Just a nitpick that I want to clear up for others who may be reading. I'm sure you're well aware and that it was just a mis-type.

The factory used aluminum electrolytic caps. Eventually the electrolyte evaporates out or the cap leaks, just like the leaky batteries in your flashlight. Had the factory used tantalums, the caps would have outlasted the rest of the car.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Thanks for the info all!

I realize JamesDean is probably the way to go, but as my amp is already broken, I haven't much to lose by attempting a repair.

Electronic component reliability has come a very long way. Even that cheap capacitor package indicated by a poster of this thread should be just fine. Just remember those capacitors are polarized.

I always found German and general European electronic design and fabrication different. From both American and oriental sources. I actually did not really like working on some of their products years ago. I wonder even if the giant Phillps electronic manufacturing still even exists today.

They build such problematic stuff they tried desperately to bribe guys like me in north America to work on their televisions. I think Phillips produced perhaps the most problematic color televisons in history. I actually felt sorry for their customers.

One further question (just scored a grab bag of capacitors).
Is there a minimum/maximum guideline when it comes to the voltage rating?

For example, when I did the clock caps, I read people using 100Uf anywhere from 16v to 50v... I settled on 35v.

The bag I grabbed contains about 12 each of:

50V1UF
50V2.2UF
50V3.3UF
50V4.7UF
50V10UF
25V22UF
25V33UF
25V47UF
16V100UF
16V220UF
16V330UF
16V470UF

Am I covered?

You should be fine.

Thanks Barry.

General rule is that caps should be rated for 2x the working voltage, and higher than that is perfectly fine.

Finally got the thing out... removed the varnish, identified a few problem joints, and now it's time to identify some of the board.

There are only two parts I've identified as capacitors (not even entirely confident), and two that are probably resistors. I've photographed them and annotated their "values" below. What do these numbers correspond to? Any capacitors I haven't recognized?

The smaller square pink chips are also contenders. They read:
+1.5 25V
+1.5 25V
+2.2 20V
+2.2 20V
+4.7 10V



Photo:



http://postimg.org/image/v4pd6w2j9/

you want to replace the electrolytic caps only. the two numbers are microfarads (capacitance) and rated voltage (potential). a cap rated for a higher voltage is fine, and there is a fudge factor even in the capacitance, but those sizes won't be hard to find. make sure you match radial and axial leads or it will be hard to install, and observe the polarity before removing each one.

i guess the 47/16 FRAKO are 47 uF and 16V. there is a black axial cap in the lower left corner. the two long grey ones you marked are resistors. there is one more metallic cylinder to the right on the top edge which may also be a cap - look for markings.

good luck!

a similar conversation on the porsche board

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'77 240D, 504H, OM617.952, etc.

Thanks!

Polarity I understand, as well as the voltage/fudge factor (read it's around 20%).
I've just read that the polarized caps are the main culprits as opposed to the pink guys, which from what I understand are a solid, non polarized material.
Well, it seems this amp has only a few polarized caps at most.

Only replace the 47uF capacitors.

Make sure you re-solder all of the rectangular green and pink capacitors. Cracks in the solder connections are the main source of problems. There is no need to remove the old solder, just add fresh electronic grade. It is not sufficient to just reflow the solder connections.

Be very careful of static. There are some very static sensitive devices on that board especially that FET in the lower left corner. The axial capacitor in the bottom left corner is not an electrolytic and does not need to be replaced.

The small pink capacitors that you listed are tantalum. There are varied opinions as to their reliability. They don't however dry out like electrolytics. Make sure they are re-soldered if not changed. I would personally not change them.

Based on what I've seen in 1980s computers that's not the case. Electrolytics might stop working, but tantalums short out and damage other parts.

-J

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1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

great additional details from Rick76. i have never seen those boxy caps before and could not decipher the markings they bear. is the axial one (Shern, that means the leads form an axle) tantalum too?

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'77 240D, 504H, OM617.952, etc.

The axial cap in the left bottom corner is polypropylene (MKP), 0.1uF 100 volt.
Later cruise amps (with the electric actuator) had axial caps that were electrolytic. 10uF or 2.2uF 63 volts I believe depending on the version.

Thanks for the tips all.
I replaced the caps, resoldered nearly half the board (I did enjoy it), but no dice... It's entirely possible I didn't fix the amp. It's also possible the issue is elsewhere.. so elsewhere I go! Thinking there's an actuator somewhere and probably something under the hood.