Lardo buys another zeddy

[Paul]

I don't know what a 16K Rampacks value is.
Is it sensible to try and recap it?
If it's a modern one with only one PCB inside that's easy.
In case it's on two connected PCBs, once you try and bend it open to access the capacitors the connection between the two PCBs will most probably fail.
In that case the rework needed consumes quite some time and it's likely to be ugly.
It might be easier to replace the PCBs by a single static RAM PCB with 32k that's Hires capable and will cost quite little.
In addition the new expansionbus connector is much more reliable and will not give wobble problems the old connector always has .

[Paul]

You could also offer an upgrade to broken 16K RAMPacks this way.

[Lardo Boffin]

I don't know what a 16K Rampacks value is.
Is it sensible to try and recap it?
If it's a modern one with only one PCB inside that's easy.
In case it's on two connected PCBs, once you try and bend it open to access the capacitors the connection between the two PCBs will most probably fail.
In that case the rework needed consumes quite some time and it's likely to be ugly.
It might be easier to replace the PCBs by a single static RAM PCB with 32k that's Hires capable and will cost quite little.
In addition the new expansionbus connector is much more reliable and will not give wobble problems the old connector always has .

A working one is worth around £20 so not financially worth it but I would have kept it as it always useful to have a working one around. It is a double board type.

However I do like the idea of fitting a 32K hires capable RAM board.

Are there details of how to do this anywhere?

Thanks!

[Paul]

I'll PM you about this.

[Lardo Boffin]

I'll PM you about this.

Thanks!

[Lardo Boffin]

A not (yet) working issue three:

An extra cap underneath (and a suspicious amount of flux residue):

And socketed chips. I’m not sure if this is good or bad at this stage. Clearly someone has tried to fix this before…

[1024MAK]

That “extra” electrolytic capacitor is in the same place the third electrolytic capacitor as on this issue 3 board:

Issue 3 board with third electrolytic capacitor

It’s connected between the +9V (nominal) input supply and 0V/GND. It decouples this supply.

Some issue 3 boards have a ceramic capacitor here, others have an electrolytic capacitor. The most unusual thing is that it’s fitted to the underside. Maybe the person assembling the board thought it was a little too big to fit nicely on the component side.

With regards to the fault, it should not be too hard to diagnose, given that with the microprocessor, ULA and ROM being socketed it’s easy to swap them with a another working board. And the SRAM can be likely ruled out if you have a working external RAM pack. Then it’s just a poor solder joint, broken through-hole/track or maybe the resonator. Less likely is one of the transistors or passive components.

Mark

[Lardo Boffin]

Thanks as ever Mark.

I have swapped chips and got a K once with a known working set and RAM pack. I didn’t get a K when it was switched off and back on again but was a stable K for a couple of mins. So first thing will be to replace the caps I guess. Then start checking for dry joints etc.

I wonder if the cap was put underneath to keep it away from the hot regulator?

[Paul]

The other side isn't remarkable cooler

[Lardo Boffin]

Progress of sorts - I have replaced the caps and reflowed the sockets that have been added.

Rather than a black screen it now produces something like this:

It is clearly trying to do something now! Thats enough for tonight.