[neonixie-l] Re: Taylor Edge Nixie Clock Kit

['threeneurons' via neonixie-l]

On Friday, March 31, 2017 at 4:42:53 AM UTC-7, Chuck wrote:
>
> 360 ohms is way too little resistance for *any* sort of 
> TTL pullup resistor!  That apparently got confused with 
> the standard *pull down* resistor used to keep an unattended 
> TTL input *low*.   360 ohms for a TTL pulldown is just right. 
>
> 2.2k ohms is the standard value to use as a TTL pullup. 
> That goes for regular old 7400 series TTL, as well as 74LS 
> series.   
>
> The old military practice was to always use 1k ohm as the 
> standard TTL pullup resistor value.  Note that even when using 
> that 1k pullup resistance, that all we are asking of any TTL 
> gate which is pulled up by this, is to be able to provide 5 
> milliamperes 
> in order for for the output to go low. 
>
> Even that value of 1k ohm would work ok with either plain 7400 or 
> 74LS. 
>
> 2.2k is much more like it, however. 
> At that value, all we are asking is 2.3 mA, and that works fine. 
>
> 360 ohms is just simply too close to being a piece of wire!! 
>
> (This is all explained in great detail on page 12 of Don Lancaster's 
> famous TTL Cookbook) 
>
>
I think he's stuck with the low value resistors, because he's making 
Schmitt triggered gates out of 7417s. The feed back resistor has to work 
both as a pulldown, and pullup. As noted, TTL source and sink, are very 
asymmetrical. 

This is one, of several reasons, I prefer, 4000 series CMOS over 74 TTL, 
when it comes to older logic families. CMOS is symmetrical. It has high 
impedance inputs, and you're not stuck with a 5V supply. On my "new" 
thermometer kit, I run the CMOS on 12V. Here is the set switch scheme on my 
old nixie clock board:



The "seconds-to-minutes" and "minutes-to-hours" pulses are passed thru 
1000pf caps, feeding 4.7K loads, that normally sit at 5V. It has to use a 
5V supply due to the 74141 drivers, also used. Short pulses are seen at the 
respective inputs, for minute, and hour, "bumps". Setting is done thru 4093 
Schmitt gates, which are made "open drain", by using 1N914 diodes, in their 
output legs. Since its 4000 CMOS, a logic-0 is anything under 1/3 supply, 
or ~1.5V or less. A logic-1 is anything over 2/3 supply (>3.5V). The 0.7V 
diode drop is a non-issue, here. Punching the "hours" or "minute" button, 
increases the count by one, per depression. No goofy accelerated clock 
scheme. This would be much more difficult to implement in TTL.

 
 

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

Yeah Chuck.. but the interesting thing is that it is supposedly very closely 
based on a TI ap note or some such.
I was looking forward to some input from the seller. But maybe this is 
public and wasn't "addressed" to him.

Still think it is/was in his interest to comment though.

John K


- Original Message - 
From: "chuck richards" 

To: 
Sent: Friday, March 31, 2017 10:12 PM
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit



360 ohms is way too little resistance for *any* sort of
TTL pullup resistor!  That apparently got confused with
the standard *pull down* resistor used to keep an unattended
TTL input *low*.   360 ohms for a TTL pulldown is just right.

2.2k ohms is the standard value to use as a TTL pullup.
That goes for regular old 7400 series TTL, as well as 74LS
series.

The old military practice was to always use 1k ohm as the
standard TTL pullup resistor value.  Note that even when using
that 1k pullup resistance, that all we are asking of any TTL
gate which is pulled up by this, is to be able to provide 5
milliamperes
in order for for the output to go low.

Even that value of 1k ohm would work ok with either plain 7400 or
74LS.

2.2k is much more like it, however.
At that value, all we are asking is 2.3 mA, and that works fine.

360 ohms is just simply too close to being a piece of wire!!

