Turning on STacy only 2 times out of 10 does it start.

[Darklord]

the test I did in the previous post is not reliable, in the sense that I realized that the STacy hard disk is not the same as a mega ste; the hard disk of the atari mega ste consumes much more current than that of the STacy. So I confirm that the problem is only with the ignition.

Is that just a function of it being a newer SCSI hard drive in the Mega STe, vs
the one in the STacy? Otherwise, to the best of my knowledge, the internal
adapter card is the same...

Thanks.

[Roberto]

Is that just a function of it being a newer SCSI hard drive in the Mega STe, vs
the one in the STacy? Otherwise, to the best of my knowledge, the internal
adapter card is the same...

Thanks.

Hi Darklord, the stacy HD controller card is an older version than the Mega STE one, and they are perfectly interchangeable. However, the HD of the Mega STE is visibly "larger" and it really seems that it needs more current to work; among other things it is perfectly functional on the Mega STE.

I was thinking.... since I have these BOOT problems with the STacy (remember that it starts only by setting the trimmer to a voltage higher than the canonical 5Volt), why not try to power the STacy with an Atari ST PSU? I mean: I would like to replace the internal DC/DC module of the STACY with a PSU from an Atari ST in order to give the 5 Volts the STacy needs to boot; in this way I can understand if the fault of all this is the DC/DC module. Can I do it or am I risking anything? Or maybe I could just try to power the STacy directly from the floppy connector?

[Roberto]

:shock: :shock: :shock: :shock: :shock: :shock:
@derkom

[Darklord]

Odd. When I first got my STacy it had a dead 20 MB hard drive in it. It seemed slightly larger and heavier
than the 80 MB SCSI drive I replaced in my Mega STe (switched to an internal Ultrasatan). I guess that was
just me... <shrugs>

When I was experimenting years ago with a color screen (before the RGB2HDMI mod came out),
I used a Pico P/S to power my STacy and I did use the floppy 5v line to do that. Alan H. was the
one who told me it could be done that way. I think only the serial port actually needs 12v?

[Roberto]

….. Alan H. was the
one who told me it could be done that way. I think only the serial port actually needs 12v?

it seems to me that besides the serial port, the port that houses the cartridge also needs 12volt (maybe someone will correct me).

I tried to power up the STacy through the floppy line with an external regulated power supply. I get a white screen at 5V and this screen that follows if I set it to 5.1 volts. Looks like the problem is in the motherboard.

6A486BE6-C6E8-4D02-BE75-6594B4612917.jpeg

I found that my RTL IC has no frequency at pin 3 (there is a stable 5v instead), despite being properly powered at 5v. Could this be the cause?

[sporniket]

….. Alan H. was the
one who told me it could be done that way. I think only the serial port actually needs 12v?

it seems to me that besides the serial port, the port that houses the cartridge also needs 12volt (maybe someone will correct me).

If it is like regular ST , there is only 5V on the cartridge ports.

[rubber_jonnie]

Two things about the cartridge port:

1. The STacy schematics found here: docs.dev-docs show it as being a standard ST cartridge port, no 12v present.
2. If it had 12v, ST cartridges would not be compatible. Only 5v is present on the cartridge port of the STacy

A normal ST will run on just 5v. I don't know about the STacy, however the schematics show +5v, +12v, -12v and -20v, so it may need more than just 5v for the STacy, though that may be purely for the battery. I would temper that with the fact that the PSU details on the schematics show a 4 pin plug with 5v and 12v, so 5v alone may be fine.

BTW, not everyone will know what the RTL IC is, it would help if you could state the IC number from the stencil on the board. ICs usually have a 'U' prefix, so it'd be something like U20, U15 etc. This will help relate it to the schematics.

Also, with regards to 5v versus 5.1v, you also need to be sure the amperage matches what the STacy PSU can deliver from your bench PSU. I tend to set the current protection of my bench PSU low to begin with and adjust up in steps, and check for hot ICs as I do it, eventually getting up to the current the original PSU can deliver. If you don't have the correct amps set, then the power @5v won't be correct, but bumping it up to 5.1v may be enough to give you the correct power. It also may be enough to give you a response, but not enough to properly power on the machine.

