On 3/25/21 11:50 AM, Robert J. Hutchins wrote:
Jeff,
Yes, I would like you to have a look at it.
My thought was RAM… But my desoldering skills are not adequate.
I managed to ruin an M102 board trying to remove the ROM
More soldering tips!
Desoldering alloy!
Remove pretty much anything with pretty much no drama.
The stuff is expensive, but for a single chip it's no big deal.
ChipQuick or SRA FastChip. They cost about the same and work exactly the
same.
Just put some flux all around the legs, wick up some of the old solder
if possible, then melt a blob of desoldering alloy on the iron and run
that blob along all the legs, letting the desoldering alloy melt and mix
with the old solder.
Run the iron around to heat up all pins, and pretty soon all the pins
will melt and stay melted even while the iron is moved on to other pins.
At that point the chip just lifts off with no damage.
Unlike with hot-air, you aren't cooking the chip or the board very much,
and you aren't melting all the neighboring joints, just the ones you
actually touch.
No rippe dup pads, no scorched pcb, no neighboring SMT parts blowing off
from the hot air.
Then wick up the desoldering alloy from the board.
Board is ready for a new part.
You need, flux, wick, the alloy, and an ordinary iron. They sell little
kits with a small amount of alloy together with a small amount of tacky
flux paste. The smallest pack is enough to do several chips.
It comes in lead and lead-free versions but they both work the same and
both work on any board and any solder. Merely the lead-free version
costs slightly more and probably meets some kind of regulatory
compliance or inspection. I don't think either version actually contains
lead itself.
--
bkw
Please tell me what to send and to where.
Thank you
Robert
*From:* M100 [mailto:[email protected]] *On Behalf Of
*Jeffrey Birt
*Sent:* Wednesday, March 24, 2021 10:36 AM
*To:* [email protected]
*Subject:* Re: [M100] Broken NEC 8201a
The black screen is an indication that the LCD is getting power but not
getting initialized properly. This is most likely because the system is
not booting properly. The RAM modules can fail causing a no boot
situation, or it might be stuck in rest, etc.
If you want, I’ll have a crack at repairing it. They are very similar to
the M100/T102 as far as fixing one.
Jeff Birt
*From:* M100 <[email protected]
<mailto:[email protected]>> *On Behalf Of *Robert J.
Hutchins
*Sent:* Wednesday, March 24, 2021 11:50 AM
*To:* [email protected] <mailto:[email protected]>
*Subject:* [M100] Broken NEC 8201a
I have an NEC 8201a that will not run.
On startup I get the black screen that does respond to the contrast control.
I don’t believe it is the typical capacitor problem. I have checked a
few voltages and they appear OK…
The unit is in good physical condition.
I also have several Model 100s and a 102 which I have been able to
upgrade the ROMs to Y2K spec and manage a few repairs on.
I am of two minds about the NEC though.
I might just sell it as is (make an offer?) or if someone would like to
have a go at repairing it, I would be happy to pay for that.
Please advise.
Thank you
Robert J. Hutchins
--
bkw
