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

[CitroJim]

Excellent all-round Zel

[Rp0thejester]

Zel, your a very smart man. Good job I don't know where you live or my C8 would be parked outside your house blocking you in till you fix it!! Any news on the VW Bus screen?

[Zelandeth]

Any news on the VW Bus screen?

Apparently the claim has been cancelled, so I can just sort it myself. Though of course I've not had the promised email to confirm that and there's nothing in the web portal to indicate as such - but then again there's never been anything visible in there regarding the glass repair claim anyway so that means nothing.

-- -- --

The work on the power supply board for the T1600 was finished up - messily but simply enough. The biggest grumble is always that for some reason I've never quite understood, I very rarely seem to be able to get the through holes in the board clear of solder. This seems to be unique to Toshiba boards which have had leaky caps on them which makes the solder really reluctant to flow properly. I don't have a proper suction fed desoldering iron (yet), but neither good quality desoldering braid nor the (admittedly usually pretty pointless) plunger type tools seem to have any impact. So putting in new components about 80% of the time involves either trying to heat both legs with the iron to keep the solder in the through holes molten while you get the component in place, or in some cases just soldering the component onto the surface of the via. Not ideal, but it's one of those cases where needs must. Plus I've never had any issues with this so long as you secure the component separately with a bit of hot glue so it's properly supported. As these are four layer boards I don't want to get too brutal in trying to remove anything.

Probably not as durable as when it left the factory in terms of shock resistance, and *definitely* not as pretty. However it's a method that works. Having seen how much easier having a decent soldering station has made things I'm definitely of a mind to add a proper desoldering station to that...might actually be able to do a tidy job of this then.

I don't think I've ever been quite so apprehensive of powering up a piece of gear for the first time as when plugging this in! I used the known good power adapter I use with the T1200 to take as many unknowns out of the equation as possible.



Well that's promising...it came to life, hard disk even span up sounding like it was put away yesterday, and we had a working display as a bonus.

The hard disk was even correctly detected.



The display on this is essentially a larger version of the one used on the T1200 and has the same gorgeous looking cobalt blue on grey colour to it. Difference between this and the T1200 and this though is that this can show I believe four shades of grey rather than being pure monochrome.

It's really hard to capture properly on camera.

Somewhat to my surprise, it then went and booted.



DOS 4.01 it looks like, and based on the file modification dates was still in use up until 1998. A pretty decent useful life for a portable!

There was a Windows installation on there as well, though it failed to start, complaining about a mouse driver being missing. Does show we do have greyscale ability present though.



All seemingly working well, I reassembled the case - albeit in the knowledge I'd be wanting to pull it apart to be cleaned at some point in the future.



It was all going really well. Right up until I switched it off and went to get dinner. When I came back and plugged it in it started tripping out the power supply it was plugged into. Something has gone short on the power supply board... however it's not gone dead short...as that would be far too easy to trace.

So now I need to try to fault find on this thing.





Which really wasn't designed with user serviceability in mind. There aren't any schematics either in the otherwise really good service manuals, as it's one of those things which would just be replaced as a unit if faulty back in the day.

So far I've checked for any shorted caps (as there are a couple of surface mount tantalums) but it's nothing that obvious. My next line of attack is...tedious. basically I've got to go over every single transistor/FET/diode on the board with the meter on diode test mode and look for anything amiss...

The problem is I don't have a known good one to compare to. I have three other boards on hand, but they're all either half dissolved by corrosion or blown up in some way - so it's a bit of a stab in the dark!

It's also long winded. Isn't going to do me any good either if the issue is actually with something driving one of the power devices rather than one of those themselves having gone short.



However I really don't know of another valid approach. Even *with* a schematic I wouldn't really know where to start with something this complex.

I do really, really wish I still had access to a thermal camera though, as that could potentially really help me narrow things down a bit more quickly... it's one of those tools that once you've had access to you really miss going forward.

