HP-65 1333A02242 display missing all the decimal dots

[albertofenini]

Hi Tony,


To which attached image are you referring ?

It should be at bottom of last post.
I have added a tag to each of the snapshots, they are labeled
Step
Disp4
Disp3
Disp2
Disp1
Disp0
Segmento a
Segmento c
Segmento b
Segmento d
Segmento f
Segmento h
Segmento e
Segmento g
I'm assuming you are referring to Step, right ?

CLx just clears the display and allows a new number entry, then pressing the DP button should result in just the decimal point showing.
We didn't hit CLX during the measure, all of the snapshot were taken with a 0.00 shown.
Don't know if this helps

You meant the 18th pin right ?
My applogies, yes.

We are in difficulties comparing our waveforms with yours and understand if ours are correct or not. What scale for the time and volt you suggest ?

For viewing a full display refresh, 2V per Div and say 40uS per div should be ok, triggered on the RCD pulse if you can, so you can see everything in a display refresh.
Will try, remember we didn't post RCD waveforms

You say that we should see 15 pulses ... in the STEP image we uploaded we see 4 square waves and noise in between
The first square wave is a little more distant of the following three, is this what you mean ?
Four is because 0.00 in theory is 4 digit ? (the 3 zeroes and the digital point ?)
Should we lit all the display digits to see the 15 pulses ?

I was pretty sure that all 15 pulses should be there regardless of how many digits are being displayed. Have a look at page 15 of the Classic Notes, it shows a HP-65 waveform.
We surely will, but just to understand with pulse you mean what we call a spike ?

(The DP coil might be open circuit as well.)
Any way we can check that too ?
From the common coil terminal to the DP coil terminal should measure low ohms. I think this should be between VBsw and pin 18 of the anode driver. VBsw is the switched side of the battery, 12th pin in from right of cpu to keyboard connector
You mean that common coil terminal is Vbsw ? I have seen that is also available
as the 11th pin of the Anode driver, can we use that ?

Thank you so much !

[teenix]

(11-10-2020 12:15 PM)albertofenini Wrote:  Hi Tony,
You mean that common coil terminal is Vbsw ? I have seen that is also available
as the 11th pin of the Anode driver, can we use that ?

Yes, correct.

This image should give you an idea of the correct RCD and STEP wave forms for the HP-65. One with a decimal point in the display and one without.



cheers

Tony

[albertofenini]

Thank you soooo much !
Will try later today
BTW what timezone are you in ?

(11-10-2020 01:08 PM)teenix Wrote:  

(11-10-2020 12:15 PM)albertofenini Wrote:  Hi Tony,
You mean that common coil terminal is Vbsw ? I have seen that is also available
as the 11th pin of the Anode driver, can we use that ?

Yes, correct.

This image should give you an idea of the correct RCD and STEP wave forms for the HP-65. One with a decimal point in the display and one without.



cheers

Tony

[teenix]

(11-10-2020 01:14 PM)albertofenini Wrote:  Thank you soooo much !
Will try later today
BTW what timezone are you in ?

It is 9:15 PM here at the moment. UTC + 8

cheers

Tony

[albertofenini]

Tony,
to measure the possibly open coil for the dot,
do we need to take the anode driver out or can we do it with anode driver soldered in place ?
Thanks again !

[teenix]

(11-10-2020 01:20 PM)albertofenini Wrote:  Tony,
to measure the possibly open coil for the dot,
do we need to take the anode driver out or can we do it with anode driver soldered in place ?
Thanks again !

Measuring across those points should be a low ohms value because of the low resistance of the coil. I don't know exactly because I haven't measured it.

If in doubt, the coil pack can be removed and then measured.

cheers

Tony

[albertofenini]

I got it now ...
the value we should look for is not between the PIN 18 (h segment) and the PIN 11 (Vbsw) of the Anode driver
instead between the 3rd pin and the 5th pin of the left coil "chip"

I thought you meant that something INSIDE the anode driver about the h segment was open and not driving current to the decimal point ...

Is the waveform for that segment good then ?

I'm asking because the display was showing some 0s, in a 0 the g segment is obviously off,
so we were expecting a flat line as waveform for that segment, while in reality it was not flat ...

Thanks again !

(11-10-2020 01:22 PM)teenix Wrote:  

(11-10-2020 01:20 PM)albertofenini Wrote:  Tony,
to measure the possibly open coil for the dot,
do we need to take the anode driver out or can we do it with anode driver soldered in place ?
Thanks again !

