Upgrading caps and resistors on game boards.

Finch

New member
Joined
Apr 27, 2006
Messages
104
Reaction score
0
Location
Santa Cruz, California
So I have a non-working Gorf that got a bit toasty in some places and blew one or two of those axial Kemet 15uf 20v caps. I found an ebay seller that sells the exact same caps, so I bought a pack, but how important is it to really replace stuff like caps and resistors with the exact same component?

I also have a G07 chassis with some fried components that aren't included in the standard cap kits and I was wondering, as long as they are the same value and rated the same it should be fine right?
 
General rules for component swapping/upgrades:

Caps- Replace with the same uF rating and the same or higher voltage. The uf rating is the function of the capacitor. The voltage is the point at which the cap begins to fail. Caps come in several varieties (electrolytic, mylar, ceramic, film, ect.). You must replace the cap with the same type unless there is already a history of someone who has successfully changed cap types (get well kits for Cinematronics monitors do this I think).

Resitors- Replace with the same resistance value and the same or greater wattage. Your danger here is that some resistors are "sacrificial" in that they are intended to fail to protect other components on the board. If you increase the wattage (similar to the failure rating on a cap) you may unintentionally disable this safety feature. On the other hand, resistors with a greater wattage rating dissipate heat better (resistance = heat and vice versa) so in some applications increasing wattage is desirable such as in the WG6100 "bulletproofing" kits.

ICs - Generally and exact match (by part number) is required. There are SOME instances where there is a different chip that is functionally the same that has other attributes that make it desirable but these instances are few and far between. In the case of memory chips there are boards out there (most famously Galaga) that are NOT tolerant of memory made by certain manufacturers.

Hope this helps.
 
CAP manufacturer brand does not matter. But type does as Mongo states. For board space, you really want to get the same type CAP with the same wire leads for installation. Either radial or axial, whatever you are taking out.

You can use a radial in place of an axial and vice versa if space allows, but you would probably have to solder longer leads to the CAP leads, and you really dont want to get into that. It looks bad too!
 
Last edited:
So I have a non-working Gorf that got a bit toasty in some places and blew one or two of those axial Kemet 15uf 20v caps. I found an ebay seller that sells the exact same caps, so I bought a pack, but how important is it to really replace stuff like caps and resistors with the exact same component?

I've seen those caps fail before too. In this particular case, the cap's value not critical. It's a filter cap. I usually just replace 'em with a 22uf electrolytic.

If you know the application of the cap, you can change it's value significantly. For example, these caps are simply filters - to reduce the noise in the DC supply on the board. Their ratings are not critical, so you can go up in value. Similarly, in power supply filter caps, you can go up in value if you want.

Another thing you run into, especially on black and white monitors, is that there are obsolete values. 200uf and 50uf are no longer commonly manufactured - they're not part of the modern standard series of capacitor values. In this case, simply round to the nearest common value, such as 220uf or 47uf. You could even go up to 68uf. And electrolytic capacitors, at *best*, have a tolerance of +/- 10% (at least, the old ones used in video games do - I'm sure better parts exist somewhere), so they're not even exact in the first place. A capacitor marked 200uf could be really 180uf, or 220uf when new.

For bulk filters in linear power supplies, such as the Atari power bricks, and the MCR game power bricks, Williams power supplies, Midway regulator boards (Galaga, Gorf, Super Pac, etc), you can fudge the value even more, as much as 50% higher than it started as. Don't go down - the thing needs a certain amount of filtering. But going up in value here won't hurt anything.

But... if you don't understand what the cap is used for - stick to the same value, or as close as possible on obsolete values. You can always use a higher voltage rating though - provided the higher rated part fits in the space.

-Ian
 
Thanks to both of you, that was exactly what I was looking for.

Makes me feel justified in tracking down exact replacement caps for my gorf :-D
 
Rule of thumb for filter caps, use the same order of magnitude for replacement. ie. you can use 22uF in place of 10uF or vice versa (in most cases). Don't use a 10uF cap in place of a 100uF cap. Voltage rules apply.
 
Those caps are notorious for burning up on these boards. I have also seen many times where they are dead shorted but look fine. The ram cards seem to have the most problem with them.
I have used electrolytics in place of them but I usually pull one off a donor board.
 
Those caps are notorious for burning up on these boards. I have also seen many times where they are dead shorted but look fine. The ram cards seem to have the most problem with them.
I have used electrolytics in place of them but I usually pull one off a donor board.

Yea, a few of mine look burnt out but test fine, and others look find but test dead, so I'm going to replace the lot of them as none of them tested at 15uf or even within the tolerance.

Luckily they are all the same cap, so I bought a 25 pack of them off ebay.
 
Back
Top Bottom