Re: Req: Help with a sick IIC !!!

[Jan <jankro@vip.fi>]

In addition to the previous post: The voltages stay steady as a rock during boot and
disk activity.
Jan

Jan wrote:

> Hello,
> First, thanks for you reply.
> All these IIC�s are european versions and so are the power bricks. I have two
> bricks with similar  results and correct voltages. Ihave tried three internal
> supply�s and they give correct voltages. How is the test screen supposed to look
> like? I�ll get different screens on all 3 IIC�s. The one I�m working now, gives
> me 24 horizontal bars, 4 pixels each. On the left upper corner, approximately
> 1/4 of the screen, there are flashing small blocks that keep changing
> constantly.No sound is present and the test will not stop (waited a couple of
> hours).
> Voltages to the memory chips are OK, (4.97V)
> I will check the voltages when the drive powers up and let you know.
> Thanks for your help.
>
> Jan/Finland
>
> eeastman@NOSPAMappple2.com wrote:
>
> > Jan:
> > Two things to check, valid IIc boot disk and power.  Try borrowing a good
> > IIc form a user in your area and try using their power supply on your IIc,
> > try one of their know good boot disks on your IIcs.
> >
> > You said you tried the disks on a IIe, are these boot disks ones that would
> > work on a IIc?  I know alot of older stuff will not boot on a IIc because of
> > the boot rom.  Of course the prodos thing confuses me because ProDOS of any
> > variety _should_ work on a IIc.
> >
> > So are you using the same power supply on all these failing IIcs?  Try a
> > different power supply.
> >
> > What pwoer frequency do you have in VIP.FI? (Your e-mail domain.)  Do you
> > have a power supply built for your part of the world?  50Hz AC power
> > generates a different voltage when rectified into DC, and may cause problems
> > with filtering capactitors.  A different frequecy will totally screw up the
> > rectifier and will produce AC laden (unstable DC) and lower current capacity
> > and higher voltage.
> >
> > Since you solder, I assume you have a VOM, check the voltages inside the IIc
> > at the memory chips, make sure it is high enough.  Watch for a voltage drop
> > when you activate the drive.  If you have access to an osilloscope, check
> > the AC component of your DC voltages and see if there is a frequency riding
> > your DC that may be causing problems in your ram.
> >
> > These are the only things I can think to check since all of your IIcs appear
> > to be having the same problems.
> >
> > Thankx,
> > Ed
> >
> > Jan wrote:
> >
> > > Yes, I tried three different disk drives,and I tested the boot floppies
> > > on my 2E.  On PRODOS I get "Unable to load PRODOS" and on DOS33, I�ll get
> > > the Hex or assembler message.