Reverse engineered Friden 130 calculator power supply - Page 1
Forum section: electronics / projects

author: robertbaruch
author_rank: Regular Contributor
timestamp: August 13, 2016, 08:42:09 pm
content: This is the power supply board for the 1964Friden 130 calculator. This was an RPN calculator with a 4-line display on a CRT. The entire logic of the calculator uses discrete transistors. I'm gonna have fun reverse engineering the logic section.The power supply provides, from 120VAC input: +6VDC, -12VDC, -80VDC and -3kVDC. It also provides 6.8VAC for the CRT heater and cathode, and integrates the focus and intensity controls. There is a video input terminal which modulates the intensity voltage.Reverse engineering this thing is made difficult by the fact that, aside from the seven logic boards, everything is soldered down and non-removable.Please enjoy! Any comments are appreciated. Note that the component designators are my own, since there were none on the board. In looking at several 60's PCB's, it seems that designators for individual components wasn't a thing. If any designator was used, it was just to index the value of the component, so for example all 0.1u capacitors were, say, C1.

author: max_torque
author_rank: Super Contributor
timestamp: August 13, 2016, 08:56:57 pm
content: WOW, they do not make 'em like that any more!

author: robertbaruch
author_rank: Regular Contributor
timestamp: August 14, 2016, 12:02:37 am
content: Also, please enjoy this image of the power supply board, and this underside shot. As mentioned, everything is soldered. Not a single terminal anywhere. Once those boards are in, they stay in.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 14, 2016, 12:23:14 am
content: I love everything about mid-century design.

author: gjruss
author_rank: Newbie
timestamp: August 14, 2016, 09:48:48 am
content: Dear RobertA delight to see your posting of Friden EC 130 power supply.I restored a EC 132 some years ago. The major problem was the power supply. I resorted to replacing all the large electrolytics with modern ones by soldering under the board to preserve the appearance. It turned out to be the diodes that were faulty.This wonderful piece of modernity now sits in my company boardroom - much to the amusement of my younger clients.My father used to sell and install this model along with other Friden equipment back in the 60s - 70s.Regards,Gordon RussellAdelaideAustraliaps I am now restoring a Flexowriter - one of the worlds 1st word processing machines - see image attached

author: woodchips
author_rank: Frequent Contributor
timestamp: August 15, 2016, 03:12:00 pm
content: Well done, making better progress than me trying to get the 130 I have running.Did you manage to get the service information? Apparently someone had a set of the service engineer circuits etc but they refused to copy them, last I heard he had died and all the information had been lost. Anyone know anything about this?

author: robertbaruch
author_rank: Regular Contributor
timestamp: August 18, 2016, 04:30:48 am
content: I lucked out and my 130 works fine. Although I can't connect it to a GFCI-protected outlet. Apparently the inrush current is quite high, causing the GFCI to trip. When I first plugged it in on my kitchen table, I turned it on and heard a "clunk" noise. I opened the 130 up to see what could possibly go "clunk", but there were only some ordinary glass fuses which were fine. Eventually I found out what the "clunk" was when I tried to turn on my soldering iron, which was on the same outlet.I don't have the service manual. I fucking hate people who hoard their manuals rather than scan them in and upload them.I am not one of those people.

author: robertbaruch
author_rank: Regular Contributor
timestamp: December 03, 2016, 07:23:54 pm
content: So I spent hours and hours... well... days... months, actually, tracing the seven logic boards in the calculator. I have the schematics done, the component placements, and many of the nets labeled. I started on a higher-level diagram, also.Pics and link to KiCAD+PDF schematics.I usedthis neat A4-sized flat light-panelto shine light through the PCB for easy tracing.There are four card-edge slots in the calculator, and three of the boards are, conceptually, double-length PCBs where they essentially cut the board in half and folded it with wires across.I'm taking a break now. I'm building a tester for the boards, which is where the5/12v logic shifter projectcame in. Each slot has 88 pins on its two edge connectors. I determined which were power, logic input, and logic output. Lined them all up, and calculated how many shifters I would need. Some positions are always input only, some are always output only, and some are both (so need direction switching when changing boards). If I just make things uniform and only use directable shifters, I will need 83 shifting circuits. At 2 circuits per board, that's 42 boards.The idea is that the tester would have the two card-edge connectors on it. They can slide because the distance between edge connectors is different for each board. That sliding motion could select which card you've put in, and control the directions of the shifters. Alternatively, there could be some detection about where the power and ground pins are (they're slightly different for each board) and then you could just have loose connectors. I'm not sure I like that solution since it relies on electrical detection on a possibly faulty board, and with loose connectors you might even flip the board around since the connectors aren't polarized.

author: snyderdc@comcast.net
author_rank: Newbie
timestamp: December 16, 2019, 03:36:57 am
content: Robert: I have a 130 that "used to work". However I appear to have misplaced the power cable for this unit. Some initial research indicates that it is a PH163 power cable. THere appears to be two varieties of this power cable, a 17280, and a 17952. The first was the "standard" cable of the day with the neutral on the left, hot on the right when the neutral is on the top. The 17952 is reversed. Your photo appears to indicate that the hot is on the left pin and common on the right? Just wanted to get your opinion on which power cable I should be looking for in the supply/scrap world.Thanks,Dave Snyder

author: robertbaruch
author_rank: Regular Contributor
timestamp: December 16, 2019, 04:00:45 am
content: Facing the back, the right side has a white wire (neutral), the left side has a black wire (hot).

author: bob91343
author_rank: Super Contributor
timestamp: December 16, 2019, 05:06:31 am
content: I think part of the problem was that the company was pretty good with gears and springs but give them capacitors and transistors and they became inept. The reason for not having the boards removable was, I suspect, a cost issue. The project was likely overrun big time but they were committed to crank out an electronic calculator.I did like their mechanical calculators and owned a couple for a few years.