Dead Elk, any ideas?.

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mark71
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Dead Elk, any ideas?.

Post by mark71 » Sun Apr 26, 2020 8:44 pm

Hi All

After getting the Gotek drive to work, using a Elk with Plus 1 and Slogger DFS interface the said Elk after using it wouldn't boot up, no light, no reassuring beeep.

I have opened the old girl up, checked the PSU, power coming out +5/-5 and AC, took out the ULA and reseated it, still no joy. Any ideas where to look next?.

It is a Issue 4 Board.

Mark

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Re: Dead Elk, any ideas?.

Post by CMcDougall » Sun Apr 26, 2020 9:03 pm

if just the bare (no plus1 etc) elk then would say one the 4x 8k ram chips bottom right.
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Re: Dead Elk, any ideas?.

Post by danielj » Sun Apr 26, 2020 9:45 pm

If the RAM has gone you invariably get a garbage display and a click of the relay as you turn it on? Is there no display at all?

d.

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Re: Dead Elk, any ideas?.

Post by KenLowe » Sun Apr 26, 2020 10:32 pm

Check the ULA socket for broken pins. It may not look obvious initially. I had a similar issue, which is discussed in this post.

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Re: Dead Elk, any ideas?.

Post by mark71 » Sat May 02, 2020 8:14 pm

KenLowe wrote:
Sun Apr 26, 2020 10:32 pm
Check the ULA socket for broken pins. It may not look obvious initially. I had a similar issue, which is discussed in this post.
Well had another go today, popped the ULA and checked, looks ok to me no broken pins and no life.

What’s the best thing to probe for to check for life?, what does it check first to boot up on the old girl?.
img_5903.jpg
Mark

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danielj
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Re: Dead Elk, any ideas?.

Post by danielj » Sat May 02, 2020 8:18 pm

Well, the first place to start is my previous question :D - is it completely dead, or is something displayed (white bars, red/yellow pattern)? Does the cassette relay click when you turn it on?

d.

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Re: Dead Elk, any ideas?.

Post by mark71 » Sat May 02, 2020 8:23 pm

danielj wrote:
Sat May 02, 2020 8:18 pm
Well, the first place to start is my previous question :D - is it completely dead, or is something displayed (white bars, red/yellow pattern)? Does the cassette relay click when you turn it on?

d.
Sorry :roll: , completely dead, no display, no beep, no click of relay, no Led. Power coming from supply +5/-5 and direct AC to board.

Mark

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Re: Dead Elk, any ideas?.

Post by rmbrowngr » Sun May 03, 2020 7:18 am

It may well be a good idea to get in touch with Dave H on this forum. He’s the best person for Electron hardware.

He’s the service manual if it helps http://chrisacorns.computinghistory.org ... tronSM.pdf
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Acorn Electrons issue 4 and 6, MRB, Plus 1, AP6, AP5, Pegasus 400, BeebSCSI, Gotek, Raspberry Pi, GoSDC MBE.
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Re: Dead Elk, any ideas?.

Post by 1024MAK » Sun May 03, 2020 7:59 am

Assuming that you have disconnected the Plus 1, is the +5V power actually getting to any of the chips? E.g. pin 8 of the 6502.
What voltage do you get on pin 40 of the 6502?

Apart from a multimeter, do you have any other test gear, if yes, what?

Mark

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Re: Dead Elk, any ideas?.

Post by mark71 » Sun May 03, 2020 12:22 pm

1024MAK wrote:
Sun May 03, 2020 7:59 am
Assuming that you have disconnected the Plus 1, is the +5V power actually getting to any of the chips? E.g. pin 8 of the 6502.
What voltage do you get on pin 40 of the 6502?

Apart from a multimeter, do you have any other test gear, if yes, what?

Mark
Pin 8 5volts, pin 40 0volts

I do have a scope, not sure it still works.

Mark

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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Sun May 03, 2020 2:01 pm

Let's start with basics:

Disconnect everything from the Electron - except the power-in plug.

I know you've done some of this already, however, let's have the results written down . . .

