HP- 67 1706A04606 - keyboard repaired weird behavior

[albertofenini]

Hi everyone
trying to make an HP-67 work, we have discovered that the numeric keys
had the underneath domes broken

We have transplanted those from an HP-45 and it may be interesting to see how
it looks now, we have followed Teenix's procedure, drilling a small hole in the
donor keyboard and soldering the strips on the HP-67

Being the firs time we are quite happy, but it could have been done a little better and nicer

Anyway, this unit was used last time in March 2021 and put away in working condition without batteries

Now, when the batteries are put inside, it doesn't turn on at the first try,
some faint numbers appear on the screen and then nothing

Sometimes keeping pressed a key while turning on does the trick, but not
always

Some times show a list of 0 and the keyboard is not responding

In the end, we have found out that if we leave it on, after a while a 0.00 appears on the display and the unit works well

What could it possible be ?

Put it in another unit shows the same behavior

As for the card reader, it reads very rarely, it writes but it cannot read the cards
written by itself, these can be read without problems in a different unit

Also, it shows a behavior that has already been discussed in the forum:

When a double sided card is inserted, the first side is read correctly and prompt
for the second side, but the second side will always make the motor run a little
after the card has gone thru and then it gives an error message

Pictures and video can die found here : HP- 67 1706A04606

Thanks in advance for any help !!! Take care !

[teenix]

Perhaps, try replacing the 47uF tantalum power supply capacitor, shown in image. 16 - 25V type should be ok.

Maybe others might need replacing as well.

cheers

Tony

(09-25-2022 04:12 PM)albertofenini Wrote:  Hi everyone
trying to make an HP-67 work, we have discovered that the numeric keys
had the underneath domes broken

We have transplanted those from an HP-45 and it may be interesting to see how
it looks now, we have followed Teenix's procedure, drilling a small hole in the
donor keyboard and soldering the strips on the HP-67

Being the firs time we are quite happy, but it could have been done a little better and nicer

Anyway, this unit was used last time in March 2021 and put away in working condition without batteries

Now, when the batteries are put inside, it doesn't turn on at the first try,
some faint numbers appear on the screen and then nothing

Sometimes keeping pressed a key while turning on does the trick, but not
always

Some times show a list of 0 and the keyboard is not responding

In the end, we have found out that if we leave it on, after a while a 0.00 appears on the display and the unit works well

What could it possible be ?

Put it in another unit shows the same behavior

As for the card reader, it reads very rarely, it writes but it cannot read the cards
written by itself, these can be read without problems in a different unit

Also, it shows a behavior that has already been discussed in the forum:

When a double sided card is inserted, the first side is read correctly and prompt
for the second side, but the second side will always make the motor run a little
after the card has gone thru and then it gives an error message

Pictures and video can die found here : HP- 67 1706A04606

Thanks in advance for any help !!! Take care !

[albertofenini]

Thanks Tony
Will give it a try
That should fix the power on issues
What do you think of the card reader problems ?
Take care and thanks !

[teenix]

(09-25-2022 08:27 PM)albertofenini Wrote:  Thanks Tony
Will give it a try
That should fix the power on issues
What do you think of the card reader problems ?
Take care and thanks !

A new capacitor (or capacitors) could fix read problems also.

cheers

Tony

[albertofenini]

Hi Tony, Hi everyone,

we replaced the 47microF capacitor, which I believe is that connected to Vbsw
old: 50,26microF, Vloss 0,6%, ESR 0,00 Ohm
new: 49,10microF, Vloss 1,0%, ESR 2,3 Ohm

nothing changed in the power-on behavior

then we also replaced the 22microF capacitor, connected to Vss
old: 24,73microF, Vloss 0,7% ESR: 0,00 Ohm
new: 22,44microF, Vloss 0m6%, ESR 0,00 Ohm

again nothing changed in the power-on behavior

We decide to change the two transistors as well :

4-071
old: hfe 331 Vbe 630mV Ic 3,0ma
new : hfe 352 Vibe 641mV Ic 3,2mA

4-668
old: hfe 433 Vbe 645mV Ic 6,2mA
new: hfe 351 Vbe 643mV Ic 3,2mA

after this replacements, the power-on behavior didn't change,
but the reading capabilities increased a lot, almost every card can be read
and also it can now write and read its own written cards

it must be said the the components we used are from an old HP-67 which
also had some issues

where could we get some equivalent new transistors ?

should we also check the six pins Motorola component 3-410 ? (what is this by the way ?)

thanks for any advice, take care !!

