Power supply C061763-11 failed

[+Spancho]

Saddly today my power supply failed and grilled my 130XE.

Now it jumbs straight into RAM/ROM Selftest.

Does not react on pressed keys on keyboard.

 

I switched my 130XE immediately off and measured the voltage output of the power supply and it gives me around +15V.

Anybody an idea if the power supply can be repaired or which component have failed?

 

I have some pictures attched in case it helps.

Thanks

spancho

 

[archeocomp]

This a european power supply I like very múch. I have drawn schematics. http://blog.3b2.sk/igi/post/Napajacie-zdroje-Atari-600XL-800XL-130XE-800XE-65XE-XEGS-Power-supply-Atari-typeIV-part-5.aspx

 

IT can be repaired easily

[+Spancho]

18 minutes ago, archeocomp said:

This a european power supply I like very múch. I have drawn schematics. http://blog.3b2.sk/igi/post/Napajacie-zdroje-Atari-600XL-800XL-130XE-800XE-65XE-XEGS-Power-supply-Atari-typeIV-part-5.aspx

 

IT can be repaired easily

Thanks for the link.

As I have not much clue how such a power supply works someone would have to guide me through a possible repair.

Any idea which part of the board might have failed?

spancho

[ivop]

If you scroll down further on @archeocomp blog post, you see a list of voltages at each pin of the 723. Check those. If they are ballpark right, probably one of the transistors has blown. Or both

 

This is my favorite PS, too. I only had to replace the fuse once, since 1985

 

[BillC]

3 hours ago, ivop said:

If you scroll down further on @archeocomp blog post, you see a list of voltages at each pin of the 723. Check those. If they are ballpark right, probably one of the transistors has blown. Or both

Failure of R1/R4/R7 would result in loss of some signals to the 723 as well, though I don't know how this would affect the output voltage.

 

I would recommend installing a crowbar circuit when repairing this power supply, less than $5 for parts and blows the fuse if the output goes too high. A 5.6V zener diode should keep the voltage from going high enough to damage chips, while also high enough to prevent false triggering. 15VDC could have damaged a lot of chips in your 130XE, the crowbar circuit reduces/eliminates this happening in the future.

https://www.electronics-notes.com/articles/analogue_circuits/thyristor-scr-triac/overvoltage-protection-crowbar-circuit.php#:

 

 

[archeocomp]

It is not my blog ? I just drawn the correct one schematics. The one without voltages. And provided Igi (it is his blog) with some pictures depicting transformer windings and transistors.

 

I quite do not believe your XE is toast. It apparently still works. In case of overvoltage Freddie is usualy first to go and that means blank screen (not sure, never happened to me).

This power supply has only very weak 15V rail, just to provide enough energy for the LM723 stabilizer. I am quite positive that under load (at least 600mA) your power supply would not show any overvoltage. My wild guess is that LM723 stabilizer  IC failed and now input pin nr.12 (V+) is internally connected to pin nr.10 (Out). And I hope that this internal connection if fairly weak and can not cause severe damage to Atari.

 

How exactly did your power fail? What happened? Can you measure voltage of broken power supply with resistor load? Can you specify what power supply are you using now?

Edited July 4, 2020 by archeocomp

[ivop]

GTIA, ANTIC, Sally, MMU and PIA are probably not damaged, or you won't get any display and selftest could not be selected and run. Pokey not sure. Can you select the sound test with the console keys? If not, GTIA might be broken, too.

 

But probaby your RAM is b0rked, just like with an ingot going over voltage. Hopefully it's limited to that.

 

[+Spancho]

4 hours ago, ivop said:

If you scroll down further on @archeocomp blog post, you see a list of voltages at each pin of the 723. Check those. If they are ballpark right, probably one of the transistors has blown. Or both

 

This is my favorite PS, too. I only had to replace the fuse once, since 1985

 

I will measure the voltages on each pin according to the link.

 

42 minutes ago, BillC said:

Failure of R1/R4/R7 would result in loss of some signals to the 723 as well, though I don't know how this would affect the output voltage.

 

I would recommend installing a crowbar circuit when repairing this power supply, less than $5 for parts and blows the fuse if the output goes too high. A 5.6V zener diode should keep the voltage from going high enough to damage chips, while also high enough to prevent false triggering. 15VDC could have damaged a lot of chips in your 130XE, the crowbar circuit reduces/eliminates this happening in the future.

https://www.electronics-notes.com/articles/analogue_circuits/thyristor-scr-triac/overvoltage-protection-crowbar-circuit.php#:

 

 

Once the PS works again I will try to get the parts needed for the crowbar.

l have a second PS like that so should build two crowbars then.

33 minutes ago, archeocomp said:

It is not my blog ? I just drawn the correct one schematics. The one without voltages. And provided Igi (it is his blog) with some pictures depicting transformer windings and transistors.

 

I quite do not believe your XE is toast. It apparently still works. In case of overvoltage Freddie is usualy first to go and that means blank screen (not sure, never happened to me).

This power supply has only very weak 15V rail, just to provide enough energy for the LM723 stabilizer. I am quite positive that under load (at least 600mA) your power supply would not show any overvoltage. My wild guess is that LM723 stabilizer  IC failed and now input pin nr.12 (V+) is internally connected to pin nr.10 (Out). And I hope that this internal connection if fairly weak and can not cause severe damage to Atari.

 

How exactly did your power fail? What happened? Can you measure voltage of broken power supply with resistor load? Can you specify what power supply are you using now?

According to the self test almost all RAM is damaged maybe Basic ROM too as I cannot start with Basic anymore.

Computer starts directly with the memory test, keyboard is not working so I guess Pokey is dead to.

 

The PS failed while the computer was switched on but I didn’t see that Since I was away from it with the TV switched off.

when I came back I switched on the TV and power cycled the 130XE and only memory selftest since then.

 

I opened up the Atari and quite some ICs got very hot so I switched it off immediately. Have not switched it on yet again.

will do so once I find my SysCheck from tf_hh again.

 

I let you know my measuring results of LM723.

 

Thanks a lot so far for your help and input

spancho

[BillC]

19 minutes ago, Spancho said:

According to the self test almost all RAM is damaged maybe Basic ROM too as I cannot start with Basic anymore.

Computer starts directly with the memory test, keyboard is not working so I guess Pokey is dead to.

I had an 130XE that showed 44 red blocks and 4 green on the OS diagnostics, my SYSCHECK 2.1 identified only 2 failed RAM chips.

 

When I had an INGOT power supply fail back in the late 80's, putting out about 8.5VDC, it only damaged the 41256 chips in a RamboXL upgrade. The RAM failed first and drew enough power to prevent damage to the rest of the chips, but this caused me to want a power supply with a crowbar circuit even if the major ICs weren't damaged, RAM was more expensive back then.