Richard1001 wrote: ↑Fri Jan 28, 2022 7:04 pm
Zueumm is good!
Nice its working again!
Richard1001 wrote: ↑Fri Jan 28, 2022 7:04 pm
The popping of the mains switch can be reduced by placing a cap over the mains voltage after the switch. Ceramic 10nf / 3KV works fine.
Thanks for the tip, I used to have a 0.04uF at the standby (only the first one, not the two after). I remember the bonamassa surge cap, maybe something to look into as it would help on both?
Richard1001 wrote: ↑Fri Jan 28, 2022 7:04 pm
Have you measured the failed standby switches after you took them out of the amp? (Ohm / continuity meter) Where they still broken?
I disposed of the first two failed switches but I will test my current one once I replace it and will report back
rccolgan wrote: ↑Fri Jan 28, 2022 4:39 pm
Note: My bias is not the modified bias that Richard/Erwin came up with. I'm still using the parallel pot to adjust the resistance (see picture).
I don't use a bias pot in my 002 and did not come up with a modified bias control. It looks like Rafael is using the parallel bias pot.
If I had to come up with a bias control, i would put the variable resistor in the voltage devider that sets the bias voltage, not in the powersupply.
New switch arrived and I replaced the standby, measured voltages and everything is fine.
I turned the amp on for maybe 10min, turned off for less than a minute and on again.
At first start up everything is fine, but if I turn off and on again, at the second start up this is what is happening, a bit of hum, a pop and then the amp is fine. I checked the 1A fuse and it is still fine. I wonder why I am having this type of noise at start up and worried it may cause issues again in the future. Any ideas?
I measured the previous defective standby, on one position it has .01Ohms and the other infinite (0.L)
You do not have the required permissions to view the files attached to this post.
Bombacaototal wrote: ↑Wed Feb 02, 2022 1:15 pm
New switch arrived and I replaced the standby, measured voltages and everything is fine.
I turned the amp on for maybe 10min, turned off for less than a minute and on again.
At first start up everything is fine, but if I turn off and on again, at the second start up this is what is happening, a bit of hum, a pop and then the amp is fine. I checked the 1A fuse and it is still fine. I wonder why I am having this type of noise at start up and worried it may cause issues again in the future. Any ideas?
I measured the previous defective standby, on one position it has .01Ohms and the other infinite (0.L)
What i hear is a powersupply hum gradualy getting louder after you turn the amp on, a pop and after this, normal operation.
So when you turn on the amp there seems to be a high current draw untill the pop. At least, this is what it sounds like to me.
If i count correctly you've now installed the 4th standby switch. The previous switch seemed broken in circuit, but when you take it out it measures fine. I think it is a valid assumption that there is another cause for the switch to appear broken than the switch itself.
Both of your problems could be unrelated, but my advise would be to first find out how it is possible that the standby switch seems broken in circuit / a connection is measured while the switch itself is open. If you find the cause of this, you can next determine if it has any relation with the hum and popping.
I would start by closely examening both sides of the powersupply board (capacitor board) and wiring.
Yeah the standby switch is an odd one, as it does function normally to start with. But at some point it just stops working, as you pointed out, only when it's inside the circuit. I wonder if Ryan's similar issue was on the PCP or P2P amp?
Attached is my power supply board. It's a PCB so not sure much can be done wrong? Underneath seems good too.
You do not have the required permissions to view the files attached to this post.
Last edited by Bombacaototal on Wed Feb 02, 2022 3:17 pm, edited 1 time in total.
Richard1001 wrote: ↑Wed Feb 02, 2022 3:18 pm
That's where the rectifier should be connected ( for B+)
Yes indeed, its the B+ OUT of the bias board. I honestly cannot find anything wrong....
By the way the issue (of hum and pop) seems to be more if I wait half a minute or so between turning the amp On and Off. If I do quickly it seems fine from both mains and standby
New power tubes will arrive on Friday and I will try them in just to be sure
Richard1001 wrote: ↑Wed Feb 02, 2022 6:45 pm
Hmm, i see the picture and post are changed...
Hi Richard, yes, sorry for that, but I edited the post before I saw your reply as I realised my initial question was redundant. I can add the picture with the label back?
Can you please share photos of your switch wiring as well?
I’m about to open mine up for tweaking and will be happy to do any experiments or measurements - just let me know what procedure to try. It’s also got the bias pot in parallel on the power line, and I use the same standby switch you have.
timrobertson100 wrote: ↑Thu Feb 03, 2022 7:57 am
Can you please share photos of your switch wiring as well?
I’m about to open mine up for tweaking and will be happy to do any experiments or measurements - just let me know what procedure to try. It’s also got the bias pot in parallel on the power line, and I use the same standby switch you have.
Find attached the switch and let me know if you need anything else
You do not have the required permissions to view the files attached to this post.
I have re tinted all the power supply board lugs and checked all ground points making sure they are as tight to the chassis as they can. Ran the test again of turning the amp on, then leaving it off between 30 seconds to a minute, then ON again and the issue persists. I will try the new power tubes as soon as they are in and report back.
I am also wondering if I could have a bogus supply capacitor?
You do not have the required permissions to view the files attached to this post.
