27 Jul
2009
27 Jul
'09
4:03 p.m.
I recently acquired a 5150. It is a 16-64k with two drives and color. I have
not been able to boot it up yet. I cleaned the inside, and made sure
everything was well connected. When I flick the power on, the CPU fan goes,
and nothing else. There is power coming out of the motherboard and drive
connectors, but there is nothing at the ISA slot. No beeps or anything. I
tested the power supply with a modern CD drive. It worked. I removed the
motherboard and inspected it for obviously bad components and scorch marks.
I then opened the power supply. It was pretty clean, except for the hornet's
nest inside. I haven't yet removed that board, but plan to soon. The fuse is
intact.
Can anyone suggest what to do next? I have PDFs of the Hardware Maintaince
manual and the technical service manual.
Thanks
Joe
27 Jul
27 Jul
8:20 p.m.
On 27 Jul 2009 at 19:03, Joe Giliberti wrote:
Can anyone suggest what to do next? I have PDFs of the
Hardware
Maintaince manual and the technical service manual.
I assume you're re-seated all of the socketed chips and probed a bit
with a scope or logic probe to see that the processor is at least
ticking over--and you've checked your display switch settings.
There are inexpensive POST cards that can display any POST error
codes, but if you're not even getting a beep, that doesn't sound
good.
It's not unknown for the old mask-programmed 8Kx8 ROMs to develop bit
rot.
If you suspect this, you can either use a 2764-type 28-pin EPROM and
rig up an adapter to fit the 24-pin socket or pick up some Motorola
68764 EPROMs and program them and use them directly. Amazingly,
during the 5150's heyday, they were near unobtainum, but I've seen
them offered NOS for something like $6 the each lately.
--Chuck
10:32 p.m.
I recently acquired a 5150. It is a 16-64k with two drives and color. I have
not been able to boot it up yet. I cleaned the inside, and made sure
everything was well connected. When I flick the power on, the CPU fan goes,
and nothing else. There is power coming out of the motherboard and drive
connectors, but there is nothing at the ISA slot. No beeps or anything. I
Perhaps I am misunderstanding you, but surely if you're getting power at
the power output connectors of the PSU, the fault is not in the PSU.
-tony
28 Jul
28 Jul
11:12 a.m.
It is very likely not a PSU fault. I wasn't sure on this, but could the PSU
behave differently with and without load??
Joe
On Tue, Jul 28, 2009 at 1:32 AM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I recently acquired a 5150. It is a 16-64k with two drives and color. I
have
not been able to boot it up yet. I cleaned the
inside, and made sure
everything was well connected. When I flick the power on, the CPU fan
goes,
and nothing else. There is power coming out of
the motherboard and drive
connectors, but there is nothing at the ISA slot. No beeps or anything. I
Perhaps I am misunderstanding you, but surely if you're getting power at
the power output connectors of the PSU, the fault is not in the PSU.
-tony
11:47 a.m.
On 28 Jul 2009 at 14:12, Joe Giliberti wrote:
It is very likely not a PSU fault. I wasn't sure
on this, but could
the PSU behave differently with and without load??
The 5150 PSU will not operate without a load. At least a diskette
drive must be attached. Unlike other later power supplies, the 16-
64K 5150 uses an AC fan, so it will keep running even though the
supply has shut down, so don't use the fan sound as an indicator of
anything.
If the PSU has measurable output (within tolerance of +5, +12, -5 and
-12) on all outputs with just a diskette drive load, connect the PSU
to the motherboard.
What wasn't clear from your narrative was the "Nothing at the ISA
slot" statement. Does this mean that you measured correct voltages
at the motherboard connector (with the motherboard attached) but not
at the ISA slot? If so, there's something really strange going on;
most likely a broken PCB trace or cold solder joint.
On the other hand if the output goes away when you attach the PSU to
the motherboard, you'll want to start checking for shorts. Quite
often, this is a motherboard capacitor gone bad. Your ohmmeter can
indicate which supply line is at fault.
--Chuck
8 Aug
8 Aug
1:19 p.m.
I imagine this was already answered, but the answer is yes. In fact some would recommend
testing a p/s before powering up an older system to see if it delivers the required
voltages w/a dummy load (i.e resistance).
--- On Tue, 7/28/09, Joe Giliberti <starbase89 at gmail.com> wrote:
From: Joe Giliberti <starbase89 at gmail.com>
Subject: Re: Problems with IBM 5150 Power
To: "General Discussion: On-Topic and Off-Topic Posts" <cctalk at
classiccmp.org>
Date: Tuesday, July 28, 2009, 2:12 PM
It is very likely not a PSU fault. I
wasn't sure on this, but could the PSU
behave differently with and without load??
Joe
On Tue, Jul 28, 2009 at 1:32 AM, Tony Duell <ard at p850ug1.demon.co.uk>
wrote:
>
> I recently acquired a 5150. It is a 16-64k with
two drives and color. I
have
> not been able to boot it up yet. I cleaned the
inside, and made sure
> everything was well connected. When I flick
the
power on, the CPU fan
goes,
> and nothing else. There is power coming out of
the motherboard and drive
> connectors, but there is nothing at the ISA
slot.
No beeps or anything. I
Perhaps I am misunderstanding you, but surely if
you're getting power at
the power output connectors of the PSU, the fault
is
not in the PSU.
-tony
28 Jul
28 Jul
12:37 p.m.
I recently acquired a 5150. It is a 16-64k with two
drives and color. I have
not been able to boot it up yet. I cleaned the inside, and made sure
everything was well connected. When I flick the power on, the CPU fan goes,
If your 5150 has a CPU fan, then it has been MODIFIED. Most of the time,
the faults lie in badly planned or implemented modifications.
If you mean the power supply fan, then that means nothing in the 5150 (AC
fan?)
and nothing else. There is power coming out of the
motherboard and drive
connectors, but there is nothing at the ISA slot. No beeps or anything. I
Is there power to the 8088? to the ROMs?
5615
days inactive
5627
days old
6 comments
5 participants
participants (5)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com -
chrism3667＠yahoo.com -
cisin＠xenosoft.com -
starbase89＠gmail.com