[teenix]

(09-27-2022 07:30 PM)albertofenini Wrote:  Hi Tony, Hi everyone,

we replaced the 47microF capacitor, which I believe is that connected to Vbsw
old: 50,26microF, Vloss 0,6%, ESR 0,00 Ohm
new: 49,10microF, Vloss 1,0%, ESR 2,3 Ohm

nothing changed in the power-on behavior

then we also replaced the 22microF capacitor, connected to Vss
old: 24,73microF, Vloss 0,7% ESR: 0,00 Ohm
new: 22,44microF, Vloss 0m6%, ESR 0,00 Ohm

again nothing changed in the power-on behavior

We decide to change the two transistors as well :

4-071
old: hfe 331 Vbe 630mV Ic 3,0ma
new : hfe 352 Vibe 641mV Ic 3,2mA

4-668
old: hfe 433 Vbe 645mV Ic 6,2mA
new: hfe 351 Vbe 643mV Ic 3,2mA

after this replacements, the power-on behavior didn't change,
but the reading capabilities increased a lot, almost every card can be read
and also it can now write and read its own written cards

it must be said the the components we used are from an old HP-67 which
also had some issues

where could we get some equivalent new transistors ?

should we also check the six pins Motorola component 3-410 ? (what is this by the way ?)

thanks for any advice, take care !!

Maybe also change the 2.2uF (10-16V) tantalum capacitor near the ACT. The +ve connection is closest to pin 1 of ACT (red dot). This is used for the power up reset pulse for the ACT.

Listed from Jaque Laporte's site...
1854-0071 = 2N3704

1854-0668 = ?? Cannot find any info on it. Maybe 2N3904??

If you check parts suppliers like Digikey and search NPN transistor for the HFE etc that you tested, you may find equivalents.

3-410 is 2 PNP transistors in the same package used for a constant current source for the LED display segments.

cheers

Tony

[AndiGer]

When I replaced transistors I used
4-071 —> 2N2222
3-393 —> 2N2907
3-374 —> 2N2907

Jebem once suggested fast switching high gain transistors capable of 0.5 to 1 A of current with at least 50 V Vcb and a minimum of 0.5 W power dissipation.

[albertofenini]

(09-28-2022 12:54 AM)teenix Wrote:  Hi Tony
is this what you call C6 in your HP-67 schematics ?

(09-27-2022 07:30 PM)albertofenini Wrote:  Hi Tony, Hi everyone,

we replaced the 47microF capacitor, which I believe is that connected to Vbsw
old: 50,26microF, Vloss 0,6%, ESR 0,00 Ohm
new: 49,10microF, Vloss 1,0%, ESR 2,3 Ohm

nothing changed in the power-on behavior

then we also replaced the 22microF capacitor, connected to Vss
old: 24,73microF, Vloss 0,7% ESR: 0,00 Ohm
new: 22,44microF, Vloss 0m6%, ESR 0,00 Ohm

again nothing changed in the power-on behavior

We decide to change the two transistors as well :

4-071
old: hfe 331 Vbe 630mV Ic 3,0ma
new : hfe 352 Vibe 641mV Ic 3,2mA

4-668
old: hfe 433 Vbe 645mV Ic 6,2mA
new: hfe 351 Vbe 643mV Ic 3,2mA

after this replacements, the power-on behavior didn't change,
but the reading capabilities increased a lot, almost every card can be read
and also it can now write and read its own written cards

it must be said the the components we used are from an old HP-67 which
also had some issues

where could we get some equivalent new transistors ?

should we also check the six pins Motorola component 3-410 ? (what is this by the way ?)

thanks for any advice, take care !!

Maybe also change the 2.2uF (10-16V) tantalum capacitor near the ACT. The +ve connection is closest to pin 1 of ACT (red dot). This is used for the power up reset pulse for the ACT.

Listed from Jaque Laporte's site...
1854-0071 = 2N3704

1854-0668 = ?? Cannot find any info on it. Maybe 2N3904??

If you check parts suppliers like Digikey and search NPN transistor for the HFE etc that you tested, you may find equivalents.

3-410 is 2 PNP transistors in the same package used for a constant current source for the LED display segments.

cheers

Tony

[teenix]

(09-28-2022 02:19 PM)albertofenini Wrote:  Hi Tony
is this what you call C6 in your HP-67 schematics ?

see image

cheers

Tony

[albertofenini]

Thanks for the picture, will try later today and let you know
take care !

[albertofenini]

Hi Tony, Hi everyone

yesterday we changed that as well, but nothing changed
truth to be told is that we replace old parts with other old parts,
will try to get new parts and see if that change something,
any other suggestion that we may try in the meantime ?

thanks again and take care !!

[albertofenini]

Hi everyone,

this has also been fixed, following all the advices we replaced :

new 2,2 microFarad capacitors (3)
new 22 microFarad capacitor
new 47 microFarad capacitor
some old but working transistors 4-071 and 4-668 for the power supply
some old but working 1818-0231 and 1818-0232

however with no improvements

then we replaced the actual 1820-1596 with a known working 1820-1956
and finally it fired up immediately and worked correctly

Apparently, the old ACT Chip was bad in the meaning the it needed few minutes of
warming in order to work properly ....

Again thanks everyone for the support and the endless suggestions
take care !!