(This is all explained in great detail on page 12 of Don Lancaster's
famous TTL Cookbook)



 Original Message 
From: neonixie-l@googlegroups.com
To: neonixie-l@googlegroups.com
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit
Date: Thu, 30 Mar 2017 19:38:26 -0700 (PDT)





I'm a little late to the party, and the discussion between old 74xx
versus
74LSxx caught my attention. In most cases, I'd favor the newer 74LS
over
the original 74xx. But the resistor values (360 ohm) paint you into
using
the older series, because 5V / 360ohms gives you 13.9mA. The value
seems to
have been chosen because of the set switch resistor values.Of course
as the
OP mentioned, removing all the 360 ohm resistors lets the unit
operate
properly. The set switches may work adequately, too.

<https://lh3.googleusercontent.com/-k_4j6X4xaEs/WN3AZVxQbgI/Y
lU/Wcu3xmkZidsfPKYgHCTU5VlWEi_nSXiWACLcB/s1600/Taylor_Clock.jpg>

Personally, I prefer 4000 series CMOS, for this kind of thing.


Good to see that the OP, and his buddy, figured it out.

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[chuck richards]

360 ohms is way too little resistance for *any* sort of
TTL pullup resistor!  That apparently got confused with
the standard *pull down* resistor used to keep an unattended
TTL input *low*.   360 ohms for a TTL pulldown is just right.

2.2k ohms is the standard value to use as a TTL pullup.
That goes for regular old 7400 series TTL, as well as 74LS
series.  

The old military practice was to always use 1k ohm as the
standard TTL pullup resistor value.  Note that even when using
that 1k pullup resistance, that all we are asking of any TTL
gate which is pulled up by this, is to be able to provide 5
milliamperes
in order for for the output to go low.

Even that value of 1k ohm would work ok with either plain 7400 or
74LS.

2.2k is much more like it, however.
At that value, all we are asking is 2.3 mA, and that works fine.

360 ohms is just simply too close to being a piece of wire!!

(This is all explained in great detail on page 12 of Don Lancaster's
famous TTL Cookbook)



 Original Message 
From: neonixie-l@googlegroups.com
To: neonixie-l@googlegroups.com
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit
Date: Thu, 30 Mar 2017 19:38:26 -0700 (PDT)

>
>
>
>I'm a little late to the party, and the discussion between old 74xx
>versus 
>74LSxx caught my attention. In most cases, I'd favor the newer 74LS
>over 
>the original 74xx. But the resistor values (360 ohm) paint you into
>using 
>the older series, because 5V / 360ohms gives you 13.9mA. The value
>seems to 
>have been chosen because of the set switch resistor values.Of course
>as the 
>OP mentioned, removing all the 360 ohm resistors lets the unit
>operate 
>properly. The set switches may work adequately, too.
>
><https://lh3.googleusercontent.com/-k_4j6X4xaEs/WN3AZVxQbgI/Y
>lU/Wcu3xmkZidsfPKYgHCTU5VlWEi_nSXiWACLcB/s1600/Taylor_Clock.jpg>
>
>Personally, I prefer 4000 series CMOS, for this kind of thing.
>
>
>Good to see that the OP, and his buddy, figured it out.
>
>-- 
>You received this message because you are subscribed to the Google
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>d1e2091fefa1%40googlegroups.com.
>For more options, visit https://groups.google.com/d/optout.



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RE: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[chuck richards]

Yep, those old plain 7400 series TTL ics are little juice-hogs!

Changing that whole thing over to 74LS is a good idea.
The plain old 7400 series TTL works ok, but it hogs a lot
more current, and it's also much more susceptible to noise
and transient spikes.  74LS series is a vast improvement!

But, you are correct in your observation that when changing
from plain 74XX to 74LSXX, that particular attention must be
paid to current availability.

Swapping out those resistors sounds reasonable.




