924Board.org

[72rallye]

Gut beobachtet! I don't know what happened. Maybe I made a typo, maybe it was one of those transistors that are simply labeled "C328", and one has to guess if it means BC328 (pnp) or 2SC328 (npn).
In my view the circuit needs an npn transistor to work properly. I am going to check the PCB again, and then update the drawing. Unfortunately, I won't have access to the relay for many weeks, so it'll take a while.

There is another issue with the Zener diode Z2. It was labeled "200", but I couldn't determine the model number. It is unlikely that the breakdown voltage is 200V, since the ignition coil probably cannot generate such a high voltage when the current shuts off. A voltage of 20.0V would be very reasonable.

Thomas
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81 931, 86 951, 86 928 5spd, 75 911S coupe

[Raize]

Whoever can remanufacture the fuel pump relay will be rich!

Well, by 924 standards.

[Siegfrieds]

Ok, thanks for your correction.

Striking rich is only possible with high numbers of products.
Who needs a relay ?

for the 924 as of 1975-1978 ?
fir the 934 as of 1979 - ?
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SiegfriedS
1976 924

[72rallye]

>>>>>BC 328 is a pnp relais, the circuit shows BC328 as a npn one. Mistake…probablyanother BC 327 .

There is nothing wrong with the circuit diagram. The npn transistor in the diagram is labeled BC238B, and NOT BC328.

I checked the Zener diode Z2 again. The two relays that I own have different components in it. One has an ITT ZY100 diode, and the other a ZY200. The listed corresponding breakdown voltages are 100V and 200V. This seems very high to me, but so be it. I verified that the breakdown voltage is definitely larger than 30V, which is how high my test setup went.

Btw, the second relay has a BC548B installed, not a BC238B. Not a problem, since they are only being used as a switch, and not as an analog device.

Thomas
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81 931, 86 951, 86 928 5spd, 75 911S coupe

[Siegfrieds]

Ok, understood, thank you!
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SiegfriedS
1976 924