On 2021-11-26 9:11 p.m., Jon Elson via cctalk wrote: The 3286 printer was part of the first generation 3270 system with 3271 &? 3272 controllers and 3277 display stations, so this is early 1970s technology the packaging is similar to SLT but the chip technology was not like the hybrid SLT modules as used in 360 systems.? I would agree that the parts would be all house numbered.? My guess is that the 139 is the type number and the other number is a date code it seems to me that this board is the drivers for the stepper motor that moves the carriage, but it has been nearly 40 years since I worked on one of these printers.? I would suspect that these transistors are pre-drivers for the power transistors and may not be super critical to get an exact replacement.? Did you get manuals with the printer?? If so it should have ALDs (schematics). One thing I remember about the 3284 (similar but slower)? and 3286 is print timing was derived from two emitter wheels on the extreme left and if you got them to far out of adjustment, the carriage would take off and slam into the right frame and then come back and slam into the left frame making enough noise to get the attention of the customer.? These printers where replaced by the 3287 which was much easier to maintain, and while it was designed for the "New Display system" they where available with a interface card that would allow them to work with 3271 and 3272 controllers. The 3286 printers and 3277 terminals where infamous for intermittent problems that you would try to isolate by swapping some of the cards with another terminal or printer and leave a note in both explaining what cards where swapped and why.? It was not uncommon to old notes half buried in dust in the bottom of 3277 terminals that went back years. Paul.

On Fri, 2021-11-26 at 22:33 -0800, Brent Hilpert via cctalk wrote: The Computer History Museum in Sunnyvale, CA has two IBM 1401's that are in operating order. One of the problems they had in getting one of them to work was that some of the IBM transistors also have plated steel leads that had rusted through. Ask Rob Garner <robgarn at mac.com>, the leader of the 1401 restoration project, if he recognizes the numbers.

Apologies for the previous email and it?s disgusting formatting, here is a second attempt, hopefully it?s readable. Thank you all for your responses and leads, Responses to some of your questions and some more questions: "Have you checked/measured whether they're actually faulty?" Yes I have, in the picture I have provided on the bottom there are the ends of 3 transistor leads. This was one that fell off as I removed the card and by far the worst corroded, so despite the fact that the rest still work. I need to replace this one. ?I would suspect that these transistors are pre-drivers for the power transistors and may not be super critical to get an exact replacement." Would an NPN or PNP with the same HFE suffice, or do I need to know more? Forgive me but I am a complete idiot when it comes to this kind of circuit design and their tolerances. "Did you get manuals with the printer? If so it should have ALDs (schematics)." Unfortunately not, and nor can I find any online. "The 3286 printers and 3277 terminals where infamous for intermittent problems" Excellent, glad I bought something that will provide the true IBM experience. Thank you, Al