]Rejuvenator Help
5 messages in this thread
Rejuvenator is now working together with Lucas/Francis after the mods
where installed. The system works fine until I try to add my Comspec hard
drive controller and Seagate drive. This conbination was working fine
before the Rejuvenator was added into my system. The amiga simply won't get
past the request for the kickstart disk once it has read the kickstart. I
suspect that it has to do with the overall noise that the hard drive has
added to the system. Also even without the harddrive installed, the system
will only successfully boot with one combination of a crystal (18.32MHZ)
and 74LS74 chip. Any and all other combos (ie. 16 or 20 MHz crystal with
74ALS74,7474,74 ,74F74,74S74, and 74AS74)won't boot period.
You have in the past mentioned that the noise can be measured with a hi
speed scope on the power lines of the Lucas board. I don't have access to
this equipment,but are the some areas on the Lucas or Francis boards that I
could add some additional grounding or perhaps capacitors to reduce the
noise?
I also know about your upcoming buffer expansion device. I assume that
this may reduce noise from the hard drive controller and drive back to the
amiga motherboard/Lucas/Rejuvenator components? Somebody here told me that
this would only stop additional noise if the design of your buffer board
included a SEPARATE power source to it ie. the buffer would not get its
power from the amiga power supply. Is this correct??
As always thanks in advance for your continued support of your product
Thanks
Ron Stein
Ron, there may be a couple more changes to lower Rejuvenator noise, which
helps everything else. It's all additive. I will Email you when I have a
good solution. At least we are going in the right direction!
I agree that Lucas is very finicky about U9 and Xtal freq. But it does seem
to work OK (expansion bus stuff excluded) on long term diagnostics.
One of the big problems with the A1000 motherboard is that it too has poor
grounding of the 68000 and the expansion bus. There will be a picture with
the buffer that shows where to put two wires on the motherboard that
significantly reduces the impeadance of the VCC and ground traces to the
expansion bus.
There are two problems with the 68000 expansion bus in the A1000. The first
is that the CPU data bus and address bus is heavily loaded. Secons is that
it is not terminated. Both of these are problems with the A500 also.
Noise can be caused by several things: Active devices, poor powersupply
voltage regulation, improper signal routing and too long traces ( cross
over noise and ringing), and poor signal drive.
My expansion bus buffer will help in several regards. First, all address
and data lines will be fully buffered, most clock and signal lines. This
helps because the poor 68000 is loaded to limit in the basic machine.
Secondly, it reduces the effective length of the bus, which limits
transmission line effects to that of the base machine with no expansion
devices. I will terminate the bus for additional help.
The board will have a place to provide external power or use internal
power. Assuming you make the two jumpers on the motherboard, I have no
problems with poor ground or VCC. It will have more than enough capacitive
decoupling to help prevent expansion bus noise from propagating too far
into the Amiga.
Commodore gave me an old ZorroI bus board for the A1000 and I put a 2058 on
it. I noticed that the ground had significant noise on it relative to the
Amiga 1000's ground, even though it was separately powered. This is why the
motherboard jumpers are needed. If you want to see a joke, look at how VCC
and ground find its way to the 68000 and tthe
expansion bus. It gets pretty narrow in spots and has to go through several
vias. Look at the Rejuvenator, it has .5 inch power busses to ensure good
power. I may go to 6 layers to go to complete power planes to help the
noise level in a future revision.
I am not claiming that the bus buffer will solve every problem, but it will
certainly help many. It will even have a LUCAS jumper option that causes it
to latch the data, so expansion devices that are known to be incompatible
will have a chance to work.
-Greg
Greg,
I have asked my dealer to order the REJUVENATOR for me each time I go
in his store and he says that "they" say they are not ready to ship. Yet,
here on CI$ I've seen several people say that they actually have one I want
one what do I do to get it. If all goes well I will buy 3 more!
Thanks.
— Gary Lucas —
There is a queue. We deal mostly direct, so a Dealer calls and gets placed
on the end of the queue. There will probably never be mass disrribution as
the profit margin is comparatively low. Most of those who have theirs,
called Expert Services direct adn placed an order over the phone.
-Greg