There are times like this when machines come to me almost in groups for repairs. I just got a TC Fireworx and a DP4+ Ensoniq. I'm starting with the TC:
This is a classic digital multi-effects from the late 1990s, early 2000s.
The machine does not start anymore. This effect rack does not seem to be a killer in the sound grain, but hey, I imagine that it must still provide good basic effects. After opening it, we see that the machine is well made. Well thought out too. There are however quite a few small connection retakes on the top of the board. In my opinion they are original. There must have been some modifications after the board was produced.
First thing to do, power up the machine. This should go well since there is no smoke or hot spot on the motherboard, and the power supply fuse is not blown.
On the other hand, in my opinion, the principle of connecting the power supply to the motherboard is a bit of a stain on the board. Why not have put real connectors? It is therefore mandatory to remove the motherboard from the machine to be able to unsolder the wires connecting to the power supply: not great!
It is also not practical to connect another power supply to it, for this it is necessary to solder the wires of the new power supply. Then unsolder them when the tests are finished: hum....
The voltage tests carried out at this time give me +26V and -26V for the analog part, knowing that I took the analog ground as a reference. This does not seem good to me at all, but I will see later. On the other hand, the +5V gives me 0V. Compared to the behavior of the machine, this seems consistent to me! At first glance, the power supply seems to pose real problems.
Fortunately, the machine is small and removing all the insides is not complicated and does not take too long.
So the next operation was to unsolder the power cables and power up this power supply without load.
I spent some time testing the operation of all the diodes and transistors before actually powering up this power supply. Having noticed nothing suspicious, I started it up. The output voltages are still +26V and -26V, but I now get the +5V dedicated to the digital part. This is better. This most certainly indicates a problem with the capacitors on the low voltage output. This power supply is so compact that you can't see at all what's happening between the components. So I decided to unsolder one of the two large capacitors, I started with the easiest to remove.
I was not disappointed with the result. Look at this 'battlefield'!
And of course, the first 'death':
But look at this!!! I have never seen a capacitor in this condition. Even low-end capacitors never gave me such a result: incredible! And yet, it is a branded capacitor!
First step. Before continuing on this power supply, I will connect the motherboard of the device to a laboratory power supply to check if it starts correctly and if the analog part works. Because with the overvoltage that I see at the output of the power supply, I still have some doubts. It would be a shame to waste my time on the power supply if the motherboard is defective because it will most certainly be irreparable.
The next step was to install terminal blocks on the motherboard of this machine, so that it was not necessary to desolder and resolder the power wires a 'number of times'.
Then turn on the machine.
A tentative conclusion: the machine starts and seems to work correctly.
However, a doubt remains. Indeed, during my first tests, I measured an analog voltage almost twice what it should be when the board was connected to the original power supply. So I don't know how much this could have affected the operation of the operational amplifiers if this voltage was actually applied when starting the machine.
Fortunately, all the digital/analog and analog/digital conversion circuits are supplied with +5V, the regulator providing this voltage on the motherboard obviously having no problem providing this +5V, I can assume that these conversion circuits are still operational.
Starting the machine with a laboratory power supply :
I just have to test the audio system before switching back to the original power supply.
The 'problem' is that all the connections on this machine are XLR. And, although I have XLR/JACK cables, I don't have any XLR/XLR ones. So a small purchase and my very first XLR machine connection :
After connecting a synthesizer directly to this Fireworx and connecting this Fireworx to my PC, the observation was very simple: it works very well.
At least I'm sure that the malfunction of the machine's switching power supply did not cause a problem on the electronic board.
After cleaning the power supply to remove all the residue due to the leakage of one of the capacitors, I started looking for replacement capacitors. In fact, I decided to replace absolutely all the chemicals in the secondary. The large filter capacitor in the primary still has a good capacity, and shows no signs of leakage. I left it in place.
It was not as easy as expected to find the right capacitors. The ones originally used are very small. So I had to 'trade' the small diameter for a larger height of the new capacitors. I finally found models that were quite suitable.
Which allowed me to finally carry out the first tests of the machine with its original power supply as shown in the previous photo.
Note that testing this power supply is not very practical. Indeed, there is a whole standby system that does not allow you to check the 'relevance' of the 5V. I was still able to see that the 22V voltage of the power supply originally, had dropped to a voltage of 16.5V, i.e. +16.5V and -16.5V. It was already better. The problem is that during my first tests, I had modified the 5V adjustment trimmer, and now that the power supply was in principle repaired, I had no idea what this voltage could be.
Fortunately, it is enough to test the voltage provided by the standby mode 'output' system (brown wire), it must be 5V, which I adjusted using the trimmer. Once this adjustment was completed, all that was left to do was to connect this power supply to the motherboard of the machine, and check the overall operation. The results were therefore conclusive, with this time +14.8V and -14.8V in charge for the analog power supply and a nice 5V for the digital part.
And now? Back in the box!
I was able to do some audio tests with this machine. The opinions that I was able to glean on the Internet are rather mixed about it. They indicate that the sound quality and the treatments are not exceptional. I find that it works very well. Afterwards, some effects can be questionable, especially those dedicated to the treatment of guitars, you have to have the use for them, but otherwise....
For a 25-year-old machine with exemplary construction (except for the power supply which is clearly not top of the range), and at a purchase price of around $800 in 1998, it is still a good machine today.
