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Hancock

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  1. Hancock

    new FPU completely blocks startup

    Final update: Received a new FPU today (from a local dealer) - it works as expected. The Mac was innocent (Sorry for having opened this topic, I just could not believe that a package of 5 FPUs contains only dead ones)
  2. Hancock

    new FPU completely blocks startup

    With some more testing, i.e. in other boards and on a network card, the conclusion is that the FPU(s) are dead. I excluded hypothesis this so far because I bought a package of 5 and they all cause the same problem. Yes, I bought them on ebay, they were coming from China and they have already been in use. In the same way I recently bought a "Quadra 630"-board which turned out to be a Performa 638 (68LC040) and a 68040 which prevents the board from starting. And this is not the first time I am getting dead components. Never again. Still I need to see that a new FPU will be working properly in the Mac to close the story. Thanks for the feedback.
  3. Hancock

    new FPU completely blocks startup

    Here is the exact testing acitivies: 1) Power supply is not connected to the board: infinite resistance between Pin 9 (GND) and Pin 61 (VCC) of the FPU socket 2) Power supply connected to the board (NOT switched on): 0 resistance for 1-2 seconds, then infinite (same pins) 3) Lift one probe for a moment, and put it on again: same behavior Can be repeated for GND (pin 9) to 16,17,18 (size),27,43,52,53,61 (all VCC) GND to GND is always 0 resistance. On a P460 #2 from above: 0 resistance just for a fraction of a second, then infinite #3 from above: resistance remains infinite. Hypothesis: On the P450 there is a capacitor slowly charging and losing the charge immediately? On the P460 the capacitor charges quickly and keeps the charge. Please don't forget: The Mac is running fine with 36Mb of Ram, SCSI2SD, Floppy, keyboard/mouse, System 7.5, Symantec CPP 7... except C2 and C4 need probably to be replaced. MacCheck is reporting "all well". That's why I am still puzzled with this "exotic" issue, it must be "local" to the socket. Rgds Btw: - The Multimeter is TE.Electronic MS8221C - Pictures will come later
  4. Hancock

    Performa 460 not starting

    Ok, this link is helpful, thanks. Apparently I have to have a much closer look on the board. So far I was assuming that the transport or the replacement of battery were the cause of the issue.
  5. Hancock

    Performa 460 not starting

    Hi bibilit, I have not yet down anything with the Mac - as said when I took it out of the parcel it was refusing any cooperation. So I have not seen the Mac running. The board looks neat and clean, and the sender confirms (more or less precisely - that the Mac was working before she sent if off. In the worst case she sold a "dead" Mac - then I have to review my assumptions and start working from scratch. "Also, the Egret chip can do that." - what does this mean? From another thread I had the impression that the PRAM/RTC-"module" must be properly working before the MCU is kind of started; the schematics seem to confirm that. So if I see 33MHz at the MCU/FPU-pin then the MCU/FPU should be running fine? Rgds
  6. Hancock

    Performa 460 not starting

    Update: Yesterday I checked the FPU clock pin (socket) with my scope: The 33MHz clock speed signal is is available and proper. Then the CPU also receive the clock speed signal and should be running. Next I will check /HALT and /BERR Is it then correct to assume that the PRAM is ok and my initial concern was wrong? Thanks for any feedback.
  7. Hancock

    new FPU completely blocks startup

    Thanks for the feedback so far. Sorry for not having mentioned the obvious: Yes, I have cross-changed all components (PSU, battery) and did the PRAM-reset command I have checked the FPU-Pins and I have checked the socket-Pins. I have also checked the board for dust or anything that could cause an unwanted connection. As already stated: there is no connection between GND and VCC on the socket as long as the PSU is not connected to the board. When I connect it, there is no more resistance between GND and VCC On a comparable box this resistance remains whether or not the PSU is connected. The only explanation for this behavior that I can see is that the FPU-specific capacitor is broken. For the next step it would be very helpful to find which one this is. I would hope that someone can provide some further information. Thanks in advance.
  8. Hancock

    new FPU completely blocks startup

    @Bolle: I was very careful in inserting the FPU - it was correctly done @superjer2000: hmm yes, ebay and China and already thought about that, but I bought 5 and they all behave the same - see below. But: VCC connected with GND on the FPU-socket is much more critical: I compared it with my P460 - there they are not connected (just a little bit of charging current - which proves that there is a capacitor in the game)
  9. Hancock

    new FPU completely blocks startup

    I meant VCC and GND is shorted ON SOCKET as soon as the power supply is connected.. The FPU does not show any shortages and I tested with several FPUs.
  10. Hi everybody, I received recently a P460. The sender affirms that it was working fine before it was sent off, but she is not expert and her statements are not very precise. Last thing she said she did was replacing the dead battery and taking out the harddisk. Starting the Mac here: no chime, no floppy is accessed, no video - nothing. The PSU is ok, power is supplied correctly, the fan is working. My assumption is that the PRAM and clock chip is not working- A reason could be that the sender has set the battery in the wrong sense - could this cause such a damage? And more important: if this was the case, can it be fixed? Again: no visible leakages and the board is clean. Thanks in advance
  11. Hi everybody, I have here a Performa 450 in which recently I wanted to install a FPU. (CPU is an overclocked 68030-16, FPU is 68882-33) With the FPU installed the P450 is completed blocked, not even the initial chime, and the PSU is "ticking". I finished by checking the pins of the FPU socket: when the PSU is connected, GND and VCC is shorted on the socket (only!), This explains the behavior. When the FPU is taken out, the Mac starts normally. My conclusion is that there must be a blcoking capacitor between VCC and GND which is broken. But which capacitor is that? Does anyone have an idea? The board is rather clean, no leakages or other damages of this kind are visible. Btw: on "normal" startup the Mac is screaming and howling. I suspect the capacitors C2 and C4 are the reason (if I touch them, the noise goes down) I thought to fix this later.
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