>
>
> Original Message 
>From: dave.do...@comcast.net
>To: neonixie-l@googlegroups.com
>Subject: RE: [neonixie-l] Re: Taylor Edge Nixie Clock Kit
>Date: Thu, 30 Mar 2017 18:25:39 -0700 (PDT)
>
>>Sorry that it took me so long to get back about this clock problem.
>We have 
>>the clock work perfectly now. I have to give my friend Mike all the
>credit 
>>for figuring this out. It appears that the original clock design
>schematic 
>>calls for 7400 series ICs but the BOM calls for 74LSXX. Mike has a
>IC spec. 
>>book and after comparing the differences in the ICs we found that
>the 
>>74LSXX have an output of 8ma and the 7400 series have an output of
>16ma. We 
>>believe that the original design was for 7400 but in shopping for
>them 
>>found that there are very few suppliers anymore. We think that this
>is why 
>>they changed the BOM to 74LSXX. With the smaller output from the
>74LSXX IC 
>>and the amount of resistance in that circuit the current was
>marginal and 
>>not enough current to drive the other ICs correctly in the circuit.
>We 
>>ended up removing R1 and R3 (360 ohm) and leaving everything else
>the way 
>>it was. It works perfect now and all of the setting switches work
>fine 
>>also. Thanks for all the feedback from everyone
>>
>>Dave
>>
>>On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net
>wrote:
>>>
>>> I'm hoping that someone out there can help me with a problem that
>I am 
>>> having with a Taylor Edge clock kit that I built. After completing
>the kit 
>>> and plugging it in it seemed to be working fine. Then I noticed
>that the 
>>> 10s second display tube and the 10s minute display tube were not
>counting 
>>> correctly. They would count from 2 to 3 to 4 to 5 but then it
>would go back 
>>> to 3 then 4 then back to 2 and then start the sequence over again.
>The 1s 
>>> second and 10s minute tubes would count fine. I asked a friend of
>mine that 
>>> knows a lot more about this stuff than I do and he recommended
>that I try 
>>> disconnecting resistors R13 and R15 (both 240 ohm) from the time
>setting 
>>> circuit to see what would happen. This fixed the counting problem
>but now I 
>>> cannot set the time. I can't believe that I am the only person
>that has had 
>>> this problem and am hoping someone out there knows the answer. I
>am 
>>> attaching the schematic.
>>>
>>> Thanks
>>> Dave
>>>
>>
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>Groups "neonixie-l" group.
>>To unsubscribe from this group and stop receiving emails from it,
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>6a31687c11a1%40googlegroups.com.
>>For more options, visit https://groups.google.com/d/optout.
>>



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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

['threeneurons' via neonixie-l]

I'm a little late to the party, and the discussion between old 74xx versus 
74LSxx caught my attention. In most cases, I'd favor the newer 74LS over 
the original 74xx. But the resistor values (360 ohm) paint you into using 
the older series, because 5V / 360ohms gives you 13.9mA. The value seems to 
have been chosen because of the set switch resistor values.Of course as the 
OP mentioned, removing all the 360 ohm resistors lets the unit operate 
properly. The set switches may work adequately, too.



Personally, I prefer 4000 series CMOS, for this kind of thing.


Good to see that the OP, and his buddy, figured it out.

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

Good outcome. I wondered what had happened.
Saw what you meant as soon as I looked at the docs. At least you know what 
tweaks to do if anymore funnies turn up [ageing, temperature etc].

You can often scavenge the old parts from recycling centres if they haven't 
actually chewed up the boards for metal extraction.
I am sure that all the boards we see leaving here for the Philipines get 
components pulled and sold on ebay.

I regret putting off getting a bigger selection of spares for all my 
'interesting' old junk - like Data General Novas.

John K.
  - Original Message - 
  From: dave.do...@comcast.net 
  To: neonixie-l 
  Sent: Friday, March 31, 2017 11:55 AM
  Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit


  Sorry that it took me so long to get back about this clock problem. We have 
the clock work perfectly now. I have to give my friend Mike all the credit for 
figuring this out. It appears that the original clock design schematic calls 
for 7400 series ICs but the BOM calls for 74LSXX. Mike has a IC spec. book and 
after comparing the differences in the ICs we found that the 74LSXX have an 
output of 8ma and the 7400 series have an output of 16ma. We believe that the 
original design was for 7400 but in shopping for them found that there are very 
few suppliers anymore. We think that this is why they changed the BOM to 
74LSXX. With the smaller output from the 74LSXX IC and the amount of resistance 
in that circuit the current was marginal and not enough current to drive the 
other ICs correctly in the circuit. We ended up removing R1 and R3 (360 ohm) 
and leaving everything else the way it was. It works perfect now and all of the 
setting switches work fine also. Thanks for all the feedback from everyone


  Dave

  On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
I'm hoping that someone out there can help me with a problem that I am 
having with a Taylor Edge clock kit that I built. After completing the kit and 
plugging it in it seemed to be working fine. Then I noticed that the 10s second 
display tube and the 10s minute display tube were not counting correctly. They 
would count from 2 to 3 to 4 to 5 but then it would go back to 3 then 4 then 
back to 2 and then start the sequence over again. The 1s second and 10s minute 
tubes would count fine. I asked a friend of mine that knows a lot more about 
this stuff than I do and he recommended that I try disconnecting resistors R13 
and R15 (both 240 ohm) from the time setting circuit to see what would happen. 
This fixed the counting problem but now I cannot set the time. I can't believe 
that I am the only person that has had this problem and am hoping someone out 
there knows the answer. I am attaching the schematic.


Thanks
Dave

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[dave.do...@comcast.net]

Sorry that it took me so long to get back about this clock problem. We have 
the clock work perfectly now. I have to give my friend Mike all the credit 
for figuring this out. It appears that the original clock design schematic 
calls for 7400 series ICs but the BOM calls for 74LSXX. Mike has a IC spec. 
book and after comparing the differences in the ICs we found that the 
74LSXX have an output of 8ma and the 7400 series have an output of 16ma. We 
believe that the original design was for 7400 but in shopping for them 
found that there are very few suppliers anymore. We think that this is why 
they changed the BOM to 74LSXX. With the smaller output from the 74LSXX IC 
and the amount of resistance in that circuit the current was marginal and 
not enough current to drive the other ICs correctly in the circuit. We 
ended up removing R1 and R3 (360 ohm) and leaving everything else the way 
it was. It works perfect now and all of the setting switches work fine 
also. Thanks for all the feedback from everyone

Dave

On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
>
> I'm hoping that someone out there can help me with a problem that I am 
> having with a Taylor Edge clock kit that I built. After completing the kit 
> and plugging it in it seemed to be working fine. Then I noticed that the 
> 10s second display tube and the 10s minute display tube were not counting 
> correctly. They would count from 2 to 3 to 4 to 5 but then it would go back 
> to 3 then 4 then back to 2 and then start the sequence over again. The 1s 
> second and 10s minute tubes would count fine. I asked a friend of mine that 
> knows a lot more about this stuff than I do and he recommended that I try 
> disconnecting resistors R13 and R15 (both 240 ohm) from the time setting 
> circuit to see what would happen. This fixed the counting problem but now I 
> cannot set the time. I can't believe that I am the only person that has had 
> this problem and am hoping someone out there knows the answer. I am 
> attaching the schematic.
>
> Thanks
> Dave
>

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

Well, I was waiting off for other comments to surface or for the kit supplier 
to pipe up.

 I see a few choices:-
- contact the supplier for comment
- measure waveforms/ logic levels and act accordingly
- try specially selecting 74LSxx that work in the location [might be 
temperamental with age, temperature etc]
- try using the components shown on the schematic, ie 74xx series. BUT, check 
power supply ratings etc first

If it were mine I would want to measure the goings-on with an oscilloscope.

John K.