Frustrating to have got so close to a working system but have another failure then appear. Will be really satisfying *if* I can repair this...but I'm not holding my breath.

-- -- --

As the weather was decent and the van wasn't on the drive (more on that in a moment), it was a good excuse to get TPA out for a run as it's been ages and I didn't want her getting too jealous of the new arrival!

Gave me a good opportunity to get a photo of the pair together.





Now...the van. This has started to really annoy me now.

Failed MOT on brake imbalance.

I don't have the time, patience nor inclination to get involved in faffing about trying and probably failing to pull calipers to bits myself right now.

Garage looked into it, declared nearside caliper in need of replacement. They couldn't source one.

Ordered caliper no 1. Turned up looking like it had been stored at the bottom of of the sea and was never going to work without a complete rebuild. Refund of that is still sitting with PayPal as the seller has completely ghosted me.

Ordered caliper no 2. Offside caliper turned up rather than the nearside one I'd ordered. At least that was promptly refunded and the seller couldn't have been more apologetic and refunded me even before I'd returned the wrong one, they didn't unfortunately have a nearside one in stock.

Caliper no 3 arrived, and was fitted Thursday afternoon. Doesn't work. Getting fluid to the union to it, but next to nothing all will pass into the caliper itself. It's working far worse than the one that came off.

So I had to get again retrieve the thing still un-fixed, and on Monday take the original caliper over to Big Redd to be rebuilt...which is what I should have just done in the first place. Then need to try to get a refund on the cost of this one, after it's been fitted. Sure that won't be at all difficult.

Excuse me while I go find a brick wall to smash my head against repeatedly.

Having driven it back from the garage, I'm inclined to agree with the garage. The nearside front where the new caliper is is now plainly doing virtually nothing at all. It's pulling way, way worse under braking than with the old one on.

Examination of the old caliper shows three of the four pistons to be pretty firmly stuck, and all the rubber boots are in need of replacement. So it definitely wouldn't have been performing as well as it should, but would have been providing at least some contribution - which ties in with the symptoms and fact that it always historically has had a tendency to be a bit lazy if the van hadn't been used for any period of time.

The thing is already sold, and it's just awaiting a fresh test before I invite the seller to come test drive and collect it - but this brake issue has been going on for something like three weeks now.

[CitroJim]

Oh dear Zel Not the most successful of days... Hope all comes good on the computer and van front very soon...

[Zelandeth]

To be fair, to at least a large extent the van issue is partly my own fault. I knew the caliper had issues, however it always resolved itself before it got to the front of the to do list.

Just hadn't expected resolving it to turn into quite such a mission.

As for the computer...things like this go with the territory. Just frustrating. That IBM portable I've been working on is also temporarily on hold because it's power supply also decided to die - though that at least just outputs normal AT voltages and has a physical on/off switch rather than having any software control. So I just need to look up the connector layout and track down something which will physically fit to replace it. Assuming it doesn't supply the HT for the display as well, as that would add a bit of complexity to the job.

Something I do need to try with this one I think is finding where the 12V and 5V outputs are and just applying power there to the system and seeing what happens. I haven't a clue whether the system would run in that state essentially just in "always on" mode, or if it requires Comms to wake up. If it's the former, I'd happily take that setup as a compromise until I could hopefully eventually get a fully functional power board to fit.

[CitroJim]

Your experiences with the laptops are a bit like those who valiantly strive to lovingly restore 405 line TV sets back to full functionality only for the line output transformer to fail after a few hours of finally having achieved a perfect picture - or the tube to develop a heater-cathode sort or even worse, for the heater to go open...

Having said that, I've been hankering after restoring a proper old telly for a while now but it would have to be both all valves and physically not too large...

I have the knowledge from my TV servicing days but sadly, I have none at all on your laptops so can't offer any useful help except to cross my fingers...

