

Anritsu use NLTLs in theire VNA samplers:


Even Ceramic capacitors have been tried:
.
18.50.18/doc/06085283.pdf?languagebutton=pt-BR

Bruce

On 25 July 2018 at 13:56 Mark Kahrs <mark.kahrs@...> wrote:


I hate to disagree with Jose, but there have been a fair number of papers
on constructing NLTLs --- some even using discrete diodes.
If you'd like to read a review of the patents, may I refer you to this
short paper? I know the author personally.

Patents and Microwave Measurements-Nonlinear Transmission Lines [TCC
Tidbits] <>
<>IEEE Microwave Magazine
<>


Year: 2016, Volume: 17, Issue: 7
<>
Pages: 78 - 81

On Tue, Jul 24, 2018 at 1:00 PM, Craig Sawyers <
c.sawyers@...> wrote:

FWIW non-linear optical methods are used to compress the length of

laser

light pulses. Somewhat
analogous to NLTL's, but at 10^14Hz.



Craig

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of

Ed

Breya via Groups.Io

Sent: 24 July 2018 17:32
To: [email protected]
Subject: Re: [TekScopes] Homemade tunnel diodes

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

Want to buy 495P v9.7 EPROMs which are installed on the A54 memory board. P/Ns 160-8316-00 and 160-8315-00. Or, complete working A54 board with these EPROMs installed.

RIck
K8EZB

When you want to align and solder a new SOC IC, I apply a little solder to one corner pin, then position the new IC on the pads. Then I heat the pin over the pad with the solder. If it looks good, IO solder the opposite corner, then go down one side, then the other. Look for solder bridges, then it's ready to power up. If there are solder bridges, my method is to tilt the board with the row of pins running vertically. Then I apply a drop of liquid RMA rosin flux along the row of pis. Apply a drop of fresh solder on the tip of the iron, then run it down the row. It will remove solder bridges, and remove any excess solder. I used to do this to ICs with .015" center to center spacing. QA couldn't tell my rework from that done by our new automated Heller reflow oven. I recommend buying a half pound spool of Multicore .015" 63/37 solder for rework. It makes soldering these parts much easier, and a half pound will last you for years. I used it with a special .015" tip from Plato, along with a collet for an Ungar Loner soldering iron. A stereo microscope is a big help if you have bad eyes.

I saw a fair number of bad 74LS244 ICs on new boards at our production facility so I could almost replace them in my sleep. I also found them in the wrong position, or installed backwards when they came out of production.


Multicore-63-37-CRYSL-502-3-015DIA-28SWG-Henkel-LOCTITE

Michael A. Terrell

Pretty clear you're not helpless!

For what it's worth, I find pulling a SOIC is simple with basic tools, I use solder wick along all the pins first then 'ping' each pin in turn by using a scalpel point - No 3 handle with 11 blade - inserted between the pin and the next and applying a *very* slight twist behind the pin as I heat it, to lift it clear of the pad and then work my way along. I find this works and leaves the PCB clean, tidy and ready for the replacement and the removed part totally reusable in the event that it was ok after all .....not that that ever happens of course...!

Sometimes a bit of flux before you start is worthwhile, depends on the solder/solder wick condition.

Also FWIW, I concur with the comments re DIP switches, don't know why they were so unreliable (PCB washing perhaps?) but I've had to replace a significant number of the GPIB address selector switches on both TEK and HP gear, had them failed open and closed but mostly open.

Adrian

On Wed, 25 Jul 2018 08:31:48 -0700, you wrote:

Sergey,

Thanks for your input on the Norway extenders. This is exactly the reason I am looking for someone who has been there and done that to repair my A54 memory board. Inside knowledge/experience important in this situation. Will use caution when using these.

I am on a mission to demonstrate that I am not helpless. Ordered the 74LS244 tri-state buffer and Grayhill DIP switches from DigiKey this AM. For less than $10 I got a lifetime supply of both. Will be a bit more complicated than I thought as the buffer is in an SO style surface mount package, not a DIP. We'll see. If I screw it up, I'll send it to you to bail me out!

The SO style makes it both easier and more complicated. I use a
metcal iron with a very specific desoldering tip for SO width
packages. If you're not familiar with metcal, it's a very nice
temperature controlled system with a 30 mhz oscillator sending power
down a flexible cable to a small wand with a plugin tip. Amazon sells
replacement tips, and I've found the Thermaltronics tips to be an
exact replacement, but not available in all configurations. Pace
makes equivalents, I'm sure as do other manufacturers.

Hot air desoldering can work, but you have to be careful not to blow
all the other chips off the board, and to not overheat anything.

Not sure that you mentioned if you'd been playing with surface mount
or not. I have transitioned to surface mount exclusively (where
practical, still use through hole pin headers) for new designs. It
was a matter of both size and the consequence of the chips simply not
being available in anything other than surface mount. Not sure that I
want to go back....

Removing a 100 pin TQFP chip with metcal equipment can be quite easy,
and done within a few seconds.