- Original Message - 
  From: dave.do...@comcast.net 
  To: neonixie-l 
  Sent: Saturday, March 11, 2017 5:28 AM
  Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit


  Here is a copy of the BOM

  On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
I'm hoping that someone out there can help me with a problem that I am 
having with a Taylor Edge clock kit that I built. After completing the kit and 
plugging it in it seemed to be working fine. Then I noticed that the 10s second 
display tube and the 10s minute display tube were not counting correctly. They 
would count from 2 to 3 to 4 to 5 but then it would go back to 3 then 4 then 
back to 2 and then start the sequence over again. The 1s second and 10s minute 
tubes would count fine. I asked a friend of mine that knows a lot more about 
this stuff than I do and he recommended that I try disconnecting resistors R13 
and R15 (both 240 ohm) from the time setting circuit to see what would happen. 
This fixed the counting problem but now I cannot set the time. I can't believe 
that I am the only person that has had this problem and am hoping someone out 
there knows the answer. I am attaching the schematic.


Thanks
Dave

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[dave.do...@comcast.net]

Here is a copy of the BOM

On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
>
> I'm hoping that someone out there can help me with a problem that I am 
> having with a Taylor Edge clock kit that I built. After completing the kit 
> and plugging it in it seemed to be working fine. Then I noticed that the 
> 10s second display tube and the 10s minute display tube were not counting 
> correctly. They would count from 2 to 3 to 4 to 5 but then it would go back 
> to 3 then 4 then back to 2 and then start the sequence over again. The 1s 
> second and 10s minute tubes would count fine. I asked a friend of mine that 
> knows a lot more about this stuff than I do and he recommended that I try 
> disconnecting resistors R13 and R15 (both 240 ohm) from the time setting 
> circuit to see what would happen. This fixed the counting problem but now I 
> cannot set the time. I can't believe that I am the only person that has had 
> this problem and am hoping someone out there knows the answer. I am 
> attaching the schematic.
>
> Thanks
> Dave
>

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1384_BOM.pdf
Description: Adobe PDF document

Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[gregebert]

Take a close look at the signal amplitudes (best to use a scope); if the 
resistor values are causing the logic gates to be overloaded [either due to 
wrong IC, wrong logic family, wrong resistor value, solder short/open] , 
you will see incorrect levels. Generally, logic-0 will be 200mV or less 
(despite the specs being Vol(max)=0.4), and logic-1 around 4V (despite spec 
being Voh(min)=2.4). Remember - clock signals are critical; they must have 
clean edges and should swing rail-to-rail. Anything other than this should 
be suspect.

In my previous life as a technician, one of the first things we did when 
debugging a large PCB was to hunt-around ICs for bad signal amplitudes. It 
took less than a minute to probe a large section, and that method found 
many problems (wrong IC, backwards IC, bent pin, solder-bridge, bad PCB 
trace, bad socket). In *rare* cases, the actual IC was bad, which seems 
counter-intuitive until you realize these devices are thoroughly tested by 
the manufacturer.

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

OK, so now I looked at the schematic you posted [it is a slightly changed TI ap 
it seems].
I took it at face value that the BOM was correct, but I don't see one in that 
pdf you attached.

The schematic uses 7400 series.

There are  "Changes to original..." at top left of sheet 4.
In those changes I see no mention of LS being considered.

I agree that it IS a good approach to check the design calculations - 
especially in this case where the documentation apparently mismatches.

A question then... are the resistors being discussed  ( sh1  R1, R2, R3 ) 
actually  the talked about 360 ohms? Have their values been changed on the 
board or in the BOM?


John K.
  - Original Message - 
  From: dave.do...@comcast.net 
  To: neonixie-l 
  Sent: Friday, March 10, 2017 10:41 PM
  Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit


  Just wanted to update everyone on where we are at on this project. One of the 
first things that my friend Mike questioned was why are we using 74LS series 
instead of 7400. I have order new ICs for everything except the 141s. Here is 
the last update that I received from him.
 
