hello. my power supply of my NS Turbo Slab is gone. I try to fix it. I know its very complicated but i will try. I have two questions:
- i need the wiring diagram. is it available for download somewhere ? i searched everything but i didn´t find anything. because the metal pins which connects the first circuit board with the second are broken. so i must fix that too.
- there is an little smd electrolitic cap on it. does anybody if it is a 2,2uf 6,3v or a 22uf 63v or a 2,2 63v or 22uf 6,3v :?. mine have some scratches so it is not clear
thanks very much and keep fingers crossed that i can fix it
This web page has some good information on repairing slab power supplies:
http://heller.no-ip.org/~heller/NeXT/power_supply.html
Quote from: "marmacc"hello. my power supply of my NS Turbo Slab is gone. I try to fix it. I know its very complicated but i will try. I have two questions:
The slab power supply is indeed awful to repair because the main circuit board is screened on top of thick aluminium plate that dissipates the PSU heat into the slab chassis. This seems to be a "feature" of Sony designed power supplies from that era as I have seen something very similar on a SUN SPARCstation 10 PSU.
Quote from: "marmacc"- i need the wiring diagram. is it available for download somewhere ? i searched everything but i didn´t find anything. because the metal pins which connects the first circuit board with the second are broken. so i must fix that too.
I did not try very hard to obtain the schematic since all the power supplies I rebuilt were functioning correctly. It would, however, be very helpful to have it, even if it is only to understand what the adjustment pots are used for on the daughter card. If you can find the right contact at Sony, they might still have the schematic archived somewhere. I do not believe that this detail of information would ever be available at NeXT since the PSU was not their design.
The metal posts are an awful design feature. They are very stiff and their coefficient of thermal expansion is undoubtedly different than the aluminium circuit board that they are butted against and soldered to. As a consequence thermal cycles from cool to hot and back will eventually induce solder cracking between the posts and the board. Indeed two out of the three PSUs that I refurbished had cracked solder between the posts and the main board.
And now comes the fun part. Because of the aluminium backing plate you will not be able to use a soldering iron for the repair. I tried a 100W Weller with a reasonably fine tip and was not successful. I even tried preheating the board by placing the aluminium plate on a cook stove element (set to low heat) before attempting the soldering iron and that also did not work. Plus this approach creates the highest risk of damaging the electronic components due to prolonged heat exposure.
The only thing that worked for me was a propane torch with the flame
very carefully applied to the bottom aluminium surface, directly below the post. You will have to keep the board assembly horizontal to prevent solder drip and you will need to pre-apply non-corrosive flux to the cracked area to allow the solder to bond. I cannot emphasize enough how cautious you have to be, since the propane torch temperature reaches almost 2000 degrees C that would instantly destroy the silicon power devices that are placed nearby. So you have to use your judgement and use just the tip of the cooler (outer) portion of the flame. This will of course also depend on the size of the propane torch that you use. I used a standard plumbing torch that is used for soldering copper pipes in North America.
You also have to watch the solder like a hawk and the moment it flows you have to remove the flame immediately to prevent damage to the semiconductors. Ultimately I experimented with flame exposure using my specific torch and, using judgement, aborted all attempts where the solder didn't flow within a few seconds of flame application. I then removed the flame and let the board completely cool down before the next attempt with a closer (hotter) flame application. I managed to repair two PSUs with cracked post solder in this way and they both function perfectly.
I was planning to prepare a writeup for slab PSU capacitor refurbishment, similar to what I have done for the main board. But in the end I decided that it was too complex and risky of a process and I really did not want to be responsible for people destroying their power supplies. But in your case you have no choice if your power supplied has failed.
Quote from: "marmacc"- there is an little smd electrolitic cap on it. does anybody if it is a 2,2uf 6,3v or a 22uf 63v or a 2,2 63v or 22uf 6,3v :?. mine have some scratches so it is not clear
This capacitor is a 22uF 6.3V SMD. A good choice here would be the Panasonic FP series, P/N EEE-FP0J220AR (DigiKey P/N PCE4510CT-ND). Please keep in mind that the same challenges that I described above for soldering cracked posts will also apply to this tiny capacitor. You may find it easier to use a standard through hole capacitor with pins shaped to fit the SMD lands as this will give your soldering iron more surface area to heat the pin & pad.
Quote from: "marmacc"thanks very much and keep fingers crossed that i can fix it
Please post back to let everyone know if you had success with your repair.
Many thanks to Mike_H and t_rexky for the help. One last question. Did i understand right that all this heating pins (in total 11 i think) have only thermal function and no connection to a circuit ?
In total it seems to be not possible to repair the PSU by me. All the capacitor things, ok. But but these pins... :roll: I will give Rob a call for a new one :D
The posts serve two purposes: to provide mechanical support and electrical connections to the output PCB.
this is what i thought already. so for that case the wiring diagram were perfect :cry: or do you know where the electrical connections from plus and minus goes to which component on the second board?
Unfortunately I have not done any reverse-engineering of the power supply...
OK. Since months i tried to fix the old power supply. It is a desaster :cry:
It is not possible to repair this PSU. For weeks i decided to buy two "new" PSU´s from Rob Blessin and everything was fine since last week the battery dies... I replaced it and have now problems to boot from HD. But this is another thread...