Hi all, I'm attempting a repair of an Ayon Spark Delta. It ran for several hours without load connected and has since developed a 100Hz humm/rattle in the left channel. It's faint but noticeable and it shows up on the scope as spikes at a 100Hz interval. Besides running with no load, it also had 12AX7's instead of 12AU7's in the preamp section, causing oscillations among other unwanted audible issues (e.g. increased noise floor)
It's not an overly complex amp for the most part, but it does have some proprietary electronics for auto-bias, startup sequence, etc. It's not immediately clear what's causing the 100 Hz spikes. Power supplies are shared between channels and the right channel is clean, so... Without a schematic, it's rather hard to get my head around. Mainly because it's a 52kg beast, it takes very little to upset the auto-bias and auto-shutdown and it's a mystery to me what topology Ayon used in this amp (besides it being single ended in the output (paralleled 6C33 triodes).
All B+ and heater voltages measure fine and clean.
Switching out the tubes changes nothing.
Tested the preamp tubes to be sure on a tube tester and they check out fine.
Amp is able to auto-bias the output tubes, but in the defective channel, one 6C33 gets set to a much lower grid voltage. Also after bias settings are renewed.
Before continuing, I wondered if there's anyone out there with more info, schematics or experience? Not an amp we see everyday, so might be an interesting ride.
It's not an overly complex amp for the most part, but it does have some proprietary electronics for auto-bias, startup sequence, etc. It's not immediately clear what's causing the 100 Hz spikes. Power supplies are shared between channels and the right channel is clean, so... Without a schematic, it's rather hard to get my head around. Mainly because it's a 52kg beast, it takes very little to upset the auto-bias and auto-shutdown and it's a mystery to me what topology Ayon used in this amp (besides it being single ended in the output (paralleled 6C33 triodes).
All B+ and heater voltages measure fine and clean.
Switching out the tubes changes nothing.
Tested the preamp tubes to be sure on a tube tester and they check out fine.
Amp is able to auto-bias the output tubes, but in the defective channel, one 6C33 gets set to a much lower grid voltage. Also after bias settings are renewed.
Before continuing, I wondered if there's anyone out there with more info, schematics or experience? Not an amp we see everyday, so might be an interesting ride.
The attached images show the speaker output with 8 ohm load connected (yellow trace). When zooming in on the spikes, they get larger (high frequency content). The yellow trace with the larger amplitude is the 12AX7 the amp came with, showing the spikes more prominent. The other image is with a 12AU7.