[Darklord]

Well, as I stated - I did run my STacy for a while from a Pico P/S by feeding 5v into the
2nd floppy drive line. It was perfectly stable like that. Alan H. (MonSTer, ImpoSTer,
Unicorn, etc) told me I could do this safely. That was when I was experimenting with
a color monitor before the RGB2HDMI mod existed. I completely removed the original
internal P/S board and powered everything off of the Pico P/S. I ran with it like this
for a month or two but was never completely satisfied with the color display so I went
back. I was going to keep the Pico P/S in place but I couldn't figure out a way to get
the -20 voltage that the original LCD needs, so I soldered in extensions and moved the
original internal P/S board to the battery compartment to make room for the Pak 68/3
accelerator board. You can see the Pico P/S in play in the pictures below:

PICO PS01.JPG

PICO_Stacy01.JPG

PICO_power jack01.JPG

PICO_power jack02.JPG

My STacy Motherboard.jpg

[Roberto]

Well, as I stated - I did run my STacy for a while from a Pico P/S by feeding 5v into the
2nd floppy drive line. It was perfectly stable like that. Alan H. (MonSTer, ImpoSTer,
Unicorn, etc) told me I could do this safely. That was when I was experimenting with
a color monitor before the RGB2HDMI mod existed. I completely removed the original
internal P/S board and powered everything off of the Pico P/S. I ran with it like this
for a month or two but was never completely satisfied with the color display so I went
back. I was going to keep the Pico P/S in place but I couldn't figure out a way to get
the -20 voltage that the original LCD needs, so I soldered in extensions and moved the
original internal P/S board to the battery compartment to make room for the Pak 68/3
accelerator board. You can see the Pico P/S in play in the pictures below:

Truly a Darklord pro job! I would never be able to do such a thing... too complicated for me! :roll:

[Roberto]

Two things about the cartridge port:

1. The STacy schematics found here: docs.dev-docs show it as being a standard ST cartridge port, no 12v present.
2. If it had 12v, ST cartridges would not be compatible. Only 5v is present on the cartridge port of the STacy

A normal ST will run on just 5v. I don't know about the STacy, however the schematics show +5v, +12v, -12v and -20v, so it may need more than just 5v for the STacy, though that may be purely for the battery. I would temper that with the fact that the PSU details on the schematics show a 4 pin plug with 5v and 12v, so 5v alone may be fine.

BTW, not everyone will know what the RTL IC is, it would help if you could state the IC number from the stencil on the board. ICs usually have a 'U' prefix, so it'd be something like U20, U15 etc. This will help relate it to the schematics.

Also, with regards to 5v versus 5.1v, you also need to be sure the amperage matches what the STacy PSU can deliver from your bench PSU. I tend to set the current protection of my bench PSU low to begin with and adjust up in steps, and check for hot ICs as I do it, eventually getting up to the current the original PSU can deliver. If you don't have the correct amps set, then the power @5v won't be correct, but bumping it up to 5.1v may be enough to give you the correct power. It also may be enough to give you a response, but not enough to properly power on the machine.

I can confirm that the STacy does not use +12 Volts in the cartridge port. I can also confirm that all the Ataris I have at my disposal (ST, STE, Mega ST and Mega STE, to make comparisons), need exactly +5 Volts to work (even something less), except of course the serial port . So my STacy, which can only boot with a minimum of 5.1 Volts, is not good, especially since it has CMOS components that should require less current. I also specify that the bench power supply that I used to power the STacy, both as a replacement for the external power supply and used directly in the floppy connector, has a maximum capacity of 5 Ampere (it is set to maximum, so I have all the necessary power that the Stacy needs). So the problem, in my humble opinion, is not due to the power supply (either external or in the DC/DC module), but to something wrong with the motherboard. Also having an Atari Mega ST (surely working and I also know that it is very similar to the STacy), I measured (on my Atari Mega ST), with an oscilloscope P16 and P17 on the RP5C15 (U15) and I have exactly what I have on the STacy , therefore no signal on P16, but only on P17 (32000Hz). instead there is a difference on TP1 (circled in white near RP5C15): I have a 16KHz on the Mega ST, while on STacy I have a constant +5V. doing a diagnostic cartridge test it tells me the real time clock works on the Mega ST but not the STacy.

I don't know if TP1 is the same thing as pin P3 of the RP5C15, because the values are reflected in the respective systems.

So I'm wondering, could a non-functioning RP5C15 have a side effect of what I'm experiencing?

RP5C15 (U15)

IMG_8250.jpeg

Update:
I was reading Mega ST Service Manual, and it says that if there are problems with the Real Time Clock, it can be Bad clock chip, bad crystal or even the RTC PAL chip which should be this one in the picture (in the STacy U25), but on Mega ST I have not found it. Can anyone tell me what it is for and where it is in the Mega ST? I would like to make some comparisons.

IMG_6440.jpeg