In this wiki you can store howto's what to know etc..
About using and preserving vintage HP computers.
Re: HP 98353A 64K RAM card developments
Arnie Berger
One indicator of overheating is bus contention, which could be attributable to bad timing. I’ve been following the thread and you indicated that the voltages are off. That’s more evidence.
Arnie
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of
Stan
Sent: Sunday, July 3, 2022 7:28 AM To: VintHPcom@groups.io Subject: Re: [VintHPcom] HP 98353A 64K RAM card developments
Hi Arnie,
Despite my limited experience with DRAM, that sounds plausible. All of the chips that are overheating are in the “LH” bank. I assume these chips make up the lower part of the data word. The other bank is labelled “TH” which I assume makes them the top part of the data word. I haven’t decoded the schematic of the card yet, but perhaps there’s a timing chip that’s only for the “LH” chips.
I’m not sure if the reason the 9836A won’t even get to the memory tests portion of the startup routine is that a power supply bus is being pulled down by the current draw of the defective memory card. I’ll have to measure the buses and see if that reveals anything.
Stan
From: VintHPcom@groups.io <VintHPcom@groups.io>
On Behalf Of Arnie Berger
Stan, This may be off-the-wall, but it occurred to me that the chips are getting hot because of a bad timing circuit driving the DRAMs. If the DRAM timing is off, you can get multiple outputs on at the same time and that could cause a lot of heat issues.
Arnie
From: VintHPcom@groups.io <VintHPcom@groups.io>
On Behalf Of Stan
After mulling over all of the suggestions about removing the defective DRAM chips from the 64K memory card, I decided to remove them by using a special DIP nozzle on my hot air gun. I applied flux to the pins of each defective chip on both sides of the board
and heated gently. Using a narrow forceps I was able to remove the chips quickly and easily, and without any lifted traces or pads or any other damage to the PCB.
|
|
Re: HP 98353A 64K RAM card developments
Steve Leibson
Studying from afar: is it possible that the -5V on-board regulator failed (it happens), and took out several of the DRAMs by applying the full -12V to them? --Steve
On 7/3/2022 10:31 AM, Paul Berger
wrote:
-- Steve Leibson Phone (Cell): 408-910-5992 Please feel free to link to me on LinkedIn History site: www.hp9825.com
|
|
Re: HP 98353A 64K RAM card developments
Paul Berger
Stan, The only thing consuming +12V on the memory board is the DRAM
chips so if installing this card pulls down +12V I think you are
on the right track. These memory chips being relatively early
NMOS have 3 supply voltages -5V pin 1, this is generated on the
memory card with a zener regulator from -12V, +5V pin 9 and +12V
pin 8 ground is pin 16. The -7V is not connected on these cards
but is likely low because it is derived from +12V. The spec sheet
for the DRAM chips says the +12V current will vary depending on
what it is doing the maximums quoted are at idle 1.5mA, refresh
25mA and operating 35mA, so the maximum for the card should be
just over 1A for the +12V. The + and - 5V loads from the DRAMs
should be small. Paul.
On 2022-07-03 12:49, Stan wrote:
|
|
Re: HP 98353A 64K RAM card developments
Stan
Hi Paul,
The hot DRAM chips are all on the LH bank, but seem roughly evenly distributed between the high byte and low byte chips.
I checked the bus voltages with the defective memory card installed, and several of the buses are pulled low. The +12V bus is at +7V, the +7V bus is around +5, and the +5V bus is around +3.5V. I checked the Ta caps on the memory card and none appear to be shorted.
I’ve cleaned the board a few times with isopropyl alcohol and distilled water, but the component side of the card itself is still very “weathered” looking, with the bare jumpers, IC pins, and solder joints all very dull and oxidized. Also, the clear coat on the PCB is coming off in several areas. I’m beginning to think that pulling and replacing DRAM chips may turn out to be a fool’s errand until and unless I can find a repairable underlying root cause of the failure.
Stan
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of Paul Berger
Sent: Sunday, July 03, 2022 7:37 AM To: VintHPcom@groups.io Subject: Re: [VintHPcom] HP 98353A 64K RAM card developments
Stan, The card has two banks of 16K x 16 LH and TH designate the two banks on the back of the board the each chip is labeled with the bit number except for LH0. The -CAS signal is common to all DRAMs and there are 4 separate -RAS signals LH high byte, LH low byte, TH high byte and TH low byte. Paul. On 2022-07-03 11:27, Stan wrote:
|
|
Re: HP 98353A 64K RAM card developments
Paul Berger
Stan, The card has two banks of 16K x 16 LH and TH designate the two banks on the back of the board the each chip is labeled with the bit number except for LH0. The -CAS signal is common to all DRAMs and there are 4 separate -RAS signals LH high byte, LH low byte, TH high byte and TH low byte. Paul.
On 2022-07-03 11:27, Stan wrote:
|
|
Re: HP 98353A 64K RAM card developments
Stan
Hi Arnie,
Despite my limited experience with DRAM, that sounds plausible. All of the chips that are overheating are in the “LH” bank. I assume these chips make up the lower part of the data word. The other bank is labelled “TH” which I assume makes them the top part of the data word. I haven’t decoded the schematic of the card yet, but perhaps there’s a timing chip that’s only for the “LH” chips.
