HP 34C

[Howard Jones]

Can anybody help me with my HP 34C.
It works fine except that sometimes when I switch it back on I get the message "Pr Error" and of course the all memory is lost.
I feel it must be losing power. It does this even when it is on the charger.
Thank you in advance.

[Vieira, Luiz C. (Brazil)]

HI, Howard;

I had an HP38C with that kind of behavior. In that case, it was a bad power supply unit. I had it replaced and it worked fine since. Unfortunately I had no time to go ahead and find the actual cause: bad contact, faulty component, etc. All I can tell you is that I replaced it and the HP38C worked fine since.

There is also a possibility of your unit being a solderless one. In this case, a bad contact in the RAM terminals would be enough causing it to be erased due to power loss. Best chance would be opening it, disassembling and cleaning contacts. It would also be a good idea to check if the IC´s terminals can be a little bit bent against the flex circuit, so contacts would enhance.

Chances are that you could have a simple bad contact in the batteries, but since you have the same problem even when it is on the charger, I´d consider the power supply unit, instead.

Not too much of help, though...

Success!

Luiz (Brazil)

[Juergen Rodenkirchen]

Hi Luiz, good to have you back :-)) Where have you been all the time?


Kind Regards from Germany, Jürgen

[Vieira, Luiz C. (Brazil)]

Hi, Juergen; danke!

Please, have a look here and I´m sure you will forgive me for not being here...

Cheers.

Luiz (Brazil)

[Juergen Rodenkirchen]

Luiz, I do not have to forgive you anything but am just glad that you're back on the scene as an expert but most of all as a good friend :-)) I'm happy that you found the "break" early enough to understand what's really important in life: lifetime, health, having good friends and having a good time! Looking forward to reading interesting posts from you.


Yours Jürgen

[Michael de Estrada]

There are several possibilities. First, are you using a B suffix charger? Use of an A suffix charger on a C suffix calculator can cause loss of "continuous memory". Second, the calculator gets its power from the battery, and not the charger. If the battery is discharged or bad, it won't properly power the calculator. Third, the battery contacts and/or connections may be bad. Fourth, the power circuitry board at the other end of the ribbon connector to the battery/charger contacts may have issues with it's circuitry that povides power to the "continuous memory" when the calculator is turned off. This circuitry is unique to the C suffix calculators, and an E suffix power board does not have this circuitry.

[Dwight Sturrock]

I lost the charger for my 34C many years ago (I bought it new in 1982). I still use the 34C with alkaline batteries. If I change the batteries in less than 10 seconds, the unit will maintain continuous memory. Based on this, temporary interruptions do not seem to affect the unit, and the original batteries or charger are not essential for regular operation.

[Vieira, Luiz C. (Brazil)]

Hi, Dwight;

you are correct. But consider that the power supply maintains the RAM I.C. continuously powered even when the calculator is turned off, so chances are that some capacitors directly connected to the DC lines take a little while to discharge prior to completely turn the RAM off (hence the 10 seconds to change the batteries). But if there is a bad contact in the circuit, mainly after the power supply, RAM contents may also be lost or become invalid too quickly if its DC line fails for a flash. It seems to be the case, here.

The main fact is that we are going ahead with the investigation, and this is what matters most. Any other thoughts?

Cheers.

Luiz (Brazil)