Date   
Re: 1502 TDR project

Majdi S. Abbas
 

On Tue, Dec 10, 2019 at 04:21:02PM -0500, Mark Pilant wrote:
However, my own problem with NiCd batteries is I use the equipment so infrequently
I would be constantly replacing batteries. I understand this is less of an issue
with NiMH and Lithium batteries, but then you can get into making changes to the
charging circuitry to get the correct charge rates.
NiCds are more forgiving than the newer chemestries -- they can
be cold stored fully discharged. Or allowed to self discharge to
nothing, and when needed, you can still trickle charge them back up.

I find them to be optimal for sporadic use applications where
NiMh or Lithium chemistry batteries would be damaged by excessive
discharge.

--msa

Re: 7854's for sale

demianm_1
 

No, they are all working with minor problems. no reason to cannibalize them.

Re: 7854's for sale

demianm_1
 

None of mine are jackfree. I did not know there were different variations like that.

Re: "parting" 2215A

robertbarker@...
 

Hello Vaclav
I recently acquired a 2217 that was dropped.The case is badlydented and the CRT broken. All else seems OK. If yours is
still available, I'd be interested as a parts donor. cash or trade.
Thanks   ...BOB...    KD0IJI     KD0IJI@...

On Sunday, November 10, 2019, 10:34:45 AM CST, vaclav_sal via Groups.Io <vaclav_sal=yahoo.com@groups.io> wrote:

I have a hopeless , dead, case 2215A .
It turns on , but  that is all she wrote.
Nothing else is alive.

It has bean left in wet garage for long time and some components are clearly rusted out.
I just hate to ditch it as is, so I am asking the group which components ( CRT - it did lash once , knobs etc,) are worth saving as future trade items.
Vaclav AA7EJ

Re: TDS3024B repair - CPU board issue. Anyone have schematics?

amirb
 

did you fix your scope? if so, how?
I would replace the SRAM chips (one at a time) . It worked for me in a similar case

On Wed, Mar 8, 2017 at 12:18 PM, @Arcticgeek wrote:


Hi folks,


I have a TDS3024B scope that refuses to boot. The only thing that shows up
on the LCD is a blank white screen. Obviously, the backlight is on but there
is no video. I've ruled out an LCD issue because I can attach a TDS3GV
option, and no video is present on the VGA output either. The relays should
normally click during boot-up, this unit does nothing.


I've verified the AC power supply is fine, and I can also power the unit from
the battery terminals using a lab supply. The unit behaves identical when
powered from a lab supply on the battery terminals.


I have been probing around, and from what I can see all the voltages on the
main board are there - +5V, -5V, +3.3V, and +2.5V and -2.5V for the
acquisition section. The pgood/power on reset generator is working properly,
reset is asserted during power on and de-asserted some ~100msec later. I can
see access to the flash memory chip select for about 200usec, and then
everything halts. Nothing is obviously wrong on the board, no burned
components and nothing gets hot to the touch.


I thought perhaps the flash was corrupted, so I copied the flash contents
from a working TDS3054B and made two copies of each flash chip. I put one set
of the copied parts into the working TDS3054B, and it still works so I know my
Eprom programmer worked okay. However, this had no affect on the failing
TDS3024B.


At this point I'm stuck....and it would be REALLY helpful if I could find
some schematics so I could know where to probe.


Does anyone have any schematics for the TDS3000 series scopes? Or know
where I might find them? I already have the service manual downloaded from
Tek, but it does not have any schematics and not really that helpful.


Thanks to all.







Re: "liquid crystal driver" sighting

p mc
 

Sounds like it has fallen into good hands!

Re: "liquid crystal driver" sighting

Glenn Little
 

I will try and get hi res pix posted this weekend.
Hope to have schematic drawn early next year.
This appears to fit a TM-500 series frame.
The unit appears to have two channels.
The main board id very good quality.
There are two "proto" type boards in the unit.
One is for fuses.
The other has a pair of 74121 ics on it.
When I got it the edge card connector was damaged, thankfully if a place where there are no used pins.
There was one power transistor missing and I can replace it with one like in the other channel.
There is also a ground binding post missing, this is easily replaced.
The pictures will be of the unit as I received it.
This has controls for PW UPPER and PW LOWER for both channels.
There is also a DELAY and AMPLITUDE control for each channel.
There is a BNC for the top channel only INPUT.
There is a BNC for SYNC.
The SYNC appears to go to both channels.
There is a label on the front REL 11, so, maybe there are others out there.
The front binding posts are UPPER OUTPUT, LOWER OUTPUT and GROUND for each channel.
The active backplane pins are 2A, 3A, 6A, 7A, 8A, 9A, 10A, 12A, and 7B.
8B, 11B and 8A are connected.
12A and 12B are connected together.
All of these pins are power related, so the only inputs and outputs are via the front panel.
There is a keyway between pins 6 and 7.
There are "flying" jumpers between some IC pins with some of these pins lifted from the sockets.
Probably still a work in progress.
The front panel is thin aluminum with, what looks like, photo etching for the labeling and shading.
Harmonica connectors are used to connect to the board.

