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Hi Steve,
Good idea collecting vintage Bosch test equipment.
I addition to the data presented here is what I found in the original Bosch books and papers.
Excerpt of Bosch coils used in early Porsches:
TK 12 A 10: prim. resistance 2-2,35 Ohm, spark length 11mm, voltage under load 14-16KV
TK 6 A 3: prim. resistance 1,2-1,4 Ohm, spark length 11mm, voltage under load 8-11KV
0 221 102 016: prim. resistance 3,2-3,9 Ohm, spark length 14mm, voltage under load 10-14KV
0 221 102 006: prim. resistance 2,0-2,35 Ohm, spark length 11mm, voltage under load 10-14KV/14-16KV
0 221 102 026: prim. resistance 1,7-2,1 Ohm, spark length 14mm, voltage under load 14-16KV
0 221 102 061: prim. resistance 1,7-2,1 Ohm, spark length 14mm, voltage under load 10-14KV
In the Bosch papers mostly part number 0 221 102 007 is listed, which is the order number for 0 221 102 006 coil plus the resistor 1 224 509 12. Bosch coil 0 221 102 026 was combined with the resistor 1 224 509 011 as mentioned above.
BR
Claudius
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I’m sure adding Bosch to the OP ss tested data will be helpful to folks in diagnosing ignition issues or testing old coils they buy.
How much as hobbyist I’ll use the vintage equipment is questionable but have pretty mich much entire set from the late sixties to early seventies catalogue ( or in some cases duplicates) — the blue box grey front Bosch series. While I’m sure professionals will have more kit and more modern it seemed like a nice thing to acquire the kit to keep as a package associated with the model 73 car. I don’t need the large Bosch volt and amp test box when a shirt pocket meter not bigger than a pen was to hand for a simple quick test. Who knows it might turn out to be handy to have it all as but even if not used much as relevant and neat to put a package together relevant and contemporary to model 73 911 if for space and inclination. Particularly if Bosch source not just actual tests.
My father was an electronics engineer and as a young kid his oscilloscope in the workshop at home or the ones when visited his workplace were just one the most fascinating things I’d ever seen. The main tool of his I kept ( couldn’t bear to ditch it when clearing family home) was his multimeter a hefty old thing now safely stored for nostalgia reasons but expect it would work and outlast me. It would be a handy weapon such is the heft but in my memories it was rarely out of his reach as he tinkered with some circuit. I do have his Radford amp and his speakers that he used to maintain fastidiously using such tools — old school British audio equipment from the genius Arthur Radford and his collaborator Mr Bailey that my dad settled on for sound quality eschewing later more modern equipment for the rest of his life. Much to the frustration of his pals who’d often show-up with the latest and greatest equipment just to leave disappointed after a back to back listening. Somewhat analogous to 73 RS not the last word in technology nor without fault but in the round often regarded as a high point and a delightful reference. Became quite collectable too with prices rising accordingly. Don’t have to be the loudest system ( or fastest car) to be preeminent but do have to be to specification. That’s why I have over the years lots of papers on that particular car (and the Radfords) because the devil is in the detail; the correct components and them conforming to spec ( Arthur’s famous transformers said to be hand wound by one woman worker to his exacting standards a contributor to the audio performance being one case in point). Mass produced ignition coil by Bosch not quite the same but nevertheless important to be performing to specification and due prominent position nice if period authentic and even stickers correct.
Steve
