Date   

Re: TM500 Plug-in Extention

Stephen
 

Colin,
How about if I reserve 1A-1B and 13A-13B on the extender? Provided the plugin then behave the same as inside the TM, wouldn’t that tell me that this is the issue?

Just a thought....


Re: Tektronix 475

Simon
 

I am beginning to suspect the CRT again as the instrument had obviously been dropped. I have not been able to increase the grid bias to more than -20 V. I will check the grid voltage again with my VTVM and see if I can change it.
I can set the voltage at TP 1364 to 15 V with the intensity control, and increase it to 26 V by pressing the beam finder as described in the manual The trace is very bright at all settings. but beam blanking is working.
I do not understand how I have gone from no trace to too much trace, the whole screen glows green even with the sweep off. All I did was take out and test three transistors on the horizontal board connecting the sweep section to the horizontal amplifier section. Maybe re-seating the transistors got the time base working normally.
Also connecting the Y leads to the tube produced a wide vertical stripe of much reduced intensity, so I think there is something odd going on inside the tube.
Simon


Re: TM500 Plug-in Extention

Stephen
 

On Tue, Aug 11, 2020 at 02:27 AM, Colin Herbert wrote:

Interleaved answers.

Time to put my thinking-hat on again. If the wiring is all correct, it sounds
as though some mysterious thing is reversing the phase somewhere in your
extender, but I've no idea how that could come about.
Me neither. Unless I’m really completely wrong about my wiring...

Can I suggest that if
you have a scope (I am sure you do)
I do have 9 scopes... But I’m trying to heal... 🤷‍♂️

then you do the trick that I suggested to
examine the phase of the two 25 VAC windings with respect to the 17.5 VAC
winding at both the end of your home-made extender and at the TM5xx backplane.
That ought to provide some more information, if not point directly to the
problem. Remember that you are only dealing with 25 VAC and 17.5 VAC, so you
would probably not even notice the voltage unless you put the contacts into
your mouth (don't do that, please!). I don't think you can do any damage to
yourself or to the scope or any other equipment. Just try to keep one hand in
your pocket, wear insulating gloves and remember to turn off mains power and
unplug the TM5xx Power mainframe from the mains before poking around inside
too much, just to give you confidence. I don't want you to get a mains shock,
for sure, but the lower voltages present at the backplane and, by inference,
at the module (plug-in) end of the extender, are relatively tame. Three 9v
batteries connected in series would give you possibly more to worry about.
I know you’re right, I should do this just for good measure.
I’ll try to build some confidence .... because I don’t feel too confortable poking around that thing.

But I’ll try.... 🤷‍♂️

PS: Remember, this is not my job, and I’ve never done that before on this type of equipment.
I only know tube amps.


Re: TM500 Plug-in Extention

Stephen
 

On Tue, Aug 11, 2020 at 02:27 AM, Colin Herbert wrote:

P.S. Just a silly thought, but you refer to the "A" and "B" sides of the ends
of your home-made extender. I hope you are identifying these correctly. If you
connect the male and female ends of your extender together, there should be no
connection between 1A and 1B or between 13A and 13B. It's to do with how you
look at the connectors. On the mainframe and looking down at the backplane
connectors, A is on the left. The male connector will have the "A" side on the
right if you are looking at it from the "business end" so-to-speak - the end
that gets mated with the female connector. This results in "A"-to-"A"
connection and "B"-to-"B" connection. To be honest with you though, I can't
see that total reversal would cause the symptoms that you describe and not
just result in something more disastrous happening.

Colin.
I was just about to clarify this by posting a little crude diagram here:
https://groups.io/g/TekScopes/photo/251875/0?p=Created,,,20,2,0,0

Did I miss something? Because this is exactly how this is at the moment...
I tend to believe the sides are correct... 🤷‍♂️

PS: I don’t know if you saw the posts on the DC503 thread, but today I received A DC505A that is behaving exactly the same way, albeit this one is not counting at all. Probably needs some further checking.


5S14N what should I know?

Szabolcs Szigeti
 

Hi,

I managed to get a 5S14n on eBay for my 5440, I reckon it is somewhat of a
rare item. While it is still being shipped, I'm preparing for what I will
need to do. So far I've already read through the archives of this list and
the descriptions on the Wiki. I know that the main problem is going to be
the mercury batteries in the samplers. I know about the simple LED based
solution and probably that is what I will go with, but I did not find a
conclusive opinion on how much the voltage matters. So for example if I
simply install some 1.5v batteries there, would it make any difference? In
the long run I guess so, but for example just to test the unit or to
operate it occasionally, is it a possibility of instead of installing LEDs?
What I have read is that eventually the 1.35V of the mercury cell is not
critical, but the stability and the source impedance is.