  Ok, did some quick calculations, and the drive current needed to drive the 
7417 from the output of the counter with the 360 ohm resistor to VCC, you need 
14ma.  The current output of the 74LSxx counter is only 8ma, and the 74xx is 
16ma.  When and if the 7417 see's a good logic low on it's input, it's output 
will switch low pulling the 510 ohm low, 9ma needed, helping drive the counter 
output low.  The 74LS17 can drive 30ma, so that can help once it can see a good 
logic low (.8V) on the input.  So, if we increase the resistance of the 360 ohm 
resistor to 625 ohms, that may be a place to start.  These are rough 
calculations, but I would go back to using the 74xx's instead of the 74LSxx's 
this would have been better.

  Mike




  On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
I'm hoping that someone out there can help me with a problem that I am 
having with a Taylor Edge clock kit that I built. After completing the kit and 
plugging it in it seemed to be working fine. Then I noticed that the 10s second 
display tube and the 10s minute display tube were not counting correctly. They 
would count from 2 to 3 to 4 to 5 but then it would go back to 3 then 4 then 
back to 2 and then start the sequence over again. The 1s second and 10s minute 
tubes would count fine. I asked a friend of mine that knows a lot more about 
this stuff than I do and he recommended that I try disconnecting resistors R13 
and R15 (both 240 ohm) from the time setting circuit to see what would happen. 
This fixed the counting problem but now I cannot set the time. I can't believe 
that I am the only person that has had this problem and am hoping someone out 
there knows the answer. I am attaching the schematic.


Thanks
Dave

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Dekatron42]

What happens if you set all three time switches and the halt/set switch in 
the SET position and then push the INCR button, do all counters advance one 
step each so that they count properly or do soem still count in the strange 
sequence?

I would also make sure that VCC and GND are present on all places where 
they should be present, like on all IC pins and on all component pins - 
having a loose VCC or GND pin can wreak havoc on a system and is very hard 
to find by reasoning or by other tests.

/Martin

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[dave.do...@comcast.net]

Just wanted to update everyone on where we are at on this project. One of 
the first things that my friend Mike questioned was why are we using 74LS 
series instead of 7400. I have order new ICs for everything except the 
141s. Here is the last update that I received from him.
   

Ok, did some quick calculations, and the drive current needed to drive the 
7417 from the output of the counter with the 360 ohm resistor to VCC, you 
need 14ma.  The current output of the 74LSxx counter is only 8ma, and the 
74xx is 16ma.  When and if the 7417 see's a good logic low on it's input, 
it's output will switch low pulling the 510 ohm low, 9ma needed, helping 
drive the counter output low.  The 74LS17 can drive 30ma, so that can help 
once it can see a good logic low (.8V) on the input.  So, if we increase 
the resistance of the 360 ohm resistor to 625 ohms, that may be a place to 
start.  These are rough calculations, but I would go back to using the 
74xx's instead of the 74LSxx's this would have been better.
Mike


On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:

> I'm hoping that someone out there can help me with a problem that I am 
> having with a Taylor Edge clock kit that I built. After completing the kit 
> and plugging it in it seemed to be working fine. Then I noticed that the 
> 10s second display tube and the 10s minute display tube were not counting 
> correctly. They would count from 2 to 3 to 4 to 5 but then it would go back 
> to 3 then 4 then back to 2 and then start the sequence over again. The 1s 
> second and 10s minute tubes would count fine. I asked a friend of mine that 
> knows a lot more about this stuff than I do and he recommended that I try 
> disconnecting resistors R13 and R15 (both 240 ohm) from the time setting 
> circuit to see what would happen. This fixed the counting problem but now I 
> cannot set the time. I can't believe that I am the only person that has had 
> this problem and am hoping someone out there knows the answer. I am 
> attaching the schematic.
>
> Thanks
> Dave
>

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

['Terry S' via neonixie-l]

First we need some clarification of the problem, as your original post 
contains a discrepancy. At one point you say the 10 minute tube is not 
counting correctly, then later you say it is fine. This is probably a typo, 
but let's hear the answer.