[Zelandeth]

Your experiences with the laptops are a bit like those who valiantly strive to lovingly restore 405 line TV sets back to full functionality only for the line output transformer to fail after a few hours of finally having achieved a perfect picture - or the tube to develop a heater-cathode sort or even worse, for the heater to go open...

Having said that, I've been hankering after restoring a proper old telly for a while now but it would have to be both all valves and physically not too large...

I have the knowledge from my TV servicing days but sadly, I have none at all on your laptops so can't offer any useful help except to cross my fingers...

While it's a bit buried somewhere in either the garage or loft (pretty sure the former), I've had a GEC BT304 been waiting for attention for...er...probably about 15 years now.

Linky

I remember checking that there was continuity through the CRT heater and the various transformers, but that was about as far as the investigation ever got.

It had been forgotten about in the loft above a friend's garage presumably since the 405 line service shut down, and was going to be getting binned if I didn't rescue it. Bit of a basket case, but it would be incredibly satisfying to see a picture on it again - and it's positively immaculate compared to some of the sets I've seen dragged back to the land of the living.

[Zelandeth]

Spent a whole 20 minutes working on the Rover today.

The last remaining oil leak I was concerned with tackling at this stage was coming from the rear of the exhaust valve tappet cover.

This was dripping down onto the starter motor and leaving quite a bit of a puddle, especially after a higher speed run.



There are probably a couple of smaller weeps here and there, but I'm really not concerned by those. I don't mind if this car leaves a drip or two overnight, trying to achieve that on something like this could have me chasing my tail forever - I just want to ensure I'm not actively dumping oil while driving.

I had originally managed due to a fat finger and touch screen interface error managed to order the wrong gasket for this, so had been waiting for the right one to turn up, which did yesterday.

I continue to be astonished by how clean the inside of this engine is.





I really do get the impression that this has been very well looked after mechanically for a large chunk of its life. If anywhere was going to be nasty I was expecting it to be in here given the proximity of the exhaust.

As I suspected my issue was plainly a flattened and distorted gasket towards the rear.



Thankfully unlike the gasket I had an absolute nightmare of removing from the inlet valve tappet cover, this one wasn't glued in place and peeled off cleanly without any issues. You can clearly see how much it has lost its shape compared to the new one (which is also about twice as thick).



A whole ten minutes later everything was back together with the new gasket in place.



I then went out for a drive for about half an hour, including a fast run up the A5 and back. No visible leaks present.



A little bit of a weep from a couple of the securing bolts, I suspect the O-rings under them have gone a bit flat, so will get those changed shortly. It's nothing serious enough to worry me though.

After the car had sat for a few hours the only drip I could see evidence of was one or two from the bottom of the bell housing, most likely due to a bit of seepage from the rear main. If I keep this car long term I know the clutch isn't in its first flush of youth, so I'd plan on sorting that if/when the clutch was changed - but I'm not going to worry about it in the meantime. Also it could equally be seepage from the leak I've just fixed still leaving the area too.

Nice simple job.

[MattBLancs]

Nice satisfaction with a job like that. Though I'd be a bit worried about the starter motor rusting or seizing up given you've isolated it's lubricating/protective coating system!

My "somewhat OCD tendencies" would likely extend your 20 minute job considerably - I would've been compelled to spend an age degreasing and repainting that cover. I'm aware it would then clash terribly with everything else in the engine bay that is just nicely "looking the age that it is".

[Zelandeth]

Nice satisfaction with a job like that. Though I'd be a bit worried about the starter motor rusting or seizing up given you've isolated it's lubricating/protective coating system!

My "somewhat OCD tendencies" would likely extend your 20 minute job considerably - I would've been compelled to spend an age degreasing and repainting that cover. I'm aware it would then clash terribly with everything else in the engine bay that is just nicely "looking the age that it is".

Haven't you seen how much the shiny new radiator cap already clashes?

-- -- --

Progress on the T1600 revival.

