repair

This was supposed to be an easy repair, and therefore not worth blogging about. But as it turns out, it might get interesting after all. (The ‘scope is not repaired yet)

The “Leidse Makerspace” owns a LeCroy 9450 350Mhz DSO. When they moved to their new location I temporarily got this oscilloscope. Not just for use or storage, but also to attempt to repair it. One of its channels was not working, sometimes it even wouldn’t display anything.

The display problem quickly turned out to be a loose connector. With this connector loose it would display nothing it al, or if it did work, it would sometimes glitch out like this:

IMG_6035_lecroy9450tobefixed

While at other times it would display normally:

IMG_6034_lecroy9450tobefixed

Probably just some transport damage, as after refitting this connector the problem has not been back. Now, on to the more interesting problem: channel 1 did not work: it did not respond to an input signal and it had a huge offset. After using the vertical position adjustment knob to bring it into view it would sometimes even oscillate on it’s own, showing needle-like pulses. The ‘scope also wouldn’t trigger on channel 1. Channel 2 functions fine, so it is still a usable 350Mhz DSO. However, 2 channels would be a lot nicer, and fault-finding is one of my hobbies. So… Time to remove the covers.

The easy-est way to measure in the analogue front-end of this oscilloscope is to turn it upside down, remove the bottom cover, remove the 12 screws holding the shielding, and remove the shielding.

IMG_6067_lecroy9450frontend

After this, an input signal can be followed, measuring before and after each subcircuit.
(I don’t have a picture of this, but I do have a picture of the 9450_7 front end, removed from the ‘scope, and from my annotated copy of the schematic)

IMG_6072_lecroy9450_7

IMG_6080_lecroy9450schematic

Close- up of the area of the board I’m looking at:

lecroy9450_7_detail

Somewhere here, the signal got lost. As you can see there is another module inserted through the pcb, this is the HHZ406. It turned out the signal entered this module (an amplifier), but nothing sensible got out.  IMG_6076_lecroy9450_HHZ406view from the other side of the board, also showing the relays. (Those metal cans)

IMG_6075_lecroy9450_HHZ406

This module does not look like it can be repaired, nothing is obviously visibly broken, and those “black blobs” don’t look promising either, because these usually cover (custom) semiconductors directly bonded to the PCB.

It also looks like it cannot be bought anywhere. Too specific, too custom… (If you know where to get these, or work for LeCroy and have spares, or if you would like to reverse-engineer them, let me know.)

But this story does not end here. This scope has 3 HHZ406 modules. One for each channel, and one for external trigger.

So I swapped the modules for external trigger and channel 1. After this, the signal got to the output of the 9450_7 board. When using the same V/Div settings on ch1 and 2, and feeding them the same input signal, the signals here would be identical.

The story does not end here either, however. Channel 1 still does not work. It does respond to an input signal and the ‘scope does trigger on this channel now, but the signal is not displayed properly. It has needle-like pulses on it. These pulses move when changing V/Div settings on the ‘scope or input signal amplitude from the signal generator. (Video: http://www.youtube.com/watch?v=wFei5CZ6lqA)

There is another defect lurking somewhere in the 9450_3a ADC boards, because when I swap them, the problem moves to the other channel (Ch2). Measuring on these boards is harder because they are not easy to get to while the ‘scope is operating, unlike the analogue front-end (9450_7).

IMG_6036_lecroy9450_3a_adccardsTo be continued (?).

Dit is hoe ik m’n iPAQ (h2200, h2210) z’n batterijklepje heb gerepareerd, met smeltlijm.

iPAQ h2210 battery door repaired
Gelijmd batterijklepje, BINAS op de achtergrond.

iPAQ h2210 battery door repaired

Om de een of andere reden plakt hotglue beter met een dun laagje tussen de te verbinden delen, ipv een dikke laag. Door met m’n heteluchtsoldeerstation de hotglue (en de te verbinden delen) warm te maken kon ik er zo’n dun laagje tussen krijgen. De warmte helpt ook om de lijm beter te laten verbinden met de te lijmen kunststoffen, en door het warm te houden blijft de lijm corrigeerbaar.
Die batterijklepjes schijnen nog al ‘s stuk te gaan, en nieuwe zijn schrikbarend duur (Een extended battery is goedkoper). Op deze manier kun je het zelf repareren. Bij gebrek aan een hot air reflow station kun je misschien ook een hairföhn gebruiken.

Repair companies are completely right they don’t repair on this level of detail, but swap an entire board instead. Much easy-er.  But I don’t have spare boards lying around and I like a challenge, so…

A friend of mine had a defective digital camera, someone forced the sd card in the wrong way, with bent contacts as a result. His camera now refused to read or write the card. Reseating the card didn’t help. Taking the camera apart and bending those contacts back to their original shape did help.

After removing ~20 tiny little screws the camera looks like this:

camera open

Might look terrifying because of all those little ribbon cable flex PCB’s, but I was able to put it all back together (I’ve done this sort of thing before).

O, and a warning for those that want to attempt this: Every camera with a flash contains a high voltage capacitor that probably is still charged. Discharge this capacitor before doing further work on the camera! (Or just don’t try this at home). In the picture above it is the big cap labelled “photo-flash”. It was charged to 140V.

sd kaart slot

This is the removed SD card slot. Instead of replacing the SD card slot, I opened it up. It contains 2 little springs (held on pins) and a tiny little metal bar, that together with the plastic sled forms the mechanism that allows you to push on the sd card to pop it out. Those tiny parts can be seen in the top half of the picture.

sdslot_detailIn this detailed picture the bent pins can be seen. The second one from the top I already bent back, the one on the bottom broke when bending it to its original shape. So I had to either replace the entire SD card slot (Might be hard to find one with the exact same footprint, not to mention the mess de-soldering it would give on the PCB, with all these tiny components nearby), or find a clever solution.

So, I replaced the bent pin with a pin from a female pinheader connector, cut and bent to shape and soldered to the remains of the broken pin.

sdslot_fix

After re-assembling everything, the camera still refused the SD card. However, this time reseating the card helped and it could access the card again.

Parts cost: Near zero.
Labour: ~ 5 hours. Yes, that’s why repair companies can’t do this.

If I had to do this again it would cost less time, because now I know where all those hidden screws are. Still, it would take too much time if I had to do this commercially. But I repair for fun, to prevent waste and for the challenge of getting something broken to work again. This certainly was a challenge. Not on the intellectual electronic level, but on the fine mechanical skill level. And it was rewarding to get this camera to read (and write) its card again.