PDP11/34 boot problem, M7891 broken chip, repaired, and memory bootcode errors, HELP! :(
asbesto - 5 Nov 2003 09:26
Newsgroup: alt.sys.pdp11
Da: asbe...@mail.ru (asbesto)
Data: 5 Nov 2003 01:26:57 -0800
Locale: Mer 5 Nov 2003 09:26
Oggetto: PDP11/34 boot problem, M7891 broken chip, repaired, and memory bootcode errors, HELP! :(
many time ago we had this PDP11/34 full working. It was a 300 kg monster
so, when we had to move from our old site, we had to transport it.
so, the only way to us was to dismember it in parts, checking all
connections and so on, move the single parts, and rebuild the pdp11.
this has worked fine the first time. but we had to move another time, so
we dismembered the pdp11 and so on...
but this time, the pdp11/34 don't boot anymore :((((
all cables and connection are identified by labels and are perfectly as
years ago...
checking all boards on the cpu main module, i found a "broken"
chip on the M7891, 128Kx18 bit MOS memory. The broken chip is
E15, a simple SN74LS175 (we have full schematics of pdp11/34)
So i asked for help in TUHS list, in which i first described our
problem; the messages can be found on the mailing list archive here,
http://minnie.tuhs.org/pipermail/tuhs.mbox/tuhs.mbox:
A more precise description of the problem was in a message
dated Date: Tue, 15 Apr 2003 00:00:37 +0000:
--------
the M7891 board (128K x 18 bit MOS MEMORY MODULE) have the D2 red
led light turned ON when turning on the CPU !
this means PARITY ERROR on this board
checking the board we found 2 problems:
1) a 74LS175 chip named E15 on our schematic diagram, that seem
phisically BROKEN on an edge (there is a fessure on the plastic
DIP package). i can't change it now because i don't have a=3D20
soldering station here to do a nice job, but looking the chip i
think it may work...
2) a 5 Kohm 4-resistor bridge named R22 on our diagram, that is phisically
BROKEN. this bridge give +5V on signals named DATA OC L, CSR OC L, OC L
and X ADD OC L. i changed it with a 4.7Kohm 4-resistor bridge, without
any result.
---------
Well
just touching the chip, part of the plastic box went out, as you can
see in the images. Maybe this can identify a real fault on this chip ?
So, i have to change it. here i have a 74ls175p from hitachi,
recovered from another board. i will try to change the chip now.
BUT, after this, pdp11/34 won't boot :(
it's the same problem. so here i want to describe anything i can.
CPU boards:
slot conn option module addr vect
------------------------------------------------------------
1 a-f cpu m8266 n/a n/a
2 a-f cpu m8265 n/a n/a
3 c-f ky11-lb m7859 n/a n/a
4 a-b boot m9312
4 c-f dl11-w m7856 177560 60
5 a-f ms11-ld m7891
6 a-f rl11 m7762 174400 160
7 c-f rx211 m8256 177170 264
8 c-f dl11-wc m7856 176500 300
9 a-b unibus m9202
9 c-f u/q bim?(*) m8217
10 a-b unibus m9202
10 c-f convert. m7066
11 a-f generat. m7067
12 a-f bitmap m7068
13 a-f
14 a-f
15 a-f
16
17
18 a-b uni/term m9302
18 c-d video a011
19 a-b-f reg.kw11 m7952 (this is written)
(19 a-b ??? m9403
c-f reg.kw11 m7952 this is what i see in CPU)
20 a-b qbus/ter m9400
20 c-f dma cont m8026
21 c-f q-bus cont m8036
22 c-f a/d mur a017
(*) unreadable
-------------------------------------------------------------------
well, this is the list as is taped on the CPU cover, compiled by hand.
i have verified, and all boards are in the place described here,
except (1)
So, let's try to boot:
----------------------
1) turning on the chassis
2) turning on the RX02 floppy module, from rear switch
3) pressing WRITE PROT and turning on the RL02 DISK module, from
rear switch
4) turning on the CPU module, from rear switch
5) checking that disk is UNLOADED (LOAD unpressed).. at this time,
all 4 RL02 lights are turned ON: LOAD, 0 READY, FAULT and WRITE PROT.