Measure the Voltage at these points (everything ON the Electron Main PCB): (sorry if the is an egg-sucking lesson!)

Power connector - you should have +5V and -5V (centre pin 0V) so measure between the centre pin and both outside pins.
Every IC - measure between the bottom left pin to the top right pin - Note that the Notch of one end of the IC indicates Pin 1.

The 6502 - measure between pins 21 to 8 and between 1 and 8.

So, let's have those result and then move on.

What test gear do you have? Have you a schematic for the Electron? Just in case . . .


Dave H :D
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Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
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Re: Dead Elk, any ideas?.

Post by 1024MAK » Sun May 03, 2020 2:59 pm

mark71 wrote:
Sun May 03, 2020 12:22 pm
1024MAK wrote:
Sun May 03, 2020 7:59 am
Assuming that you have disconnected the Plus 1, is the +5V power actually getting to any of the chips? E.g. pin 8 of the 6502.
What voltage do you get on pin 40 of the 6502?

Apart from a multimeter, do you have any other test gear, if yes, what?

Mark
Pin 8 5volts, pin 40 0volts

I do have a scope, not sure it still works.

Mark
Pin 40 on the 6502 is the reset input pin. This is an active low logic signal. 0V here means the 6502 is being held in reset. It should normally only go to 0V briefly when the board is powered up or when the BREAK key is pressed. The rest of the time, the voltage here should be greater than 3V. The ULA drives this signal low at power up, then it should go to a logic high level.
:arrow: Before continuing, it's wise just to double check the voltage.
With the reset input active (at 0V), the 6502 will do nothing useful, hence the machine will appear to be dead.
Is the ULA fitted correctly?
Is the BREAK key stuck down?
With the power disconnected, use the multimeter on the resistance range, with the black probe connected to a suitable 0V GND rail point, use the red probe to measure the resistance from 6502 pin 40.
If you get a low value, carefully disconnect the keyboard "ribbon" cable. If this clears the fault, the problem is the BREAK key. If not, either there is a short circuit on the board, or the ULA is incorrectly fitted or is faulty. As you have recently had a Plus 1 fitted, it's worthwhile checking the edge connector to see if there is anything wrong on the PCB tracks that make up the edge connector contacts.

It is still worthwhile doing the steps suggested by Dave, as if there is a loss of power to part of the board, that could include power to the ULA, hence why it is may be malfunctioning.

Mark

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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Sun May 03, 2020 3:27 pm

1024MAK wrote:
Sun May 03, 2020 2:59 pm
mark71 wrote:
Sun May 03, 2020 12:22 pm
1024MAK wrote:
Sun May 03, 2020 7:59 am
Assuming that you have disconnected the Plus 1, is the +5V power actually getting to any of the chips? E.g. pin 8 of the 6502.
What voltage do you get on pin 40 of the 6502?

Apart from a multimeter, do you have any other test gear, if yes, what?

Mark
Pin 8 5volts, pin 40 0volts

I do have a scope, not sure it still works.

Mark
Pin 40 on the 6502 is the reset input pin. This is an active low logic signal. 0V here means the 6502 is being held in reset. It should normally only go to 0V briefly when the board is powered up or when the BREAK key is pressed. The rest of the time, the voltage here should be greater than 3V. The ULA drives this signal low at power up, then it should go to a logic high level.
:arrow: Before continuing, it's wise just to double check the voltage.
With the reset input active (at 0V), the 6502 will do nothing useful, hence the machine will appear to be dead.
Is the ULA fitted correctly?
Is the BREAK key stuck down?
With the power disconnected, use the multimeter on the resistance range, with the black probe connected to a suitable 0V GND rail point, use the red probe to measure the resistance from 6502 pin 40.
If you get a low value, carefully disconnect the keyboard "ribbon" cable. If this clears the fault, the problem is the BREAK key. If not, either there is a short circuit on the board, or the ULA is incorrectly fitted or is faulty. As you have recently had a Plus 1 fitted, it's worthwhile checking the edge connector to see if there is anything wrong on the PCB tracks that make up the edge connector contacts.

It is still worthwhile doing the steps suggested by Dave, as if there is a loss of power to part of the board, that could include power to the ULA, hence why it is may be malfunctioning.

Mark
But with all the above you'll still get some video output!

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Dead Elk, any ideas?.

Post by 1024MAK » Sun May 03, 2020 4:42 pm

daveejhitchins wrote:
Sun May 03, 2020 3:27 pm
But with all the above you'll still get some video output!

Dave H :D
Hi Dave

If it was as simple as just the reset line being low, yes, I would expect the ULA to display something (garbage/undefined RAM contents).

If there is a problem with the ULA however, or the connections or power to it, then as you know, there may be no video signal for the TV/monitor to display.

Mark

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Re: Dead Elk, any ideas?.

Post by mark71 » Sun May 03, 2020 7:14 pm

daveejhitchins wrote:
Sun May 03, 2020 2:01 pm
Let's start with basics:

Disconnect everything from the Electron - except the power-in plug.

I know you've done some of this already, however, let's have the results written down . . .

Measure the Voltage at these points (everything ON the Electron Main PCB): (sorry if the is an egg-sucking lesson!)

Power connector - you should have +5V and -5V (centre pin 0V) so measure between the centre pin and both outside pins.
Every IC - measure between the bottom left pin to the top right pin - Note that the Notch of one end of the IC indicates Pin 1.

The 6502 - measure between pins 21 to 8 and between 1 and 8.

So, let's have those result and then move on.

What test gear do you have? Have you a schematic for the Electron? Just in case . . .


105,000-C Circuit Diagram For Electron Microcomputer Main PCB.jpg.zip


Dave H :D
Hi Dave

No sucking of eggs here, am a CAD designer by trade for the automotive industry, hobbist as far as electronics, done some basic stuff as an apprentice many years ago, spent a month on a work exchange in Bosch in Germany as an apprentice who beat me into getting good soldering skills always useful, given a basic circuit diagram and told to make it work by laying out the tracks......

Done some more testing today, to say there is no video is techniclly true, however when power is applied with the RGB cable in the monitor detects some sort of power and switches to the right Channel but displays nothing/black

Power to PCB -5.095V and +5.135V
as to measurements 6502 between pin 1-8 5.1v between 8-21 5.1v

Dram chips reading -5.1v

All other IC's except the bottom left IC reading +5.1v

Bottom left IC looking from above LM something -0.007v

Also to note whilst trying this swapped the keyboards from a known working Elk and same thing no life.

Also to note the ULA was getting warm, so power is getting in there not sure if it's fried or not.....

Mark

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Re: Dead Elk, any ideas?.

Post by mark71 » Sun May 03, 2020 7:28 pm

1024MAK wrote:
Sun May 03, 2020 2:59 pm
mark71 wrote:
Sun May 03, 2020 12:22 pm
1024MAK wrote:
Sun May 03, 2020 7:59 am
Assuming that you have disconnected the Plus 1, is the +5V power actually getting to any of the chips? E.g. pin 8 of the 6502.
What voltage do you get on pin 40 of the 6502?

Apart from a multimeter, do you have any other test gear, if yes, what?

Mark
Pin 8 5volts, pin 40 0volts

I do have a scope, not sure it still works.

Mark
Pin 40 on the 6502 is the reset input pin. This is an active low logic signal. 0V here means the 6502 is being held in reset. It should normally only go to 0V briefly when the board is powered up or when the BREAK key is pressed. The rest of the time, the voltage here should be greater than 3V. The ULA drives this signal low at power up, then it should go to a logic high level.
:arrow: Before continuing, it's wise just to double check the voltage.
With the reset input active (at 0V), the 6502 will do nothing useful, hence the machine will appear to be dead.
Is the ULA fitted correctly?
Is the BREAK key stuck down?
With the power disconnected, use the multimeter on the resistance range, with the black probe connected to a suitable 0V GND rail point, use the red probe to measure the resistance from 6502 pin 40.
If you get a low value, carefully disconnect the keyboard "ribbon" cable. If this clears the fault, the problem is the BREAK key. If not, either there is a short circuit on the board, or the ULA is incorrectly fitted or is faulty. As you have recently had a Plus 1 fitted, it's worthwhile checking the edge connector to see if there is anything wrong on the PCB tracks that make up the edge connector contacts.

