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Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 8:35 am
by McKlaud
moordean, good advise about soldering SMD components. PersonallyI found that soldering any 1206, 805 or even 603 packages is not difficult with a tip 0.8mm dia. At first I clean the PCB with IPA, then apply a bit of good quality flux on the pads and finally solder with a small portion of solder on the tip. An ESD teasers are very helpful. When all SMD components are in their places I do final cleaning any residue of flux from the board.

I would not agree that the soldering the adapter to the ZX81 board directly is the solution. In my opinion any modification should reversible as far as practically possible. I don't like any mods that require traces cutting, drilling additional holes, and so on. I've repaired a few boards (mainly ZX Spectrums) where someone solder "add-on" directly to the board. In most of the cases there was a bad joint, broken traces or very badly overheated board with lifted/broken traces.

Coming back to your adapter, could you use all components in SMD packages including both capacitors in next revision of the board? MLCC 4.7uF/10V is available in 805 size. In KiCAD you can also find components' footprint for hand soldering. Pads are longer and they are really handy. Yes, they require more space on the PCB but it is not the case on your board.

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 9:26 am
by Paul
McKlaud wrote:
Fri Dec 22, 2017 8:35 am
I would not agree that the soldering the adapter to the ZX81 board directly is the solution. In my opinion any modification should reversible as far as practically possible. I don't like any mods that require traces cutting, drilling additional holes, and so on. I've repaired a few boards (mainly ZX Spectrums) where someone solder "add-on" directly to the board. In most of the cases there was a bad joint, broken traces or very badly overheated board with lifted/broken traces.
Once you insert anything not equal to the shape of the standard ROM pin into a SinclairZX socket a normal ICs pin will not make reliable contact again. So plugging in the Adapter is irreversible :!:

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 9:39 am
by McKlaud
Come on, round pin header are perfectly fine with most of the IC sockets.

Image

I know that IC sockets that Sinclair used in 80-ties are cr... (not decent), but you can replace them very easy with a modern and good quality ones in less than 10 min.

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 12:02 pm
by Paul
If you are happy with desoldering the socket you can desolder the Adapter as well :mrgreen:

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 12:47 pm
by 1024MAK
The least destructive thing to push into an existing socket (apart from a real IC) is a stamped pin socket:
Stamped pin DIL socket (bottom)
Stamped pin DIL socket (bottom)
IMG_5906.JPG (31.11 KiB) Viewed 1640 times
Stamped pin DIL socket (top)
Stamped pin DIL socket (top)
IMG_5905.JPG (35.42 KiB) Viewed 1640 times
So if there is sufficient height available, use an inexpensive stamped pin socket in-between the adapter and the original PCB socket.

If height is a problem, then some creative thinking is required :mrgreen:

Mark

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 12:51 pm
by Paul
Yes Mark
You are absolutely right.
It's a solution to the problem which I wasn't aware of (the problem, not the solution :ugeek:)
Only way to have a reversible adaption.

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 1:06 pm
by Andy Rea
Flip pins are an alternative but not very cheap.

http://oshchip.org/products/Flip-Pins_Product

Regards Andy

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 1:22 pm
by McKlaud
Andy, thanks for this info. They are an interesting option, but pricey, very pricey, over $35 for set of 12 units with the delivery to the UK.

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 1:49 pm
by PokeMon
You can buy single pieces on spark fun for 1.50 per 14 pin, so 3.00 for a dip28 socket. Not know how much shipment will be charged but it could be send in an envelope.

https://www.sparkfun.com/products/14086

Re: Yet another ROM adapter

Posted: Fri Dec 22, 2017 2:10 pm
by Paul
What about buying a cheap IC, cracked up und pins reused?
To be honest I prefer to desolder the socket and solder the adapter directly to the PCB. :geek: