Amps from currently production with bad engineering unfortunately are often to find. Now I have a device on my table with damaged triac, which is located in series to one of the two 230VAC wires - go to schematic on last page under
http://schems.com/bmampscom/eden/Eden WT500, WT600, WT800 - Schematic.pdf
This triac was already replaced two times by the official service department with the result, that the same triac defect occurs again after a short time of use.
The tread about
http://www.diyaudio.com/forums/chip-amps/167683-triac-softstart-switching-point.html
don't provide the right advices.
First question: is this a soft start circuit (inrush current limiter), a zero voltage switch or only a protection for the internal contacts of the very small rocker switch against damage?
Second question: is the selected type from Tekkor (now "Little Fuse") "Q6025P5" the right choice (RDC of primary windings are 3,5 ohms) ? - go to
http://www.littelfuse.com/data/en/data_sheets/e2triac.pdf
for looking datasheet.
I have heard, that there are components similar to triacs, but special made for switch-on of big toroidal transformers (inrush current limiter without relay).
At first step I connected all wires from main socket at rear pannel direct to the main transformer, i. e. without Triac. Switch-on was performed by the integrated switch at power strip. This provides no issues through inrush current and the amp works fine. Nevertheless I want to create the genuine condition with an appropriate semiconductor device instead a normal triac.
Thank you for helpful hints in advance.
http://schems.com/bmampscom/eden/Eden WT500, WT600, WT800 - Schematic.pdf
This triac was already replaced two times by the official service department with the result, that the same triac defect occurs again after a short time of use.
The tread about
http://www.diyaudio.com/forums/chip-amps/167683-triac-softstart-switching-point.html
don't provide the right advices.
First question: is this a soft start circuit (inrush current limiter), a zero voltage switch or only a protection for the internal contacts of the very small rocker switch against damage?
Second question: is the selected type from Tekkor (now "Little Fuse") "Q6025P5" the right choice (RDC of primary windings are 3,5 ohms) ? - go to
http://www.littelfuse.com/data/en/data_sheets/e2triac.pdf
for looking datasheet.
I have heard, that there are components similar to triacs, but special made for switch-on of big toroidal transformers (inrush current limiter without relay).
At first step I connected all wires from main socket at rear pannel direct to the main transformer, i. e. without Triac. Switch-on was performed by the integrated switch at power strip. This provides no issues through inrush current and the amp works fine. Nevertheless I want to create the genuine condition with an appropriate semiconductor device instead a normal triac.
Thank you for helpful hints in advance.
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Well Andreas
Either replace the all circuit with a robust switch or replace the all thing with a decent soft start circuit .
Amplifier doesn't look that big to need soft start actually simple switch will solve the problem.\
May as well use a relay if you like
In general though i dont see the point
Either replace the all circuit with a robust switch or replace the all thing with a decent soft start circuit .
Amplifier doesn't look that big to need soft start actually simple switch will solve the problem.\
May as well use a relay if you like
In general though i dont see the point
The triac is a simple power switch. yes, it allows the relatively small rocker switch to control the higher currents of the transformer and circuit.
That is a TO3 case style, right? You might consider a 40 amp instead of a 25 amp. A Q6040 or equivalent.
Triacs have been used as power switches in higher power amps for decades. They have worked well and reliably.
This is only a guitar amp, and it has no special needs other than the current capacity of the switching. The Eden amps do not have a reputation as triac killers. How are the triacs failing? Open? Shorted? I would believe this particular amp has some ongoing problem, but I don't believe the design is defective, or all the Edens would be blowing them out.
That is a TO3 case style, right? You might consider a 40 amp instead of a 25 amp. A Q6040 or equivalent.
Triacs have been used as power switches in higher power amps for decades. They have worked well and reliably.
This is only a guitar amp, and it has no special needs other than the current capacity of the switching. The Eden amps do not have a reputation as triac killers. How are the triacs failing? Open? Shorted? I would believe this particular amp has some ongoing problem, but I don't believe the design is defective, or all the Edens would be blowing them out.
These should switch at zero crossing. I have seen them blow before, not on amps but lighting control.
I've never seen such a use, all the TRIAC's I have seen have been for soft-start circuits, in highish power amps that use toroidal transformers - with the TRIAC shorting out a high wattage resistor after a couple of seconds.
Conventional transformer aren't usually a problem, but TOROID's have far higher surge currents.
It would be 'nice' if they used zero crossing, but the ones I've seen (and replaced duff TRIAC's in), only had crude 'anytime' switching.
If there was zero crossing, it would be more reliable but from the crude drawing it looks like the triac uses a 220R resistor to switch the gate. If the mains it at full phase, there will be too much current feeding the gate and that will cause damage to the triac. 1Amp in fact! Use a MOC3032 to drive the triac.
Nigel: Some examples, the transformers are EI types. Simple on/off, no soft starts.
Peavey Roadmaster, see bottom center, 120v mains switch, this was 30 years ago already:
http://bmamps.com/Schematics/Peavey/peavey_roadmaster.pdf
Peavey CS800, a workhorse amp for 40 years, see bottom center:
http://www.6v6power.ru/inf/Amplifier/Peavey/Peavey CS-800 (series C).jpg
They still use triacs on high power amps in the same manner. Other makers besides Peavey use the circuit, but theirs were what came readily to mind.
I have drawers full of TO3 triacs, 25A and 40A, and aside from an occasional light dimmer, power switching is about all I use them for.
Peavey Roadmaster, see bottom center, 120v mains switch, this was 30 years ago already:
http://bmamps.com/Schematics/Peavey/peavey_roadmaster.pdf
Peavey CS800, a workhorse amp for 40 years, see bottom center:
http://www.6v6power.ru/inf/Amplifier/Peavey/Peavey CS-800 (series C).jpg
They still use triacs on high power amps in the same manner. Other makers besides Peavey use the circuit, but theirs were what came readily to mind.
I have drawers full of TO3 triacs, 25A and 40A, and aside from an occasional light dimmer, power switching is about all I use them for.
Thank you for all replies.
The faulty triac are shorted between MT1 and MT2.
Maybe the reason for the defect is the absence of a snubber network, which is necessary by switching of inductive loads (phase shift between voltage and current flow). I have heard, that alternistors or SSR devices (Solid State Relays) are the right choice to switching of inductive loads for use without additional snubber network. What exactly is the main different between a triac, alternistor and SSR ?
The case style (outline) isn't TO-3, but fastpak (go to page E2-4 of linked datasheet)
The faulty triac are shorted between MT1 and MT2.
Maybe the reason for the defect is the absence of a snubber network, which is necessary by switching of inductive loads (phase shift between voltage and current flow). I have heard, that alternistors or SSR devices (Solid State Relays) are the right choice to switching of inductive loads for use without additional snubber network. What exactly is the main different between a triac, alternistor and SSR ?
Interesting facts. The resistor value for gate switching is 22R at my amp device and not 220R.
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I can't quickly spot any triac in the schematic, but in general zero volt switching a transformer (and in particular a toroidal transformer) is about the worse way to do a "soft start". If the zero cross over switching is carried out on a core that is already saturated from previous operation, extremely high currents can result. The order of magnitude of these currents can be as high as the mains voltage divided by the primary DC resistance, so many hundreds of amperes.
You would need a zero current switching, but then this is not what a triac would work nicely with.
You would need a zero current switching, but then this is not what a triac would work nicely with.
Difficult to read what is put on a hole in the paper. Could be either. Imagine 22R with a momentary 230Volt drop, that is a lot of instantaneous gate current!
Thanks for that, I see on those circuits it's a 120V mains thing only - the 240V versions don't do it - which explains why we never see it over here.
Lower mains voltage means higher current. No surprise mains switches last shorter in 120 V AC areas.... Also need for thicker cabling, higher copper losses etc. There is a reason most countries in the world use 230/240V AC. In Europe it will be 250V within time. Power distribution is best done with high voltages and low current. The rising copper price adds to that.
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Goodday all,
I Intend switching an 800VA EI transformer at 230Vac with a bta40-600a triac. This triac switches at 360 deg angle and is rated at 40A 600V. Should the 220 Ohm resistor be ok inline with the switch and will the triac be ok for the load ?
I Intend switching an 800VA EI transformer at 230Vac with a bta40-600a triac. This triac switches at 360 deg angle and is rated at 40A 600V. Should the 220 Ohm resistor be ok inline with the switch and will the triac be ok for the load ?
You will need soft switching with that power. Here it is needed by law above 500 VA but it is also nice in practice that the lights, TV and such don't flicker when a device is switched on. So you need a triac and some circuitry. The triac will like it too as it will switch way lower inrush current. Triacs don't like inductive loads too much. Over dimensioning the triac is a brute force method to keep the triac healthy but soft switching will have more benefits.
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Jean-Paul, thanks, I understand that and I will be using a softstart. Why I want to do it like this is because I don't want to use a relay to do the high power switching. The switch on the front panel can only switch 3 A at 220V AC so I will just use it to switch the triac.
A Paul Kemble web page - PA power supply soft start designs.
I would advise to use a PCB based design and not hardwire this for safety reasons. There are many ready built similar devices on Ebay etc. Mount such a PCB with 4 stand offs and make it as safe as you can with insulated connectors, shrink sleeve etc.
Although I do understand that you want to avoid relays in the application they can last a very long time as they switch lower current. It is best to use a hard silver contact relay. When powered up the transformer will be switched on via power resistors and after a short while those resistors will be "bridged". That is different to using relays to switch inductive loads directly. With switching inductive loads directly a relay will probably last longer than a semiconductor but that is an assumption. I have relays at work that will be replaced after a service life of 35 years switching inductive loads (also more current than the relay was intended for). They now start to have flaky contacts. They will be replaced by SSRs. I think those won't last 35 years 😉
I would advise to use a PCB based design and not hardwire this for safety reasons. There are many ready built similar devices on Ebay etc. Mount such a PCB with 4 stand offs and make it as safe as you can with insulated connectors, shrink sleeve etc.
Although I do understand that you want to avoid relays in the application they can last a very long time as they switch lower current. It is best to use a hard silver contact relay. When powered up the transformer will be switched on via power resistors and after a short while those resistors will be "bridged". That is different to using relays to switch inductive loads directly. With switching inductive loads directly a relay will probably last longer than a semiconductor but that is an assumption. I have relays at work that will be replaced after a service life of 35 years switching inductive loads (also more current than the relay was intended for). They now start to have flaky contacts. They will be replaced by SSRs. I think those won't last 35 years 😉
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Why do you imagine that?, the supposed 'change' to 230V was actually no such thing - you still have 220V and we still have 240V.
The only 'change' was the specification for manufacturers, who have to supply equipment that works across a wider range, including below 220 and above 240.
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