A500 oddities & upgrade suggestions

[JezC]

Hi,

I'll start with the excuse that I'm a total noob with Amigas - always been more focused on the ST and successors (due to my music/MIDI hobbies) but happy to embrace other 68k brothers as my advancing years bring some level of discernment ;)

Odd/unreliable boot issue
Anyway, as well as a couple of non-booting systems (A500+ with some battery damage, A500 which just doesn't play ball) I recently acquired a couple more A500 systems (at the Cyber Legends 2.0 event as it happens).

One of these boots OK pretty much all the time & has a 1/2 Meg memory upgrade in the trapdoor expansion slot. It sows a RED LED (top LED near the floppy drive but loads & plays games OK, which is as far as I've got due to the problems with another system noted below)

The other didn't boot, so I pulled out the expansion on that one & removed the evil VARTA on the RTC circuitry. It looks like there isn't any damage on the actual PCB, though the expansion connector might need some TLC.
This one is somewhat erratic with booting & it seems to be able to boot when there is a good connection between the back of the keyboard & the inner top metal screen. When it boots (keyboard resting directly on the top metal screen) then all appears to work fine but moving the keyboard off the screen & it puts on the upper green LED near the floppy & then does nothing.

Is this normal? Or does it indicate some other fault that I need to find & fix?

What upgrades
Second point is to ask what upgrades I should entertain for at least one of the A500s.
I have an external 3.5" floppy drive (not yet tested) and a Gotek ready to replace an internal drive (maybe?) to explore a wider range of the s/w available.
I also have a TF536 (currently programmed up to work with an ST but I have the programmer to covert it back to native Amiga mode).

I'm using an Amigakit VGA adaptor for video so I guess I'm after any recommendations for what upgrades to use & their relative pros & cons.

Any & all advice will be most welcome (even if it's to stick with the Atari's ;))

Thanks!

[stephen_usher]

Can the second one boot without the keyboard connected? It should be able to.

[JezC]

Can the second one boot without the keyboard connected? It should be able to.

I've not tried that...and didn't know it was an option!
I did say I was a total noob re Amigas :lol: :roll:

Will report back later today with the results!

Edit: Yes, boots fine without the keyboard - so is there possibly a fault with the keyboard or an intermittent fault somewhere else?

[JezC]

Can the second one boot without the keyboard connected? It should be able to.

...

Edit: Yes, boots fine without the keyboard - so is there possibly a fault with the keyboard or an intermittent fault somewhere else?

@stephen_usher Is there a good guide on the Amiga h/w that you can point me towards?
I've got a reasonable level of general h/w knowledge, just a bit rusty having been mostly on the s/w side of the fence for the last 20+ years so it's really finding out the common causes of Amigas behaving badly...

[rubber_jonnie]

Since it boots without the keyboard, and with the keyboard touching ground, it may be worth buzzing out the keyboard cable to see if any of the wires are broken.

Also, since you have another Amiga, have you tried to boot with the keyboard from the other machine connected? If it does, that might point at the keyboard rather than the machine, in which case I'd pull the keyboard apart and have a poke round.

If it is still problematic with the know ngood keyboard, then you're probably looking at an issue with the Amiga.

[JezC]

Since it boots without the keyboard, and with the keyboard touching ground, it may be worth buzzing out the keyboard cable to see if any of the wires are broken.

Good idea - I'll have to find some schematics/cable wiring details but they'll come in handy when I finally look at the other faulty Amigas...

Also, since you have another Amiga, have you tried to boot with the keyboard from the other machine connected? If it does, that might point at the keyboard rather than the machine, in which case I'd pull the keyboard apart and have a poke round.

If it is still problematic with the know ngood keyboard, then you're probably looking at an issue with the Amiga.

I've refrained form pulling the other Amiga to bits...but now that I have more confidence in the other Amiga (and what I need to do to disassemble them) then that is certainly a reasonable plan.