It is still worthwhile doing the steps suggested by Dave, as if there is a loss of power to part of the board, that could include power to the ULA, hence why it is may be malfunctioning.

Mark
Hi Mark

Just done a quick check from ground to pin 40 of the 6502, measures 4kohms

Mark

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Re: Dead Elk, any ideas?.

Post by CMcDougall » Sun May 03, 2020 8:41 pm

did it get struck with lighting?? or did you pull anything out the Plus1 two cart slots while it was using them, or drop it off the side of a table???

had lots of elks in different states / faults, always got some screen garbage , then fixed them.

have you tried both RGB & AV out to TV :?
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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Mon May 04, 2020 7:18 am

mark71 wrote:
Sun May 03, 2020 7:14 pm
Done some more testing today, to say there is no video is techniclly true, however when power is applied with the RGB cable in the monitor detects some sort of power and switches to the right Channel but displays nothing/black

Power to PCB -5.095V and +5.135V
as to measurements 6502 between pin 1-8 5.1v between 8-21 5.1v

Dram chips reading -5.1v

All other IC's except the bottom left IC reading +5.1v

Bottom left IC looking from above LM something -0.007v

Also to note whilst trying this swapped the keyboards from a known working Elk and same thing no life.

Also to note the ULA was getting warm, so power is getting in there not sure if it's fried or not.....
Ah! Yes . . . The LM324 - that's a quad op-amp for the Cassette curcuit. you need to measure between pins 11 & 4 for that one.

It would be useful to know which issue board you have so I can be on same 'page' as yourself. Download the service manual from here and then try following the Diagnostic flowchart on page 15 - There is an issue 3 manual but let's start with this one.

More later - Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
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Re: Dead Elk, any ideas?.

Post by mr-macrisc » Mon May 04, 2020 7:31 am

Issue 4 :)

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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Mon May 04, 2020 7:58 am

mr-macrisc wrote:
Mon May 04, 2020 7:31 am
Issue 4 :)
That's good, as that's the one I have open on my bench . . .

Dave H :D
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Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
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Re: Dead Elk, any ideas?.

Post by 1024MAK » Mon May 04, 2020 8:14 am

daveejhitchins wrote:
Mon May 04, 2020 7:58 am
mr-macrisc wrote:
Mon May 04, 2020 7:31 am
Issue 4 :)
That's good, as that's the one I have open on my bench . . .

Dave H :D
But Dave, I would expect you to have an example of all the various issue Elks open in your operating theater, err, I mean on your work bench :mrgreen:

Mark

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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Mon May 04, 2020 11:09 am

1024MAK wrote:
Mon May 04, 2020 8:14 am
But Dave, I would expect you to have an example of all the various issue Elks open in your operating theater, err, I mean on your work bench :mrgreen:
Mark
I do 8) It's just coincidence that I pulled the correct issue out of the cupboard first . . .

Dave H :D
Parts: UM6502CE, GAL22V10D, GAL16V8D, AS6C62256A, TC514400AZ, WD1772, R6522, TMS27C512, AT28C256
Products: ARA II, ARA III, ABR, ATI, AP6, MGC, AP5 . . .
For a price list, contact me at: Retro Hardware AT dave ej hitchins DOT plus DOT com

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Re: Dead Elk, any ideas?.

Post by mark71 » Mon May 04, 2020 9:19 pm

CMcDougall wrote:
Sun May 03, 2020 8:41 pm
did it get struck with lighting?? or did you pull anything out the Plus1 two cart slots while it was using them, or drop it off the side of a table???

had lots of elks in different states / faults, always got some screen garbage , then fixed them.

have you tried both RGB & AV out to TV :?
Well thinking back and coming up with a time line and possible theory why it stopped working, I was experimenting with a Gotek Drive using a Slogger 400 DFS cartridge in a Plus 1 with a external USB power to run the Gotek drive, Apple iPhone power adaptor, all was going well, switched off the Electron, then the Gotek drive. Disconnected the slogger 400 cartridge from the Plus one and powered up the Electron and nothing.

