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Hi 搁别苍é,

I've checked the details on the SRAM chip in my controller and it is

CY62128BLL-70SC

Is this the correct part used on the latest G1?

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich <Rene@> wrote:

Hi Andy,

The SRAM is a 128kx8 chip, f.i. a UPD431000AGE-70LL. It must be
carefully replaced, because some traces are below the chip.
I don't know about the commercial conditions of Scott or your dealer, I
can only speak as an engineer. A good electronics shop or someone with
good experience in soldering SMD parts should be able to replace the chip.

搁别苍é


tillyscope schrieb:

Hi 搁别苍é

I've measured the voltages as you've described and found the following.

With external supply and battery fitted:
- SRAM -ve/+ve = 4.6V
- SRAM -ve/D1 RHS middle pin = 4.6V
- SRAM -ve/D1 LHS upper pin = 5.2V
- SRAM -ve/D1 LHS lower pin = 2.6V

With battery only and 100R across D1 (lower/middle):
- D1 LHS lower pin (battery)/D1 RHS middle pin = 0.37V

Therefore, from your diagnosis, either the SRAM or RTC is draining too much current. This would explain the 2 new batteries I've fitted dropping to ~2.5V after only 24 hours or so.

I've run the RTC for several hours today on external power and it appears to keep time OK.

So, the SRAM is faulty?

If you agree, then please can you confirm if this can be replaced without the unit being returned to Losmandy. Do you have a part number/details to allow me to purchase a SRAM chip in the UK?

Again, thank you very much for your continuing help.

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich<Rene@> wrote:

Hi Andy,

after trying reset of the key SRAM values such as time, location and trying many, quick power re-cycles I'm still having the same problem...

Hi Tom

But I now see a new tips on your (really useful) gemini-2 website under G1 FAQs...

I've tried the following from tips 14& 15

1. Short-out C3 for ~0.5s. This cuases a reset that returns me to the same SRAM failure/WD reset warnings.

2. I've measured the voltage across pins 16& 32 of the SRAM chip. With battery only I have ~1V.

Much(!) too low, SRAM and RTC need at least 2.5V.

With external power I have ~4.6V. I've fitted a second, new battery and have the same readings (and problems).

So, could one of the 'steering' diodes have failed? What are the idents on the PCB (latest with rocker switch)?

This is D1, a BAT54C, located left of the big SRAM chip. What you can
try: measure the voltage at the pins of D1 against ground. You should
see about 5V at one pin at the left side, the battery voltage at the
other and at voltage with a drop of 0.3..0.4V at the middle pin.

What you can do is to bridge this diode with a 100 Ohm resistor (from
the battery plus pole to the middle pin) _while Gemini is powered off_.
If there is only a negligable voltage drop, O.K. If the loss is bigger
than 0.3V, one of the two components powered by the battery is faulty
and draining too much current.

In this case, please check if the RTC is running correctly while
externally powered. Check time and alarm settings. If all works
correctly there, the SRAM is more probably faulty, otherwise maybe the
RTC. It is complicated because both share the same data bus and both can
spoil the other's operation and cause a WD reset if faulty.

Many thanks to both of you for the helpful support!

You're very welcome.

搁别苍é

Regards,

Andy

Hi all,

looking for UK source for a single CY62128BLL-70SC SRAM chip.

This chip is available from RS Components (but currently on back order!), but only in packs of 25 @ ?62.75.

Has anyone got a single chip that I could buy?

TIA,
Andy

--- In Gemini_Users@..., "tillyscope" <andy.wellington99@> wrote:

Hi 搁别苍é,

I've checked the details on the SRAM chip in my controller and it is

CY62128BLL-70SC

Is this the correct part used on the latest G1?

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich <Rene@> wrote:

Hi Andy,

The SRAM is a 128kx8 chip, f.i. a UPD431000AGE-70LL. It must be
carefully replaced, because some traces are below the chip.
I don't know about the commercial conditions of Scott or your dealer, I
can only speak as an engineer. A good electronics shop or someone with
good experience in soldering SMD parts should be able to replace the chip.

搁别苍é


tillyscope schrieb:

Hi 搁别苍é

I've measured the voltages as you've described and found the following.

With external supply and battery fitted:
- SRAM -ve/+ve = 4.6V
- SRAM -ve/D1 RHS middle pin = 4.6V
- SRAM -ve/D1 LHS upper pin = 5.2V
- SRAM -ve/D1 LHS lower pin = 2.6V

With battery only and 100R across D1 (lower/middle):
- D1 LHS lower pin (battery)/D1 RHS middle pin = 0.37V

Therefore, from your diagnosis, either the SRAM or RTC is draining too much current. This would explain the 2 new batteries I've fitted dropping to ~2.5V after only 24 hours or so.

I've run the RTC for several hours today on external power and it appears to keep time OK.

So, the SRAM is faulty?

If you agree, then please can you confirm if this can be replaced without the unit being returned to Losmandy. Do you have a part number/details to allow me to purchase a SRAM chip in the UK?

Again, thank you very much for your continuing help.

