HP-65 - card reader with WB wave noisy - FIXED and RESTORED

[albertofenini]

Ciao Tony
We played a little with the unit but if used with a “driverless” keyboard pcb
WA and WB remain flat, no matter the position of the PRGM switch or the type of card

We remounted the keyboard pcb with the led drivers and we returned to the initial situation, it reads but WB is noisy

We played a little with the capacitors on the card reader
If we detach the capacitor on the motor the unit will read
but when recording it will display a 00 00
way before the card is ejected
I understand that the capacitor on the motor has an influence on the writing behavior
Then we changed with a new 3.3 microF and it worked well in reading, took the right time to write but still WB too noisy
So we changed also the other capacitors on the card reader pcb but nothing changed

What drive us crazy is that the logic board works great in any another unit of the HP65 we have producing good waves and recording well

So do the card readers if mounted on other units but when joint together they behave weird

We have two card readers units both inclusive of the battery compartment and then
With the card reader switches on the back
Both behave equally bad
Could both have a damaged amplifier ??
Could be the heads ?

We have a third back panel which we will try tomorrow trying to recover an additional head and will see what happens

As always any idea is welcome !
Take care !!!