Thanks for the feedback, Mark.
I ended up taking out the faulty board and wired both transformers to the one correctly functioning board.
One thing I failed to mention. It appears the relay clicks on and off correctly at 0.5, 1 , and 2 seconds but full AC voltage is being sent through the soft start as soon as the switch is pushed.
I just installed the faulty board into another amp to see if it behaves the same way and it does.
I ended up taking out the faulty board and wired both transformers to the one correctly functioning board.
One thing I failed to mention. It appears the relay clicks on and off correctly at 0.5, 1 , and 2 seconds but full AC voltage is being sent through the soft start as soon as the switch is pushed.
I just installed the faulty board into another amp to see if it behaves the same way and it does.
Then a good hypothesis to explore further, is: Either the relay contacts are shorted together, or the Inrush Current Limiter disc is shorted, or (unlikely): both are shorted.
The short could be external, meaning poor soldering or components stuffed incorrectly or a flywire gone wrong,
OR the short could be internal, meaning the relay's contacts inside the sealed box have failed to a short circuit, or the ICL disc has internally developed a zero-resistance pathway from one lead to the other.
With the board completely disconnected from the external world, and allowed to discharge itself for ten minutes, you could use an high precision ohmmeter to measure across the pins of the ICL disc. Is it close to the datasheet specification "Rcold" for the ICL that you used? For example: 20 ohms for the Ametherm SL22-20007? Measure resistance across the relay contact pins, is it greater than 200 ohms? These may tell you whether either component is shorted.
The short could be external, meaning poor soldering or components stuffed incorrectly or a flywire gone wrong,
OR the short could be internal, meaning the relay's contacts inside the sealed box have failed to a short circuit, or the ICL disc has internally developed a zero-resistance pathway from one lead to the other.
With the board completely disconnected from the external world, and allowed to discharge itself for ten minutes, you could use an high precision ohmmeter to measure across the pins of the ICL disc. Is it close to the datasheet specification "Rcold" for the ICL that you used? For example: 20 ohms for the Ametherm SL22-20007? Measure resistance across the relay contact pins, is it greater than 200 ohms? These may tell you whether either component is shorted.
Ok. Right now I have two soft start boards not operating correctly and one that IS working correctly I left in the Aleph J.
Both of the bad boards have the same problem so I’m troubleshooting both hoping maybe the issues are the same.
I pulled the thermistor on one of them and each time I check it it ranges from 28 to 35 ohms instead of the 20 ohms it’s rated for at cold temp.
I also pulled the relay and it seems to be reading correctly. Pins 11 and 14 are open.
Another weird issue I have is when I first plug in my power cord to the amp the LEDs on my psu pop on and some music starts playing. Checking the soft start out of the amp on my bench there is 70VAC across a 90k resistor (soft start not engaged) and after pushing the switch it automatically jumps to 124VAC before the relay clicks on.
Both of the bad boards have the same problem so I’m troubleshooting both hoping maybe the issues are the same.
I pulled the thermistor on one of them and each time I check it it ranges from 28 to 35 ohms instead of the 20 ohms it’s rated for at cold temp.
I also pulled the relay and it seems to be reading correctly. Pins 11 and 14 are open.
Another weird issue I have is when I first plug in my power cord to the amp the LEDs on my psu pop on and some music starts playing. Checking the soft start out of the amp on my bench there is 70VAC across a 90k resistor (soft start not engaged) and after pushing the switch it automatically jumps to 124VAC before the relay clicks on.
Attachments
I had a similar issue, AC present at the output when off, and it turned out I fitted 220N in place of 22N for C3.
Good luck.
Mike
Good luck.
Mike
This PCB limits the current, not the voltage, during the first 2 seconds after turn on. If the load is sufficiently easy to drive, even a small and limited current will drive that load to full AC voltage. You can see this with a little 2 watt "bathroom night light" bulb: it lights up to full intensity immediately, even before the bypass relay pulls in. On the other hand, a 150 watt incandescent bulb will be dim for 2 seconds, then the bypass relay pulls in, then it will light up to full intensity.