The other question is whether the 7S14 manual is good for this? I will most
likely buy the Artek scan for the 5S14N, but it looks to me that they are
actually the same units, even to the point of having the 5S14N PCB inside
for the 7, but with additional boards for readout and interfacing.

Which brings me to the third question. Based on the 7S14 schematics, the
readout is provided by a separate board, feeding from the main boards' cam
switches. I don't know what parts are populated on the 5000 unit, but maybe
it would be possible to add readout capabilities for this one too, by
adding a similar board like in the 7S14? Has anyone attempted this?

Is there anything else to know in advance? Other than to resist the
temptation to collect all 5000 plugins? :-)

Szabolcs


Re: TM500 Plug-in Extention

Colin Herbert
 

Time to put my thinking-hat on again. If the wiring is all correct, it sounds as though some mysterious thing is reversing the phase somewhere in your extender, but I've no idea how that could come about. Can I suggest that if you have a scope (I am sure you do) then you do the trick that I suggested to examine the phase of the two 25 VAC windings with respect to the 17.5 VAC winding at both the end of your home-made extender and at the TM5xx backplane. That ought to provide some more information, if not point directly to the problem. Remember that you are only dealing with 25 VAC and 17.5 VAC, so you would probably not even notice the voltage unless you put the contacts into your mouth (don't do that, please!). I don't think you can do any damage to yourself or to the scope or any other equipment. Just try to keep one hand in your pocket, wear insulating gloves and remember to turn off mains power and unplug the TM5xx Power mainframe from the mains before poking around inside too much, just to give you confidence. I don't want you to get a mains shock, for sure, but the lower voltages present at the backplane and, by inference, at the module (plug-in) end of the extender, are relatively tame. Three 9v batteries connected in series would give you possibly more to worry about.

P.S. Just a silly thought, but you refer to the "A" and "B" sides of the ends of your home-made extender. I hope you are identifying these correctly. If you connect the male and female ends of your extender together, there should be no connection between 1A and 1B or between 13A and 13B. It's to do with how you look at the connectors. On the mainframe and looking down at the backplane connectors, A is on the left. The male connector will have the "A" side on the right if you are looking at it from the "business end" so-to-speak - the end that gets mated with the female connector. This results in "A"-to-"A" connection and "B"-to-"B" connection. To be honest with you though, I can't see that total reversal would cause the symptoms that you describe and not just result in something more disastrous happening.

Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 11 August 2020 13:22
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

I understand Colin,

You made me doubt my wiring. So I went and triple checked it. I can’t assure you that not a single wire is crossed. Surely enough not A1-B1 and A13-B13.... Each wire goes to the same side at the other end of the extender... All A’s go to the A side, same with the B’s...

Am I missing something??


Re: Tektronix 475

Chuck Harris
 

Tektronix occasionally had some issues with welds inside of
the CRT's. The last time I saw a CRT that was very bright,
and didn't respond to intensity, grid bias, or any Z-axis
changes, it turned out to be a broken weld inside of the CRT
that opened the control grid, leaving about a 1/32" gap between
the wire that went to the tube base, and the strap that
connected to the control grid.

I have heard of at least one other instance (on this group)
where this exact failure happened on a 465/475 scope.

Similarly, a bad socket or a bad connection to the grid
would do the same thing.

Connect a floating DVM to the grid lead, and the cathode
lead of the CRT.... it must be insulated to withstand 2KV,
and don't touch it. Adjust the intensity, and look for
a corresponding change in the grid cathode voltage.

This is going directly to the horse's mouth.

-Chuck Harris

tenareze32@gmail.com wrote:

Some progress, I tested the PDA voltage with an ignition lead and spark plug. It produced a good spark that would certainly start my lawnmower, and I put the CRT back. The time base is working and I have an extremely bright trace. If I connect the Y leads to the tube, I get a fuzzy vertical stripe which responds to the time base and X position and magnifier. The voltage on one Y lead responds to a test signal on both channels, while the other rises to +10V and stays there.
Incidentally I do not recommend piercing the PDA/HT lead with a hypodermic needle as it leaves a path for the electrons to escape. It is much safer to push an ignition lead into the socket and connect it to a spark plug.
I don’t know why the trace is so bright (even on minimum intensity, also responds to focus) and I don’t understand why attaching the Y leads give a fuzzy vertical stripe that goes from top to bottom with only a few volts on the Y plates.
Thanks to everyone for pointing me in the right direction. This pastime is rewarding as it forces one to revise one’s hypotheses in the light of evidence and other people’s input.
Simon




Re: TM500 Plug-in Extention

Stephen
 

On Tue, Aug 11, 2020 at 12:56 AM, Colin Herbert wrote:

It is a shame we can't do this conversation face-to-face (phase-to-phase? - no
pun intended but it sort-of happened!).
Colin.
LOL, we could! 😂


Re: TM500 Plug-in Extention

Stephen
 

I understand Colin,

You made me doubt my wiring. So I went and triple checked it. I can’t assure you that not a single wire is crossed. Surely enough not A1-B1 and A13-B13.... Each wire goes to the same side at the other end of the extender... All A’s go to the A side, same with the B’s...

