ELAD DUO ART REPAIR

If you’re a frequent visitor, you’ll know I like a bargain and I’ve managed to bag a few over the last few years. The last one was a dead Micro PA-100 Amp which I bought for peanuts and then fixed it for a few more peanuts. So when I spotted this £1300 Elad Duo Art for very little money, I couldn’t resist, despite my spidey-senses tingling like crazy (spidey-sense is an extrasensory, near-precognitive awareness of impending danger) 😂.

Well, to cut a long story short, it was super cheap because it had a serious fault - there was no power output on the 40M band! In all fairness though, it worked perfectly in every other respect including the built-in ATU. When I attempted to use 40M, I could immediately detect that dreaded burning component smell 🔥 Oh dear! 😥 I'm guessing that the previous owner had simply had one of those 'fat finger' moments and transmitted into a non-resonant antenna without realising 😖.

I contacted the amazingly helpful Vianney at ELAD and described the problem. He  responded very quickly with a useful schematic and some advice on what the problem might be and gave some recommended specs for replacement capacitors. Thank you Vianney 🙏🙏🙏

I delayed tackling the job for quite a while because, in all honesty, I was scared to dismantle the Duo Art. It looked quite complicated and I could easily end up with a useless electronic jigsaw! 

Anyway, for some reason I decided that today was the day to grow a pair of ball$ and dive in! I removed the top cover and saw that there were basically 3 boards and I had to deal with two of them. Looking at all the electrical and SMA connectors, I felt a little overwhelmed, but carried on regardless. 

I started off by taking as many photos as possible to aid reassembly and then started to snip all the cable-ties. Then it was a case of removing the various screws holding the boards in place. 

Once I had removed the smaller top pcb (the ATU), I could see a metal shield which also needed to be removed. 

You have to be careful with this because it has a set of cables taped along its edge. In the end, rather than removing it completely, I managed to slide it to one side.

With that (awkward) bit out of the way, I could see the Low Pass Filter board and after careful examination, could see no signs of burned components or any other damage. The damage must be on the other side of the board 🙄 which meant more stripping down, so out came the camera again. To remove this (large) board, you have to undo the three DB-9 sockets from the chassis’s backplate and then carefully manoeuvre it out. 

Straight away I could see the damage on the underside! It didn’t look pretty, but apart from the thought of removing and replacing those incredibly tiny SMD caps, I was really worried that the tracks on the PCB might be damaged too!

I felt that I would really be stretching my luck by tackling this repair myself, so I emailed a friend in Scotland to ask if I could post the PCB to him for repair. I'm waiting to hear back from him, but if he isn't able to help, I think I'll just have a go myself. I've found the 1206 caps on Farnell's website. They're 1000V instead of 630V, but I'm guessing that doesn't matter.

I'll update this page soon, with a big smile or floods of tears, LOL.

73, Tom, M7MCQ.

UPDATE : 

My friend didn’t get back to me so I can only assume that my email went straight into his spam folder or he’s away on hols. Looking around for someone else to do the smd soldering, I found a page on Facebook called The DX SHOP run by Roger GW4WND, over in mid Wales. 

I contacted Roger and he responded incredibly quickly, confirming that he could carry out the remedial work, so I packed up the pcb and sent it to him. It was back with me 3 days later! It cost just £80 plus the cost of the caps.

Looking at the repair, it seems that the tracks were not damaged after all and so I now wish I'd had a go at repairing it myself, but it's too late for that, and I'm very grateful for Roger's fast work.

Putting the amplifier back together was not a simple job, but thanks to all the photos I took, I managed to get it done fairly quickly, but I must admit I was a bit hesitant when it came to firing it up for the first time, LOL.

Anyway, I needn't have worried because there was no snap, crackle or pop when power was applied. I connected the Elad FDM DUO transceiver and set the input-attenuation to 5dB to keep the power output down for the first test transmission.

Pressing the PTT showed a healthy 35W on the VU meter and it remained stable, so I reduced attenuation to 3dB and got a steady 60W and 85W with 2dB attenuation. Finally, I switched to full power output and saw a plump 128W of power.

The tests were carried out with an input power of 2W which is my default level in the transceiver's menu. I increased it to 5W just to see what would happen and the amp showed over 150W, so I went back to 2W. 

Feeling comfortable with the performance of the repaired and rebuilt amp, I setup FT8 at 25W and worked stations for two consecutive hours to make sure it coped with the long data transmissions. I'm pleased to report that it did.

I bought this amplifier to make a bit of money but couldn't do that with a known fault - now I can - and despite the repair cost, I will still make a handsome profit and someone will get a superb amp.