I’m not sure if the reason the 9836A won’t even get to the memory tests portion of the startup routine is that a power supply bus is being pulled down by the current draw of the defective memory card. I’ll have to measure the buses and see if that reveals anything.
Stan
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of Arnie Berger
Sent: Saturday, July 02, 2022 6:41 PM To: VintHPcom@groups.io Subject: Re: [VintHPcom] HP 98353A 64K RAM card developments
Stan, This may be off-the-wall, but it occurred to me that the chips are getting hot because of a bad timing circuit driving the DRAMs. If the DRAM timing is off, you can get multiple outputs on at the same time and that could cause a lot of heat issues.
Arnie
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of Stan
After mulling over all of the suggestions about removing the defective DRAM chips from the 64K memory card, I decided to remove them by using a special DIP nozzle on my hot air gun. I applied flux to the pins of each defective chip on both sides of the board and heated gently. Using a narrow forceps I was able to remove the chips quickly and easily, and without any lifted traces or pads or any other damage to the PCB.
|
|
Re: HP 98353A 64K RAM card developments
Arnie Berger
Stan, This may be off-the-wall, but it occurred to me that the chips are getting hot because of a bad timing circuit driving the DRAMs. If the DRAM timing is off, you can get multiple outputs on at the same time and that could cause a lot of heat issues.
Arnie
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of
Stan
Sent: Saturday, July 2, 2022 4:28 PM To: VintHPcom@groups.io Subject: [VintHPcom] HP 98353A 64K RAM card developments
After mulling over all of the suggestions about removing the defective DRAM chips from the 64K memory card, I decided to remove them by using a special DIP nozzle on my hot air gun. I applied flux to the pins of each defective chip on both sides of the board
and heated gently. Using a narrow forceps I was able to remove the chips quickly and easily, and without any lifted traces or pads or any other damage to the PCB.
|
|
HP 98353A 64K RAM card developments
Stan
After mulling over all of the suggestions about removing the defective DRAM chips from the 64K memory card, I decided to remove them by using a special DIP nozzle on my hot air gun. I applied flux to the pins of each defective chip on both sides of the board and heated gently. Using a narrow forceps I was able to remove the chips quickly and easily, and without any lifted traces or pads or any other damage to the PCB.
|
|
Please Ignore My last message
Me Bad
Posted to wrong group. I have deleted the message. Dave VE7HR
|
|
SS/80 Exerciser software for 9816
Manuel Maseda
Can somebody point me to a download of the SS/80 Exerciser software that will run on the 9816. Only download I found was the CS/80 exerciser for the 300 series.
Manuel
|
|
Re: File /HP 9000 Series 200 300/Hardware related/HP 9836 Repair Notes.pdf uploaded
#file-notice
updated ... added some notes on how to use BASIC to write to the graphics RAM and how to embed and call small machine language programs from BASIC code. As an example I wrote a simple BPLOT routine to quickly output bitmaps with logos.
All this as a first step without the need to go through Pascal and CSUBs.
|
|
Re: Recommended methods for through-hole DIP IC removal
Mark Moulding
> Four layer boards are always problematic because anything connected to the power and ground planes will such the heat out of the solder pad and make a clean extraction much more difficult. Mark Moulding
|
|
Re: Recommended methods for through-hole DIP IC removal
On June 30, 2022 12:39:07 AM "Mark Moulding" <mark@...> wrote:
Well, Dave, I hope you're right. I just ordered $250 worth of Lindstrom pliers and a pair of Erem dikes to replace all the crappy ones I've acquired over the years... :-)You're gonna love 'em! -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
|
Re: Recommended methods for through-hole DIP IC removal
Mark Moulding
Well, Dave, I hope you're right. I just ordered $250 worth of Lindstrom pliers and a pair of Erem dikes to replace all the crappy ones I've acquired over the years... :-) Mark Moulding
|
|
Re: HP 9835A Repair Success (Finally!)
Stan
I removed the keyboard from the case and cleaned up the dust and debris that was on the black metal plate that held the switches using Simple Green and Q-Tips. I worked all the keys several times and cleaned the keycaps.