Nick, the 10s are driven by 92's and the 1s by 90's. Another minor 
correction for clarity.

Here is where I would break out the logic analyzer and hang some probes, 
watch the count sequence. This appears to be a case of the counters not 
resetting properly as they roll over from 5 to 0.  This could be for a 
number of reasons, maybe the parts are faster than the used to be, subtle 
changes in setup & hold times can occur with die changes, shrinks, 
technology changes, etc. Maybe a ringing clock that never used to be a 
problem is now..

USB based logic analyzers are handy tools, and have gotten pretty cheap.

Check the counting with & without the 74141s installed. If they are loading 
the counter outputs, they could affect the count sequence, as some outputs 
are also used internally on the counters to sequence the F/Fs.

Terry


On Wednesday, March 8, 2017 at 9:07:27 PM UTC-6, Nick wrote:
>
> ...Also, reading your problem description isolates the issue to the 10s 
> digits. 
>
> The 10s are driven by 7490s whereas the units are driven by 7492s. Do you 
> have the right chips in the right places?
>
> I'd also try swapping round the 74141s between the 10s and units to see if 
> the problem moves with them - 74141s can fail
>
> Isolate the problem.
>
> Nick
>
>

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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[David Speck MD]

Along the same line, is there a chance that you have a counterfeit 7490 
chip?  A lot of chips coming from Asia are marginal manufacturing 
rejects or remarked circuit pulls that may have been mid-labeled.


Dave


On 3/9/2017 4:21 AM, JohnK wrote:

Very very good advice from Nick in these two posts.

Changing like-for-like or interchanging if easy is valid -
modifications aren't. [Unless you deduce something from a *temporary*
mod to allow you to fix the original problem.]
I have had to deal with the fallout from bad approaches: "We"
discovered that, in the Chinese factory, there was an 'engineer'
modifying the units that failed test until they worked or passed.
Things like changing the value of a resistor in a voltage divider that
supplies a ref voltage to a comparator making up for an IC with a
leaky input ( or a solder bridge to a different part of the circuit as
in one of the customer returns that I analysed). Eeek!!

John K


- Original Message - From: "Nick" 
To: "neonixie-l" 
Sent: Thursday, March 09, 2017 1:37 PM
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit



...Also, reading your problem description isolates the issue to the
10s digits.

The 10s are driven by 7490s whereas the units are driven by 7492s. Do
you have the right chips in the right places?

I'd also try swapping round the 74141s between the 10s and units to
see if the problem moves with them - 74141s can fail


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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[JohnK]

Very very good advice from Nick in these two posts.

Changing like-for-like or interchanging if easy is valid - modifications 
aren't. [Unless you deduce something from a *temporary* mod to allow you to 
fix the original problem.]
I have had to deal with the fallout from bad approaches: "We" discovered 
that, in the Chinese factory, there was an 'engineer' modifying the units 
that failed test until they worked or passed. Things like changing the value 
of a resistor in a voltage divider that supplies a ref voltage to a 
comparator making up for an IC with a leaky input ( or a solder bridge to a 
different part of the circuit as in one of the customer returns that I 
analysed).Eeek!!


John K


- Original Message - 
From: "Nick" 

To: "neonixie-l" 
Sent: Thursday, March 09, 2017 1:37 PM
Subject: [neonixie-l] Re: Taylor Edge Nixie Clock Kit


...Also, reading your problem description isolates the issue to the 10s 
digits.


The 10s are driven by 7490s whereas the units are driven by 7492s. Do you 
have the right chips in the right places?


I'd also try swapping round the 74141s between the 10s and units to see if 
the problem moves with them - 74141s can fail


Isolate the problem.

