i connected up the amplifier as instructed to the no4ba transformer with a 60 watt light bulb in line and the first time the light went out but nothing came out the amp then the next time i tried the light stayed on but the amp made a humming noise but nothing else came out the speaker - any suggestions where i should check first for problems?
thanks
Please provide more info. What transformer did you use, how did yuO hook it up, what source did you use, what speakers, what heatsink, did you adjust the bias, etc… If you cannot provide more info, then the only thing we can do is have you send in your project for repair.
Thanks for getting back to me promptly
The Transformer is a NO4BA Maplin Transformer that delivers 160VA 2@ 30v it has colour coded wiring that matches the amp. The speaker is an 8ohm 12" unit and the heatsink is the same size as specified in the manual but the finns are much longer at approx. 10cm - the bias was not adjusted as i didnt get that far but it is turned fully anti clockwise.
I do have a multimeter if this is of help
The neon light does not illuminate but I have checked and the multimeter does read that power is coming out of the transformer
Many thanks for your help so far
Neon light ? There is no neon light in this project. Do you mean the led that indicates that the +35/-35V is present ?
Check the transformer secundaries when they are not connected to the K8060 board. Make sure your multimeter is set to AC volts.
Check the direction of the large power diodes. If applicable, make sure the lacker of the transformer leads has been properly removed.
O K I have looked into these already but will try these again - If these are O k what else would you suggest please?
Many thanks
I have tried your suggestions and the results are
When the transformer is not connected to the board the mains light doesnt come on and the secondaries read 30v
When connected to the board the mains light comes on and the Power Diodes read 5v [ between the points on the board where its printed +40 & -40 ] and the LED doesnt come on
Many thanks for your continued help
This clearly indicates that something is drawing too much current on your board. Check the power diodes with a multimeter. Check the power transistors. Desolder them and measure between their pins. If you measure a low impedance between any of the pins, the transistor is most likely defective. In this case, replace all semiconductors. Make sure to replace them with the exact same types. If you do not feel confident, return kit for inspection/repair. Address can be found in the manual.
The impedence between 2 of the pins of each transistor and between the poles on each of the power diodes read 7-8 ohms. Is this okay? if yes what do I test next please?
Many thanks for your help
I forgot to mention that the Diodes only show a reading when tested one way round - when you reverse the test leads there is no reading
Thanks
The diodes look ok. Did you measure a low impedance between any two pins of the power transistors ? If this is the case, they are defective.
The impedance between 2 of the pins of each Transistor reads 7 - 8 ohms - is this okay?
Thanks
What do you mean by low please. Is between 7 & 8 Ohms considered low? or do you mean almost dead short.
Thanks for your help
Such a low impedance can be considered as defective.
The amplifier is now up and running - Many thanks for your help - just a minor question - the LED is quite dull - can this be replaced with a brighter one and what would i need to ask for and what might the disadvantages of replacing this be?
Once again many thanks
Not so much a novice
You could replace the led with a low-current type. Check your distributors catalogue. The more mcd, the brighter it will be.
O K Thanks for that
One other thing please - in the manual it states - replace the caps with 4700uF/50V types for even better performance - in what form does this increased performance take please - does it give a higher output and to what level please and where would I get these from please as they do not appear in the Maplin Catalogue
Many thanks
There is no need to do so. This is only a hint for die-hard tweakers. It will give slightly higher output, but don’t expect miracles.
O K Thanks for all your help
Sorry but I need your support again - on trying the amplifier it appeared to be okay when it suddenly sparked and flashed and some components burnt - these are resistors numbers R4, R16 & R17 - the most charred being the R17 - can you please tell me what might have caused this to happen and also what other components may have been damaged that I need to check/replace
Once again - many thanks for your continued support
maplin transformer?