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Re: Tek 495P A54 Memory Board Repair

 

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
Re: Tek 495P A54 Memory Board Repair

 

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
Re: Weird serial number on 7L14

 

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
Re: Tek 495P A54 Memory Board Repair

 

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. *
*
Re: 2215A LVPS repair

 

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
Re: Tek 495P A54 Memory Board Repair

 

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
Color match for 500 series knob

 

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
Re: Tek bits

Craig Sawyers
 

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
Re: Weird serial number on 7L14

 

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@...

On 7/25/2018 2:11 AM, Bruce Lane wrote:
(Facedesk!)

Right, I forgot.

OK -- I've posted the two photos in question to the 'kc7gr' album in
the group's photo storage area.

Thanks, Dave.


On 24-Jul-18 00:04, Artekmedia wrote:
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: Tek bits

 

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

I can probably scrounge up a few HV diodes too, as they suck for the intended use but would be fine to replace annoying vacuum rectifiers made of finest unobtainium.Vmax 24KV 10mA IIRC
www.cwgsy.net/private/mandoline "Error 008472. Horrible bug encountered. $Deity knows what happened."

On Tuesday, 24 July 2018, 11:58:46 GMT+1, Craig Sawyers <c.sawyers@...> wrote:

Hi Andre

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

Regards

Craig

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Andre de guerin via
Groups.Io
Sent: 24 July 2018 10:57
To: [email protected]
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: Homemade tunnel diodes

 


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

Anritsu use NLTLs in theire VNA samplers:


Even Ceramic capacitors have been tried:


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
Re: 2215A LVPS repair

 

Hi all,

Quick check of the FET's learned this:

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

Time will tell if the transistor driving the FET is able to drive this larger capacity.

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

To be continued,

Un saludo,

Leo
Re: 2215A LVPS repair

 

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
Re: Weird serial number on 7L14

 

(Facedesk!)

Right, I forgot.

OK -- I've posted the two photos in question to the 'kc7gr' album in
the group's photo storage area.

Thanks, Dave.

On 24-Jul-18 00:04, Artekmedia wrote:
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!
--
---
Bruce Lane, ARS KC7GR

kyrrin (at) bluefeathertech dot com
"Quando Omni Flunkus Moritati" (Red Green)
Re: Looking for Power Cord for 400-series Scope

 

Okay - I'll take a look again at that. Perhaps it isn't as much trouble as I was thinking it was.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jim Olson" <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 10:51:07 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope

The panel is easy to get off it is held on just two flat head phillips screws
and the fuse cover box it lifts off with the cord attached you just need to
take off the wires the ground is bolted to the frame right at the cord in
and the white neutral wire is soldered to the fuse box and the power is
attached to a blue piece on the main board soldered too.

Jim
Re: Replacing Electrolytics in a 465/465B

 

Here is what I found on digikey after some searching.
5600uf 50v Nichicons same class as yours.
330uf 160v Nichicon
1500uf 100v Nichicon
560uf 63v Nichicon
A couple of them are different class but all are 105 degree 20%. can't find 10% anywhere so 20 will have to do not sure what effect they will have on performance?

Jim
Re: Looking for Power Cord for 400-series Scope

 

The panel is easy to get off it is held on just two flat head phillips screws and the fuse cover box it lifts off with the cord attached you just need to take off the wires the ground is bolted to the frame right at the cord in and the white neutral wire is soldered to the fuse box and the power is attached to a blue piece on the main board soldered too.

Jim
Re: Looking for Power Cord for 400-series Scope

 

Hmmm. I'm not sure if that would work with the existing panel and not sure how much effort it is to replace the entire back panel. Also, shipping would start to climb with the panel and we're virtually on opposite sides of the country. If nothing else turns up, then I might take you up on it.

Truthfully, I wouldn't be terribly concerned about it except that I notice that at a certain, rather slow, sweep speed, there's an AC part that the signals are riding on. If I ground the chassis, that disappears so I'd really like to have that ground connection in the plug.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jim Olson" <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 10:29:11 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope

I actually have one that is at an angle but it is only a small plastic knob
it that helps but all the rest are in the large rubber style boot. I can
leave it in the panel if you like that way you don't have to mess around
with the lock.

Jim
Re: Looking for Power Cord for 400-series Scope

 

I actually have one that is at an angle but it is only a small plastic knob it that helps but all the rest are in the large rubber style boot. I can leave it in the panel if you like that way you don't have to mess around with the lock.

Jim
Re: Looking for Power Cord for 400-series Scope

 

That would probably work but I'd have to cut off the boot and I kind of hate to do that as those are hard to find. Perhaps I'll find one of the "plain" style cords.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Jim Olson" <v_12eng@...>
To: [email protected]
Sent: Tuesday, July 24, 2018 9:49:19 PM
Subject: Re: [TekScopes] Looking for Power Cord for 400-series Scope

I have some but they are the ones that come out in the 90 degree rubber boot.

Jim
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