More to follow
Glenn

On 12/10/2019 12:50 PM, p mc wrote:
(seeing this a few weeks later)

Glenn,

Like DaveD says, lots of people here can help with TekWiki. Or you can ask kurt.harlem@... for a TekWiki account if you want to get into that yourself.

Back in October I made a stub page with crops from the pictures from the eBay listing:
http://w140.com/tekwiki/wiki/Liquid_Crystal_Driver

A first question might be what type of mainframe the plugin plugs into. If you haven't already sussed that, a picture of the edge connector cut-outs will help.

Curious to see what you've got...





--
-----------------------------------------------------------------------
Glenn Little ARRL Technical Specialist QCWA LM 28417
Amateur Callsign: WB4UIV wb4uiv@... AMSAT LM 2178
QTH: Goose Creek, SC USA (EM92xx) USSVI LM NRA LM SBE ARRL TAPR
"It is not the class of license that the Amateur holds but the class
of the Amateur that holds the license"

Re: "liquid crystal driver" sighting

p mc
 

I've updated TekWiki with the better images. Clearing browser cache & reloading the page may be required to see them.

Strange sidebar re the images: In October I thought there were better images but when I went to collect the images to crop , it seemed not so. Now prompted by keantoken to look again I see that on my phone the lo res image in the listing "expands" into the same lo res image on a cleaner background. So I chalked up the memory of better resolution to false/suggested memory, since "liquid crystal driver" appears in the description, and went ahead with the poorer images. This time, before the listing goes away, I went back with a desktop browser to get the better images with semi-legible front panel text.

The better picture almost shows the connector key slots. But not convincingly. So I'll not bias anyone else's speculation with my speculation.

Hopefully better images & info from Mr. Little will replace all that anyhow.

Re: 1502 TDR project

Tom Gardner
 

NiCd cells have a longer shelf life than lithium cells - I believe.

The 1502/3 has a nasty characteristic - even when turned off there is
a current drain of ~1mA through the chart recorder. If left
discharging then eventually the weakest cell will discharge first and
then be reverse charged - and that's bad news, It is behind the
statement that the battery should be fully charged once a month,

My solution is simply to remove the battery pack when not in use. Even
if each cell self-discharges, it won't be reverse charged.

But you should treat that with caution; I'm not a battery expert.

On 10/12/2019, Mark Pilant <mark@...> wrote:
> tabbed C NiCd cells are easily available, so the battery can be
reconstructed.

Very true.

However, my own problem with NiCd batteries is I use the equipment so
infrequently
I would be constantly replacing batteries. I understand this is less of an
issue
with NiMH and Lithium batteries, but then you can get into making changes to
the
charging circuitry to get the correct charge rates.

I may try the bench power supply just to see if it turns up additional
information.

- Mark N1VQW




Re: 1502 TDR project

Mark Pilant
 

tabbed C NiCd cells are easily available, so the battery can be reconstructed.
Very true.

However, my own problem with NiCd batteries is I use the equipment so infrequently
I would be constantly replacing batteries. I understand this is less of an issue
with NiMH and Lithium batteries, but then you can get into making changes to the
charging circuitry to get the correct charge rates.

I may try the bench power supply just to see if it turns up additional information.

- Mark N1VQW

Re: 1502 TDR project

Tom Gardner
 

I've had a "battery eliminator" that worked in one 1502 but not
another. That's one reason I don't like them. Another is that tabbed C
NiCd cells are easily available, so the battery can be reconstructed.
Battery operation is pleasing; I used one of my 1502s last Saturday in
the middle of a field, to diagnose the cable between a glider's
cockpit and antenna.

You may well be right about the source of a (possibly the) problem,
but using a bench PSU is quick, easy, and eliminates one significant
variable.

On 10/12/2019, Mark Pilant <mark@...> wrote:
Hi Tom.

> I just increased the size of the capacitor in the emulator and she runs
> first time, every time now.

I have a 2200uF cap, per the TekWiki. Works fine for the 1503, so I expect
there is something else going on in the 1502.

> As he said, gotta pay close attention to the "subtleties" of this one!
:-)

That's why I'm still scratching my head. I really need to find some (of
that
rare substance) time to probe with my scope. That way I see what is
happening.
(At least I hope :-)

Re: "liquid crystal driver" sighting

keantoken
 

Liquid crystals are used in welding masks to darken the weld flash instantly. I think they have other applications in high speed photography, and electronic shutters. So maybe this was part of some kind of optics laboratory?

In the original Ebay picture it was possible to read the text on the plugin. On the wiki page the test is unreadable. Here is the full size image with readable text.

https://www.ebay.com/itm/LOT-OF-3-TEKTRONIX-PLUG-IN-5A18N-DUAL-TRACE-AMP-5A15N-AMP-LIQUID-CRYSTAL-DRIVER-/312803078179?nma=true&si=0Rv3bZb%252FLMGiec3%252F7Qc8K%252F3QYFs%253D&orig_cvip=true&nordt=true&rt=nc&_trksid=p2047675.l2557

Re: 1502 TDR project

Mark Pilant
 

Hi Tom.

