I'm new to this site so be gentle with me please! I'm a 68 year old retired IT Manager with a passion for repairing and programming vintage HP & TI Calculators. I have in full working order an HP-41CX complete with numerous modules, printer and card reader which needs some TLC. I also have a couple of TI-59s, one permanently locked to a printer (key is lost) which work but both card readers need repair. I'm also a member of the Hewlett Packard Calculator Club (HPCC).
I'm currently trying to get an HP-97 to work which shows no sign of wanting to power up.
My degree is in Pure Mathematics and I've reached a point where I'm being hampered by lack of knowledge in both Electrical and Electronic fields. I've been searching the Net for free online Electronic courses, which is how I found this site. Can other members advise me of the best books/courses, either free or reasonably priced, to start an introduction into Electronics (assume all I have in that area is A Level Physics from 1966).
An example of what is frustrating me - the HP-97 Desktop Calculator (RPN) was the first machine I wrote business programs on in 1979. I've picked up an used one from EBay complete with case, power adaptor and 2 battery packs.
The power adaptor works (my friend tested it with a multi-meter) and gives out 8v AC ≈ and the battery packs should be 4.5v DC output. Of The 2 packs that came with the calculator, one is useless and the other although brand new in a box will not hold charge - it's 35 years old but new in box. I've got a brand new battery pack from the USA which should be with me in 2 weeks.
Reading the Service Manual it appears that you have to have a good battery pack as well as the power adaptor input, but once battery pack is fully charged you can then run 3-7 hours on battery pack alone.
What I want to learn and understand is the circuitry involved, what it does, why it does it and how to be able to trouble-shoot and fix a power problem like this. How to track from the adaptor power in terminals and battery terminals as to how far in the chain power is getting to the point where it fails. To find any components that are not working and to be able to replace them, basically electrical and electronic diagnosis. Any help and guidance would be appreciated.
I'm currently trying to get an HP-97 to work which shows no sign of wanting to power up.
My degree is in Pure Mathematics and I've reached a point where I'm being hampered by lack of knowledge in both Electrical and Electronic fields. I've been searching the Net for free online Electronic courses, which is how I found this site. Can other members advise me of the best books/courses, either free or reasonably priced, to start an introduction into Electronics (assume all I have in that area is A Level Physics from 1966).
An example of what is frustrating me - the HP-97 Desktop Calculator (RPN) was the first machine I wrote business programs on in 1979. I've picked up an used one from EBay complete with case, power adaptor and 2 battery packs.
The power adaptor works (my friend tested it with a multi-meter) and gives out 8v AC ≈ and the battery packs should be 4.5v DC output. Of The 2 packs that came with the calculator, one is useless and the other although brand new in a box will not hold charge - it's 35 years old but new in box. I've got a brand new battery pack from the USA which should be with me in 2 weeks.
Reading the Service Manual it appears that you have to have a good battery pack as well as the power adaptor input, but once battery pack is fully charged you can then run 3-7 hours on battery pack alone.
What I want to learn and understand is the circuitry involved, what it does, why it does it and how to be able to trouble-shoot and fix a power problem like this. How to track from the adaptor power in terminals and battery terminals as to how far in the chain power is getting to the point where it fails. To find any components that are not working and to be able to replace them, basically electrical and electronic diagnosis. Any help and guidance would be appreciated.