Topics

DC503 Not Working


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.


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...


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.



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...



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
 

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
 

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 😕


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
 

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
 

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.