I now have three functioning in some form but fundamentally broken power supply boards. Which given the complexity of them and that the two further ones I've worked on had been subject to violent enough failures to blow apart semiconductors, I'm not surprised.

I reckon I without having a known good one, proper fault finding guide or a schematic I've reached the limits of what I can really do short of changing every transistor and FET on the board - which is nigh impossible as about 90% of the surface mount ones are unmarked, and the service manual doesn't list them. Brute force isn't going to win us a battle this complex.

However I had a theory, that despite the smarts inside the supply, the computer would most likely at least power on if you simply feed it 5V. Yes you'd be missing the power management features, but the machine should function. As you'd expect for a 286 era machine, basically everything on the board itself runs on 5 volts.

12V on the system is only used by the display backlight driver and is provided to the expansion bus connector for accessories which might need it. There is a -9V rail, but that's only used by the modem (which I don't have). The only really awkward one we DO need is a -22V rail which is used as a bias voltage for the display.

I just need to figure out what goes where in this mess.



Of course the manual has a lot of connector pin diagrams...but not one for the 50-pin one on the power supply. Thanks Toshiba.

Finding the logic 5V one was nice and simple as there are a few 74 series logic ICs on the board, so I just used the meter set to continuity to tone it out from their VCC pin.

Somewhat tentatively I fed it 5V from an external source - and we got the relevant lights come on...and even more promisingly, the correct power on beep. Obviously no display, and the hard drive made it very plain that it wasn't seeing anywhere near the required current for the spindle motor to start up properly, but that was expected. From the manual it looked like there were three or four individual 5V rails, so I'll need to find where those run to.

Then I need to figure out the best way to get us a combined 5V, 12V and -22V power supply. If I can make that work reasonably reliably and come up with a tidy solution that could help a lot of people I think given that power supply issues are basically universal to all of these machines nowadays.

Feels like I've got a plan of action in place now at least! I'm not totally sure how I'll get around finding us -22V yet, but I'm sure we can figure something out - especially as it's only a bias voltage so we only need to supply a max of 10mA.

[CitroJim]

Watching this with great interest Zel

[Zelandeth]

It seems that there are variable voltage DC to DC converters which run in the 5-30V range readily available, rated to around 3A.

I don't think space is likely to be too much of a challenge given we've got the volume occupied by the original power board (I'll probably chop the board off the badly corroded one and just use it's connector as a means to interface with the backplane), and if necessary the expansion card bay - or possibly even gutting one or both of the battery packs.

Big question I see is whether they provide a clean enough supply to not cause stability issues and whether they'll play nicely with their ground connections commoned together. Only one way to find out.

Also noted when putting things away that I was down to only one or two caps in stock for a lot of values, so just did a stock order to bring everything back up (I try to keep a minimum of four in stock of everything aside from really obscure values) - over £70 of bloody capacitors!

Probably overkill, but I like having a decent stock in place as there's nothing more frustrating than getting 3/4 of the way through a project then having to pause for two days while you wait for that £0.05 part to arrive - especially as Farnell slap a £5 surcharge on small orders. Given I can't just pop round to Maplin for stuff like this any more, forward planning is key.

I really do need to come up with a more elegant solution to storage some day, the sandwich bags in a box works but is a bit of a faff as they're hard to keep in order. Those little cases you get things like O-ring assortments in would be ideal for the smaller ones at least. I'll sort it out one day!

[myglaren]

I have stacks of these things Zel, and a vertical one that can be hung on a wall. All from places like B&M, Home Bargains and Poundland/world. Cheap as chips.

[Zelandeth]

I have stacks of these things Zel, and a vertical one that can be hung on a wall. All from places like B&M, Home Bargains and Poundland/world. Cheap as chips.

I always forget those shops exist these days for some reason! Will go have a rummage tomorrow.

[myglaren]

The vertical cabinet that I think was about a tenner, and more boxes.