I have just joined the forum. I tried to get the K8060 kit to work some months ago, but gave up as it kept blowing the fuse. I have now built a lot of chip amps and modified Class D amps, and with the knowledge that I have gained thought I might be able to get it working. Answer…No…the light bulb still shines brightly !
I am not using a Velleman transformer, but a 120va 30+30. I cannot see why the tags on the board are marked AC and AC0, when the suggested transformer is a dual secondary without a centre “0” tap ?
How can you get the wires round the wrong way ? Both secondary’s carry 30v AC.
I see that you suggest checking the power transistors in nearly every post that has had this problem. Are they mostly faulty ? I will desolder and check mine, but would be intersted in your answer to the way the tranny is wired.
Take one wire from each winding and tie them together (NOT from the same winding!).
If you get approx. 60VAC between the remaining wires, then your wiring is correct. The tied together wires are the AC 0.
If you get 0 VAC or just a couple of volts, swap two wires.
I tried that. There are 4 connections required on the board, Two AC and Two OV. If you wire it the way you suggest you get a centre tapped tranny. I then had two Ov’s to connect to. I ran a link between the two 0v’s, but this was clearly not the right solution. Help !
By the way what does *start wire mean ? It says this on the Velleman transformer?
Usually, * means start of winding, this allows you to connect two winding correctly so that you get a center tapped transformer.
Sorry, at this time we have no clue regarding the problem you experience. Check all semiconductors, if necessary, replace them.
The store where you bought the kit would be a good place to look for spare parts… If they cannot help you, we’d suggest to send in the kit for inspection/repair. If sent by regular mail, repair cost is less than the price of a new kit.
In most of the replies I have seen to the problems with the K8060, the advice has been to change the semiconductors as they may be faulty. It seems that there is a problem with this kit and it has either been a) designed incorrectly, or b) the main parts (semiconductors) to make it work are faulty. Do you agree ?
In the U.K if you buy something that is faulty you either get a replacement or a refund of your money. As you will probably know Maplin who sell these kits do not stock Epitaxial Darlington Semiconductors so are you able to supply two working ones free of charge ?
We understand that you are frustrated that it does not work, but please do not jump to the wrong conclusions. We are very serious about kit building and we cannot afford to release faulty kits. It is wrong to assume that the problem lies with the design or the components. This is a classic circuit, it has been choosen for its robustness, ease of use and performance. Furthermore, it uses off-the-shelf components. You are correct, there is a two-year warranty on all our components, however, we cannot guarantee your work. If you send in your kit, and our engineers find that the problem is caused by a manufacturing error, then we will fix it for free. However, if the problem is caused by an assembly or other user mistake, then we ask a small fee (always less than the price of a new kit). A stunning 90% of all returned kits feature assembly mistakes or problems caused by (ab)use.
In this particular case, we recommend to change the semiconductors, after all, they are the only active part. Resistors and caps usually don’t go bad overnight, and if they do, you can tell by looking at them. Furthermore, we recommend to change ALL semiconductors. If two are faulty and you replace just one, it is very likely that the faulty one will take out some other parts at the next power-up. Sorry, no refunds or free parts.
Thank you for your prompt reply. Over the weekend I will re-check the whole board. I did in fact by two of these kits in order to build a stereo amp. I will measure both sets of chips and see what the conclusion is.
I checked the board at the weekend. All components are where they should be. I measured the NEW and OLD chips. NEW chips no output from centre pin to left or right pins. OLD chips centre pin showing low ohms value 3-4 ohms.
Both sets of chips showing ohms rating of between 4 & 5 Ohms on left and right pins. What does this mean ?
The new transistors seem OK, but please check again, they measure 4-5 K Ohm between outer pins, not 4-5 Ohms.
Old transistors are definately defective.