|
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
|
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
toggle quoted message
Show quoted text
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
|
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
toggle quoted message
Show quoted text
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
|
Hi Bogdan,
I did not trz up to now, but I think, it will goon with working with
all the parameters from before and with the waveforms retained !
Herbert
?
Am 21-01-2013 15:20, schrieb bogroca:
toggle quoted message
Show quoted text
?
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the
NORMAL behaviour when power-up with the battery back-up
connected?
The manuals, both the op and service, say on page 1-7 and
1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up
applied)..."
Bet never gets back to the topic, WITH the memory back-up
applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@...,
"Herbert" wrote:
>
> Hi Bogdan,
>
> it is normal for the HM62256B to keep the data down
to approx. 1V.
> I think what zou see is, that the system does not
recognnize the power off phase .
>
> Herbert
>
>
> --- In TekScopes@...,
"bogroca" wrote:
> >
> > Hi all,
> >
> > After replacing the ROMs (document to come
soon), I got on to the RAM.
> >
> > Replaced all 91L24 chips with 2x HM62256B
(that's all I had at hand), thinking to first try out the
simple SRAM and then, if all OK, to move over to NVSRAM
like DS1230.
> >
> > First boot with the new chips went fine, but
then, to my surprise, from the second boot on, it bypassed
the self-check routines, booting (seem correctly) directly
into the scope mode. Quickly digitized a wave and display
it. All good. Powered off and then on again...
> >
> > ...It booted directly in the "stored" mode with
the right wave displayed.
> >
> > I can assure you that the first impulse was to
check if the battery backup is present. The second was to
see if, by mistake, I did not inserted the NVRAM chips
instead. None of this was true. It must be some energy
stored in the caps. Tested some more and got to fully
discharge in about 3-4 minutes, when it boots with the
self-check.
> >
> > One question, before proceeding further: is it
normal to bypass the self-check if the contents of the RAM
is still present, like when the backup battery is present?
I find this a little weird.
> >
> > Sorry for the long post and thank you inadvance!
> >
> > Bogdan
> >
>
|
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird. Yes, it is normal.
|
I believe the behavior you are seeing is normal. I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup. In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run. In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY". On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca" <bogroca@...> wrote: Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
|
David,
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
Regards,
David Partridge
toggle quoted message
Show quoted text
-----Original Message----- From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David Sent: 21 January 2013 16:35 To: TekScopes@... Subject: Re: [TekScopes] Re: 7854 RAM magic I believe the behavior you are seeing is normal. I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup. In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run. In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY". On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca" <bogroca@...> wrote: Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
------------------------------------ Yahoo! Groups Links
|
On Mon, 21 Jan 2013 16:44:41 -0000, "David C. Partridge" <david.partridge@...> wrote:
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
I assume that the self test/memory backup switch function relies on the newer firmware. I think the hard part would be copying the new firmware to the old memory layout. The schematic and layout for the newest board are in the same directory: The SRAM is always backed up in the newest revision. The mainframe's startup behavior is controlled by just the switch on the back. The switch connects into line K7 of the front panel and calculator keyboard interface: The Artek documentation for the 7854 covers all of the hardware revisions as far as I know.
|
Hi David
I had wondered about upgrading my 7854 with newer RAM and ROM boards and was even considering laying out new PCB's. I havn't looked at pricing for a small run of PCB's but it is probably cheaper than buying new Tektronix boards.
I don't think it would be worth trying to modify an old RAM card for battery backup as the standby current is probably too high. Will look into it at a later date.
Chris
toggle quoted message
Show quoted text
--- In TekScopes@..., "David C. Partridge" wrote:
David,
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
Regards,
David Partridge
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David
Sent: 21 January 2013 16:35
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM magic
I believe the behavior you are seeing is normal.
I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup.
In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run.
In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY".
On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca"
wrote:
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
------------------------------------
Yahoo! Groups Links
|
Stick an edge card connector on the bottom of some perforated board
and you could use point to point wiring. I have built ISA cards that
way.
If you can find them, I think NEC uDP444 SRAMs which draw 5 microamps
maximum in standby mode could be used as replacements for the original
AMD AM91L24 SRAMs.
Unfortunately besides swapping some of the TTL LS logic for HCT logic,
some other circuit changes would be required to get true micropower
standby operation.
If it is not available online somewhere already, I can probably
arrange for copies of the newer firmware at some point. I originally
planned on backing mine up and replacing the unreliable MOSTEK ROMs
but the 7854 I picked up did not use them. At the time I was not even
aware that there was a newer hardware revision.
toggle quoted message
Show quoted text
On Mon, 21 Jan 2013 21:48:55 -0000, cleyson@... wrote: Hi David
I had wondered about upgrading my 7854 with newer RAM and ROM boards and was even considering laying out new PCB's. I havn't looked at pricing for a small run of PCB's but it is probably cheaper than buying new Tektronix boards.
I don't think it would be worth trying to modify an old RAM card for battery backup as the standby current is probably too high. Will look into it at a later date.
Chris
--- In TekScopes@..., "David C. Partridge" wrote:
David,
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
Regards,
David Partridge
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David
Sent: 21 January 2013 16:35
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM magic
I believe the behavior you are seeing is normal.
I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup.
In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run.
In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY".
On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca"
wrote:
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
------------------------------------
Yahoo! Groups Links
|
Hi David,
I am very interested in that ROM image you have! If you get to make a copy, let me know, please!
It looks like Tek found a way to get everything in a 16k (x16) ROM. Up to version -02, there was a small (about 256-260 words, depending of the version) above that 16k limit. That is the reason that one had to keep the patch ROMs in (the 2716 chips). It is possible they let go of something too. I would be very curious what...
Best regards,
Bogdan
toggle quoted message
Show quoted text
--- In TekScopes@..., David wrote:
Stick an edge card connector on the bottom of some perforated board
and you could use point to point wiring. I have built ISA cards that
way.
If you can find them, I think NEC uDP444 SRAMs which draw 5 microamps
maximum in standby mode could be used as replacements for the original
AMD AM91L24 SRAMs.
Unfortunately besides swapping some of the TTL LS logic for HCT logic,
some other circuit changes would be required to get true micropower
standby operation.
If it is not available online somewhere already, I can probably
arrange for copies of the newer firmware at some point. I originally
planned on backing mine up and replacing the unreliable MOSTEK ROMs
but the 7854 I picked up did not use them. At the time I was not even
aware that there was a newer hardware revision.
On Mon, 21 Jan 2013 21:48:55 -0000, cleyson@... wrote:
Hi David
I had wondered about upgrading my 7854 with newer RAM and ROM boards and was even considering laying out new PCB's. I havn't looked at pricing for a small run of PCB's but it is probably cheaper than buying new Tektronix boards.
I don't think it would be worth trying to modify an old RAM card for battery backup as the standby current is probably too high. Will look into it at a later date.
Chris
--- In TekScopes@..., "David C. Partridge" wrote:
David,
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
Regards,
David Partridge
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David
Sent: 21 January 2013 16:35
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM magic
I believe the behavior you are seeing is normal.
I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup.
In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run.
In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY".
On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca"
wrote:
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
------------------------------------
Yahoo! Groups Links
|
It took me a while to figure out the 7854 address decoding because it is split between the memory boards and the microprocessor board. It is even more confusing if one starts out assuming that the firmware is at the top of the address space since it is not. The microprocessor board decodes the low half of the address space, 16K x 16 which is 32KBytes total, for the 4 x 8K x 8 (old) or 2 x 16K x 8 (new) ROMs via the -ROM signal. I suspect that means one could split the newer firmware into 4 ROMs for use in the old board with the patching PROM and FPLA disabled except one would still need to deal with the MOSTEK ROM pinout. I have never seen any 7854 documentation describing firmware revision differences so this seems pointless unless you have a bad FPLA or the wrong firmware for a good FPLA. The memory board(s) handle the RAM and expansion/patch ROM decoding with the ROMs starting at 8000h and the RAM starting at A000h leaving 4K x 16 of address space at the top of the memory map of which a small part is decoded on the microprocessor board for memory mapped I/O and the GPIB interface. 8K x 16 of RAM is the maximum supported by the memory map. On Wed, 23 Jan 2013 12:44:37 -0000, "bogroca" <bogroca@...> wrote: Hi David,
I am very interested in that ROM image you have! If you get to make a copy, let me know, please!
It looks like Tek found a way to get everything in a 16k (x16) ROM. Up to version -02, there was a small (about 256-260 words, depending of the version) above that 16k limit. That is the reason that one had to keep the patch ROMs in (the 2716 chips). It is possible they let go of something too. I would be very curious what...
Best regards,
Bogdan
--- In TekScopes@..., David wrote:
Stick an edge card connector on the bottom of some perforated board
and you could use point to point wiring. I have built ISA cards that
way.
If you can find them, I think NEC uDP444 SRAMs which draw 5 microamps
maximum in standby mode could be used as replacements for the original
AMD AM91L24 SRAMs.
Unfortunately besides swapping some of the TTL LS logic for HCT logic,
some other circuit changes would be required to get true micropower
standby operation.
If it is not available online somewhere already, I can probably
arrange for copies of the newer firmware at some point. I originally
planned on backing mine up and replacing the unreliable MOSTEK ROMs
but the 7854 I picked up did not use them. At the time I was not even
aware that there was a newer hardware revision.
On Mon, 21 Jan 2013 21:48:55 -0000, cleyson@... wrote:
Hi David
I had wondered about upgrading my 7854 with newer RAM and ROM boards and was even considering laying out new PCB's. I havn't looked at pricing for a small run of PCB's but it is probably cheaper than buying new Tektronix boards.
I don't think it would be worth trying to modify an old RAM card for battery backup as the standby current is probably too high. Will look into it at a later date.
Chris
--- In TekScopes@..., "David C. Partridge" wrote:
David,
Do you have the schematics of this later memory board? I think it would be a great modification to change the earlier board to do this too.
Regards,
David Partridge
-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...] On Behalf Of David
Sent: 21 January 2013 16:35
To: TekScopes@...
Subject: Re: [TekScopes] Re: 7854 RAM magic
I believe the behavior you are seeing is normal.
I have the most recent 7854 hardware version which has a lithium backup battery mounted on the memory board. On the back of the mainframe where the connections for external memory backup power used to be, there is a toggle switch which selects between self test and memory backup.
In self test mode, the memory is cleared every time the mainframe is powered up and the self test is run.
In memory backup mode, the self test is skipped and the mainframe starts in stored mode. "SELF TEST" on the ID screen is replaced with "NV MEMORY".
On Mon, 21 Jan 2013 15:20:24 -0000, "bogroca"
wrote:
Hi Herbert,
I assumed that myself.
The question that bothers me, is that about what is the NORMAL behaviour when power-up with the battery back-up connected?
The manuals, both the op and service, say on page 1-7 and 1-3 respectively:
"Power-up Conditions
When the 7854 is turned on (without the memory back-up applied)..."
Bet never gets back to the topic, WITH the memory back-up applied.
Any thoughts?
Best regards,
Bogdan
--- In TekScopes@..., "Herbert" wrote:
Hi Bogdan,
it is normal for the HM62256B to keep the data down to approx. 1V.
I think what zou see is, that the system does not recognnize the power off phase .
Herbert
--- In TekScopes@..., "bogroca" wrote:
Hi all,
After replacing the ROMs (document to come soon), I got on to the RAM.
Replaced all 91L24 chips with 2x HM62256B (that's all I had at hand), thinking to first try out the simple SRAM and then, if all OK, to move over to NVSRAM like DS1230.
First boot with the new chips went fine, but then, to my surprise, from the second boot on, it bypassed the self-check routines, booting (seem correctly) directly into the scope mode. Quickly digitized a wave and display it. All good. Powered off and then on again...
...It booted directly in the "stored" mode with the right wave displayed.
I can assure you that the first impulse was to check if the battery backup is present. The second was to see if, by mistake, I did not inserted the NVRAM chips instead. None of this was true. It must be some energy stored in the caps. Tested some more and got to fully discharge in about 3-4 minutes, when it boots with the self-check.
One question, before proceeding further: is it normal to bypass the self-check if the contents of the RAM is still present, like when the backup battery is present? I find this a little weird.
Sorry for the long post and thank you inadvance!
Bogdan
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