[sebhc] H89 Power-up problems.
billwilkinson at mindspring.com
Tue Jul 4 21:06:38 CDT 2006
The H89 computer is basically an H19 terminal with a CPU board added.
Instead of the terminal serial port connecting to the outside world, it
connects to a serial port on the CPU board. This isn't the H88-3, but an
onboard circuit known as the Console Serial Port.. When an H19 powered up,
its terminal logic board (TLB) would beep the speaker once to indicate that
it was ready. In an H89, the TLB will still beep once while the CPU board
is initializing itself. Once done, the CPU board sends a control-G through
its Console Serial Port to the serial port on the TLB, which in turn beeps
the speaker for the second time.
If everything's normal and the CPU is on line, you'll hear two beeps. One
beep and the TLB board is probably okay, but the CPU board is either bad or
it's off line. No beep and the TLB should be suspected (assuming a good
power supply, etc.).
The console serial port on the CPU board consists U559, U560, and U561.
The serial connector is P513. Its counterpart on the TLB is U451, U452,
and U453. The serial connector is J404.
The keyboard is processed through the TLB by U431. There's also a Z80 on
the TLB, U421, which ties everything together on that board. I don't
recall how thoroughly it tested the TLB circuits before sending a beep to
the CPU board, however.
It's possible that there may be a bad electrolytic, but I think I'd try the
old standby of reseating the components first...just in case it's an
intermittent socket connection.
> [Original Message]
> From: <jmacgraith at cox.net>
> To: <sebhc at sebhc.org>
> Cc: Mark Garlanger <garlanger at gmail.com>
> Date: 7/4/2006 7:59:59 PM
> Subject: Re: [sebhc] H89 Power-up problems.
> I believe the second beep indicates the operating system is up. When mine
only beeped once, I had no "H:" prompt. It seemed to be associated with a
bad connection at the 4 pin connector on the top of the motherboard.
> I have the same problem with my keyboard. I haven't found a solution yet,
but most of my problems have been corrosion/connection related.
> ---- Mark Garlanger <garlanger at gmail.com> wrote:
> > Does anyone know what the power up beeps mean? One of my H89's beeps
> > twice on power-up (on-line) and once if off-line key is depressed.
> > This H89 works fine. Another one I recently received, only beeps once
> > on power-up (on-line) and zero (off-line). It was initially working
> > fine, but now the keyboard no longer works (except for the
> > 'shift-reset' combo), all other keys don't even keyclick (they had
> > initially). It doesn't matter with if it's on-line or off-line, no
> > keys work except for the 'shift-reset'.
> > Between the time it was working and now, during a few power-ups the
> > screen the screen went a little crazy, for example, the "H:" was
> > shaking and showing up in two places, another time various characters
> > showed up on the screen. I'm wondering if a CAP or other component
> > failed. I've looked through the operation/service manual, that have,
> > but it provided no trouble-shooting except for the power supply or
> > video. First, I was thinking the cable to the keyboard may have been
> > loose, but since the reset works, I doubt that is the issue. Without
> > the keyboard, the only diag I could get to is the memory test (by
> > setting switch SW501). That test runs without any errors.
> > If anyone has any ideas why the keyboard would suddenly stop working
> > or what areas I can look at, let me know, otherwise it looks like it
> > may become my spare-parts machine.
> > BTW: The memory is installed strangely in the system. The top row of
> > memory ICs have a second memory chip soldiered on top of each one,
> > along with a wire that connects them all to one of the lines on the
> > slot that you would normally install the extra memory card to bump it
> > up to 64k. This must have been a cheaper way to get to 64k than adding
> > the board.
> > --
> > Delivered by the SEBHC Mailing List
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