atkelar | HP 91 Desktop Calculator @atkelar | Uploaded December 2022 | Updated October 2024, 11 hours ago.
Restoration #39 - HP 91 Desktop Calculator
This video is rather dear to me. Not so much for the device, I have only recently found this style of calculator when I randomly came across an ebay auction; but rather because how I was able to actually fix it!
Spare parts are not easy to come by when it comes to vintage HP stuff that is made up from almost 100% custom chips.
I now have a working scientific caluclator on my desk! Woohoo! Now how does this RPN thing work...?
0:00 Intro / Presentation
1:40 Interior Overview
2:35 LED and Keyboard Matrix
4:08 Case Cleanup / Paint
5:23 Paper Feed Button / Keyboard / Glue Bezel
6:19 Printer Deep Clean
7:50 Printer Assemble
9:40 Recapping! (Motor cap)
10:15 Assembly (first one) / Power On Problem #1
11:29 Printer PCB Suspect / Missing Digits!
12:58 Matrix Debugging / Decoding the Matrix
13:57 Attempt with CMOS / "Ero r o"
14:57 TPIC Alternative! / Issue #1: Upside Down Logic
16:15 Issue #2: Multi-Clock!? / "Fixed"
17:39 Battery Indicator
18:07 Printer Issue / Power Supply Design Issue
19:58 New Battery Pack!
20:45 Assembly (second one) / Testing!
21:17 R.I.P.
22:12 6V is 0V is broken?
23:05 Slight ToDo's for later... / PSA! / Overview
Music:
My Train's A Comin'
Unicorn Heads
(YouTube Audio Library)
You can support me on Ko-Fi: ko-fi.com/atkelar
HP 91 on the HP museum: hpmuseum.org/hp91.htm
Voltage monitoring circuit based on: circuits-diy.com/simple-battery-monitor-using-2n4401-transistors
Restoration #39 - HP 91 Desktop Calculator
This video is rather dear to me. Not so much for the device, I have only recently found this style of calculator when I randomly came across an ebay auction; but rather because how I was able to actually fix it!
Spare parts are not easy to come by when it comes to vintage HP stuff that is made up from almost 100% custom chips.
I now have a working scientific caluclator on my desk! Woohoo! Now how does this RPN thing work...?
0:00 Intro / Presentation
1:40 Interior Overview
2:35 LED and Keyboard Matrix
4:08 Case Cleanup / Paint
5:23 Paper Feed Button / Keyboard / Glue Bezel
6:19 Printer Deep Clean
7:50 Printer Assemble
9:40 Recapping! (Motor cap)
10:15 Assembly (first one) / Power On Problem #1
11:29 Printer PCB Suspect / Missing Digits!
12:58 Matrix Debugging / Decoding the Matrix
13:57 Attempt with CMOS / "Ero r o"
14:57 TPIC Alternative! / Issue #1: Upside Down Logic
16:15 Issue #2: Multi-Clock!? / "Fixed"
17:39 Battery Indicator
18:07 Printer Issue / Power Supply Design Issue
19:58 New Battery Pack!
20:45 Assembly (second one) / Testing!
21:17 R.I.P.
22:12 6V is 0V is broken?
23:05 Slight ToDo's for later... / PSA! / Overview
Music:
My Train's A Comin'
Unicorn Heads
(YouTube Audio Library)
You can support me on Ko-Fi: ko-fi.com/atkelar
HP 91 on the HP museum: hpmuseum.org/hp91.htm
Voltage monitoring circuit based on: circuits-diy.com/simple-battery-monitor-using-2n4401-transistors
