Amiga 1000 Rejuvenator Recreation Project: The Finale

[m0c]

Insider A1000 on BBoAH

The Spirit board takes up to 48x 41256, making a total of 1.5MB fastram. The Rejuvenator requires either 8x 414256 (1MB chipram) or 4x 514400 (2MB chipram).

[A1-X1000]

@ m0c

Thanks for the clarification..so I dug up some old dram chips in he cave here but they are HYB514400BJ-70...quick search says they are 1M chips so can I use 2 of them instead of 4? I'm confused

update: also found some V53C408HK60 drams and these are 512kb each so 4 would give me 2MB so can I use these or do they have to be 514400 chips?

[m0c]

HYB = Siemens prefix
A single 514400 = 1Mbit x 4 bits wide
4x 514400 = 1Mbit x 16 bits wide
With 8 bits being 1 byte, 1Mbit x 16 bits equals 2MByte
For a 2MB Rejuv 4x 514400 is essential, as the Amiga has a 16 bit databus

I'm not familiar with the V53C408HK60, but it appears to be pin compatible with the 514400.

[A1-X1000]

@ m0c

ok great so I just have to desolder 4 514400 chips from that old dram I found then

also, just noticed the SOJ-to-DIP adpaters don't come with any pins so I guess I'll have to see if I have any spare sockets so I can cut pins off them and solder them onto the SOJ-to-DIP adpaters

[PRS]

Hi,

Although cutting off pins could work, but is a very messy solution. I would advise to get some male-male machined (rounded) headers. Like these.

I bought them from Aliexpress.

[A1-X1000]

Hi,

Although cutting off pins could work, but is a very messy solution. I would advise to get some male-male machined (rounded) headers. Like these.

I bought them from Aliexpress.

cool thanks for the time saving tip

[m0c]

I just finished building a second Rejuvenator and once again, it worked first time. I'm using this one in conjunction with a Parceiro II and the combo works a treat. Notice the 2MB 318069-18 Agnus, the 100nF VBB hack, the 514400 RAM chips on SOJ-to-DIP adapters, the hires Denise and particularly the missing Kickstart ROM. Quoting David Dunklee on using the Rejuvenator with the Parceiro: "Make sure the ROM jumper is OPEN... meaning, use the ROM. BUT... keep the ROM chip removed. This tells the Rejuv to NOT attempt to load from floppy. The ROM to be used will be the Parceiro's ROM."

Now stop procrastinating already and get the ol' soldering iron out!

[luvwagn]

the 100nF VBB hack

Can you point this out? Is it near the PAL/NTSC jumper location?

I have some linux-jedi style adapter boards that i'll solder in to use "standard VBB fat agnus, with 2MB DRAM on board" in the hopes of eliminating the SOJ adapter boards and RAM, and avoiding the hard-to-find 8372AB agnus chips (although I have one of these)

You seem to have the knack for building these, I've yet to start because I'm a slacker

[m0c]

Can you point this out? Is it near the PAL/NTSC jumper location?

[m0c]

You seem to have the knack for building these

Note of caution to anyone who is using IC sockets with machined round contacts, like me:

Don't rely too much on proper contact, even though the socket pins have a gold plated insert. Especially if you align your IC pins with a straightening tool.

So what's this all about? First of all, the straightening tool itself works great. As a matter of fact, it performs too well... It aligns the pins so perfectly straight that ICs can almost be "dropped" into their sockets and only remarkably low pressure suffices to get the IC fully seated. Smooth as a hot knife through butter. This has made me suspicious about the socket's internal tiny contact leaf quality. I was fiddling with a Rejuv last night, swapping some known good ICs back and forth when it suddenly stopped working. Only after firmly pressing down on one of the DIP chips, the Rejuv came back to life. This has led me to believe that the contact can be flawed when a perfectly straight IC pin is inserted right in the very center of the 4 contact leaves.

Admittedly, I am using fairly cheap sockets and I would imagine that the more expensive sockets from reputable manufacturers like Harwin, Mill-Max, Preci-dip etc. don't have any contact issues. Shape and diameter of the IC pins may be a factor too. All my 74-series ICs are from Texas Instruments and maybe their pins are thinner than others. Who knows.