Repair.IT – or not, Panasonic DMR-EX77 DVD Recorder not powering up

On Saturday I received a Panasonic DMR-EX77 DVD Recorder to evaluate for repair. At the time of purchase (2007 or 2008), it was quite expensive. It has a hard disk drive inside so could record to disk and then recorded videos could be written to DVD. Of course everything can physically be repaired but sometimes we need to consider whether it is worthwhile to repair it.

One considerations is what the current replacement models cost – if they can be had for only a couple of hundred dollars, then spending a significant fraction of this cost to repair an older unit is not economical. Another consideration is whether this unit has a digital tuner, remembering that analogue television transmissions in Sydney have been stopped for some time. Another question to ask if whether the client still records television programs given that much of what it on television is often available through other means such as Netflix. My recent changeover from Telstra Bigpond to Optus came with the Optus Fetch TV box, which is also a TV recording device, but of course, the recordings cannot be exported – which the DVD Recorder could do.

I checked the specifications of this DVD Recorder, it does have a digital tuner, so +1 except that it is standard definition, but still able to be used, the hard disk is a 160GB size, ok – not large but adequate. Replacement costs of similar devices are still over $350 for a DVD Recorder and over $500 for a Blu-Ray Recorder. The newer models come with more than one digital tuner, so can record one channel while watching another channel or even record two channels at the same time.

Incidentally, it is important to ask about the symptoms – like, does it power up, any lights on, etc. In this case, it was no power, nothing happens – which sounds like a power supply problem, which is usually the best kind of repair in that the components are usually readily available. But sometimes a power supply failure can cause failure of other parts of the unit, such as a main processor board – in that case, it would not be economical to repair as often those parts if obtainable are expensive.

So, now we need to work out what is wrong, how do we go about it? First thing usually is to connect the unit to the power point, and switch on the power. I did this, and nothing appeared on the screen. I waited a short time as usually these will be in some sort of standby condition, and then pressed the power switch. Again nothing happened, so it looks like either a fuse or other problem inside.

Time to open the case, I removed two black screws from the side panel, and three silver screws from the back, then the top and side cover could slide off towards the back. This unit by the way, was a little heavy, so having a look inside – I could see why. A power supply board sits in the back left, then a DVD drive in front of it. There was a 3.5″ hard disk drive on the right front, then between that and the DVD drive is a processor board with all the cables going to it, and underneath is a larger main box which has most of the video circuitry and connections on it.

I could see on the power supply, that one capacitor was decidely bulged – not a good sign, but an indicator that this capacitor needs replacement. To remove the power supply, I removed one screw from the back panel and three screws on the board, then disconnect the output cable, then lift the front of the power supply board and wiggle the board out, while pushing the back panel slightly to allow it room to come out.

The capacitor is a 1200uF 6.3V electrolytic made by Elna, marked C1401. You can see the bulging of the top of the capacitor – sorry, it wasn’t my best photo, but it was the only one I took of this power supply. No obvious other signs of failure, although the circuit board around the heatsink on the left showed signs of heating – so it is good also to check that integrated circuit, which I did and found no obvious short circuits.

A quick search on Google gave me access to a service manual and also found information that showed that other people have had this problem. C1401 can be accompanied by other capacitor failures on the main board. I couldn’t see anything else, but part of the main board was obscured by a shielded processor board. To remove that, it was necessary to remove four screws, then five cables, and it would lift off a large connector to the main board and a small connector to a smaller board in the front.

SONY DSC

Then I could see that capacitor C4056 and C1557 had also bulged tops. C4056 is a 470uF 16V and C1557 is a 680uF 6.3V electrolytic capacitor. Checking my parts, I had a 470uF 16V on hand, and a 680uF 10V available, which could be used in place of C1557. It is quite acceptable to use a higher voltage rated capacitor but not too much higher. The 6.3V rated capacitor is for the 3V power line, so 10V should be fine – I wouldn’t put in a 25V capacitor as its ESR is likely to be higher than a 10V capacitor. I didn’t have a 1200uF on hand, but I did have a 1000uF 10V that could be tried temporarily while I order the 1200uF capacitor.