I also found why the space bar would often stick in the depressed position. The switch for the space bar is dead center. At either end of the space bar there is a flat plastic tab inserted into the underside of the space bar that passes through a slot in the PCB to keep the space bar tracking straight up and down without binding. One one end the tab had come out of the space bar. It was a simple matter of pressing it back into place. Now the space bar and all the other keys are working as they should. I found an extra expansion ROM drawer with a set of four I/O ROMs in it. When I plugged it in and powered on the 9835A, it beeped once then hung. Pulling out the drawer restored normal booting. Then I removed all four ROMs, checked for dirt or other problems in the drawer, reinstalled the ROMs and tried again. Much to my relief, the 9835A booted just fine. I also happen to have two extra OS ROM drawers with ROMs installed. I tried each of them in the 9835A. To my surprise, neither ROM drawer allowed the 9835A to boot. No power on beep, and when the CRT came alive it just showed a blank green raster. Are the OS ROMs prone to failure? Based on what I learned with the I/O ROMs, I'm going to remove and reinsert the 14 ROMS and try again. If this doesn't work, I thought I'd swap the ROMs in groups from the non-working drawer into the known good drawer until the 9835A fails to boot, then "divide and conquer" to find the defective one(s). If I can swap all the ROMs and the 9835A still boots, then I would have to conclude that it is a failure of the actual drawer. Is there any harm in trying this, assuming I don't power cycle the 9835A too rapidly and stress the power supply? Thanks (yet again), Stan
|
|
Re: Recommended methods for through-hole DIP IC removal
Paul Amaranth
I have a number of Lindstrom pliers and cutters; very nice tools.
toggle quoted messageShow quoted text
I also like Excelta. Cheap tools are false economy when doing precision work. I could hardly believe the difference when I got my first set of quality pliers. That convinced me to get rid of the junk (or at least move it to secondary storage). Paul
On Wed, Jun 29, 2022 at 04:15:42PM -0400, Dave McGuire wrote:
On 6/29/22 16:00, Mark Moulding wrote:(Admittedly, my dikes aren't the quality of Dave M's - now I'm gonna orderDon't let the "Weller" part scare you off; Erem is a Swiss manufacturer --
Paul Amaranth, GCIH | Manchester MI, USA Aurora Group of Michigan, LLC | Security, Systems & Software paul@... | Unix/Linux - We don't do windows
|
|
Re: Recommended methods for through-hole DIP IC removal
Arnie Berger
I would also recommend one of those board holding fixtures with a rotatable head. That enables me to keep the board vertical so I can access both sides at once.
toggle quoted messageShow quoted text
Four layer boards are always problematic because anything connected to the power and ground planes will such the heat out of the solder pad and make a clean extraction much more difficult. I've never used the toothpick method, but that might work very well because the solder doesn't wet it and its thermal conductivity is pretty bad. My technique is pretty much what has been described. Cut the body of the IC away, leaving as much of the pin as possible. Then grab the pin on the IC side and heat the pad on the opposite side. Then pull the IC leg out from the top. After I do that I go back and use a solder sucker to clean the hole (although I think the toothpick would work well here). If you do have the clearance, use sockets. If in the process, you trash a pad or two, you can still rescue the board with fine wire. I use the 30 gauge wire that was used for wire-wrapping prototypes. You can wrap it and solder it around the protruding pin, even if the pad is gone. Then solder the other side to the trace, or to another accessible node somewhere else. Arnie
-----Original Message-----
From: VintHPcom@groups.io <VintHPcom@groups.io> On Behalf Of Dave McGuire Sent: Wednesday, June 29, 2022 1:16 PM To: VintHPcom@groups.io Subject: Re: [VintHPcom] Recommended methods for through-hole DIP IC removal On 6/29/22 16:00, Mark Moulding wrote: (Admittedly, myDon't let the "Weller" part scare you off; Erem is a Swiss manufacturer that makes the very finest of small cutting tools. Weller bought them some years ago, for some odd reason. And speaking of which, Snap-On bought Lindstrom, the Swedish company that makes what are arguably the best small pliers available. Try them and you'll see what I mean. (I don't work for either company of course, but I have an eye for excellent tools.) -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
|
Re: Recommended methods for through-hole DIP IC removal
On 6/29/22 16:00, Mark Moulding wrote:
(Admittedly, my dikes aren't the quality of Dave M's - now I'm gonna order me some of those Weller/Erem ones...)Don't let the "Weller" part scare you off; Erem is a Swiss manufacturer that makes the very finest of small cutting tools. Weller bought them some years ago, for some odd reason. And speaking of which, Snap-On bought Lindstrom, the Swedish company that makes what are arguably the best small pliers available. Try them and you'll see what I mean. (I don't work for either company of course, but I have an eye for excellent tools.) -Dave -- Dave McGuire, AK4HZ New Kensington, PA
|
|
Re: Recommended methods for through-hole DIP IC removal
Mark Moulding
I've actually had pretty good luck using exactly that technique (a Dremel with a cut-off wheel). Naturally, I'm *extremely* careful, and I use compressed air to blow off the board afterwards, but I've never had any problem in the several dozen times I've done this. As others have noted, I cut as closely as possible to the chip body (that's easier for the cutting wheel orientation anyway) and cut very slowly. I've actually had better success (with success defined as "not destroying the PCB") with this method rather than clipping the pins. (Admittedly, my dikes aren't the quality of Dave M's - now I'm gonna order me some of those Weller/Erem ones...) Mark Moulding
|
|
Re: Recommended methods for through-hole DIP IC removal
Ansgar
+1 for Dave's comment. Saving at the wrong side may be the cause for continuous pain.
Metal dust is not the only problem with a Dremel, a Dremel, as powerful as it is, is per se not a tool for fine works. If you are losing control just for a moment, you have damaged the PCB seriously. -Ansgar
|
|