Topics

DC503 Not Working


Stephen
 

Update:
I’ve changed Q540 (2N3904). -22V is back on track.

B wasn’t triggering. Changed bad Q150 from a PN3565 (which I couldn’t find) to a BC546B, and the unit is back in business and working beautifully.

All it need now is a modern replacement display because mine is missing 3 segments.
If anyone knows of a good modern alternative, let me know. I tried to contact the person that made
a board for a DC508, but I didn’t get a reply.


Stephen
 

At any rate, now the DC503 stopped counting altogether. And this is no longer related, I think, to the mainframe.

I measured -1.05V across C548 with the tips on the correct + and - leads of the cap, and 1.05V from ground to the pos lead of that cap. I don’t believe that is correct...

2 out of 3 voltages are good: 15V and 5V. -22V is gone.


Stephen
 

After some long posts spanning over 2 threads, trying to figure out why the DC503, then the DC505A did not display anything else than just a randomly placed single “0” at any one time while plugged inside the mainframe, I finally founded out, without understanding why, that Option 12 messed everything up (see topic here, on the extender:

https://groups.io/g/TekScopes/topic/tm500_plug_in_extention/76102597?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,76102597

Also, the DC505A that was working when plugged into the extender did display all the digits, but was not counting at all, is now working perfectly inside the mainframe, after I disconnected option 12.
It turns out that even if no pins are need to power the modules, you have to connect them all in order for some plugins to properly work. I found that out the long way.

I’m sorry if it took 2 threads to finally figure this out.


Stephen
 

This evening the DC503 that was sort of okay and counting when on the extender, just stopped counting altogether... Just showing zeros.

PS: The DC505A I received a few days ago is just randomly displaying numbers.
I must be cursed with counters... or something...

Feeling puzzled 😕


Dave Daniel
 

There is nothing to forgive.

On Aug 11, 2020, at 06:54, Stephen <stephen.nabet@...> wrote:

On Mon, Aug 10, 2020 at 11:40 PM, Dave Daniel wrote:


In order to have a “circuit” there has to be a loop that includes all
components. I the case of the DC-503, there is a signal that goes “to” the
plug-in which carries current. That current must go back to the mainframe in
order to complete the circuit.

Your problem could be caused by either the signal to the plug-in or the return
path part of the circuit.

I’d suggest that you buy a basic circuit theory book. While not my favorite,
a copy of Horowitz and Hill’s “The Art of Electronics” would proabsbly
be a good choice.

DaveD
Oh ok. I know what you mean then. I thought you were referring to something else more obscure (to me).
I do have some mid level electronics training, although from 40 years ago.
Forgive my lack of better education when it comes to proper terminologies.



Stephen
 

On Mon, Aug 10, 2020 at 11:40 PM, Dave Daniel wrote:


In order to have a “circuit” there has to be a loop that includes all
components. I the case of the DC-503, there is a signal that goes “to” the
plug-in which carries current. That current must go back to the mainframe in
order to complete the circuit.

Your problem could be caused by either the signal to the plug-in or the return
path part of the circuit.

I’d suggest that you buy a basic circuit theory book. While not my favorite,
a copy of Horowitz and Hill’s “The Art of Electronics” would proabsbly
be a good choice.

DaveD
Oh ok. I know what you mean then. I thought you were referring to something else more obscure (to me).
I do have some mid level electronics training, although from 40 years ago.
Forgive my lack of better education when it comes to proper terminologies.


Dave Daniel
 

No, you’re on the right track. Something about the extender connector vs. the plug-in connector is different.

On Aug 11, 2020, at 05:55, Stephen <stephen.nabet@...> wrote:

I just right this very moment received a DC505A. And guess what,
It displays the exact same behavior!!!! Only one digit randomly comes up when inside the TM506,
but all are present when connected to the extender!
To me, that doesn’t make any sense, unless, on each and every slot, somehow the plugin makes a deeper contact inside the slot, that the actual plugin is incapable of making... But even that assumption is flawed.

Mind boggling...



Dave Daniel
 

In order to have a “circuit” there has to be a loop that includes all components. I the case of the DC-503, there is a signal that goes “to” the plug-in which carries current. That current must go back to the mainframe in order to complete the circuit.

Your problem could be caused by either the signal to the plug-in or the return path part of the circuit.

I’d suggest that you buy a basic circuit theory book. While not my favorite, a copy of Horowitz and Hill’s “The Art of Electronics” would proabsbly be a good choice.

