| Electronics > Repair |
| HP 3852A, Memory Lost, Repair and other stuff (o; |
| (1/1) |
| davorin:
Recceived a 3852A this week....powering it on...it reports: "Memory Lost"....but self-test is okay and functions seem to work on panel and via GPIB... The controller board has a 3.7V lithium cell soldered onto it....which is empty....and oddly...powering it up again without cell shows that there is no built-in chargin circuit for buffering the 4 6264 SRAMs.... Can it be HP forgot to add a charger circuit? Seems this is just a one-way cell....not even mAh printed on it... |
| davorin:
Guess this type would be the best fit besides building in a hacky charger circuit for a rechargable cell (o; http://www.distrelec.ch/en/Lithium-battery-3-6-V-2400-mAh-Tadiran-Batteries-SL-360-PT/p/16932078?q=%09972545&page=1&origPos=1&origPageSize=10&simi=99.3 Hooked up a charged 3.7V cell now...and after 2nd power-up the "memory lost" is gone... |
| davorin:
Just out of curiiosity...I traced some signals on the controller board to the edge connector...not sure how easy it would be to add the 4MB memory extension (o; So here is the pinout of the 100-pinn edge connector: --- Code: ---HP 3852A Edge Connector 1 NC 2 NC 3 NC 4 NC 5 NC 6 NC 7 NC 8 NC 9 NC 10 NC 11 NC 12 NC 13 NC 14 NC 15 GND 16 GND 17 NC 18 NC 19 NC 20 NC 21 NC 22 NC 23 GND 24 GND 25 NC 26 NC 27 NC 28 NC 29 NC 30 ??? 31 NC 32 NC 33 NC 34 ??? 35 GND 36 GND 37 RESET 38 NC 39 GND 40 GND 41 NC 42 NC 43 LDS 44 UDS 45 R/W 46 AS 47 GND 48 GND 49 NC 50 A1 51 A2 52 A3 53 A4 54 A5 55 A6 56 A7 57 A8 58 A9 59 A10 60 A11 61 GND 62 GND 63 A12 64 A13 65 A14 66 A15 67 A16 68 A17 69 A18 70 A19 71 A20 72 A21 73 A22 74 A23 75 GND 76 U27 1820-4147 Pin 4 (74HCT573 Octal Latch?) -> D2 77 D0 78 D1 79 D2 80 D3 81 D4 82 D5 83 D6 84 D7 85 VCC 86 VCC 87 D8 88 D9 89 D10 90 D11 91 D12 92 D13 93 D14 94 D15 95 NC 96 NC 97 NC 98 NC 99 NC 100 NC --- End code --- Haven't found out yet what the missing 3 signals are doing...one going towards data bus transceivers to D2. Some assuming ti checks the presence of a card inserted, as pin 77 is connected to GND, but with a finer trace than power traces. The other two I don't know yet...somehow DTACK is missing....and not sure yet if CLK is routed out...but must somehow... The ROM images are available here...seems 4.22 is latest version...and I got 4.21 only *sniff (o; http://www.dalton.ax/hp3852a/ |
| kawal:
The memory card seems to be the same as the cards used in the Hp 9000 computers. To be more specific the card is a HP 98257A https://www.hpmuseum.net/display_item.php?hw=213. The interface pin out you provided has some mistakes. I attached the pin out for the HP 9000 DIO card . Not all the pins are used on the 3852A. |
| kawal:
In case someone else tries this - the HP 9000 card has exactly the same pinout but the addressing scheme is not the same. The card will not be identified correctly in the HP 3852A. I created a modified version of the card that works with the 3852A based on the HP9000 design. I will be offering these up for sale at some point. The unit will accept up to 4MB of SRAM cards. The board allows the card to function as 1MB, 2MB or 4MB boards depending on the amount of SRAM used and solder bridges. |
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