[T3] My Brain looks fine...

Jim Adney jadney at vwtype3.org
Fri Oct 23 09:38:43 PDT 2020

On 22 Oct 2020 at 20:30, Keith Park wrote:

> the thing that does worry me is that there are electrolytic capacitors in
> there that are nearly 50 years old now, yea, there Wima

I think those capacitors are very high quality film caps. They should be good. 
I've never seen a bad one. I have 2 of them sitting on one side of my bench. 
One is WIMA and one is ERD (or ERO.) They are 6.8 uF/100 V and 5.8 
uF/100 V. They measure well above those values on my cheap meter.

Fortunately, I don't think Bosch used ANY electrolytic caps in these 
assemblies. All the parts in there look to be chosen to last forever. The only 
part I've seen that was poorly chosen was the red paper fiber spacer that 
was used for a couple years under the fuel pump relay driver transistor. That 
tended to absorb moisture and corrode the transistor leads. I have plastic 
replacements that should be MUCH better.   

Bosch went to the red fiber spacer when they added the heat sink fins in the 
C or D brains. Prior to that, this transistor got the same tall plastic spacer 
that all the other transistors got, but the heat sink created overhead 
clearance problems, so Bosch needed to bring that transistor down closer to 
the board. They choose poorly, at least at first. They may have changed to 
plastic later.  

Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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