DaveD

On Aug 11, 2020, at 05:49, Stephen <stephen.nabet@...> wrote:

On Mon, Aug 10, 2020 at 10:10 PM, Dave Daniel wrote:


You probably also need to check the return path in the same manner.
I don’t understand what the “return path” is.
I have a very basic training in electronics.



Stephen
 

I just right this very moment received a DC505A. And guess what,
It displays the exact same behavior!!!! Only one digit randomly comes up when inside the TM506,
but all are present when connected to the extender!
To me, that doesn’t make any sense, unless, on each and every slot, somehow the plugin makes a deeper contact inside the slot, that the actual plugin is incapable of making... But even that assumption is flawed.

Mind boggling...


Stephen
 

On Mon, Aug 10, 2020 at 10:10 PM, Dave Daniel wrote:


You probably also need to check the return path in the same manner.
I don’t understand what the “return path” is.
I have a very basic training in electronics.


Dave Daniel
 

I’ve been fooliwing this thread but not really paying close attention.

I assume that you’ve tried the DC-503 in all mainframe slots?

On Aug 11, 2020, at 04:29, Stephen <stephen.nabet@...> wrote:

On Mon, Aug 10, 2020 at 09:24 PM, Dave Daniel wrote:


I would make six measurements with an oscilloscope:

- Measure the signal of pin 6A at the backplane where the connector is
soldered to the motherboard with the extender disconnected

- measure the same signal at the connector contact (front side)

- with the extender inserted, make the same two measurements

- with the extender inserted, measure the signal on the extender contact on
the plug-in end

- measure the signal at the plug-in itself (“after” the extender)

DaveD
I will certainly do that and report back.
Thank for the suggestion, Dave.



Dave Daniel
 

You probably also need to check the return path in the same manner.

On Aug 11, 2020, at 04:29, Stephen <stephen.nabet@...> wrote:

On Mon, Aug 10, 2020 at 09:24 PM, Dave Daniel wrote:


I would make six measurements with an oscilloscope:

- Measure the signal of pin 6A at the backplane where the connector is
soldered to the motherboard with the extender disconnected

- measure the same signal at the connector contact (front side)

- with the extender inserted, make the same two measurements

- with the extender inserted, measure the signal on the extender contact on
the plug-in end

- measure the signal at the plug-in itself (“after” the extender)

DaveD
I will certainly do that and report back.
Thank for the suggestion, Dave.



Stephen
 

On Mon, Aug 10, 2020 at 09:24 PM, Dave Daniel wrote:


I would make six measurements with an oscilloscope:

- Measure the signal of pin 6A at the backplane where the connector is
soldered to the motherboard with the extender disconnected

- measure the same signal at the connector contact (front side)

- with the extender inserted, make the same two measurements

- with the extender inserted, measure the signal on the extender contact on
the plug-in end

- measure the signal at the plug-in itself (“after” the extender)

DaveD
I will certainly do that and report back.
Thank for the suggestion, Dave.


Dave Daniel
 

I would make six measurements with an oscilloscope:

- Measure the signal of pin 6A at the backplane where the connector is soldered to the motherboard with the extender disconnected

- measure the same signal at the connector contact (front side)

- with the extender inserted, make the same two measurements

- with the extender inserted, measure the signal on the extender contact on the plug-in end

- measure the signal at the plug-in itself (“after” the extender)

DaveD

On Aug 11, 2020, at 04:06, Stephen <stephen.nabet@...> wrote:

On Mon, Aug 10, 2020 at 04:48 PM, Chuck Harris wrote:


I have once, or twice, gotten a 7000 series plugin where
the middle fiberglass layer was missing, leaving a small
slot between the top surface, and the bottom surface of
the circuit board connector. I am guessing it was a defect
in the circuit board material that just happened to be
in that relatively benign location. It did make the
card edge springy, and slightly thinner than usual.

-Chuck Harris
Yes, I can see how that could be a problem. It’s not the case here, but I was thinking that maybe inserting the plugin repeatedly, may have, over time, worn out the copper pads to the point where some don’t make good contact.
I went ahead and lightly tinned the first 13. That didn’t help...
I must admit that I’m quite confused... 🤷‍♂️



Stephen
 

On Mon, Aug 10, 2020 at 04:48 PM, Chuck Harris wrote:


I have once, or twice, gotten a 7000 series plugin where
the middle fiberglass layer was missing, leaving a small
slot between the top surface, and the bottom surface of
the circuit board connector. I am guessing it was a defect
in the circuit board material that just happened to be
in that relatively benign location. It did make the
card edge springy, and slightly thinner than usual.

