Hello,
I have switched the main voltage for the first time (no valves plugged yet) on my amplifier and when after one minute, the relay energised, the fuse has blown. When I watch the main board I don’t see any short cut but maybe…
Does anybody know what I could check ?
Thank you
Paul
Are you using a 5A slow blow fuse ? If not, replace the fuse with this type.
Apparently, the problem happens when the high voltage activates.
Use a multimeter to check for shorts in the HT section. Warning ! HT voltages can kill. Unless you know what you are doing, do not measure on a live amp. Hint: Keep one hand in you pocket at all times.
Thank you,
I have tried several times but I blew my fourth fuse… Can I send you the main board for checking ? Do I need to order the special shipping box dm4040 ? What is the good adress ?
You can send the board to the address that you can find in the manual, however, are you sure that you’ve checked everything ? Maybe there is a simple explanation. Can you get local help from a friend who can take a look at your assembly. Check the wiring of the power supply transformer. Following hints are for advanced users, be extremely careful! Once again, the voltages in this amp can kill ! Remove all tubes first.
Remove the primary of the power supply transformer. Check if fuse blows. Turn off power. If not, connect primary and disconnect all secondaries. Make sure none of the secondaries touch eacht other or other parts. Check if fuse blows. Turn off power. Now start connecting each secondary until fuse blows. Turn off power every time. This should allow you to determine if problem is located in HT, bias or heater wiring.
Be extremely careful. If you do not feel confident, don’t try the above. Keep us informed.
Hello,
well, I have disconnected the primary and now, when the relay energised every thing is good. The front panel led become green. So have specially checked the HT. But nothing looks bad. What could I check now ?
Thank you
Please check my previous post
[quote]Remove the primary of the power supply transformer. Check if fuse blows. Turn off power. If not, connect primary and disconnect all secondaries. Make sure none of the secondaries touch each other or other parts. Check if fuse blows. Turn off power. Now start connecting each secondary until fuse blows. Turn off power every time. This should allow you to determine if problem is located in HT, bias or heater wiring.
Be extremely careful. If you do not feel confident, don’t try the above. Keep us informed.[/quote]
Well,
I have removed the primary of the power supply transformer. Fuse didn’t blow. So I have connected primary (with out green and grey wires) and disconnected all secondaries… and fuse has blown (none of the secondaries was touching each other).
I saw something that could be interesting :
Earth wire has a black spot (burned) on it.
Can you check the impedance of the primary winding with a multimeter ? Be aware that the impedance is very low. Measure with an analogue meter if possible.
Did you check the transformer for physical damage, e.g. windings that touch the chassis or eachother due to impact damage. Examine the transformer closely.
Hello, sorry, I didn’t undertand what you called “primary” before. In fact primary is ok. Fuse blows when I plug the two 300V red wires on the main board.
OK, so apparantly there is a problem in the HT section of the amp.
Check with a multimeter if there is an apparent dead-short on the board or if it is simply drawing too much current somewhere. Check D11-D14, resistors and smoothing caps (polarity), check solder joints. Look for shorts between solderings.
I have watched and watched again all the soldering, looking for a short. About D11-D14 when I use the diode tester on my multimeter I see 630 every where except on D13 where I find only 600.
A first sight, the diodes look OK. Maybe it is time to seek local help, and have a friend or collegue take a look at your circuit. Sometimes, someone else spots something you’ve overlooked. If you cannot get local help, you can return your kit for inspection and repair. All repair is treated in our main office in Belgium (for US: Velleman Inc, Ft. Worth, TX). Please keep in mind that if you decide to return your amp, it should be boxed in such a way that it cannot get damaged during shipping. We cannot take reponsability for damage during shipping.