History of Bosch CDI ... toubleshooting info, parts list changes, and schematics ...

[petro206]

Perfect, I tested my SCR and the result is positive.
First I switched S2 and after I pushed S1, and the lamp stays on ( 3 watt + 3 watt)

WP 20141110 21 27 01 Pro - YouTube

Now, who is the guilty?

[petro206]

Does anyone know what to do?

[wout]

Hello all

Thanks for this very useful topic!!!

Can someone help me out with an OT104 thyristor? We found out that's the part that got broken in the CDI but can't find a new one and don't know if it could be replaced by some other part that have similar function?

Any help would be very appreciated!!!

Thanks!

Wout
almost desperate to get my '74 chocolate brown rolling

[jmchrist]

The best replacement for this thyristor i have found in Europe is the BTW30-800 from STMicroelectronics. It has the same package (TO-48) and is specified with a Tq max of 12 µs.

The replacement by a International Rectifier 50RIA80 or similar which is not specified with a Tq max is at risk of blocking when operating at high temperature.

[wout]

Thanks!!!!

gr
Wout

[0396]

Excellent information. Thanks!

[911GT2]

Very good thread!, subsd.

[1-ev.com]

There are should be US version of the BTW30-800 replacement...

[jmchrist]

The electrically equivalent thyristors I found with a 2Nxxxx number are not using a TO48 case.
The 2N692A Which in available worldwide is not specified with a Toff max.
It is specified with a Toff typical (not max) of 15 µs by only one US manufacturer : Central Semiconductors Corp, Hauppauge NY.

[wout]

Originally Posted by jmchrist

The electrically equivalent thyristors I found with a 2Nxxxx number are not using a TO48 case.
The 2N692A Which in available worldwide is not specified with a Toff max.
It is specified with a Toff typical (not max) of 15 µs by only one US manufacturer : Central Semiconductors Corp, Hauppauge NY.

Hi jmchrist

Have you received my pm?

Thanks for the information!!!

gr
Wout

[Wolf82]

Thanks for these useful info!
Does anybody know what transformer is used in this circuit (windings,...) and/or where I can get that part?

Thanks

[Wolf82]

Thanks for these useful info!
Does anybody know what transformer is used in this circuit (windings,...) and/or where I can get that part?

Thanks

[ppge]

does anyone have more info about this bosch unit?

[scarceller]

This may help:
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Originally Posted by ppge

does anyone have more info about this bosch unit?

[ischmitz]

I could be wrong but this is essentially very similar to the ignition transistor output stage found in an early Bosch DME.

The box gets triggered by the distributor and replaces the classic points. It charges the primary of the coil. Think of it as transistorized Kettering setup.

Ingo

[Trackrash]

Can a similar test be performed on the 6 pin CDI?

Originally Posted by Early_S_Man

This is the board layout/picture for the 1972 CDI unit ... it corresponds to the fig. 17 layout in the test document:



Here is the early schematic for 1969 - 1972 CDI units ... Please note that the test point labels in the test document do NOT correctly correspond to all of the labels in this version of the schematic [TP #1 and TP#2 are OK for scope tests, but to short main capacitor -- TP#4 & TP#4a are used ] ... based on an estimated 1974/75 revision:



Here is an annotated picture/layout for an early 1972 CDI unit corresponding to fig. 16 in the test document.



Here is the revised parts list showing R4 and 33 Ohm 5 Watt version of R3:

[dicklague]

You can duplicate the test and use a square wave generator for the distributor I have done it on the bench many times.

[Trackrash]

Can I manually turn the distributor, since it is off the car?

I have a rebuilt SC motor, with unknown history, which will go in to my '71. I hope to verify the SC's CDI operation before I build a custom harness.

Thanks.

[ischmitz]

You can trigger the 6-pin by hand with the distributor or even with an AA battery but ideally you run the box over night at high RPM to ensure it'll not shut down when it gets hot. When I test boxes some fail only after 6h - 8h and you'd never catch that with a quick test. Alternatively you'd have to put the box into an oven heated to ~150 degF to simulate engine bay conditions.

That's why some sort of automated trigger (e.g. signal generator or your drill connected to the distributor) is preferred.

[ischmitz]

See here for a simple triggering device for 3-pin and 6-pin boxes 6 pin CDI problem under temp.