Nick

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RE: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Tidak Ada]

It is also possible one of the 7490 or 4717 chips isn't functioning correct or 
damaged or a bad soldering. Check your soldering work with a magnifier glass

eric

-Oorspronkelijk bericht-
Van: neonixie-l@googlegroups.com [mailto:neonixie-l@googlegroups.com] Namens 
Nick
Verzonden: donderdag 9 maart 2017 4:07
Aan: neonixie-l
Onderwerp: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

...Also, reading your problem description isolates the issue to the 10s digits. 

The 10s are driven by 7490s whereas the units are driven by 7492s. Do you have 
the right chips in the right places?

I'd also try swapping round the 74141s between the 10s and units to see if the 
problem moves with them - 74141s can fail

Isolate the problem.

Nick

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Nick]

...Also, reading your problem description isolates the issue to the 10s digits. 

The 10s are driven by 7490s whereas the units are driven by 7492s. Do you have 
the right chips in the right places?

I'd also try swapping round the 74141s between the 10s and units to see if the 
problem moves with them - 74141s can fail

Isolate the problem.

Nick

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Nick]

If the BOM specified LS, use LS. The Taylor stuff is good - it's more likely 
that you have an assembly error.

Randomly changing stuff to see what happens is not a good approach.

I'd start by very thoroughly checking that you have the right components in the 
right places, that you don't have any dry joints or solder bridges. Put the 
resistors you took out back in - they are there for a reason as I mentioned 
previously.

My money is on you having made a mistake somewhere - problem solving requires a 
methodical approach, following the signal chain from source, in this case from 
the 60Hz take off from the power input to the board...

Do you have a 'scope?

Nick

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[dave.do...@comcast.net]

Your question about the TTL type was discussed between my friend and I. He 
asked me why I used 74LS instead of 7400. I told him that 74LS00, 74LS90, 
and 74LS92 is what was on the BOM for the kit. He also thought that a 7400 
may work better. I will try that first and see what happens. Will let you 
know what happens. Thanks for the advise.  

On Tuesday, March 7, 2017 at 6:37:54 PM UTC-6, dave@comcast.net wrote:
>
> I'm hoping that someone out there can help me with a problem that I am 
> having with a Taylor Edge clock kit that I built. After completing the kit 
> and plugging it in it seemed to be working fine. Then I noticed that the 
> 10s second display tube and the 10s minute display tube were not counting 
> correctly. They would count from 2 to 3 to 4 to 5 but then it would go back 
> to 3 then 4 then back to 2 and then start the sequence over again. The 1s 
> second and 10s minute tubes would count fine. I asked a friend of mine that 
> knows a lot more about this stuff than I do and he recommended that I try 
> disconnecting resistors R13 and R15 (both 240 ohm) from the time setting 
> circuit to see what would happen. This fixed the counting problem but now I 
> cannot set the time. I can't believe that I am the only person that has had 
> this problem and am hoping someone out there knows the answer. I am 
> attaching the schematic.
>
> Thanks
> Dave
>

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[Nick]

I suspect they're there to "latch-up" the buffer to debounce the switches - 
pulling the input to ground with "de-latch" it. - these are o/c buffers, 
hence R12, R14 & R16.

Nick

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[neonixie-l] Re: Taylor Edge Nixie Clock Kit

[gregebert]

Clocking problem. I've been looking at the peculiar buffering on the clock 
signals (7417 open-collector buffer), and cant come up with a good reason 
why R11, R13, and R15 are present. I'd be especially concerned about 
unstable operation, as this circuit has positive feedback. 

Are you using the exact parts,which seem to be 7400-series TTL, or did you 
 use something similar, such as 74LS, 74LV, 74HC ? I suspect the circuit is 
very fussy about threshold values and output-drive-strength, so swapping 
devices that are functionally, but not parametrically equivalent, could 
cause problems.

If you have a digital scope (you will need to capture the signal), best to 
start looking at clock-edges for odd behavior (ringing/glitches, incorrect 
amplitudes). 

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