hello I have assembeled k4040 upon measuring voltages i find that there is something wrong. at r10 there should be -50v .But i mesure 12v pos. I have cheched that c31 is correctly mounted so what can bewrong.It should not be possible to measure pos votage here is there a leak of pos voltage into the bias sircuit and where should i look too find it?
Are you sure you are measuring with reference to GND ?
[quote=“VEL417”]Are you sure you are measuring with reference to GND ?[/quote] yes gnd taken from j26 the other chanel ok measures -50v there
Check with a multimeter if you have zero resistance between a leg of R5 and R10. Maybe there is an interruption somewhere.
[quote=“VEL417”]Check with a multimeter if you have zero resistance between a leg of R5 and R10. Maybe there is an interruption somewhere.[/quote]I had placed r9 in the sockets of r10 and vice versa.the bias sircuit seems ok now.But something must have happened elsewhere hopefully due too mentioned misplacement.All high currencies are only half of what they should be. Can there be something wrong in the slow start sircuite?
Check the voltage on the HT winding of the transformer (285VAC)
Check the voltage over R81 (+400V)
Check the voltage between one leg of R80 and GND (+360/+400V)
Check the voltage between one leg of R82 and GND (+360/+400V)
Warning: do not probe on a live amp unless you know what you are doing. Voltages in this amp can kill! Always keep one hand in your pocket.
[quote=“VEL417”]Check the voltage on the HT winding of the transformer (285VAC)
Check the voltage over R81 (+400V)
Check the voltage between one leg of R80 and GND (+360/+400V)
Check the voltage between one leg of R82 and GND (+360/+400V)
Warning: do not probe on a live amp unless you know what you are doing. Voltages in this amp can kill! Always keep one hand in your pocket.[/quote]The resistor r81 was broken now replaysed.measurements suggested ok still no activity in the slow start sircuite.The relay ry5 does not activate.The amplifier does not finish warming up.It is not possible to do the bias adjustment suggestions?
There must be one or more assembly problems in the timing circuit. As you have already encountered two assembly problems, we strongly suggest that you have your assembly checked by a qualified technician, to avoid future problems. Pay special attention to solder joint quality, position of the components, polarity of diodes, caps,… Make sure you did not swap 547 and 557 transistors etc… Check if all wire jumpers are placed correctly and that none have been forgotten.
[quote=“VEL417”]There must be one or more assembly problems in the timing circuit. As you have already encountered two assembly problems, we strongly suggest that you have your assembly checked by a qualified technician, to avoid future problems. Pay special attention to solder joint quality, position of the components, polarity of diodes, caps,… Make sure you did not swap 547 and 557 transistors etc… Check if all wire jumpers are placed correctly and that none have been forgotten.[/quote] Let me go through this form the beginning:When i had finnished the assembly and conected to the mains,every thing looked normal,the front led flickered red green ,and after a while the green was continuously.I cheched the voltages as mentioned in the manual, they were normal at sk3 and sk4 and in the tube sockets.I fit the small tubes,connected the mains and there was a minute of red/green flickering before stabile green came on.I checked the votages on the pcb as mentioned and they were all normal, but i must have forgot to check the voltage at r 10.So i placed the large tubes and connected to the mains.Now the fuse blew.I disconnected the mains replaced the fuse and pulled out the large tubes.connected the mains and cheched the voltages on the pcb again r10 must have been forgotten.I disconnected placed the large tubes and after the warming up had finnished the tubes in the v5-v8 got terribly hot.Beeing a newbie I didn`t understand that the best would have been to turn of the mains and search for faults.anyway the tube in sockets number 5, or six got to hot and the assosiated resistance 10 ohm burned out.I disconnected replaced the resistance and begann to search for mismounts.I found the mismount of r9 and 10 and changed them to correct values. Now the votages are correct in the bias sircuite and i mesure correct voltage in tube pins number 5 in tube sockets number 1-8.I have checked for mismounts elsewhere and every thing seems to be correct.I have replaced the broken resistor of r80 as mentioned but the high votages are half of given values. I cannot see that the slow start sircuite is functioning.The ry5 does not work. My question is What damages can have occured due too the above mentioned.I have cheched the resistor for failure and there seems to be no voltage over r69,70,73,74,r11,r12,r16.I shall replace these later today. Is there something more I shall look for?
[quote=“vega”][quote=“VEL417”]There must be one or more assembly problems in the timing circuit. As you have already encountered two assembly problems, we strongly suggest that you have your assembly checked by a qualified technician, to avoid future problems. Pay special attention to solder joint quality, position of the components, polarity of diodes, caps,… Make sure you did not swap 547 and 557 transistors etc… Check if all wire jumpers are placed correctly and that none have been forgotten.[/quote] Let me go through this form the beginning:When i had finnished the assembly and conected to the mains,every thing looked normal,the front led flickered red green ,and after a while the green was continuously.I cheched the voltages as mentioned in the manual, they were normal at sk3 and sk4 and in the tube sockets.I fit the small tubes,connected the mains and there was a minute of red/green flickering before stabile green came on.I checked the votages on the pcb as mentioned and they were all normal, but i must have forgot to check the voltage at r 10.So i placed the large tubes and connected to the mains.Now the fuse blew.I disconnected the mains replaced the fuse and pulled out the large tubes.connected the mains and cheched the voltages on the pcb again r10 must have been forgotten.I disconnected placed the large tubes and after the warming up had finnished the tubes in the v5-v8 got terribly hot.Beeing a newbie I didn`t understand that the best would have been to turn of the mains and search for faults.anyway the tube in sockets number 5, or six got to hot and the assosiated resistance 10 ohm burned out.I disconnected replaced the resistance and begann to search for mismounts.I found the mismount of r9 and 10 and changed them to correct values. Now the votages are correct in the bias sircuite and i mesure correct voltage in tube pins number 5 in tube sockets number 1-8.I have checked for mismounts elsewhere and every thing seems to be correct.I have replaced the broken resistor of r80 as mentioned but the high votages are half of given values. I cannot see that the slow start sircuite is functioning.The ry5 does not work. My question is What damages can have occured due too the above mentioned.I have cheched the resistor for failure and there seems to be no voltage over r69,70,73,74,r11,r12,r16.I shall replace these later today. Is there something more I shall look for?[/quote]Jippi. I bought myself a better mesuring instrument and found out that som of the diodes was broken.So I replaced them all.Of course I did check for other misplacements of component .Every thing was ok.I also checked for misconnections and bridges on the pcb.Now every thing is fine.The only thing I dont understand is why the voltage at r 65,65 are both 90vdc should be 110vdc
Whar can the reason be?
Glad to read it works.
It is normal to have a certain tolerance on voltages due to component tolerances and mains voltage fluctuations.