1. VintHPcom@groups.io
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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
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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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:

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:

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:

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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan

-- 
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:

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:

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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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:

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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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:

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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
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.

With the six "hot" chips off the board, and having cleaned all of the through holes with a desoldering iron, I installed the board in my 9835A. I thought I'd at least get the initial power-on beep, but I didn't. Then I noticed a few more DRAM chips were getting hot. Not as hot as the original six, but hot enough. Now it looks like I'll be removing a few more chips. At least it goes quickly!

I've attached a regular image and an IR image of the board with the six chips removed and then powered up. You can see that all of the heat seems to be coming from chips in the two rightmost columns of the block of DRAMs. Is there something about those particular chips that would explain why they're getting hot but not the ones on the left?

As always, I'll keep you posted!


Thanks,
Stan
Please Ignore My last message

Dave Miller
 

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

Martin Hepperle
 

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.

Often, four-layer boards will have a "thermal relief" on the inner layers, for just this reason (to ensure that the inner pad gets hot enough for a good solder joint).  These consist of a standard pad connected to the rest of the ground plane by small short traces (typically four, at 90-degree angles, about as long as the width of the pad trace [outer diameter - inner diameter]).  I always use these on boards I make unless there's some very special reason not to (possibly very high current at that pin).  Most layout packages know how to do these automatically.
~~

Mark Moulding
Re: Recommended methods for through-hole DIP IC removal

Dave McGuire
 

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.

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 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







!DSPAM:62bcb2f4163242093828979!
--
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.
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, 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

Dave McGuire
 

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...)

Most of the time now, at least on newer boards, I just use a solder sucker from the bottom side. This usually gets enough of the solder that the pins will break free with a slight sideways push, and I can then carefully lift out the IC intact.  If a pin or two doesn't quite break free, I can re-solder it, then use the solder sucker again.  I keep my iron hot (700 F) and use 63/37 eutectic solder, so I'm in and out on a joint in under two seconds.  I used to have boards for a product I sold assembled by a PCB house (those are hard to find for through-hole now...), and I noticed  that this was the technique that these actual professionals used, so I adopted it - it took a little practice, but I'm pretty good at it now, and it also leaves the holes clean and clear for the replacement part.
~~

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
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