HP 3852A, Memory Lost, Repair and other stuff (o;

[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: [Select]

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

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.