I just increased the size of the capacitor in the emulator and she runs
first time, every time now.
I have a 2200uF cap, per the TekWiki. Works fine for the 1503, so I expect
there is something else going on in the 1502.

As he said, gotta pay close attention to the "subtleties" of this one! :-)
That's why I'm still scratching my head. I really need to find some (of that
rare substance) time to probe with my scope. That way I see what is happening.
(At least I hope :-)

- Mark N1VQW

Re: 577 AC collector supply not reading zero on display

DW
 

All done

I used some sand paper and pressed on the variac windings I carefully slid the carbon brush across it to make sure there is even and complete contact patch on the windings.

The stop is adjusted so the brush is setting similar as before, safely on the windings.

I now get at 6.5V and at 50mV a division a 2 division line.

My work is officially done with the variac and everything still works, everything together, covers back on

I should add when i had the wiper parked so far back previously to minimize the collector supply issue, parked off the winding on the plate, I noticed the transition being non linear. Slightly turning the control the voltage would suddenly instantly increase instead of being smooth

Re: 1502 TDR project

fiftythreebuick
 

Mark, as Tom said, it can be a transient condition that trips the power supply.

When developing a battery emulator for my units, at one point mine would fail when the unit was first powered up after sitting idle for a long time, but if you just turned the power off and right back on, it would work every time. The inrush current to all the capacitors in the 1502 was causing a transient low-voltage condition that would trip the power supply. I just increased the size of the capacitor in the emulator and she runs first time, every time now.

As he said, gotta pay close attention to the "subtleties" of this one! :-)

Tom

On Mon, Dec 9, 2019 at 08:53 AM, Tom Gardner wrote:


On 09/12/19 16:38, Mark Pilant wrote:
Hi Tom.

I haven't tried supplying power directly to the banana plugs, but the
parallel cap/resistor battery substitute (ala TekWiki) seems to work
fine, as the battery meter on the front panel indicates the battery is
"good" and I do see 14.4VDC supplying the DC converter.
That's insufficient.

You realise that PSU trips if there is a transient overvoltage. At that point
the voltmeter reads "excessively good" :)

I presume you have read the circuit operation section of the manual?


So it would seem the battery portion of the power supply is working and
I need to determine why the rest of the power supply isn't working.

My general sense is the DC converter is an oscillator driving the T6535
primary to then generate all the secondary voltages needed.  I suspect
the oscillator isn't oscillating (well?), but I'm not sure of the best
way to investigate.  (Not sure how many ways there are to shut it down;
lack of a battery is one.)
One way is the overvoltage detection, via q6547/8/9.


I'm a little wary just probing around with my scope (7904 with the usual
vertical / horizontal plugins), because of potential ground issues.
Although I do have a Tek 224 I can use that shouldn't have any ground
issues.
If you power off a bench supply, then clipping the scope shield to the chassis

is fine.

The 1502's transformer is fully isolated, so**clipping the scope shield to the

chassis is fine.


I just checked, and the power supply for the 1503 is the same as the one
for the 1502.  I may be able to open up my 1503 and use its power supply
to troubleshoot the 1502 power supply.
Yes.

Re: 1502 TDR project

Mark Pilant
 

Hi Dave.

I checked the three caps, and C6415 is open. The other two read good
on my cap/ESR meter (about 400uF and ESR both < .5ohm). I'll definitely
replace the open one, and may do the other two as well.

Looking at the schematic, it looks as though I may be able to test the
board outside the TDR, with a couple of appropriate connections. This
would certainly make things easier.

- Mark N1VQW

Re: 465B soft start?

Abc Xyz
 

Worked on many 465B Scopes?

On Tue, Dec 10, 2019, 10:14 AM <radioconnection@...> wrote:

I have had a few of the 5-volt power0supply bridge rectifiers fail in 465
scopes.



Re: 465B soft start?

Mlynch001
 

I have heard that sitting idle is the worst thing one can do to a scope, such as the 465. I exercise all of my scopes regularly, by turning them on and feeding a signal through the inputs. I have no idea if this helps or not. But I had heard the same advice years ago and thought it made sense to run the scopes from time to time.

--
Michael Lynch
Dardanelle, AR

Re: 577 AC collector supply not reading zero on display

DW
 

You bring a valid point Chuck, I obviously don't want to do more harm than good.

As of wring this I am defaulting the variac brush to its previous state and adjusting the tab stop so the brush sits on the windings. I am making sure the brush will make a contact with a appropriately wider patch on the windings so as to distribute the power in a way that doesn't cause premature wear.

When I am at 5mV a division that is at the 6.5V setting, not 1600V

At this point I will perform some final touches on this curve tracer, after everything is appropriately set I will put the covers back and and leave it alone. Like you mention I don't want to break anything, leave well enough alone. Thanks for all your helpful advise by the way, I learned some things.

Re: 465B soft start?

radioconnection@...
 

I have had a few of the 5-volt power0supply bridge rectifiers fail in 465 scopes.