Am I missing something??


Re: TM500 Plug-in Extention

Colin Herbert
 

There exists a Tektronix plug-in for testing TM500/TM5000-series mainframes. It does all sort of things that could be useful, including checking the phase of the two 25 VAC windings with respect to the 17.5 VAC winding. It does that very simply by checking if there is an AC voltage difference between the "B" ends of the windings when the "A" ends are grounded. It does it with a 30 V silicon diode and a 100mA light-emitting diode with an appropriate current-limiting resistor. If the windings are in-phase, there should be no appreciable voltage between the "B" ends and the led remains unlit. Otherwise, one or more of the leds will illuminate, indicating which of the winding(s) is/are out-of-phase with the 17.5 VAC winding. You can find the details of this plug-in on TekWiki if you look up 067-1201-99. My method just makes the process more visual, in that the output from the windings are displayed on a scope screen. It is possible that you are not really appreciating the significance of the phase of these windings. I also suggest that you have crossed some of the AC winding pairs in your home-made extender. It should be that if you connect a "B" end to and "A" end of windings that are in-phase and then check the AC voltage at the remaining ends of those two series-connected windings, the voltage seen should be the sum of the voltages of the two windings. If they are out-of-phase, the voltage will be the difference between the two voltages. Don't forget that we are dealing with AC voltage here. Since your DC 503 works when connected via the extender, the two 25 VAC windings are in-phase at the module (plug-in) end; when you simply plug it in to your TM mainframe, it doesn't work, suggesting that the 25 VAC windings are out-of-phase at the backplane. If you have then managed to cross-over the connections to one 25 VAC winding (i.e. wire "A" to "B" and vice versa) in your extender, you will have got the connectors and AC windings back into phase.

It is a shame we can't do this conversation face-to-face (phase-to-phase? - no pun intended but it sort-of happened!).
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Stephen
Sent: 11 August 2020 11:05
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

Colin,

Although I didn’t fully understand all the theory behind your post, I do get the general idea.
I’m not sure I feel confident enough to do that.
But at any rate, “if” the windings were out of phase, wouldn’t the plugin not work also when connected to the extender? That wouldn’t make any difference regarding the windings, would it?


Re: DC503 Not Working

Dave Daniel
 

There is nothing to forgive.

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



Re: DC503 Not Working

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.


Re: DC503 Not Working

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@gmail.com> 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...



Re: DC503 Not Working

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@gmail.com> 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.



Re: TM500 Plug-in Extention

Stephen
 

Colin,

Although I didn’t fully understand all the theory behind your post, I do get the general idea.
I’m not sure I feel confident enough to do that.
But at any rate, “if” the windings were out of phase, wouldn’t the plugin not work also when connected to the extender? That wouldn’t make any difference regarding the windings, would it?


Re: DC503 Not Working

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...


Re: 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.


Re: TM500 Plug-in Extention

Colin Herbert
 

I have a DM 502 that would work in all of my TM5xx mainframes except one. This puzzled me until I read the section of the FG 504 manual on transformer phasing and decided to investigate. In the DM 502, two of the 25 VAC transformer windings are connected in series to a transformer in the plug-in which supplies +9 VDC unregulated and +12 VDC and -12 VDC regulated. If the mainframe transformer windings are out-of-phase, the plugin's transformer will receive nothing, because the windings cancel out. Although the method in the FG 504 manual is supposed to be easy, that nearly always isn't quite the case. I have found what I think is a pretty fool-proof method.

My method for checking the phasing of these windings is to gain access to each end of the two 25 VAC windings and each end of the 17.5 VAC winding. These will be 1A & 1B (one 25 VAC winding), 13A & 13B (the other 25 VAC winding) and 5A & 5B (the 17.5 VAC winding). Connect all of the "B" connectors together and take them to earth on a two (or more) channel scope. Connect 5A to one channel and display the sine-wave at an easily-viewable amplitude, TRIGGERING THE TIME-BASE OFF THAT CHANNEL ONLY. Then with the other channels, check connections 1A and 13A, leaving the triggering from the 17.5 VAC. Any out-of-phase-ness will become apparent. It is good to use the 17.5 VAC winding as the benchmark, as that's what Tektronix seem to suggest in their method of checking the phase. Also, the connections 1A, 1B, 13A and 13B on the backplane are easier to access, once the outer casing is removed. You will find that 5A and 5B are more buried and harder to access. If you find that either or both of the 25 VAC windings are out-of-phase with the 17.5 VAC winding, then reverse the connections to the backplane. Check all of the plug-in bays; you just never know what might (or might not) have been going through the head of the person wiring-up your mainframe.