Now, I'll be back to the usual problems of insufficient time to spend on these hobbies... ;) :roll:

[rubber_jonnie]

Since it boots without the keyboard, and with the keyboard touching ground, it may be worth buzzing out the keyboard cable to see if any of the wires are broken.

Good idea - I'll have to find some schematics/cable wiring details but they'll come in handy when I finally look at the other faulty Amigas...

Also, since you have another Amiga, have you tried to boot with the keyboard from the other machine connected? If it does, that might point at the keyboard rather than the machine, in which case I'd pull the keyboard apart and have a poke round.

If it is still problematic with the know ngood keyboard, then you're probably looking at an issue with the Amiga.

I've refrained form pulling the other Amiga to bits...but now that I have more confidence in the other Amiga (and what I need to do to disassemble them) then that is certainly a reasonable plan.

Now, I'll be back to the usual problems of insufficient time to spend on these hobbies... ;) :roll:

Good luck :)

[JezC]

Good luck :)

Boots OK with the keyboard from the "working" A500 (well, had time at lunch to just disassemble the working A500 & move the keyboard across and try one boot with it)...

Later I'll try the suspect keyboard in the "working" system...

[Higgy]

A500s are pretty bullet proof.
Old style caps and just a few socketed chips that might need pulling out and pushing in again.
Red LED shows that it is an early A500, PCB Rev probably lower than Rev 6.

Amiga Test Kit is really useful:
https://github.com/keirf/Amiga-Stuff/releases

I wonder if your keyboard just has 'something' on the membrane causing multiple key presses being simulated causing the boot issue.
Just the other day on eBay there were a few Keyboard Controllers for sale. Membranes also easy to get.

For the 500+ with it's 2mb Chip Ram chip, then maybe a PiStorm or fit your TF card.
With the bogo A500 I would keep it oldskool. Just use the 512kb expansion and have internal Gotek.

Did you know with the VGA adaptor you will still need a 15khz compatible monitor. It just changes the wire pinout (some have a buffer circuit inside).
There are RGB-HDMI solutions using Pi Zeros.

[JezC]

A500s are pretty bullet proof.
Old style caps and just a few socketed chips that might need pulling out and pushing in again.
Red LED shows that it is an early A500, PCB Rev probably lower than Rev 6.

Amiga Test Kit is really useful:
https://github.com/keirf/Amiga-Stuff/releases

I wonder if your keyboard just has 'something' on the membrane causing multiple key presses being simulated causing the boot issue.
Just the other day on eBay there were a few Keyboard Controllers for sale. Membranes also easy to get.

For the 500+ with it's 2mb Chip Ram chip, then maybe a PiStorm or fit your TF card.
With the bogo A500 I would keep it oldskool. Just use the 512kb expansion and have internal Gotek.

Did you know with the VGA adaptor you will still need a 15khz compatible monitor. It just changes the wire pinout (some have a buffer circuit inside).
There are RGB-HDMI solutions using Pi Zeros.

Many thanks for the suggestions @Higgy.

I have a few 15kHz monitors (Benq BL702A, NEC 1970NXp and a Dell 27"that I can't get to at the moment) so have at least got that one covered (but always best to take the the 'ass' out of any assumption!)

I'll get hold of that Amiga Test Kit - I actually bought some Goteks and a Greaseweazle from Keir a couple of years back, so I can put one of those in one of the A500s - one has a working 1/2 Meg upgrade, the RAM upgrade board in the other one was killed by the Varta on the RTC circuit :cry:

I have some battery damage to rectify on the A500+ (happened before I owned it sadly) but then maybe the TF536 would find it's home (though I currently have it keeping an ST remake board gainfully employed ;))

Good thought re the keyboard - I think I have a spare keyboard PCB & membrane from another source, so I can try that as well.

The A500 with the 'problem' keyboard is a Rock Lobster, not yet checked the other one (which had the red power LED on the keyboard) but I'll prise off the top shielding to check tonight.

I'd better start putting together an order for the 'essentials' ready for any money left come January!

:thumbup: