AlfaRAM 1200-1 Repair

psodas

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Today, an Amiga card AlfaRAM 1200-1, arrived from a friend as <<stop working>>. At a first glance, it appears repaired from previews damage (battery acid).
Seems to have undergone further oxidation by cleaning rather bad in the previews repair. Also dont like the cord that is used for connections of the printed board. I prefer the kynar cable.

To have better access to printed board, I want to desolder the base of coprocessor. I would like to know if is useful to something, so to decide if sold this again. There are several memory cards with coprocessor, or is rare and not very useful?? In each case the base will extract without damaging.

Well... one from the next days I start the repair process.:coffee:


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Zetr0

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@psodas

Wow, you have some work ahead of you,

but theres some good work done on that card, although theres also some rather (quick) work also lol.

I am really looking forward to the re-work pics =)

good luck (y)
 

psodas

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Hi Zetr0,:)

Ok, Gals removed (static electricity reasons), wires, 2 caps, clock ic with base and the fpu base. I think look better now for pcb inspection. Lets start rewire....:whistle:

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Oh,....another card :shhh:with full 9 mb ram and fpu with external crystal! Just as a reference.

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Jon Hare

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Oh interesting...

I have two of those boards and bought some ZIP Ram for them recently. If I put them in my A1200 without any Ram both work without problems. But if I put ZIPs on it and set the jumpers a red screen appears always with a warning "board defect" or something like that. Any advice?
 

psodas

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@Zetr0

After rewire, I tried to work the card in Amiga 1200 but without luck.:( The Amiga dont boot at all.
I change all the Gals and RTC ic with others from the working card, but nothing change.
If I set the jumber to 0Mb, Amiga boot normally... but without extra Ram.
Some advice? Bad stock ram ic maybe? There are two chip ram at bottom side of pcb.
 

rkauer

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Naive possibility: the jumpers are in the correct place?

Vulturing: if the card is dead, are you willing to sell the ZIP chips?
 

Zetr0

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@psoda's

my friend this is quite a quandary, however you have done a fair bit of work.

1. Memory works okay with other unit.
2. CPLD / Programmable logic chips work with other unit.

If we are assured the work you have done is the same as what was then the board has a developed problem.

Although its possible any of the capacitors or discrete components, it could also that be more copper track has been eaten up by the acid, underneath the PCB laqure.

I would continuitiy test all the GAL/PAL sockets and the memory array, its quite likely you will have some more re-routing to do...

best of luck! (y)
 

salaxi54

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Are we supposed to be seeing some pictures in these posts here? Because i for one can not see a thing, no matter what browser..:)
 

psodas

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After major inspections again and again, its time to extract some ics.

First I remove the 74F86, and try the card to Amiga. But as a result got a yellow screen!

After I remove the 74F38, and try again the card. Not boot at all, as when they are received.

Then I resold the first ic 74F86, and.... IT WORK!!:) But only with 1 Mb stock Ram.:( When I try the card with known working 4 or 5 MB zipram configuration, I take a red screen with a message of bad card.:unsure:

Maybe a bad 74F38 ic? Or another after this, who give the problem when the first is in his position? Who knows! To morrow I try to search this at the local stores.

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LTAC

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7 month later :blink:
Do you have some news about your card?

I'm looking for information to install Quartz/Crystal on this board. Nothing in the manual and I've found two pictures makes me puzzled.
Check the position of the installed quartz on these 2 boards.

- the original box of the AlphaRam 1200




LINK ON AMIBAY

On the last picture I noticed that the Jumper J7 is not validated to use 33MHz quartz/crystal installed on the AlfaRam 1200 board.

So what is the orientation of the quartz for correct installation?

Thank you for your help.
 

Zetr0

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@LTAC

I have a sneaky suspision that the original photograph is incorrect - but to make sure we are 100% certain we can use a multi-meter and test two points on the card.

1. remove the crystal oscilator (xtal)
2. place the card memory side up with the connector to the left
3. switch your multimeter to continuity mode

lets begin =)

first we will need to assume an orientation of the xtal - for this purpose I am inclined to go with the linked unit on AmiBay

4. place your black probe into the top left (should be ground) (pin 7)
5. place your red probe onto the FPU ground (pin 9) - bottom right pin of the plcc conector do you get a buzz? if so then the layout should be - (o) = pin 1

X-----O

X-----X

6. lets test the Xtal output - pin 8 - bottom left - test this with pin 11 of the FPU
- this is one pin up on the right side of the plcc with the card oriented as in (1)
If this buzzes then its confirmed - if not try changing the jumper

7. testing the VCC (+5v power) - connect a probe to pin 14 (bottom right pin) and then probe this to the bottom left pin of the FPU PLCC (pin 61)

if you get a buzz on both Gound (5) and power (7) then there is a problem with the clock source / selector on the card - i.e. the jumper might be causing a problem - give it a clean and try again.


of course if you dont get any continuity test on VCC or VSS (Point 5 and 7) then the XTal is orientated differently - like this

X-----X

O-----X

Again this is with the card's memory facing straight up - the edge connector to the left.
 

Zetr0

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I believe you are right my friend,

to confirm test pin 14 of the XTal (bottom right) with Pin 11 of the FPU (VCC)

that should match as well - with this we have garanteed it's proper orientation -

It would seem that the Box art - was just that - an artistic impression LOL.
 

psodas

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@LTAC

First of all, the electronic design isn't much at two cards!;) Look carefully the position of crystal in pcb. Maybe is correct for EACH card.:)
 

rkauer

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Anyway, on all cards that the crystal is removable, the pin #1 have some kind of identification: a square solder pad, a silk screen indication, whatever.

On the Alfa RAM case is the silk screen indication.
 

LTAC

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I believe you are right my friend,

to confirm test pin 14 of the XTal (bottom right) with Pin 11 of the FPU (VCC)

that should match as well - with this we have garanteed it's proper orientation -

It would seem that the Box art - was just that - an artistic impression LOL.

YEAHH!!!
Test OK between Pin14 (crystal) & PIN10 (Vcc) [not the PIN11 as you write ???]
Thank a lot Zetr0!

@LTAC

First of all, the electronic design isn't much at two cards!:wink: Look carefully the position of crystal in pcb. Maybe is correct for EACH card.:smile:
Yep I think you're right! It seems to be some differents versions of this model. Thx.

Anyway, on all cards that the crystal is removable, the pin #1 have some kind of identification: a square solder pad, a silk screen indication, whatever.

On the Alfa RAM case is the silk screen indication.

Yep but no indication on the circuitboard or on the manual about the installation orientation on the socket :(
Thx.
 

rkauer

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No brainer: put the small sharp corner of the crystal (the one that normally have a dot on the metal shield top) aligned with the silk screen on the board.
 

Merlin

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I have a question that's bugging me from the photos....

The Ricoh DIL chip in the photos; is it me, an optical illusion due to the camera angle used, or is that chip really not seated correctly? From some of those shots it looks like the chip's pins are between the contacts?
 

LTAC

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"It's just an illusion" :D

I have a question that's bugging me from the photos....

The Ricoh DIL chip in the photos; is it me, an optical illusion due to the camera angle used, or is that chip really not seated correctly? From some of those shots it looks like the chip's pins are between the contacts?
 
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