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Date:         Tue, 4 Sep 2007 18:21:07 -0700
Reply-To:     jon <jon@KENNEKE.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         jon <jon@KENNEKE.COM>
Subject:      Re: It's time to hit that idle Stabilizer on the head!!!
Comments: To: "T.M." <tinkerman007@YAHOO.COM>
In-Reply-To:  <vanagon%2007090420234796@GERRY.VANAGON.COM>
Content-Type: TEXT/PLAIN; charset=US-ASCII

For some reason, I thought you were part of the original ISCU discussion (and knew about the web site). Oooops. Here is the site for folks that are just tuning in:

http://kenneke.com/vwfi/

I've not made any great progress in the ISCU reverse engineering. When I get back to it, I'm going to finish my research, which basically involves putting a 'scope on the output and inputs. From that data, digital implementations could be developed.

That would leave the valve itself as the weak link. But, with a modern control system, it could be protected from being fried. That might go quite a long way in solving the problem.

I've not seen the C model, so that's quite interesting.

My VW project now is to come up with an AFM "upgrade" that doesn't cost an arm and a leg. I'll probably get back to that as the cold weather sets in.

As always, I'm always happy to post pics, data, etc to the VW FI project web site. Send what you got in!! (Meaning email to me, I don't have any spoffier way to accomplish that at the moment)

Jon

On Tue, 4 Sep 2007, T.M. wrote:

> Wow, I'm honored! > While searching the list for BD438, I came across some very interesting > posts by the two Jo(h)ns responding to this/my thread, and see that you > and others have made great progress already. Your website (KENNEKE.COM) is > awsome! Why didn't you hint you have such a nice website?... > Looking at your ISCU page I see that our units are quite different (I have > a 251 907 393C, while you have a 'B' model). My unit has two BD438 > transistors connected to each other, while yours has only one as far as I > could see. Otherwise, the design looks quite similar with three LM2902 and > one LM2903. You mentioned analog V->F converters, I said integrator > circuits, basically they're the same thing, right? > > And I saw your posts planning to reverse engineer the ISCU... > Well, I've done part of it by now, mostly the power supply circuits and > the output driver, but it's not complete yet. And I see there's no point > comparing voltages between two different designs (B & C). > > I think it would be best that we post our pictures (with annotations and > test points marked) on the web somewhere, so people could add their > measurements too. I don't think we even need to reverse engineer the thing > completely - several crucial test points could provide most of the info we > need. > > And now to your post - > > On Tue, 4 Sep 2007 15:58:38 -0700, jon <jon@KENNEKE.COM> wrote: > > >Very interesting. I've never seen an ISCU with any other failure than the > >high current transistors. I have seen a rare case where the diode check > >came out good...on a bad transistor. > > Yup, I was thinking of that possibility...I probably hurried a bit in > soldering them back in because I didn't have a spare and hoped to find the > problem elsewere, but no problem taking them out again with my superquick > technique... > > >Also, with electronic items of that age, check out the electrolytic > >capacitors (or, simply replace them all...sometimes that is just as easy). > > Not so easy with mine, because it was completely dipped in/covered with > laquer before being put in it's box, to seal it against the elements. > Heck, it's tough touching the PCB and getting a connection at all!...:-) >


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