Others have used a product called chip-quick, which is apparently a
low melting point bismuth solder that reduces the melting point of the
existing solder and makes desoldering easy. A decent desoldering tip
might be made with a length of brass channel and a conventional
soldering tip. You could even use a destroyed tip since you will be
attaching the channel to the tip and don't care about the tip tinning.

Thought of another technique which will work. You use solder wick to
suck up all the solder on the pins. This may or may not completely
move the solder between the pin and the pad. Using a dental tool,
while heating the pad, gently lift the pin off the board on one side.
it should just lift and not stick at all.

If you have a soldering tool with a very wide (but temperature
controlled) tip, then you could do an entire side at a time, simply
(and gently, of course) lifting the chip body. Repeat with the other
side and the chip is off. Works well with two sided chips. Again,
VERY gentle is the trick.

I'd suggest practicing with things like old cable boxes first, if
you're uncertain with the technique.

Perhaps a brass bar and a soldering iron tip would work well.


At any rate, good luck on this. Hope that others might benefit from
the advice.

Harvey

RB

Sergey,

Thanks for your input on the Norway extenders. This is exactly the reason I am looking for someone who has been there and done that to repair my A54 memory board. Inside knowledge/experience important in this situation. Will use caution when using these.

I am on a mission to demonstrate that I am not helpless. Ordered the 74LS244 tri-state buffer and Grayhill DIP switches from DigiKey this AM. For less than $10 I got a lifetime supply of both. Will be a bit more complicated than I thought as the buffer is in an SO style surface mount package, not a DIP. We'll see. If I screw it up, I'll send it to you to bail me out!

RB

The "B04" tag indicates it was a B-phase prototype build - fairly close to what went into production. These were used for final environmental, EMC, and other testing, and as demos for pre-introduction field training. The phases were E (engineering), then A, then B, then production.

Ed

On Wed, 25 Jul 2018, Rick Boswell wrote:

John,

Thanks for your reply. I'll check the DIP switches again. Thanks for the
tips on removing these switches - will be helpful if I do the repairs
myself. Norway Labs ( ) does currently offer
extender boards for the 49x series, so I will order a set.

Quick note about those extenders from Norway Labs -- they are OK and work
for repairs (I refurbish 492BP/494AP instruments on a regular basis and use
those) but one should be very careful when putting a board on those
extenders. They are not keyed, there is absolutely no mechanical support
other than connector pins, no connector shrouds and it is very easy to
insert them with an offset that might cause serious damage not just to that
board but also to other ones. Ask me how I know :)

Other than that those extenders are OK and there are nothing better
available anyway. Just be very careful and check everything twice before
powering your instrument with a board on extenders.

One other thing about extenders -- when putting the VR board on extenders
one absolutely must follow Tektronix instructions on mechanically securing
that board. That Tektronix-provided method is kinda flimsy and barely
adequate but it is better than nothing. Unsecured VR module will be rocking
from just glancing on it losing electrical connections via those extenders.

---
*
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
*

On 7/25/2018 3:09 AM, satbeginner wrote:

Hi Bert & Vincent,

I'll check capacity specs on the FET's as well -although already ordered :-) - but the good news in relation to the secondary power supply:
The scope has been running fine for several hours now on an external 43VDC :-)

I needed it to run, because it turned out there was a problem with CH1 as well. (trace yes, but no signal showing)
I cleaned the switches using IPA, but it looked like it was one of the small trimpots in the attenuator having a dodgy contact.
As soon as I touched that one the signal came back on CH1.

After all repairs are done I will calibrate it.

I updated the album to show the progress.

Thanks for the feedback, un saludo,

Leo

-=-=-=-=-=-=-=-=-=-=-=-

Keep in mind that the upper section has current limiting so it should be able to run, at least for several seconds, with a dead short across the 43VDC secton.

I had a 2213A at one time that was a real dog.
It showed many signs of having been worked on before and not by someone that knew that they were doing.
It ended up as a parts scope because both the voltage multiplier and the upper switching transformer were gone... plus many! other parts.

That was a long time ago but I seem to remember that I was able to check out the IC and gate drive circuit by removing
the fet and adding a small cap between the scource and gate.

-Bert

John,

Thanks for your reply. I'll check the DIP switches again. Thanks for the tips on removing these switches - will be helpful if I do the repairs myself. Norway Labs ( ) does currently offer extender boards for the 49x series, so I will order a set.

RB

Hey all,

Does anyone know of a paint which is a close match to the knob color on 500 series scopes? Vallejo Air "Dark Sea Grey," "Dark Grey Blue," or "Black Grey RLM66" seem like they might be close.

Best,
Evan

Cool. Got a postal address/PO box I can send them to?

Do you have a private email address, rather than do all this on public forum?

Cheers

Craig

Bruce
Serial number indicates it was Pilot build/ engineering unit there was a thread about these serial numbers but it was years ago.
One of the Tek veterans can probably provide a little? more info.

Interesting piece of history
-DC
manuals@...

--
Dave
Manuals@...
www.ArtekManuals.com