6) turning on main CPU from frontal knob (from DC OFF to DC ON):
fan & rumors, "DC ON" red led led on.
inside the cpu:
- RED led on M7891 board on
(this led, identified as "D3" on my schemes, is described as
"PAR ERR INDICATOR", connected to pin 6 of E33, a 74S74.
- The green led on the board is OFF. looking at the board, i can
see that is JUMPERED! so, it CAN'T turn on ... someone know why ?
- in every restart, the display show a different number (this is
normal, i think)
- RL02 Lights status: LOAD is on, 0 READY is off, FAULT is off and
WRITE PROT is on.
7) pressing LOAD, the LOAD light turn OFF, the disk will spin up
and after about 30 seconds the "0 READY" white light turn on.
8) pressing "CTRL-BOOT" on the CPU CONSOLE will flash FAULT lights on
RL02 just for an istant, and after this nothing happen:
- RL02 lights status is : LOAD off, READY on, FAULT off, WRITE PROT on.
- CPU show "165504" and RUN led is off. BUS ERR led is off. MAINT is
off, the only led on is "DC ON".
9) pressing again CTRL-BOOT obtain the same effect.
during this, nothing happen on serial console.
------------
Booting manually (inserting the octal code to boot from RL02):
this is the boot code, found in "E-10 Loading Software Bootstrap" into one
of our manauls:
location contents
001000 012701
001002 174400
001004 012761
001006 000013
001010 000004
001012 012711
001014 000004
001016 105711
001020 100376
001022 005061
001024 000002
001026 005061
001030 000004
001032 012761
001034 177400
001036 000006
001040 012711
001042 000014
001044 105711
001046 100376
001050 005007
HORRIBLE NEWS:
--------------
i wrote stuff in 001000, and i read OTHER THINGS. so i can't
manually boot!!!
writing 111111,222222,333333,444444,555555,666666,777777, i
read 000111,000000,000110,000440,000101,002640,000100
but i read every time different contents :(((
maybe i have to add the bootstrap code in a different location?
maybe the 7891 board is totally broken ???
maybe the problem was the substitution of the SN74LS175N with an
hitachi HD74LS175P ?
HELP!!!
Photos of boot sequence, chips, schematics details and something
can be seen on http://www.freaknet.org/asbesto/pdp11 . sorry for the
bad quality but they was taken from a color quickcam.
we are working on a pdp11 section of www.freaknet.org to collect any
useful information.
any help will be appreciated (and ... maybe .. any SPARE PART :)
--
[asbesto : freaknet medialab : radio#cybernet : GPG key on keyservers]
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asbesto
12 Nov 2003 01:58 mostra opzioni
Newsgroup: alt.sys.pdp11
Da: asbe...@mail.ru (asbesto) - Trova messaggi di questo autore
Data: 11 Nov 2003 17:58:00 -0800
Oggetto: PDP11/34 boot problem, M7891 broken chip, repaired AGAIN, now it's better but NO BOOT
Rispondi all'autore | Inoltra | Stampa | Messaggio singolo | Mostra originale | Segnala illeciti
asbe...@mail.ru (asbesto) wrote in message ...
> checking all boards on the cpu main module, i found a "broken"
> chip on the M7891, 128Kx18 bit MOS memory. The broken chip is
> E15, a simple SN74LS175 (we have full schematics of pdp11/34)
> 1) a 74LS175 chip named E15 on our schematic diagram, that seem
> phisically BROKEN on an edge (there is a fessure on the plastic
> DIP package). i can't change it now because i don't have a=3D20
> soldering station here to do a nice job, but looking the chip i
> think it may work...
> writing 111111,222222,333333,444444,555555,666666,777777, i
> read 000111,000000,000110,000440,000101,002640,000100
> but i read every time different contents :(((
> maybe the 7891 board is totally broken ???
> maybe the problem was the substitution of the SN74LS175N with an
> hitachi HD74LS175P ?
OK,
i changed the HD74LS175P with an original SN74LS175N, and now
i write and read correct data to/from memory :))))
the PARITY ERR led on the M7891 board now turn OFF (sometimes turn
ON but in working condition it's off).
The PDP11 can't boot anyway, also with manual bootstrap routine.
stay tuned / please help !
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