For information, I used my Dan Meeks extender with a JAMMA male connection to access the various backplane connectors. I modified the JAMMA male connector by disconnecting the "twinned" contacts with a Dremel-type tool and soldered short lengths of tinned copper wire to the connectors that I wanted to access. This enabled me to not only do this phase-checking (all of the bays on one mainframe had a 25 VAC winding wired out-of-phase), but also to check the series-pass transistors. I did this latter with one of the cheap Chinese component checkers and it was easy. Incidentally, I wouldn't do any "tinning" of the contact surfaces. I think they may be gold-plated and already therefore have a two-metal contact - copper and gold. Adding a third metal (solder - actually several metals alloyed together) is likely to achieve the possibility of two extra problems - thermocouple effects and generating a contact that will oxidise readily and eventually cause resistance problems. You might find that you can put a little more "spring" back into the backplane contacts with an appropriate tool. I have a set of metal probes, but what you want is some kind of short hook that you can get behind the backplane connector to apply a little pressure to bring the connector back to a better position. Don't overdo it to the extent that you make contact between the contact and its A-or-B relative. This may not matter when a plug-in is in place, but it could cause a disastrous short with no plug-in present. Also, avoid damaging the connector, as replacement looks to be almost an impossible job - at least fiddly and time-consuming. I have a backplane connector which has been damaged and thought to solve the problem by either trying to replace that one connector or the entire backplane connector. Looking at the problem and trying to de-solder the connector was a pain and since the connector was an otherwise unused 22B, I decided to "let sleeping dogs lie".

You should now find that any plug-ins that use any of the transformer AC windings in series will now work correctly and that any excessive ripple which might give FG 504 (and perhaps similar) plug-ins problems will be solved. Easy when you know, or get told, how.

Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Chuck Harris
Sent: 10 August 2020 23:28
To: TekScopes@groups.io
Subject: Re: [TekScopes] TM500 Plug-in Extention

There is some discussion in the FG504 manual that suggests
that many TM50X frames were built with one of the power
transformer windings out of proper phase for the FG504 to
work well.

I would guess that the windings, being AC were just a pair
of unmarked wires, and the assemblers didn't know that they
needed to pay attention to which wires went to which pad.

It wouldn't be a problem most of the time, but in some of
the many possible configurations it could result in issues.

Perhaps now?

-Chuck Harris

Harvey White wrote:
interleaved responses

On 8/10/2020 4:13 PM, Stephen wrote:
I figured that the plugins that were not working before but are now were the ones
needing the NPN transistor.
The PS503 probably needs the PNP only.
Actually, looking at the TM503A manual gives you an idea of the reason. The outputs
of the supplies go through the frame transistors. However the drivers for those
transistors also provide a path for the regulated output. It's a very "weak" current
limited output, which would show up with a good meter, but the supply would not
provide anything near full current. The 5 volts uses a 7805 regulator, hence the 1
amp current limit.

Now that all my plugins are powering on, I have to figure out 2 things. Not that
the 1st is a real issue, but I’m just trying to understand the concept.

1- While the unit is inside the 506, and when my DMM ground lead is connected to
ANY of the ground banana plugs can I measure the +/- 20VDC as well as the 5VDC.
But when the plugin is connected To the extender, I have to switch the ground lead
to the appropriate one on the PS to be able to read the voltages
The DC503A 5 volt ground is common to all modules. The common lead for the +/-
supply is floating. I'd measure from the frame to frame of the power supply to see
what's going on there. However, a possible suggestion is to look on the backplane to
see if there any added wires.



2- I still don’t get why the DC503 shows only 1 digit or nothing at all when
plugged in directly into the 506, but is showing every single one, albeit some are
missing a segment, when used with the extender... A mystery to me. But I’ll
follow up on this in the appropriate thread I started on troubleshooting it.
I'd suggest backplane wiring, as in there shouldn't be any. If someone used this
with backplane wiring, then the slots become dedicated to a particular module. You
didn't connect the additional wires to bring out the plugin signals, where in the
frame, they're connected.


Harvey







Re: DC503 Not Working

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@gmail.com> 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.



Re: DC503 Not Working

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@gmail.com> 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.


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