My valve pre amp makes a tick or tick-tick noise like a spark on start up, not through the speakers just from inside the case, can't really see/hear where. The question is a general one - for example do capacitors or diodes sometimes do this when they are starting to fail? The preamp works fine, BUT it sounds like the start of something to be concerned about?
Any ideas?
Any ideas?
Did it just start or has it always done it?
If the design uses relays to select inputs it could be the relays powering up. Relays tend to make a sharp snap when they are energized or de-energized.
If the design uses relays to select inputs it could be the relays powering up. Relays tend to make a sharp snap when they are energized or de-energized.
it's just started, initially one tick every now and then and now every time and sometimes multi ticks
Sounds like it could be something arcing. I had a similar problem once that was caused by a bad connection/joint on a board. I powered it up and looked - eventually I could see it arc once in a while. Redid the joint and all was well.
That's how we find ignition sparks that are misfiring...
Open the hood, and dim the lights.
It depends on their mode of failure and how much potential they have across them. Other possible causes of "ticks" is LF oscillation. Another thought occurs, some ECC** valves glow when heater voltage is applied from the inrush current, potentially a click or tick might be heard as things settle.
As mentioned, look at it in the dark and scope the preamp, starting at the front working forwards looking for spikes.
Andy.
I had some similar crackles on a preamp, and I read an interesting article here about heater/cathode insulation breakdown. My preamp is a pair of cascodes, but just one heater winding, so the upper tube is only just within limits with the heater/cathode voltage limit. The article said this is not an ideal situation, and as the tubes age the insulation can degrade, which manifests itself as crackles and pops.
I tested the tubes (ECC83s), and I did get one to flash and trigger the voltage protection on my AVO Mk3, but then it tested fine when I tried it again.
Maybe try a different set of tubes and see if that makes a difference?
I tested the tubes (ECC83s), and I did get one to flash and trigger the voltage protection on my AVO Mk3, but then it tested fine when I tried it again.
Maybe try a different set of tubes and see if that makes a difference?
well as it happens 2 6dj8s do receive a huge influx of AC heater voltage and you can see the flare at the start. I could swap these and see if the sound/issue changes. It just on first impression does not have the classic valve chime sound.
Noise like a spark on start-up could be produced by L-input chokes while crossing zero current. Frequenly seen when tubes heat up so long time and there is not enough ballast resistor applied.
Sometimes the tube glass envelope makes a “ping” sound when it’s heating up or cooling down. Could this be what you are hearing?
How long have you had this pre? Is it something that has just started, or has it always done this?
How long have you had this pre? Is it something that has just started, or has it always done this?
thanks, but it does not sound like that - it's more of a large 'tick' and only on start up (5-10 seconds after switch on). The amp I have had for 10 years or more, and it is a new 'sound' unfortunately.
Capacitors usually develop high internal resistance until they overheat and then let out the magic smoke. So it doesn't immediately sound like a failing cap, although anything is possible. (e.g., it could be a cap that is overheating, causing a stress on a pcb trace, which then develops an arc.)
Have you moved it lately? Put it under any sort of stress to cause a broken joint? What's the make/model number or do you have a schematic? Any pics of the board?
Have you moved it lately? Put it under any sort of stress to cause a broken joint? What's the make/model number or do you have a schematic? Any pics of the board?
hey - thanks for all the help. I am pretty sure I found the problem. There is a 12BH7A valve in the power supply that get very hot. I put a valve cooler on it and I think it might have made matters worse. The valve seems to have developed micro cracks in the glass near the pins, and the sparks occur on initial start up. The valve cooler was hiding the light show, but in complete darkness I tracked it down when it did some major sparking last night. A replacement valve seems to have cured it, I have never seen this before.
Glad you found the issue.
Mr. Carlson's Lab on Youtube has a video that might be of interest to you. Look under "Playlists" then "Tech tips Tue". The video is called "Dirty little secrets".
I found it after I freaked out because one of my preamp tubes had "filament flash". As Paul explains in the video it's easy enough to solve ( if it bother's you and you have the room inside the case ) with a switch and a resistor.
Mr. Carlson's Lab on Youtube has a video that might be of interest to you. Look under "Playlists" then "Tech tips Tue". The video is called "Dirty little secrets".
I found it after I freaked out because one of my preamp tubes had "filament flash". As Paul explains in the video it's easy enough to solve ( if it bother's you and you have the room inside the case ) with a switch and a resistor.
