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

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

2017-03-31 Thread 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.



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

2017-03-31 Thread 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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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

2017-03-30 Thread 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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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

2017-03-12 Thread 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

Thanks
Dave

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

2017-03-10 Thread 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

2017-03-10 Thread 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

Thanks
Dave

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

2017-03-09 Thread 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

2017-03-09 Thread 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

2017-03-09 Thread 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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Re: [neonixie-l] Re: Taylor Edge Nixie Clock Kit

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