can someone please help me?
the 2.5 amp fuse blow’s not melt…i have narrowed down the fault to the left hand channel output transformer 03zdo43 the common black connection (brown and orange winding feeding v1 and v2 are ok. if the black wire is removed from the terminal block feeding v3 and v4 and winding green and violet, the fuse will not blow. the readings of the windings were checked against the other output transformer the readings seemed to be ok, on voltage and resistance. no valves were plugged in . so far i’ve not been able to get passed the setting up of the bias, i was about to set them when the blow started, hence the removal of the valves to enable me to try and trace the fault.
Since a while, we have been shipping the amps with 5A slow blow fuses instead of 2.5A slow blow fuses, as we have experienced that during turn-on, the 2.5A fuse sometimes blows for no reason, e.g. when the mains grid is at a peak when the relay actuates.
If there is no obvious short or assembly error, you might want to try inserting a 5A slow blow fuse.
thank you for your reply. i was aware of the 5amp slow blow fuse. i did try it,but it still blew. when i say blew, the fuse was black in colour indicating a short, unlike a fuse that melts and looks brown,with a gap in the wire. as ive stated no valves were plugged in, and only the windings concerned are the black, (centre tap)green, and violet feeding v4 and v5. if the green and violet wires are removed from the connector, the fuse
still blows, with the black wire still in the connector. of course the fuse does not ‘blow’ if the black wire is removed.
the black,brown and orange windings feeding v1 and v2 are ok 415 volts can be read on +ve
this fault happend after i corrected a bias fault on the oppersite channal. and refitted the pcb. there are no marks or punctures seen on the transformer indicating a possible fault. the load resistors were in place, not that would make a differance in my opinion. the transformer windings were checked against the oppersite channal and look ok. HEEEEELP PLEEEEASE
Looks like a dead short between the HT and GND.
Measure between black wire and GND, most likely there is a short.
hi thanks for your last, i’ve checked for ‘shorts to earth’ but didn’t find any.i did check the readings of both output transfomers against each other, both disconnected from their connectors. i used both a digital and analog meters to measure the d.c resistance. the left hand channel (the one blowing fuses including 5 amp)black to green =7.6 ,black -violet 22, violet -green =14.8, the other channel was black-green=8.7, black -violet 21.8. and violet -green 14.6 ohm not the sort of readings that would blow a 5 amp fuse! do you think the output transformer has shorted turns?(thats my feelings) if so,what should i do about it, does this component have a garantee? i would love to hear a rearly simple answer that ive overlooked.
I’m sure you’ll understand that troubleshooting this from a distance is difficult.
If you are positive that there is no mechanical cause (i.e. a short to gnd somewhere), then we must suspect the output transformer.
There is a 2 year warranty on all parts, so you can return the transformer for inspection/exchange.
Please return it to:
Velleman Project Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium
thank you for answer, yes i do belive that the transfomer has a fault, i will send it as soon as possible. just to re cap, no valves were pluged in. only the left hand channel is affected. and only one winding on the output transformer. all wires were disconnected one at a time, only the black wire blew the 5 amp fuse. no marks, indentations, or burns could be seen on the tx. no readings were possible to earth.
many thanks i look forward to a replacement soon. kind regards colin
[quote=“penttos”]thank you for answer, yes i do belive that the transfomer has a fault, i will send it as soon as possible. just to re cap, no valves were pluged in. only the left hand channel is affected. and only one winding on the output transformer. all wires were disconnected one at a time, only the black wire blew the 5 amp fuse. no marks, indentations, or burns could be seen on the tx. no readings were possible to earth.
many thanks i look forward to a replacement soon. kind regards colin[/quote]
Hi Penttos - it’s your old pal Plonka - I can confirm all that you have said because as you know I was there with you during much of these tribulations. Let’s hope the ‘new’ trannie fixes this fault and you can move on to hearing some glorious music - Heavy Metal and Rap is your preference I believe? Just kidding mate; I believe the small unit that feeds the ‘Beast’ (the k4040) is not giving you the gain that you would expect; is that correct? I suppose its a pre amp set up and there are no valves involved so my idea about looking at the A/B/C class of amplification settings in order to squeeze out a bit of extra gain does not apply? I would guess that the same settings to bias on the base of a transistor would be inappropriate - perhaps? You are right if you think I am groping in the dark here. You will excuse me, knowing how many long years it has been since I had the pleasure of dealing with such matters!! I am available to assist you this weekend if the trannie is back though I believe you said it may take a while. Bacon rolls with no butter would be nice along with an Earl Gray or two.
Cheers Old Chap - Plonka
Hi Vel417, do you have a update of the output transformer replacement?. i presume you recived the fulty one i sent to you?
Repair dept. informed us that the unit will be exchanged.
please can you tell me when i can expect delivery of the replacement output transformer ? it has been approx. 5 weeks since i sent the faulty one to be exchanged. i know your repair department is now involved. is it possible for them to give an approx date of dispatch from you. penttos