Measuring across those points should be a low ohms value because of the low resistance of the coil. I don't know exactly because I haven't measured it.

If in doubt, the coil pack can be removed and then measured.

cheers

Tony

[teenix]

(11-10-2020 01:35 PM)albertofenini Wrote:  I got it now ...
the value we should look for is not between the PIN 18 (h segment) and the PIN 11 (Vbsw) of the Anode driver
instead between the 3rd pin and the 5th pin of the left coil "chip"

I thought you meant that something INSIDE the anode driver about the h segment was open and not driving current to the decimal point ...

Is the waveform for that segment good then ?

I'm asking because the display was showing some 0s, in a 0 the g segment is obviously off,
so we were expecting a flat line as waveform for that segment, while in reality it was not flat ...

Thanks again !

Electrically wise, same points.

Yes, there could indeed be a fault inside the anode driver. Hopefully testing the coil, solder connections and PCB traces for the decimal point will confirm this or a fault on the board.

From your wave forms for 0.00 I would expect the same activity on segments a b c d e f, with no activity on g except for noise. Segment h (I would expect) should have similar activity to the g segment but, with a higher pulse once per display refresh indicating the decimal point. I cannot say for sure without being home to test myself.

cheers

Tony

[albertofenini]

That's what I was expecting myself as well ...

We have seen :
2 volts on segment f
4 volts on segment h
6 volts on segments c, b, d, e, a
2 volts with an offset of 2 volts (.ie. waves do not start on the line of 0 volts) for segment g

We may have mixed up things, will check again this evening and let you know
take care !

(11-10-2020 01:54 PM)teenix Wrote:  

(11-10-2020 01:35 PM)albertofenini Wrote:  I got it now ...
the value we should look for is not between the PIN 18 (h segment) and the PIN 11 (Vbsw) of the Anode driver
instead between the 3rd pin and the 5th pin of the left coil "chip"

I thought you meant that something INSIDE the anode driver about the h segment was open and not driving current to the decimal point ...

Is the waveform for that segment good then ?

I'm asking because the display was showing some 0s, in a 0 the g segment is obviously off,
so we were expecting a flat line as waveform for that segment, while in reality it was not flat ...

Thanks again !

Electrically wise, same points.

Yes, there could indeed be a fault inside the anode driver. Hopefully testing the coil, solder connections and PCB traces for the decimal point will confirm this or a fault on the board.

From your wave forms for 0.00 I would expect the same activity on segments a b c d e f, with no activity on g except for noise. Segment h (I would expect) should have similar activity to the g segment but, with a higher pulse once per display refresh indicating the decimal point. I cannot say for sure without being home to test myself.

cheers

Tony

[albertofenini]

Tony it works !!!!

Thank you very much for all the help and the explanations !!!
We have updated the iCloud shared album with new pics
At first we took a snapshot for STEP and RCD in 0.00 and in PRGM 00 00
These waves are very similar to yours
We have however noticed that while taking these values the display showed a weird array of zeros rather than 0.00 or 00 00
Then we measured again segments activity
This time we marked the segments with upper case uploading the snapshots
Than we measured the coil resistance for the H segment and it was open
On e we replaced the faulty 1810-0146 with a spare one it worked like a charm !

We will apply this troubleshooting method to the unit that miss all the G segments and we will see ...

Thanks again for the continuous support !!!

Updated link: Updated link for HP-65 missing the decimal dot

[teenix]

Hi Alberto,

Nice one, well done on all your efforts to get this and others working again.

cheers

Tony

(11-10-2020 11:37 PM)albertofenini Wrote:  Tony it works !!!!

Thank you very much for all the help and the explanations !!!
We have updated the iCloud shared album with new pics
At first we took a snapshot for STEP and RCD in 0.00 and in PRGM 00 00
These waves are very similar to yours
We have however noticed that while taking these values the display showed a weird array of zeros rather than 0.00 or 00 00
Then we measured again segments activity
This time we marked the segments with upper case uploading the snapshots
Than we measured the coil resistance for the H segment and it was open
On e we replaced the faulty 1810-0146 with a spare one it worked like a charm !

We will apply this troubleshooting method to the unit that miss all the G segments and we will see ...

Thanks again for the continuous support !!!

Updated link: Updated link for HP-65 missing the decimal dot