Don't focus upon the output voltage, and don't gauge "success" by measuring the voltage across a 90K resistor. Measure the output current, either with a clamp-on current probe for an oscilloscope, or with a high wattage load (>= 150 watts) like an incandescent lamp, for which it's easy to tell that the current is limited. In the case of a lamp, it will be dim when current is limited and bright when current is not limited. It may be that your boards are working perfectly now, have been working perfectly since day one, and you are misinterpreting their behavior.
If it turns out that they are faulty even when evaluated correctly with a high wattage load, then you know a few things about the "bad board":
- The delayed relay pull-in "timer" circuits are working correctly, for all three delay settings: 0.5sec, 1.0sec, 2.0sec
- The Inrush Current Limiter disc is not a short circuit
- The relay "NO" contacts (normally open) are not fused into a short circuit
- Wrong part stuffed and soldered for Q4. Maybe you didn't stuff a TN2106 device in that position. Maybe Q4 and Q3 are accidentally swapped.
- Q4 rotated 180 degrees. Maybe you accidentally reversed the orientation of Q4 when stuffing and soldering.
- Wrong part number stuffed and soldered for D1. Maybe you accidentally didn't put a 1N4748A Zener diode (22V, 1Watt) here
- D1 backwards. Maybe you accidentally reversed the orientation of D1.
- U5 pins bent underneath the chip and not fitted into the DIP socket. Remove U5 from its socket and check that no pins are bent; all pins are inserted into their socket holes
- Poor soldering on Q4, D1, U5. Maybe you've got cold solder joint(s). Maybe you've got solder bridges between adjacent pins. Maybe you've got one or more pins that were never soldered.
- Q4 failed. Maybe it needs to be replaced
- D1 failed. Maybe it needs to be replaced
- U5 failed. Maybe it needs to be replaced
Ok. Here is where I stand on the board and I’m now thinking the board works as intended but my expectations were too high because one of my boards does operate differently.
I bought a 150w incandescent bulb and tried it on the board. The light turns on about 80%, then when the relay clicks on it is at its brightest.
I confirmed c3 is 22n.
I followed Mark’s list from 1-6. Re-soldered all joints.
Haven’t tried removing and testing parts yet but wanted to conclude my findings first.
Thanks to everyone for helping.
I bought a 150w incandescent bulb and tried it on the board. The light turns on about 80%, then when the relay clicks on it is at its brightest.
I confirmed c3 is 22n.
I followed Mark’s list from 1-6. Re-soldered all joints.
Haven’t tried removing and testing parts yet but wanted to conclude my findings first.
Thanks to everyone for helping.
NVM. I am reading from earlier threads that the bulb should dim first, then brighten, and when the relay clicks it turns completely on.
With my testing, the bulb turns on quickly to 80% brightness, then when the relay clicks it goes fully bright.
With my testing, the bulb turns on quickly to 80% brightness, then when the relay clicks it goes fully bright.
This is good!
So you know that the soft-start is working properly... The current limiter is being switched in at start, hence the dim, then after X time, the limiter is switched out and the bulb can go bright as the current is no longer being strangled by the triac.
I have been enjoying this softstart board for the past year and am about to implement another one. Thanks for this cool 'gadget' Mark.
I was wondering, naively as a novice would, if one could wire an always off thermal switch in parallel with the momentary switch, to turn off the amp in case of overheating? As always, when one doesn't know too much, everything seems simple 😊
Cheers,
Soren
I was wondering, naively as a novice would, if one could wire an always off thermal switch in parallel with the momentary switch, to turn off the amp in case of overheating? As always, when one doesn't know too much, everything seems simple 😊
Cheers,
Soren
Maybe the safest implementation is to install a normally open thermal switch directly across the incoming AC mains, after the fuse of course!! Amp too hot? Blammo, blow the fuse and make the owner (a) replace the fuse; (b) reflect upon WHY this has happened; possibly investigate (gasp!). Now you need a thermal switch good for 230VAC and 5 Amps, which, in my limited experience, most of them are.
I think the idea in #814 is risky and I wouldn't try it. Too many unknowns about the precise details of how the thermal switch contacts "bounce" and how the flipflop on H9KPXG would react.
I think the idea in #815 is less risky but I still wouldn't try it.
I think the idea in #814 is risky and I wouldn't try it. Too many unknowns about the precise details of how the thermal switch contacts "bounce" and how the flipflop on H9KPXG would react.
I think the idea in #815 is less risky but I still wouldn't try it.