SE/30 with SCSI problem after warming up. Error 41

[BEU]

Recently I got a SE/30 that was not working. Simasimac and no sound. After recapping and cleaning its working almost. The internal SCSI drive was not detected, the fuse F3 was blown. After replacing it the termpwr on the SCSI port is 4.7 V.

When I start the SE/30 its working perfect, booting from the internal SCSI drive and the floppy is also working. Sound is good.



After a couple of minutes the problems begin. Usally the first thing is that the mouse pointer is not responding. The harddisk and trash icons suddenly disappears. Some kind of error message like “system error, Finder , error 41”. No respons from mouse. When I reboot the SCSI drive is not found. The floppy with questionmark appears and I can boot from floppy . It is working but the SCSI drive is not detected. Whan I run Apple HDSC setup from floppy it cant detect any SCSI unit.

When the mac has been resting for some hours and “cold” its always working for 2-4 minutes then the problem starts. I have repeated this several times. If I use another logic board from a working SE/30 there are no problems.

There are a lot of threads in the forum about SCSI problem and most often problems with bad connection to or from the SCSI chip. I have tested continuity from UJ11,UG12 and UK11 to SCSI chip and from SCSI chip to internal SCSI port J5, without any fault detected. I have also tested continuity both in “cold” and “warm” condition.

Obviously the problems starts when the SE/30 is warm, I have measured the temperature on the chips (infrared thermometer) after starting the Mac. The only one that’s gets warmer ( 30 deg C) is UG12, don’t know if that is of interest.  

I need some advice before i replace the SCSI chip. Is it the SCSI chip or is it another chip? The fact that the F3 was blown, can that affect the SCSI chip? Can the SE/30 work if another chip is bad? I'm greatful for all advice.

 

[takimoto]

Hi BEU!

Before dig into SCSI,are you sure Power Supply Unit is OK?I got similar problem caused by leaked PSU.

 

[takimoto]

And from your photo,Harness between AB and MB looks like not original.Do you elongate this? I got voltage drop when I elongate harness with bit weaken PSU.

 

[Elfen]

Sounds like an Iffy Bournes Filter (Those yellow resistor chip near the connectors). Check them with a multimeter cold and then after they warmed up.

 

[BEU]

Thank You takimoto and Elfen for supporting help

Takimoto: I tested the voltage on the external floppy connector and its 12.4 V and 4.9 V. Same result at beginning when the HD is working and later when only the internal floppy is working. Is that OK?

Elfen: I tested the Bourns filter and I think RP10 is defect. There is no capacitance between pin 19 and 20. Between pins 12-18 and Earth (pin20) its 220-300pF when measured on the board. Pin 19 and 2 is named RDDATA in the schematics and is connected to RDDATA and SENSE on the SWIM chip and connected to the external floppy connector. No change during Cold and hot. The resistors are OK  The other two Bournes filter are OK.

I connected a working external floppy drive and the floppy disk is spinning but the disk is ejected. Strange that the internal floppy connector is working.

I will replace the Bourns filter RP10 from another SE/30 bord . That board is destroyed by a Maxell battery but the

Bourns filter measured OK.

A new error message today when HD stops working: "System error  "Finder" bad F-line instruction.

I will report later.

 

[BEU]

I just realized that I  tested the external floppy port with a M0130 floppy drive and that drive is not supposed to work with SE/30. Probably the external port is OK. I will replace the Bourns filter anyway.

 

[takimoto]

I think 4.9v is OK.In my case,it was about 4.8v.But I still think you want to be sure capacitors in PSU are healthy.I heard SCSI bus took almost 1Amp when many lines change between 0 and 1.makes ripple on power line if capacitors are weak.When I got problem like yours,floppy drive was removed and only CF-SCSI drive was attached,so load on PSU had to be lighter then usual.

 

[techknight]

Are you sure the SCSI drive is even any good? Its becoming a real big problem. 

 

[BEU]

Are you sure the SCSI drive is even any good? Its becoming a real big problem. 

I have tried with two SCSI drives with the same result. They are not working with this logic board, but when I try with another  board from a working SE/30, both SCSI drives are OK and everything is working. Same AB, PSU and cables. So the problem should be in the logic board.

After replacing the the Bourns filter RP10 from another board: same result , no progress.

I measured the voltage on the external floppy drive with the different boards with the same result. Replaced the ROMSIMM from the working logicboard: not better.

Maybee its time to replace the SCSI chip???

 

[techknight]

that or the VIAs just below the SCSI IC are breaking with heat. 

 

[BEU]

that or the VIAs just below the SCSI IC are breaking with heat. 

Hi, good news; the SE/30 is working perfect after replacing the SCSI chip.

You were right techknight!

After the NCR 53C80 was removed I checked all traces to the SCSI chip. From UK6, UI8, UK11 and UJ11 to UI12. From UI12 to internal SCSI connector J5. All OK. The earth and +5 V connections also OK . The VIAs under the chip: OK when measuring from top layer to bottom layer on the board. After cleaning I replaced the chip with a AMD 53C80 from a board destroyed by battery leakage.







Its working perfect, I have run it for one hour without problems. Its booting much faster than before. With the old SCSI chip it took about 30 sec from turning on to starting the SCSI disk. Now its 5 sec.

Thanks for all help and advice.

Bengt

 

[uniserver]

yeah just sometimes the act of removing the chip and cleaning the pads and the legs and re soldering can solve many issues.

IIsi has chips like that for ram...   Iici has chips like that for startup/shutdown..  Se30 is known for that for Audio/SCSI/UE8...   ColorClassic is known for that with EGRET and AD chip  Mac Classic II EGRET,  Mac Classic Audio.  Etc... 

 

[uniserver]

you can clearly see here the bottom row of pads were toast!

 

[uniserver]

I would of even scraped that black crud off, i have a tool that i made with my grinder that works great for such purpouses.

 

[uniserver]

solder don't like to stick to no nasty pad.

 

[BEU]

Thank You for information uniserver.

So probably the NCR chip is still working.

I used solder wick to clean the pads and aceton for the board. Solder with Pb and flux. Hope that will be sufficient for some years.

 

[takimoto]

Nice work BEU! glad to hear it's working!

 

[360alaska]

I would of even scraped that black crud off, i have a tool that i made with my grinder that works great for such purpouses.

When I run into pads like this I take a tiny jeweler's screwdriver and gently scrape the nasty black off. The I clean er with rubbing alcohol.

 

[Elfen]

yeah just sometimes the act of removing the chip and cleaning the pads and the legs and re soldering can solve many issues.

IIsi has chips like that for ram...   Iici has chips like that for startup/shutdown..  Se30 is known for that for Audio/SCSI/UE8...   ColorClassic is known for that with EGRET and AD chip  Mac Classic II EGRET,  Mac Classic Audio.  Etc... 

This is nice to know!