[Fixed/solved] Dead TT030

[wolfman]

Hi @all,

this is my first posting - so let me introduce myself briefly:
My name is Rüdiger (living in germany) and my first Atari was a 260ST back in 1987 (which I still have today).

The last entry to my collection was a TT030 presumably in "working condition", but it seems to be dead as a door-stopper.

TT030 specs:
- "daughterboard"-variant
- 32MHz (not 16)
- mainboard is CA400310
- daughterboard is CA400771

Actions taken so far:
- disassembled and cleaned the mainboard
- pulled all socketed chips, cleaned contacts of chips and sockets
- checked a lot of traces with a multimeter
- swapped PSU with a known-working-good PSU (voltages are OK)
- I made myself a diagnostic cartridge and verified it by testing the diagcart with a working TT030 and a RS232-connection to a terminal program
- the fuse at the cartridge port seems not to be blown

Issues found:
- some bent pins of the FPU
- resoldered some suspicious solder joints

No signs of life via RS232 (besides some odd characters sent while turning on/off the TT030)
CPU/FPU are getting warm over time but none of the chips of the mainboard are too hot to touch.
All RAM-Chips are cold to the touch.

Any suggestions for me?

Unfortunately I have no oscilloscope nor logic probe.

My guess is faulty RAM but I have no spares: onboard ST-RAM is Micron MT 4c4256-8 (MT's seem to fail quite often)

Thanks in advance

[Icky]

It might be useful to post pictures of the motherboard especially some zoomed in views around the areas you mention as having issues.

[alexh]

Test the reset button? I've had a few STs that seemed dead but the reset button was "stuck"

[wolfman]

IMG_20230308_101012.png

DIP-Switches (bottomside)
It seems that some liquid/water was dripping through the block of DIP-Switches at some point.

IMG_20230308_101038.png

Keyboard-Connector

IMG_20230308_101056.png

More corrosion at the reset-switch and Cinch-connectors (audio)

IMG_20230308_101107.png

Near TTVIDEO / PSU-Connector

IMG_20230308_101224.jpg

Mainboard / overview

IMG_20230308_101315.png

Serialports

I cleaned the solderside of the mainboard with IPA and reworked some solderjoints.

[wolfman]

Test the reset button? I've had a few STs that seemed dead but the reset button was "stuck"

Yes - I checked the reset button: not stuck

[derkom]

Since you are getting nothing from the known-good diag cart setup, you should probably start working through the TT030 Service Manual, starting with section 3.2, "Troubleshooting a Dead Unit".

Some of the testing there unfortunately requires an oscilloscope, but some of it you can do without one. At the places where it says to use a scope to check frequencies, you can use a multimeter to get some idea, as it will average out what it sees, and you'll see some fraction of 5 V. It's not the best tool for the job obviously, but it's better than nothing, and it will certainly reveal if you've got no clock at all.

[wolfman]

IMG_20230315_DB_top.jpg

IMG_20230315_DB_bottom.jpg

J100 is connected to the 32MHz oscillator quartz.

I measured J100 of the daughterboard:
DB popped out: 580 Ohms (J100)
DB in place: both pins of J100 are dead short to ground.

R1 (above J100) seems to have an open loop.

But: I have no clue what to do next.

[wolfman]

ehm - is it possible that the jumper connector is turned wrong (flipped)??

I turned the jumper /w brown/black cable (black cable is now facing to the socket) and J100 is no longer shorted to ground on both pins:
One pin to ground and the other pin shows 580 Ohms.

Is it safe (in terms of "blowing all up") to turn the TT on or is it even worse?

[wolfman]

IMG_20230315_163916.jpg

Yeah!

Silly me ... easiest bugfix ever ...

It freaking works!

A few resets were necessary ( I got a lot of wierd characters on screen), but now its working!
RAM-test: passed ...

Thanks for pushing me in the right direction!

[alexh]

:bravo: