Date   
TM503 in scope cart

Kurt Rosenfeld
 

This scope cart seems to have a TM503 mounted in it: https://www.ebay.com/itm/264244929767

Was that an official mod, or was it just something the owners did to their scope cart?

thanks, -Kurt

Re: 1502 TDR project

Chuck Harris
 

I'm not sure how you came to that conclusion.

If you take the pack out of its instrument, and
just set it on the shelf, until it self discharges,
the cells will simply go to zero, and will not
reverse charge.

If you leave the pack in the 1502, there is a
sneak load that will discharge the cells at a
couple of ma, and will reverse the weakest cells.

Battery management circuitry is what kills lithium
battery packs. The management circuitry keeps
discharging the pack at a very slow rate, until
the lithium cells go past their point of no safe
return voltage, and the management circuitry will
prevent you from recharging them.

They do this because if the lithium cell discharges
beyond a certain point, charging will cause the cell
to rapidly out gas, rupture the vapor barrier around
the cells, and when the humidity gets to the lithium
material, create heat, hydrogen, and maybe blow up.

-Chuck Harris

John Griessen wrote:

On 12/11/19 8:59 AM, Chuck Harris wrote:
Everything you say is absolutely true, as long as
you never, ever, ever allow a cell to reverse charge.
So, just stopping the pack discharge is not enough.
The cells need to be managed separately as in today's
lithium ion battery manager IC's and no cells in series...



Re: 465B soft start?

DaveH52
 

For what it's worth, the power transformer will provide some degree of current limiting. I suppose you could add an inrush limiting thermister, but that really doesn't seem necessary to me.

Re: 465B soft start?

DaveH52
 

I should have mentioned before that the capacitor can completes part of the circuit. So if you don't want to add some jumper wires, use a tubing cutter to cut the base off the old capacitors and use that as an interposer between the new caps and the circuit board. I don't recommend putting the can back over the new caps because it will hold in heat.

Re: 1502 TDR project

Tom Gardner
 

On 11/12/19 17:04, John Griessen wrote:
On 12/11/19 9:50 AM, Tom Gardner wrote:
So, just stopping the pack discharge is not enough.
The cells need to be managed separately as in today's
lithium ion battery manager IC's and no cells in series...
A cell cannot reverse charge itself. The weakest cell in a battery can be reverse charged as the other cells continue to discharge themselves through the load.
So, self discharge can never pull charge in from other cells in series?
I find it difficult to understand what you are thinking of there.

No cell can "pull in charge"; charge has to be forced in.

There is a difference between self discharging and reverse charging.
Self discharge occurs in an /isolated/ cell, i.e. where there is no electric circuit and hence no current outside the cell. The self discharge currents are solely inside the cell.
Reverse charging can only occur where multiple cells are connected in a circuit and current is flowing in that circuit.

Perhaps it is best to try to understand all my statements together, not to take one in isolation.

Re: 1502 TDR project

John Griessen
 

On 12/11/19 9:50 AM, Tom Gardner wrote:
So, just stopping the pack discharge is not enough.
The cells need to be managed separately as in today's
lithium ion battery manager IC's and no cells in series...
A cell cannot reverse charge itself. The weakest cell in a battery can be reverse charged as the other cells continue to discharge themselves through the load.
So, self discharge can never pull charge in from other cells in series?

Re: 1502 TDR project

Tom Gardner
 

On 11/12/19 15:38, John Griessen wrote:
On 12/11/19 8:59 AM, Chuck Harris wrote:
Everything you say is absolutely true, as long as
you never, ever, ever allow a cell to reverse charge.
So, just stopping the pack discharge is not enough.
The cells need to be managed separately as in today's
lithium ion battery manager IC's and no cells in series...
A cell cannot reverse charge itself. The weakest cell in a battery can be reverse charged as the other cells continue to discharge themselves through the load.

If there is no complete circuit (e.g. battery pack not connected to a 1502), then a cell can only self-discharge.

A NiCd cell should be capable of being continuously trickle charged at the C /10 rate or lower, independently of whether or not it is in a battery. If you want to "trickle" charge a NiCd battery at >C/10, then it would be prudent to manage each cell individually.

It is not entirely clear to me whether the C/10 rate is peak or mean. In the 1502 the peak current each 20ms (or 16ms in the US) is noticeably more than the mean current. In the 1502, R6131 sets the mean current to be around C/10.

Other chemistries, especially Li, cannot tolerate continuous trickle charge and each cell has to be managed individually.

Re: 1502 TDR project

John Griessen
 

On 12/11/19 8:59 AM, Chuck Harris wrote:
Everything you say is absolutely true, as long as
you never, ever, ever allow a cell to reverse charge.
So, just stopping the pack discharge is not enough.
The cells need to be managed separately as in today's
lithium ion battery manager IC's and no cells in series...

Re: 1502 TDR project

Tom Gardner
 

Precisely.

That's why I remove my 1502 battery packs when I'm not using them. If I don't then sooner or later the 1mA trickle /dis/charge will reverse charge the weakest cell.

On 11/12/19 14:59, Chuck Harris wrote:
Everything you say is absolutely true, as long as
you never, ever, ever allow a cell to reverse charge.

If you do, it will grow a nickel dendrite through the
inter plate insulation, and become a dead short.

-Chuck Harris

Majdi S. Abbas wrote:
...

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: 1502 TDR project

Chuck Harris
 

Everything you say is absolutely true, as long as
you never, ever, ever allow a cell to reverse charge.

If you do, it will grow a nickel dendrite through the
inter plate insulation, and become a dead short.

-Chuck Harris

Majdi S. Abbas wrote:
...

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: 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