-Chuck Harris
Yes, I can see how that could be a problem. It’s not the case here, but I was thinking that maybe inserting the plugin repeatedly, may have, over time, worn out the copper pads to the point where some don’t make good contact.
I went ahead and lightly tinned the first 13. That didn’t help...
I must admit that I’m quite confused... 🤷‍♂️


Chuck Harris
 

I have once, or twice, gotten a 7000 series plugin where
the middle fiberglass layer was missing, leaving a small
slot between the top surface, and the bottom surface of
the circuit board connector. I am guessing it was a defect
in the circuit board material that just happened to be
in that relatively benign location. It did make the
card edge springy, and slightly thinner than usual.

-Chuck Harris

Stephen wrote:

On Mon, Aug 10, 2020 at 12:32 PM, Glenn Little wrote:


If the connector in the TM5xx has loss some of its tension and the
thickness of the extender paddle is slightly thicker than the DC503 edge
card connector, that would explain it.
If this is the case, the connector(s) in the TM5xx need to be replaced.

Glenn
Yes, I thought about that too. But that would mean that all of them lost their tension. Also, all the other plugins are working properly... 🤷‍♂️
Maybe this particular plugin has a very slightly thinner backplane? I could try and thinly tin the pads maybe? Hmmmm....




Stephen
 

On Mon, Aug 10, 2020 at 12:32 PM, Glenn Little wrote:


If the connector in the TM5xx has loss some of its tension and the
thickness of the extender paddle is slightly thicker than the DC503 edge
card connector, that would explain it.
If this is the case, the connector(s) in the TM5xx need to be replaced.

Glenn
Yes, I thought about that too. But that would mean that all of them lost their tension. Also, all the other plugins are working properly... 🤷‍♂️
Maybe this particular plugin has a very slightly thinner backplane? I could try and thinly tin the pads maybe? Hmmmm....


Glenn Little
 

If the connector in the TM5xx has loss some of its tension and the thickness of the extender paddle is slightly thicker than the DC503 edge card connector, that would explain it.
If this is the case, the connector(s) in the TM5xx need to be replaced.

Glenn

On 8/10/2020 4:20 PM, Stephen wrote:
This is a partial copy of a post a posted while trying the extender work.

Something very unexpected and quite puzzling just happened.
As many pointed out, I forgot to connect pin 6A. I just did.
Some of you may have seen my post regarding the DC503 that is not showing more than 1 digit (0) at any one time, if at all, when I power it on. Never ever.

Now that pin 6A is finally connected, not only the DC503 power on normally with the extender, but all digits are there!!! Not when connected inside the TM506 itself!! It’s not counting anything, though.
Everything is not lost, it gives me hope that at least something is showing now...

It’s also missing some segments. If anyone knows if the individual LED’s can be replaced, that would be nice to know of a modern replacement. I found some, but the panels look too thick, I think.

--
-----------------------------------------------------------------------
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"


Stephen
 

On Mon, Aug 10, 2020 at 10:04 AM, Harvey White wrote:


I think that someone designed a readout board using more modern (hence
more available) displays.  Might have been for the DC509, but the DC503
is what triggered the memory.

Harvey
Interesting. Here on this forum? I’ll try a search then. If you remember anything else...

Thanks Harvey.

PS: Forgive the numerous typos.


Harvey White
 

I think that someone designed a readout board using more modern (hence more available) displays.  Might have been for the DC509, but the DC503 is what triggered the memory.

Harvey

On 8/10/2020 4:20 PM, Stephen wrote:
This is a partial copy of a post a posted while trying the extender work.

Something very unexpected and quite puzzling just happened.
As many pointed out, I forgot to connect pin 6A. I just did.
Some of you may have seen my post regarding the DC503 that is not showing more than 1 digit (0) at any one time, if at all, when I power it on. Never ever.

Now that pin 6A is finally connected, not only the DC503 power on normally with the extender, but all digits are there!!! Not when connected inside the TM506 itself!! It’s not counting anything, though.
Everything is not lost, it gives me hope that at least something is showing now...

It’s also missing some segments. If anyone knows if the individual LED’s can be replaced, that would be nice to know of a modern replacement. I found some, but the panels look too thick, I think.