Would you pay $100 for 8MB RAM?

[orcish75]

Hmm, clearly I'm struggling with the uploads, I can see the pics fine if I'm logged into amiga.org, but won't display if I'm not logged in.

I created a new album in my user CP, made sure it was set to "public", uploaded the pics and then used the URL for each pic shown at the bottom when I used the "insert image" icon.

I've done this on other forums but doesn't seem to work here.

What am I doing wrong? :huh:

[Ral-Clan]

Orcish 75,

THANK YOU FOR POSTING THOSE PICS

It's not only good to see that another Amiga user has already attempted to do what I am about to do, but your idea to use IC (DIP) sockets is genius! It will save me from buying perf board and pin headers!  I have a TON of old IC sockets on various scrap gear!

I can desolder the IC sockets with a desoldering pump.  I plan to use a hot air gun to desolder the SOJ RAM chips from the SIMMs. How did you desolder the RAM chips?

It looks like you bent the little curved-under legs outward to extend them to the DIP socket holes, is that right?

THANK YOU!

PS: My chips are SOJ like yours. I had been referring to them as SMD (Surface Mounted Device?) because because they were soldered straight to the SIMM board without through hole, but I guess my terminology was wrong.  I thought ZIPs were SOJ because of the little bend in the legs - but I am all "straightened" out now!

[jkonstan]

There is also a commercial adapter for SOJ DRAM (for 1Meg & 4 Meg DRAMs) to 20Pin DIP  
AK20D300-SOJ
http://www.accutekmicro.com/pdf/ProductPDF-470.pdf

[Ral-Clan]

There is also a commercial adapter for SOJ DRAM (for 1Meg & 4 Meg DRAMs) to 20Pin DIP  
AK20D300-SOJ
http://www.accutekmicro.com/pdf/ProductPDF-470.pdf

Thanks,

Yes, I had seen the commercial adapters. But for the cost of them (about $3) I might as well have gone with the original 20PIN DIP RAM chips I saw for sale at $3-4 each.

[orcish75]

Hi Ral-Clan,

It will save me from buying perf board and pin headers!

Yup, it'll make it a whole lot easier than using perf board and if you have a whole bunch of sockets in old gear, even better!

Ja, definitely use the heatgun to desolder the RAM chips. A hint with the desoldering pump, suck out as much solder as you can from each hole in the PCB, then use the heatgun to melt the small amounts of solder left in the PCB holes and then remove the IC socket/component. This'll make it a lot easier to remove the IC socket as well as prevent the IC socket legs from potentially breaking. It also prevents the through-hole plating and tracks from potentially being lifted or damaged. Just don't keep the heatgun on the board for too long otherwise it'll discolour and delaminate.

I've used this method lots of times, from removing the Agnus socket in my A500 to removing Zorro2/ISA edge connectors on my A2000 and it works very well.

For the RAM chips themselves, I first of all bent the legs straight where they bend underneath the chip. I then bent the outer legs to a near horizontal position. VERY important though, when you bend them to the near horizontal position, you also need to twist the leg by half a turn otherwise the leg will snap off where it meets the ceramic package. Hopefully you can see this in the second last picture of my post.

The inner legs can just be bent normally as they don't have to bend very far. You'll need to cut the inner legs a bit shorter so that the chip sits flat on the IC socket. The outer legs were just not long enough to reach that outer pins on the IC socket, so I soldered a short piece of wire-wrap wire to the leg of the RAM chip to reach the pin on the IC socket.

When you're ready to solder the RAM chip onto the IC socket, take a spare IC socket and solder it into a spare scrap PCB. Place the IC socket that you want to solder the RAM chip onto and place it into the IC socket that you've just soldered onto the scrap PCB. This'll stop the legs from moving when you solder the RAM chip onto the IC socket.

I suggest practicing  a couple of times with bending the legs of the RAM chips and soldering them onto the IC socket with some scrap components before doing the real deal. It's VERY time consuming, so a lot of patience is required.

PS: My chips are SOJ like yours. I had been referring to them as SMD  (Surface Mounted Device?) because because they were soldered straight to  the SIMM board without through hole, but I guess my terminology was  wrong.  I thought ZIPs were SOJ because of the little bend in the legs -  but I am all "straightened" out now!

Ha ha! Yup, it's easy to get caught up in in all the jargon, but I'm sure everyone knew what you meant.

Let us know how it goes, I'll help out whereever I can. :laugh1:

Cheers!

[Ral-Clan]

Thanks!  I will have to look at your pictures to see what you mean by "inner" and "outer" legs (I think I know what you mean).

I will post pictures with the results (hopefully good results)!

Great tip, about using a spare IC socket as a holder while soldering, by the way.

[Ral-Clan]

Okay, I got 2MB of the chips working now.

My soldering / adapter construction job looks hideous (those little legs are TINY), but they work and have passed five RAM test passes so far.

Initially I thought it wasn't going to work, as I got a yellow screen.  But testing showed there were lots of cold solder breaks (from the way I was pushing in the adapters - now corrected).

Unfortunately, I did not have the nice DIP sockets that Orcish used for his adapters.  Mine are the more common, cheaper kind and you cannot stick a blob of solder on the pin openings to solder the chip legs directly to.  So, I've had to stick short pieces of wire in each pin socket, then solder the chip legs to those.  Because of this, the chips are suspended above the DIP socket on stilts.  I'd be embarrassed to show anyone this, but here is a picture (click to enlarge).



Sorry about all the messy solder, but even with a fine tip soldering iron, the legs are so small it's like doing surgery with a meat cleaver.

Two MB done - and it took me about FOUR hours!  I'm getting better at it though.  Only six more MB to do.  So far one RAM chip ruined (broken leg) and one socket ruined (through my initial practicing).  I have extras, fortunately.

[orcish75]

Good stuff! Yup, it is time consuming but it works out MUCH cheaper than buying the DIP chips.

Glad you've got it working so far.

Cheers

[bbond007]

My soldering / adapter construction job looks hideous (those little legs are TINY), but they work and have passed five RAM test passes so far.

if that works and is stable after you are done, then I think it's a work of art

[Ral-Clan]

Up to 4MB RAM now (another four chips done and passed a RAM test).  This batch didn't pass the initial RAM test (no yellow screen though) and again it was a solder joint problem.

Going for the long stretch - I have to do a batch of 8 chips (another 4MB) to bring it up to the 8MB maximum.

My soldering job is getting much neater and I'm getting slightly quicker, but it should still take about 5-8 hours!

[Ral-Clan]

Setback: my desoldering iron burnt itself out.  I guess I left it on too long???  I didn't know you could leave something like this on too long - it was on all afternoon while I was working as I was constantly switching back and forth between the soldering iron and the desoldering iron.

So things are on hold 'til I can source a new one (I prefer the kind that heats up on its own).

[Ral-Clan]

I've ordered a new de-soldering iron (solder sucking iron) off of ebay, but it will take a few weeks for it to arrive.

However, I am able to continue working as I've found I can heat up the old de-soldering iron with a butane torch and use it that way for now.

I also ran out of sockets for 20-pin DIP IC's.  So I've had to switch to using 24-pin sockets.  This is not a problem because I will just leave part of the socket extending out beyond the RAM sockets on the Supra 500XP board.

The one good thing about these 24-pin sockets is that they are the higher quality, thick pin type that Orcish used on his RAM hack.  I must admit, this type of socket makes the job MUCH easier.  I can put a solder blob right into the little pin holes on the DIP socket and not have to use little wire "stilts" like I was before (except I still need four wire jumpers for the corner "outside" legs of the SOJ chips where they don't reach).  I wish I had had enough of these sockets to do the whole job!  Cuts assembly time down by half.

Here is a picture (Canadian penny is the same size as a US penny and a little larger than a Euro-cent).  PS: this is the last year we will have Canadian pennies (boo-hoo!) as the gov't has begun eliminating them from circulating currency.

(click picture to enlarge)

[yogisumo]

I paid about $800 cdn way back for a Commodore 8 meg expansion board with 2 megs of ram on it way back. For my A2000.
Paid $240 for 4 megs of ram for my 22mhz GVP accelerator when they were originally released.
Just for reference.

[Ral-Clan]

I paid about $800 cdn way back for a Commodore 8 meg expansion board with 2 megs of ram on it way back. For my A2000.
Paid $240 for 4 megs of ram for my 22mhz GVP accelerator when they were originally released.
Just for reference.

Yeah, I remember I paid (or maybe my parents paid) about a hundred bucks for the 16K RAM expander for my VIC-20 around 1982.  I also think I paid $95 for the A501 512K RAM expansion for my A500 back around 1988 - and that was the best price I could find at the time.

Almost nothing depreciates in value as fast as technology, eh?

The problem with the 1M x 4 DIPs that this Supra needs (to get a full 8MB) is their rarity.  That's what's keeping the value up compared to other chips of the era. Few devices seem to have used them in their DIP format back in the day. If you Google for them, the top 100 results are Amigans looking for these chips. So, unlike the more abundant 256K x 4 DIPS, they have increased in value (if you can even find a source to sell you them).

However, the SOJ version of the 1M x 4 chips seem to be much more common - almost all the old PC memory modules I have from the 486/Pentium days have them soldered on.  They are electrically identical/compatible, but the plastic "package" and arrangement of the pins is different, however.  So while you can probably get them for free, the hard part is that you have to manually unsolder them from the RAM modules and make (or buy) SOJ to DIP adapters.

[Ral-Clan]

The total 8MB has now been installed and has passed the first RAM test!

(click to enlarge)

 

WOW! That was a bit of an ordeal and a challenge! The trickiest part was tracking down bad connections. With the chips all soldered to the adapters, it made for a VERY tight fit for some, and a connection might come loose or a solder joint might break (not visible) if they squeezed against each other during insertion. Amongst the cheaper socket risers I had to contend with bent legs when a misalignment occurred during insertion.

Tracking these mis-connections down over 16 chips (times 20 solder points each) was a bit of a (masochistic) game. I've lost count of how many yellow RAM error screens or red Zorro card diagnostic error screens I've seen over the past three days!

Oh, in the first photo you may notice a layer of electrical tape in between each chip and its neighbour JUST IN CASE one of the connections touched another (the chip sockets on the Supra 500XP board abut each other with no room to spare).

Fortunately, all seems to be working now (knock on wood!).  The chips are snugly inserted into the Supra 500XP and have passed two cycles of RAM testing (I'm going to run them all afternoon on test mode tomorrow).

Sooo....8MB of 1Mx4 SOJs adapted to DIPs, totally from spare parts lying in my parts stash.  I came close to saying this project cost me nothing, but yesterday my de-soldering iron burnt out and I had to buy a new one for $30 - I don't know if I would count that toward the cost.  Even so, I'm still a little ahead.  A lot of labour though!  Was a fun exercise....now I can REST and the family will be shocked to see me again - I've been in my workshop so long!

PS: the pink dots (nail polish) on the chips just indicates to me which way they should be inserted - I was doing things by rote near the end - inserting and removing chips to diagnose problems - and so I was afraid I'd miss the tiny black orientation dimple on the chip if I didn't mark it more obviously.

[orcish75]

Excellent! Glad you got it working. Supreme hackery there! :lol: I love seeing success stories like these..