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich<Rene@> wrote:

Hi Andy,

after trying reset of the key SRAM values such as time, location and trying many, quick power re-cycles I'm still having the same problem...

Hi Tom

But I now see a new tips on your (really useful) gemini-2 website under G1 FAQs...

I've tried the following from tips 14& 15

1. Short-out C3 for ~0.5s. This cuases a reset that returns me to the same SRAM failure/WD reset warnings.

2. I've measured the voltage across pins 16& 32 of the SRAM chip. With battery only I have ~1V.

Much(!) too low, SRAM and RTC need at least 2.5V.

With external power I have ~4.6V. I've fitted a second, new battery and have the same readings (and problems).

So, could one of the 'steering' diodes have failed? What are the idents on the PCB (latest with rocker switch)?

This is D1, a BAT54C, located left of the big SRAM chip. What you can
try: measure the voltage at the pins of D1 against ground. You should
see about 5V at one pin at the left side, the battery voltage at the
other and at voltage with a drop of 0.3..0.4V at the middle pin.

What you can do is to bridge this diode with a 100 Ohm resistor (from
the battery plus pole to the middle pin) _while Gemini is powered off_.
If there is only a negligable voltage drop, O.K. If the loss is bigger
than 0.3V, one of the two components powered by the battery is faulty
and draining too much current.

In this case, please check if the RTC is running correctly while
externally powered. Check time and alarm settings. If all works
correctly there, the SRAM is more probably faulty, otherwise maybe the
RTC. It is complicated because both share the same data bus and both can
spoil the other's operation and cause a WD reset if faulty.

Many thanks to both of you for the helpful support!

You're very welcome.

搁别苍é

Regards,

Andy

so, an update...

sent off my G1 PCB to Losmandy for repair (diagnosed as requiring a new SRAM chip) and returned to UK in double quick time - hats off to Scott for the prompt service!

All nows seems well...except for the random& intermitant but sometimes continuous (~5-10sec) beeping coming from the main unit. This happens mainly when simply tracking, but also slewing. When guiding using PHD it is largely non-existant. Mechanically all appears to be well, scope balanced, no lagging reported, guiding is very good, RA safety limits checked& reset, etc. But when beeping away the handset response is poor and the noise sounds worse than my old LX200 classic slewing @ 8deg/s! I need to fix this noise!

Any ideas?

TIA
Andy

--- In Gemini_Users@..., "tillyscope"<andy.wellington99@...> wrote:

Hi all,

looking for UK source for a single CY62128BLL-70SC SRAM chip.

This chip is available from RS Components (but currently on back order!), but only in packs of 25 @ ???62.75.

Has anyone got a single chip that I could buy?

TIA,
Andy

--- In Gemini_Users@..., "tillyscope"<andy.wellington99@> wrote:

Hi Ren???,

I've checked the details on the SRAM chip in my controller and it is

CY62128BLL-70SC

Is this the correct part used on the latest G1?

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich<Rene@> wrote:

Hi Andy,

The SRAM is a 128kx8 chip, f.i. a UPD431000AGE-70LL. It must be
carefully replaced, because some traces are below the chip.
I don't know about the commercial conditions of Scott or your dealer, I
can only speak as an engineer. A good electronics shop or someone with
good experience in soldering SMD parts should be able to replace the chip.

Ren???


tillyscope schrieb:

Hi Ren???

I've measured the voltages as you've described and found the following.

With external supply and battery fitted:
- SRAM -ve/+ve = 4.6V
- SRAM -ve/D1 RHS middle pin = 4.6V
- SRAM -ve/D1 LHS upper pin = 5.2V
- SRAM -ve/D1 LHS lower pin = 2.6V

With battery only and 100R across D1 (lower/middle):
- D1 LHS lower pin (battery)/D1 RHS middle pin = 0.37V

Therefore, from your diagnosis, either the SRAM or RTC is draining too much current. This would explain the 2 new batteries I've fitted dropping to ~2.5V after only 24 hours or so.

I've run the RTC for several hours today on external power and it appears to keep time OK.

So, the SRAM is faulty?

If you agree, then please can you confirm if this can be replaced without the unit being returned to Losmandy. Do you have a part number/details to allow me to purchase a SRAM chip in the UK?

Again, thank you very much for your continuing help.

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich<Rene@> wrote:

Hi Andy,

after trying reset of the key SRAM values such as time, location and trying many, quick power re-cycles I'm still having the same problem...

Hi Tom

But I now see a new tips on your (really useful) gemini-2 website under G1 FAQs...

I've tried the following from tips 14& 15

1. Short-out C3 for ~0.5s. This cuases a reset that returns me to the same SRAM failure/WD reset warnings.

2. I've measured the voltage across pins 16& 32 of the SRAM chip. With battery only I have ~1V.

Much(!) too low, SRAM and RTC need at least 2.5V.

With external power I have ~4.6V. I've fitted a second, new battery and have the same readings (and problems).

So, could one of the 'steering' diodes have failed? What are the idents on the PCB (latest with rocker switch)?

This is D1, a BAT54C, located left of the big SRAM chip. What you can
try: measure the voltage at the pins of D1 against ground. You should
see about 5V at one pin at the left side, the battery voltage at the
other and at voltage with a drop of 0.3..0.4V at the middle pin.

What you can do is to bridge this diode with a 100 Ohm resistor (from
the battery plus pole to the middle pin) _while Gemini is powered off_.
If there is only a negligable voltage drop, O.K. If the loss is bigger
than 0.3V, one of the two components powered by the battery is faulty
and draining too much current.

In this case, please check if the RTC is running correctly while
externally powered. Check time and alarm settings. If all works
correctly there, the SRAM is more probably faulty, otherwise maybe the
RTC. It is complicated because both share the same data bus and both can
spoil the other's operation and cause a WD reset if faulty.

Many thanks to both of you for the helpful support!

You're very welcome.

Ren???

Regards,

Andy

------------------------------------

Yahoo! Groups Links

so, an update...

sent off my G1 PCB to Losmandy for repair (diagnosed as requiring a new SRAM chip) and returned to UK in double quick time - hats off to Scott for the prompt service!

All nows seems well...except for the random & intermitant but sometimes continuous (~5-10sec) beeping coming from the main unit. This happens mainly when simply tracking, but also slewing. When guiding using PHD it is largely non-existant. Mechanically all appears to be well, scope balanced, no lagging reported, guiding is very good, RA safety limits checked & reset, etc. But when beeping away the handset response is poor and the noise sounds worse than my old LX200 classic slewing @ 8deg/s! I need to fix this noise!

Any ideas?

TIA
Andy

--- In Gemini_Users@..., "tillyscope" <andy.wellington99@> wrote:

Hi all,

looking for UK source for a single CY62128BLL-70SC SRAM chip.

This chip is available from RS Components (but currently on back order!), but only in packs of 25 @ ?62.75.

Has anyone got a single chip that I could buy?

TIA,
Andy

--- In Gemini_Users@..., "tillyscope" <andy.wellington99@> wrote:

Hi 搁别苍é,

I've checked the details on the SRAM chip in my controller and it is

CY62128BLL-70SC

Is this the correct part used on the latest G1?

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich <Rene@> wrote:

Hi Andy,

The SRAM is a 128kx8 chip, f.i. a UPD431000AGE-70LL. It must be
carefully replaced, because some traces are below the chip.
I don't know about the commercial conditions of Scott or your dealer, I
can only speak as an engineer. A good electronics shop or someone with
good experience in soldering SMD parts should be able to replace the chip.

搁别苍é


tillyscope schrieb:

Hi 搁别苍é

I've measured the voltages as you've described and found the following.

With external supply and battery fitted:
- SRAM -ve/+ve = 4.6V
- SRAM -ve/D1 RHS middle pin = 4.6V
- SRAM -ve/D1 LHS upper pin = 5.2V
- SRAM -ve/D1 LHS lower pin = 2.6V

With battery only and 100R across D1 (lower/middle):
- D1 LHS lower pin (battery)/D1 RHS middle pin = 0.37V

Therefore, from your diagnosis, either the SRAM or RTC is draining too much current. This would explain the 2 new batteries I've fitted dropping to ~2.5V after only 24 hours or so.

I've run the RTC for several hours today on external power and it appears to keep time OK.

So, the SRAM is faulty?

If you agree, then please can you confirm if this can be replaced without the unit being returned to Losmandy. Do you have a part number/details to allow me to purchase a SRAM chip in the UK?

Again, thank you very much for your continuing help.

Regards,

Andy

--- In Gemini_Users@..., Rene Goerlich<Rene@> wrote:

Hi Andy,

after trying reset of the key SRAM values such as time, location and trying many, quick power re-cycles I'm still having the same problem...

Hi Tom

But I now see a new tips on your (really useful) gemini-2 website under G1 FAQs...

I've tried the following from tips 14& 15

1. Short-out C3 for ~0.5s. This cuases a reset that returns me to the same SRAM failure/WD reset warnings.

2. I've measured the voltage across pins 16& 32 of the SRAM chip. With battery only I have ~1V.

Much(!) too low, SRAM and RTC need at least 2.5V.

With external power I have ~4.6V. I've fitted a second, new battery and have the same readings (and problems).

So, could one of the 'steering' diodes have failed? What are the idents on the PCB (latest with rocker switch)?

This is D1, a BAT54C, located left of the big SRAM chip. What you can
try: measure the voltage at the pins of D1 against ground. You should
see about 5V at one pin at the left side, the battery voltage at the
other and at voltage with a drop of 0.3..0.4V at the middle pin.

What you can do is to bridge this diode with a 100 Ohm resistor (from
the battery plus pole to the middle pin) _while Gemini is powered off_.
If there is only a negligable voltage drop, O.K. If the loss is bigger
than 0.3V, one of the two components powered by the battery is faulty
and draining too much current.

In this case, please check if the RTC is running correctly while
externally powered. Check time and alarm settings. If all works
correctly there, the SRAM is more probably faulty, otherwise maybe the
RTC. It is complicated because both share the same data bus and both can
spoil the other's operation and cause a WD reset if faulty.

Many thanks to both of you for the helpful support!

You're very welcome.

搁别苍é

Regards,

Andy