Ok, so now I have a list of components that definitely require replacement, is it likely that replacing them will allow this unit to work? The cost of these components are not high, so the repair cost could be kept down.  Incidentally, most quotations for repair essentially require repairing enough of the problem in order to determine how much time and parts are needed. In many cases the unit is actually repaired and then a quotation is provided, unless they happen to have replacement boards on hand, in which case, swapping enough boards will give an indicator of the problem board and hence the likely repair cost.

This main board doesn’t look easy to remove since everything appears to be either attached or screwed onto it. A handy hint for people is that I tend to group screws that I remove in small piles in the order that I remove them from the unit.  I.e. the five screws are in a small round plastic tray that I keep with the top cover.  I put the power supply screws with them as well. In order to get the main board out, I am likely to be removing a lot more screws. Again, I group them as long as they are similar screws, otherwise we need some way of remembering which screw goes where. Some repairers will actually place screws on the bench next to them in the rough alignment of where they came out. Then removed boards, parts can be placed there so that we know which screw goes with which part or board. So here goes…

The hard disk drive is held by four screws, of two types. The DVD drive is held by three screws but it would not come out, seems to be attached to a metal bracket under the front panel. The front panel is held by some plastic latches, one on top, two on the side and three on the bottom – then it just slides out the front. SD card reader and FireWire board is attached by one black screw. The front AV board is held by one screw. Then the front metal bracket was held by one screw and the DVD drive now comes out. The HDMI board at the back is held by one screw on the back, then a plastic standoff is unclipped, and the board can come out. Are we counting screws, yet?

The main board is held by two screws inside, and six screws on the back that fasten the connectors like the SCART sockets, AV sockets, optical sound, tuner, etc. The power switch board is held in a slot and attached by wires, not by a connector, so this just dangles. Next thing, now that the main board is out, it to remove the two capacitors and replace them. Most electronic devices now are lead free, meaning that non-leaded solder is used, and we should perform the repairs with non-leaded solder. Also this solder has a higher melting point which takes slightly longer to desolder. However, this board is single sided meaning that the copper tracks are only on the bottom. That explains the numerous wire links on the top of the board.

Why is this good? Because to remove the capacitors, I can do this quickly by heating up the pads alternately, then with my fingers I can lever the capacitor out without risk of damaging the pads which could happen if this was a double sided board. Hence it was a matter of 20 seconds or so to remove each capacitor, then with a solder sucker, remove any excess solder. Otherwise, I would have to fire up my desoldering station, which takes time to heat up the pads sufficiently before it could suck the solder away. Both capacitors were replaced, then I did the same to the power supply board, removed and put in my substitute capacitor. Non-leaded solder was used to resolder these capacitors – hence this repair is EU compliant, at the least.

Next step is to put everything back in, the same way it was removed. This was relatively straight forward, after a little head scratching to work out where the two screws for the main board go. Of course 30 minutes is a long time, from removing to the screws and to remember where they go, because the main board has lots of places where screws go, because other parts attach later. Eventually this was done, no screws left – final count, 32 screws taken out, 32 screwed put back in! There were three other screws that did not have to be removed and replaced, two of which are for the fan, which I didn’t mention had a power cable going to the main board.

Now, the acid test – will it power up? Connected the power cord and switched on the outlet… Good, a message was displayed on the front panel VFD display – PLEASE WAIT – this was displayed for some minutes. Eventually it stopped, and 0:00 was blinking, which I gather is the time, that hasn’t been set. I pressed the power switch, and it started up. I connected up the antenna cable and proceeded to look through the user manual to find out how to set the date and time. I set it to Automatic and chose NSW, ACT and after a short time, the clock was updated.

Everything else seems to be ok, the recordings are still on the hard disk and will play back, although I noticed some distorted sound – which got better once the unit warmed up a little. The distorted sound is a known issue with these units, which is expensive to repair as it requires the replacement of a surface mount chip with 100 tiny leads. Anyway, the unit is working, as such and this sound problem would have been there for a long time – and now I can let my friend know how much it would cost and when it would be ready. I have ordered the appropriate capacitor since I had used a substitute to test the unit, so when that is ready, I still have to replace it – then check again.

Overall, if the repair cost can be done for less than about 20% of a new unit, it is worthwhile. In some cases, where specific features are required, even up to 30% can be acceptable. Anyway, I have an email telling me that the capacitor has been picked, packed and ready to collect.