Zel's Fleet Blog - BX, Jag XJ-S, Sinclair C5, Mercedes 208D & 230TE, AC Model 70.

[Zelandeth]

Yeah, if it's just the A/C compressor I'll re-route the belt. Imagine it's a compressor out job to change the bearing isn't it? In which case it will need to be re-routed on a temporary basis so I can take it to get the refrigerant recovered.

Interesting to see that new compressors are around the £175 mark, given the time saved (in theory) by just dropping a new one in, and the fact that I have no idea how much life there is left in this one, almost seems like just changing the compressor as a unit might be sensible. Will have a think about it. Anyone know what the average life of these compressors usually is?

While I'm getting bits though, definitely going to pick up a seal kit for the hydraulic pump in the hope that will stop the thing weeping LHM as it's done since I got the car which I am well aware can't be doing the alternator any favours. If memory serves there is a kit with a full compliment of O-rings for the pump isn't there?

[CitroJim]

Yes, with an A/C compressor at that price Zel, it does make sense...

Not sure on a seal kit. I've always bought mine separately...

[Zelandeth]

Hoping that things will quiet down a bit in the next couple of weeks so I'll be able to actually look into things properly regarding seals and such and get myself a shopping list together. If I'm getting the A/C evacuated anyway, it may well make sense to take the opportunity to pull the front of the car apart to sort the fan wiring properly etc, rust proof the bits you can't get at with the bumper on etc. ...Possibly throw the bumper at a body shop and see what they'd charge to paint it as well given the number of scuffs on it and that pretty much the entire left side is sans clearcoat.

Further to my mentioned project a couple of days ago, here are some photos of the instrument panel I'm looking to hack into a PC status display.

Anyone remember these?



The complexity and overall density inside the thing I have to admit was a bit of a surprise!



The fuel/temp gauge unit is a four board construction that pretty much entirely fills that metal can, which is about 1 1/2" thick.



Interesting that it's set up so that the fuel gauge switches to a higher resolution scale below 1/4 a tank...That's actually quite a clever idea I think!

Have successfully had the clock working...sadly it apparently doesn't have a common power supply with everything else as it didn't all spring to life. Really wish I could find *any* documentation on the thing, as a pin-out diagram would make this a walk in the park! Reverse engineering is the order of the day though, especially as virtually none of the connectors etc seem to be labelled.

[CitroJim]

Gosh, that's a heck of a panel Zel Interesting it resorts to good old-fashioned mechanical Veeder counters for the trip and odometer. I guess the panel pre-dates cheap NV RAM...

Someone somewhere must have the information you need...

[Zelandeth]

Well I got a spare hour or so this evening to poke around with the silly dash project again.

I can definitely state now that this is one of the most downright *annoying* pieces of electronic design I've ever worked on. To be honest, that's probably largely down to the fact that component placement was predominantly dictated by the available space which is bound to result in some slightly odd board design. The single biggest grumble though: Absolutely *nothing* is labelled. There's silk-screen on all the boards, and labels for things like "green" where a green cable connects and such...would it have been too much to actually put down something like, I don't know...GND, +12V...something like that?

The oddball layout made even tracing the ground plane a hassle, eventually I managed to find three or four caps on the one board that all had continuity on the -ve side and concluded that was *probably* the ground. Now, finding the main 12V line took longer. One of the (four) boards sandwiched into the speedo assembly is the main power supply board, and it contains an unreasonable number of regulators, but is so awkwardly shaped and densely packed that actually tracing out the pins from them to anywhere useful is really hard. I ended up using a combination of questionable tracing and slightly educated guesswork to eventually track down what I was *reasonably* sure was the main 12V line...surprise surprise, it actually *was* the red wire to the other modules, and then it was trivial to buzz that out to the relevant pin on the backplane.

So...Gritted my teeth, connected the test leads, and turned on the power supply.

This was what I was greeted with:



Given I was repeatedly picking up, putting down, knocking over and such a bunch of glass things, I decided to use the bed as a workbench so I didn't crack anything.

Twenty minutes later and some tidied up wiring and it was back together - and I even managed to get it back together without killing it. Just need to figure out how to actually drive the gauges now, speedo seems to use a little inductive pickup like a cycle computer so that should be easy enough. Heck, I could even just stick a little coil next to it and pulse that, save hacking the original circuitry more than I have to...

Really surprised that I've got to this stage without getting zapped by the HT supply for the VFDs yet...sure it will happen mind you.

Getting "first light" on the display though felt like quite a milestone.



Hopefully I'll actually get time (and dry enough weather) to actually look at the cars soon rather than just random stuff like this...but I know we have a few electronics enthusiasts here, so figure this is probably of some interest to them...

[CitroJim]

Progress

[Zelandeth]

Further progress this evening on the dash project.

