Hard to see how all those caps could be bad tbh. I think something might be amiss with the testing there...
🙂
🙂
C10 C19 C16 are all definitely faulty. My DMM can’t measure the caps C15 C16 C4 C1 C12 C7 C8 C11 on either board, I am getting a new DMM tomorrow.
The new multimeter is better. I have been over the board it has 4 resistors that are faulty R33, 27, 29 & 13. Capacitors C10, 19, 15 and 16 are faulty. Tr7, 8, 9 & 10 are faulty. I tested everything on the board doing a comparison with the good board. The capacitors which I couldn’t measure any capacitance were on the board so I measured the resistance and compared that to the good board (I am guessing if I removed them I would get a reading). My new DMM is a ANENG 8002 and cost £15.
As a general rule all parts need to be isolated to test them even to a basic level of functionality. It is not just interaction with other surrounding parts that can give incorrect readings but also residual voltage from the power supply. Even a few hundred millivolts floating around can upset the reading of many meters.
I didn’t want to desolder everything, it would be impractical and also result in more faults induced by my lack of skill. I understand that a faulty component on the damaged board can effect the measurements of others.
I guess you are saying remove the suspect components and test them. I am confident about the resistors and capacitors that I have identified are faulty. I am not so with Tr7, 8, 9, & 10 and will check them off the board. Actually I will test all the faulty components off the board.
Thanks for the advice Mooly
I guess you are saying remove the suspect components and test them. I am confident about the resistors and capacitors that I have identified are faulty. I am not so with Tr7, 8, 9, & 10 and will check them off the board. Actually I will test all the faulty components off the board.
Thanks for the advice Mooly
All the resistors and capacitors tested ok off the board and are back on (so much for my confidence). I guess I have to remove and test all of the transistors?
Any part checked in circuit can give misleading results. Resistors may be paralleled with semiconductor junctions which can effect the reading on the resistor and/or make the semiconductor look bad. Lots of possible scenarios and the only sure way is to isolate them. A quick dab with solder braid and a hot iron usually removes all the solder to leave the component lead free.
Good luck 🙂
Good luck 🙂
Tr1, 7, 8, 9 & 10 tested faulty, I had already replaced the others. I don’t have a replacement for Tr1 as I was sent the wrong ones. Once I replace Tr1 I will compare the boards again.
Both boards test the same 🙂 They didn’t until I changed the fuses, I was worried as I had tested and changed everything that was likely to be faulty. I was measuring around C2 Tr9 & 10 and getting big differences until I changed the fuses. I will test it later.
I'm losing where you are up to on this 🙂
If at this point and if you can not find any obviously faulty parts then I would look at taking voltage measurements with it all powered up. Always use a bulb tester to prevent damage. Voltage checks should hopefully show any problem areas.
If at this point and if you can not find any obviously faulty parts then I would look at taking voltage measurements with it all powered up. Always use a bulb tester to prevent damage. Voltage checks should hopefully show any problem areas.
I rebuilt the amp, powered it up and no fuses blew. I then went to bed. When I woke up I wired up the amp and tried it out. It sounds absolutely amazing. I had been using my TPA3255 class D, my 405 sounds better in every respect! I have only listened to Hotel California on this playlist (had to listen to it a few times)
I can hear some noise when I am right next to the tweeters so I think this is the power supply. I will do some of the Bernd Ludwig mods to the power supply. But for now I am going to enjoy my music 🎶 Thanks everyone for all your help and advice.
I can hear some noise when I am right next to the tweeters so I think this is the power supply. I will do some of the Bernd Ludwig mods to the power supply. But for now I am going to enjoy my music 🎶 Thanks everyone for all your help and advice.
Yes 👍 I started getting into audio electronics during covid lockdowns. I could not afford the stereo I wanted so I put together a class d, a RaspberryPi running volumio and put it into a cheap case. Now I am messing about with a current dumper. I can’t believe I made a mistake while soldering and took out every single transistor on the board. Well I have learnt a very good lesson in soldering and fault diagnosis.
I have been playing with my Focusrite Solo and Rew. I was using the Solo as a balanced DAC a year or so ago and thought it was very good for the price. This is how the 405 measured. I think there are some power supply problems.
I am getting 110v instead of 100v across my caps and I don’t know why. My transformer is wired for 230v as I am in the UK.
My clamp circuit board has reached the end of its life. It was in a terrible state when I replaced its caps, with tracks lifting etc. I stupidly removed it again and on closer examination it had wire soldered over the tracks, also two of the pads have totally detached (they were partially detached). I was on the lookout for a new one but couldn’t find one. I did make one on a prototype board and used wires to connect it to the speaker terminals but I don’t trust it. I have two 405-2 M12565-7 board that are tested and in very good condition on the way, an expensive way to replace the camp board!
My clamp circuit board has reached the end of its life. It was in a terrible state when I replaced its caps, with tracks lifting etc. I stupidly removed it again and on closer examination it had wire soldered over the tracks, also two of the pads have totally detached (they were partially detached). I was on the lookout for a new one but couldn’t find one. I did make one on a prototype board and used wires to connect it to the speaker terminals but I don’t trust it. I have two 405-2 M12565-7 board that are tested and in very good condition on the way, an expensive way to replace the camp board!
Although the UK is now (and has been for ages) a '230 volt region' nothing actually changed in the supply and distribution network, only the tolerance of the supply on paper changed. It used to 240v -/+ 6% and is now 230v at -6 and +10%. You can easily see voltages in the 250 volt range in the UK.
If you have your Quad set to 230 v and not 240 v the output from the secondaries will be higher. I would recommend you set it to 240 volt if possible.
If you can not hear any hum and buzzing on the audio output (speakers) then I wouldn't worry. Before hunting down problems with measured results you really need to get a base line for the test and measurement setup. You can easily get ground interactions and so on in testing.
If you have your Quad set to 230 v and not 240 v the output from the secondaries will be higher. I would recommend you set it to 240 volt if possible.
If you can not hear any hum and buzzing on the audio output (speakers) then I wouldn't worry. Before hunting down problems with measured results you really need to get a base line for the test and measurement setup. You can easily get ground interactions and so on in testing.