So theory 1 the Gotek through the FDC cable sent some power to the ULA and fried it. Or theory 2 using the Elk for a period the ULA was getting hot and died from the heat. Plus 1 working fine still.

So to the original issue I’m thinking that the ULA is fried, but cannot prove that yet, only tried in RGB will give TV/AV a go to see if there is any output.

Mark

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Re: Dead Elk, any ideas?.

Post by daveejhitchins » Mon May 04, 2020 10:50 pm

Mark . . .

Another quick Voltage measurement. If you look at the schematic you'll find 2 x 24 Ohm resistors above the ULA (R5 & R58). On the Electron PCB these are the 2 large resistors - one either side of the ULA. Please measure the Voltage ACROSS each resistor. This will let us know what Current the ULA is drawing.

I measure ~2.7V across each which equates to around 113mA through each resistor. Oh! and the ULAs do run 'warm'!

Dave H :D
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Re: Dead Elk, any ideas?.

Post by CMcDougall » Tue May 05, 2020 5:20 pm

I feed my drives also with external power, a 1amp mobile 5v phone charger.
There is no power going to the FDC ribbon cable, so defo not that.

must be ULA fried :?
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Re: Dead Elk, any ideas?.

Post by mark71 » Sun May 24, 2020 10:07 am

Hi All

On further investigation with a different monitor/tv am getting the above pink colour distortion, also when switching off am now hearing the cassette motor relay click, so guessing that as others concluded the ULA is dead.
IMG_6010.jpg
Also with another Elk just aquired via ebay a similar thing but with a more observable pink colour output indicating again that the ULA on this one is fried too?, both are issue 4 boards.
IMG_6011.jpg
Seems to me on a very small sample that Issue 4 ULA's have a potential failure mode?, i see for the future keeping these working needs idealy a drop in replacement for the ULA like on the Speccy''s and ZX81's easy to say but complex to do. I have seen the extrodinary work done on this board about using FGPA's as a drop in replacement work.

Mark

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Re: Dead Elk, any ideas?.

Post by 0xC0DE » Sun May 24, 2020 10:11 am

That's why I only buy UK issue 6 or German issue 1 Electrons with the black blob ULA. I have six of them and all working :mrgreen:
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Re: Dead Elk, any ideas?.

Post by sP1d3r » Sun May 24, 2020 10:21 am

:^o Hi
I get the same screen as the one that you've posted, but it's only when I put my Slogger Pegasus into my Plus 1.
I was wondering what issue pcb you have in yours, an Issue A by any chance?
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WP_20200224_001.jpg

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Re: Dead Elk, any ideas?.

Post by davidb » Sun May 24, 2020 12:02 pm

Having experienced problems at boot up when my cartridge experiments don't respond to the bus correctly, maybe it's just the case that the edge connector on the Pegasus cartridge needs cleaning. Something to try, perhaps. :)

Edit: Fixed typo.

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Re: Dead Elk, any ideas?.

Post by sP1d3r » Sun May 24, 2020 1:39 pm

davidb wrote:
Sun May 24, 2020 12:02 pm
Having experienced problems at boot up when my cartridge experiments don't respond to the bus correctly, maybe it's just the case that the edge connector on the Pegasus cartridge needs cleaning. Something to try, perhaps. :)

Edit: Fixed typo.
That's interesting, the edge connector on the Pegasus cartridge is clean but as the issue A PCBs that I've seen differ somewhat from each other I think that the arrangement and value of the capacitors on the PCB may be relevant to the particular display.

I've bought the two PCBs in the middle of the picture from Dave H and as I haven't yet got either working, I don't know what works.
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C__Data_Users_DefApps_AppData_INTERNETEXPLORER_Temp_Saved Images_Slogger_Pegasus400_Prototypes-Front.JPG
Slogger Pegasus iss. A PCBs

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