Using a bit of logic, both coolant and fuel gauge usually use resistive sensors to ground...so should be easy to find them...they will be the ones with power on won't they?

Out with the meter, and sure enough two pins have voltage on them, 5V in fact, a pretty sensible voltage for something like this.

Resistor tray out and stuck a few K between each of those pins and ground. Nothing. Reduced values further and suddenly the temp gauge sprang to life at about 100 ohms. Looks like FSD is about 25 ohms...way lower than I expected! Same value on the fuel gauge (guessed) terminal resulted in me swearing and dropping the resistor which simply got stupidly hot very quickly so appeared to be sinking a lot of current...not what I would expect from something meant to be in the fuel tank...further investigation needed.

...Oh what a difference a dash wiring diagram would make. ...and how much it would reduce the odds of me frying the thing!

[CitroJim]

Watching this with great interest Zel...

[Zelandeth]

Drove the 107 for the first time literally in about a year for reasons other than tracking down what's wrong with it or taking it to an MOT!

...and noted that one of the rear wheel bearings is rumbling slightly. Oh well, at least they are the easy ones to change. As I've got the car all week this week I'll be giving it a Darn Good Clean (TM) and the annual service (a month early, but who's counting?), also finally put the front bumper properly back together! It will also be getting a new wiper blade as that is utterly shot and the A/C cleaned as it smells like something died in there...

Will order a bearing as well, not worried about it just now though, will keep an eye on it and change it once I can tell which side it is.

Also spent the evening eyeing up a Hammond L122 organ on eBay...it's cheap (no bids, usual end price for this model seems to be 40-70 quid), it's complete, collection only and is only.a couple of hours away...tempted to check dimensions to see it it will fit in the Saab (reckon it will) and if so stick a cheeky bid in...

[CitroJim]

The bearing must be bad if you can hear it Zel, the 107 family are not that quiet inside my my experience!!!

The Hammond organ sounds interesting! let us know how that goes...

[Zelandeth]

The bearing isn't actually bad, the only reason I can notice it is because, well...I'm me! I have a very good ear for tracking down things like that, which is why when back at the garage I was generally the default first test pilot for anything that came in.

It's only (just) noticeable at all at a very particular speed and on a smooth surface. Anything other than that it's totally drowned out by normal road noise etc.

You're right though, it is easy to forget how quiet the 107 isn't, especially in the road noise department!

Speaking of loud, the Saab's bodged (twice) front expansion box on the exhaust is blowing again from somewhere...and the bit of weld trapped inside it is rattling and driving me mad. Seriously considering getting a generic bit of pipe, some clamps and attacking it with the grinder at this point and just deleting that box. I know from prior experience that other than a slightly raspier exhaust (which I count as a good thing) it doesn't do anything to the running of the car and the pipe itself is in generally good order. Not sure where to get stuff like that around here though, knew a shop up north where you could just buy exhaust pieces in common sizes and shapes to make your own, but not sure down here...

As for the organ, I blame a mate of mine back up north who has one. I can't actually play properly, but have always wanted to learn. I know enough to noodle around sounding tuneful (to be fair, not that hard once you figure out what's in tune with what), and can entertain myself for significant periods of time like that. However actually having the thing there in front of me day to day should be a good incentive to actually learn properly.

Wasn't paying attention when I first saw it apparently because I thought it was an L122, when it's actually a T202 which is a very slightly later and better specified model. Proper tonewheel organ as well, one of the last before they switched over to electronic tone generation for the "smaller" organs.

[CitroJim]

That organ sounds like a lot of fun Zel,

I've always fancied a Mellotron for its sheer engineering ingenuity...

Barclay James Harvest made great use of the Mellotron...

[myglaren]

My youngest daughter bought a house a couple of years ago and it has a built-in Hammond organ under the stairs.

Here's a nice organist for you - multi-instrumentalist actually but mainly organ and vocals.

[Zelandeth]

Mellotron...interesting, yes...would I like to own one? Well...yes...but in the same sort of way I'd like to own a V12 Jag XJS. I'd love it precisely as long as it lasted before I had to do the first bit of maintenance or fix something...that said, access has to be easier on the Mellotron.

Hammond is something you'd probably quite enjoy nosing around, Jim. The actual tone generator on this is still done using inductive pickups and physically spinning tonewheels. Given the age I'd be surprised if it's not entirely based around discrete components. The T series uses transistorised amps rather than valves but should still all look very familiar to someone who knows their way around kit like you do.

Couldn't find dimensions for a T200 series, but the L series is basically the same organ but with a more basic audio setup and a few less features, cases look identical though...so a T202 should be basically the same size as an L122 for which I have found dimensions. Result? Should fit in the back of the Saab with a comfortable amount of space left. ...now...what to bid, that is the question...

[CitroJim]

Hammond is something you'd probably quite enjoy nosing around, Jim.

You're not wrong there Zel

You have whetted my appetite good and proper!