Electronic Tips And Tricks Pertaining To Amiga

[Loedown]

I see quite a few threads here that talk about intermittent faults, sometimes my Amiga does this and sometimes it does that, this thread is a look at reasons behind certain faults.


1. Loose contacts in IC sockets.

A very common fault but something that some people may not be aware of is that in really old hardware tarnishing can often be a factor in pins not making proper contact. Some of the very old synthesizers I repair, the IC legs are actually black! The easiest ways to fix the problem is to use a brass brush to gently clean the pins or if you have it Microscrub or incredibly fine sandpaper. Often also a reseating of the IC in the socket can help fix problems because it automatically clears through the tarnish by allowing the IC socket internal contacts to forge a new path, even if it's just a few microns from the old one on the legs. After you have finished cleaning the IC legs it's important to use something like a household toothbrush or paint brush to clear away any remaining debris before you put the chip back in.

2. Cleaning contacts.

The gold edge connectors on ram chips or the edge connectors on the various Amiga models pick up dust and grime over their lifetime, may people recommend using isopropyl alcohol. I would also recommend using Contact Cleaner and a toothbrush or similar. A pencil eraser is also a great way of cleaning up pins, simply run it along the edge connector and then use a brush afterwards to clean away debris.

3. Tin Whiskers / Dendrites.

Obscure phenomenon that to be fair I don't know much about apart from what I have read. Tin whiskers can form from components and knowing that Amiga boards would have been made using eutectic solder Sn 63 / Pb 37 solder or similar they will be prone to these. With the diameter of the whiskers I would suggest a stiff brush should be enough to dislodge them from the pins. Here's the trick though, making sure that the pieces do not for a short circuit over SMT pins in chips which can be very hard to spot. If you notice tin whiskers forming then I would advise removing the board from its housing and using a stiff brush with a vacuum cleaner nozzle close by to the area you are brushing, this will minimize the chances of the whiskers becoming lodged under a fine legged chip. I don't recommend using compressed air to blow the board because this generates static, the vacuum will as well but it would generate less.

4. Retainer Clips.

Ram sockets for SIMMs in particular have retainer clips at either end for a reason. It's very true that you may get away with having one clip broken and the ram still working but that doesn't mean it will always work. Mechanical vibration will slowly move components that are under tension, like ram chips and cause unusual faults that can cost hours of time in trying to find and repair. Replacement sockets aren't hard to find and anyone qualified can remove an old socket and fit a new one.

5. Heat

Heat causes all sorts of problems particularly in the accelerator cards available for the various Amiga models. Heatsinks are there for a reason as is thermal paste. The trick is to have good contact but not too much pressure, as that causes stress to be placed on the board which can crack SMT capacitors. If a fan solution can be applied then do it, if a fan system is already in place but not working although the board may work for a time you are placing extra stress on components which can lead to premature failure.

6. BGA

Ball Grid Array is a poorly thought out technology for my eyes. Read the forum here for failed PPC and the work of Stachu100. If you have a board that has BGA then try to not put any mechanical stress on it or move it around too much, also keep it well cooled.

7. Overclocking

Can be applied very carefully, but ultimately puts more stress on components due to running them beyond their recommended limits, for anyone familiar with an IC data sheet, you have Absolute Maximum Ratings and Recommended Ratings. Absolute maximum is where a component will theoretically still work but may prematurely fail and recommended ratings are what it should be run at. This is why some overclocked cards will work at 66Mhz and others may work at 70MHz or even 80MHz. But keep in mind, the faster you clock something the more heat it will generate and the more stress it will put on components which requires better cooling. Think of it like you are putting the chips more into the Absolute Maximum Rating range from the Recommended.

[pandy71]

Heat - When we need to remove heat we should to not forget about heat pipes (unknown in Amiga time, nowadays quite common especially for mobile PC computers - old notebooks however they should be quite modern) they can be bought for bargain on ebay or junkyard and they are very good source for dense, efficient cooling solutions especially for small Amiga computers.

[Loedown]

Originally Posted by pandy71

Heat - When we need to remove heat we should to not forget about heat pipes (unknown in Amiga time, nowadays quite common especially for mobile PC computers - old notebooks however they should be quite modern) they can be bought for bargain on ebay or junkyard and they are very good source for dense, efficient cooling solutions especially for small Amiga computers.

How would you attach a heat pipe solution to an Amiga chip where most of them are preformed and require screwing down to the chip?

[pandy71]

Adhesive tape? epoxy glue?

http://solutions.3m.com/wps/portal/3...rmalSolutions/

heatsink with heatpipe and fan should fit nicely
http://www.ebay.com/itm/gateway-NV55...item27ce210f4d

[Loedown]

Originally Posted by pandy71

Adhesive tape? epoxy glue?

http://solutions.3m.com/wps/portal/3...rmalSolutions/

heatsink with heatpipe and fan should fit nicely
http://www.ebay.com/itm/gateway-NV55...item27ce210f4d

Heat tape I agree with, epoxy glue absolutely not, as expansion and cooling would crack the die.

[tesla]

Loedown, you have some great tips. perhaps I can add a few things from my experience.

1st: The sockets in my experience, (500 and 2000) are terrible, and were a low-cost solution. I replaced all of them on my 3000T with a much higher quality, gold contact version, no-more problems. However, this solution is not for the beginner or faint of heart.

All of your cleaning methods will work, but often will need repeated applications.

Tin whiskers;

I have an old Hammond organ, circa 1961. It uses a Scanner to provide a vibrato or chorus. The problem with whiskers is common with these, and the explanation I've heard is that the tin-zinc plate they used didn't have enough lead in it.

The place I worked in recently used ROHS (lead-free) solder to meet Euro specs, and we suspected the ROHS solder was having whisker problems related to the lack of lead.

Hi guys,
This may be off beat but I have just got back on the amiga scene from the mid 90`s now I am older and wiser I have picked up a A1200 (Commodore not ESCOM, ROM 3.0 WB 3.0) I have been having major trouble with the CF HD setup, It simply did not get a HD LED blink at all and WB install no drive recognized I used 10 different CF cards all posted on this forum as good and working types no luck I tried 3 CFtoIDE converters 2x EBay 1 Amiga kit no luck. I was getting well pissed off when I trying using the unit in my old CRT tv in the loft with the RF modulator. The picture was really bad, I tuned the set and adjusted the tuner pot on the RF mod no luck, I decided to de solder the RF modulator and take a closer look, I noticed and second trim pot on the underside of the unit I was going to try adjusting that and soldering it back on but I decided to see if it would power up without it and display on composite, guess was it did and the CF HD worked!!!!!! I am think the RF unit must have been way off tune with some bad grounding issues to cause the problems with the IDE interface, or it could be some other related problem, any thoughts?