If it is working, it must be okay, I guess ?
Depends on solder type, temp and airflow.
In my SMT soldering technique, I hand solder everything, under 10x mag using 15 mil no-clean glow core eutectic solder. Very little pkg stress. I only use the hot air machine to remove comp's or re-flow very small areas.
That's my problem though, is there a way to test without powering on?
I use a 63/37 paste with an airflow of 4-5, right in the middle of the dial, with about a half inch to one inch away. It took about 60 seconds to have the ground plane freely flowing, and that was after I did the pins first.
Do have any recommendations for adjusting my technique? Thanks for the help
xray
Not that I am aware of!!I do not use the paste technique for hand assembly, as I find it more work/material, with little or no benefit.
Without a stencil/squeegee, it is impossible to meter out the correct amount of paste, it is so small, calculate the volume of paste required. So without the correct amount of paste, you usually have too much paste, which means more heat is required to melt all that volume, which means ... too much heat = too much pkg stress
We had one of those paste metering machines, we never used it.
It really comes down to trial and error. If you are not confident, work on some practice stuff, i.e a cheaper IC in a similar pkg.
I use a low air flow on the Hot air machine
Cheers
Rick
Yeah I did have a heck of a time getting it to spread out thinly without it losing coverage. There were a few where I know I used too much, but the majority appear to have done well. I did manage to blow out the excess solder to the rear of the IC though. Thanks for the tips and advice. I hope I didn't ruin a few of them!
Hi Neofeed,
The LPUHP would definitely be the better candidate for this application. I would suggest trying a pair running single ended with the increased voltage mod described by multisync earlier in this thread. That should give you enough power to drive the ATC to pretty good levels. If you find that it's not sufficient, then adding another pair of amplifiers and running one bridged pair per channel should give you more than enough power even for very high listening levels.
Cheers,
Owen
The LPUHP would definitely be the better candidate for this application. I would suggest trying a pair running single ended with the increased voltage mod described by multisync earlier in this thread. That should give you enough power to drive the ATC to pretty good levels. If you find that it's not sufficient, then adding another pair of amplifiers and running one bridged pair per channel should give you more than enough power even for very high listening levels.
Cheers,
Owen
Hi Neofeed,
The LPUHP can be built for either Balanced on SE input. If you plan to use them with single ended output (one amplifier per driver) then you will need to build them with balanced input. If you want to bridge the amplifiers (two amps per driver) then you will want to build them as single ended modules and drive each input from each of the two balanced phases per channel.
Regardless of the configuration, the high voltage mod can be done.
I also have "MPUHP" amplifiers ready to go, so if you're interested in a completed amplifier that is already fully balanced input and output with 50W of power, then that might be an option. Send me a PM if you're interested.
Cheers,
Owen
The LPUHP can be built for either Balanced on SE input. If you plan to use them with single ended output (one amplifier per driver) then you will need to build them with balanced input. If you want to bridge the amplifiers (two amps per driver) then you will want to build them as single ended modules and drive each input from each of the two balanced phases per channel.
Regardless of the configuration, the high voltage mod can be done.
I also have "MPUHP" amplifiers ready to go, so if you're interested in a completed amplifier that is already fully balanced input and output with 50W of power, then that might be an option. Send me a PM if you're interested.
Cheers,
Owen
Hi!
I ordered 4 boards and the rest of the parts except transformers recently. I have a question about transformers:
When browsing through this thread I get the impression that a 15V 50VA is suitable. Can one of these be used for a stereo setup (with dual secondaries)?
Best regards,
Mattias
I ordered 4 boards and the rest of the parts except transformers recently. I have a question about transformers:
When browsing through this thread I get the impression that a 15V 50VA is suitable. Can one of these be used for a stereo setup (with dual secondaries)?
Best regards,
Mattias
Hi All,
I just wanted to put a note in here for people using AnTek transformers in areas with EU-derived mains voltage standards. (I'm not familiar with NA mains voltage standards, someone else can comment perhaps on how relevant this is in Northern America).
The below is based on the following conditions:
AnTek AS-0515 transformer
Output current 1.41Amps (8*(0.25/sqrt(2))
Mains voltage drops to 230 or 115V or below
With the above conditions, the 15V AnTek transformers are likely to starve the regs of volts with the BOM specified 18.17V regulator output voltage when the mains drop even 3% from 120V (or 240V) [NB AnTek transformers have no load voltage specified at 115V and full load ratings with 120V input which is .... odd, but it is clearly documented].
For EU-based mains voltage standards this might cause some problems, because at 230V nominal we're already outside the -3% and at nominal mains voltage the regulators are potentially going to see voltage dropout during full current peaks. (filtered voltage drops to 18.4V and is about 0.4V below dropout assuming 1.4A is roughly the peak current)
This isn't a big problem for me in Australia because we're in this odd transition from 240V standard to 230V standard but with high residential PV adoption here in residential areas and the fact that the distributors haven't changed the way they do distribution transformer tap settings ... it is exceedingly rare to see 230V in a domestic environment.
Suggestion 1
- select a different transformer specified for 15V @ 230V
Seggestion 2
- drop the regulator voltage to 17V [R7, R35]
- reduce gain to 14.5dB. [R6] (for SE - I haven't looked at the BAL BOM)
This will keep the SE input ~2V RMS input voltage clipping level, continuous power drops to 14W and regulators don't see any dropouts until ~111V or 222V mains. Which is only 3.5% below nominal supply voltage for 115/230V areas. As noted above in Australia at least I'd be reasonably confident with this configuration outside of rural settings. Others might comment on how things go for mains regulation in different parts of the world?
NB checking capacitor voltage rating, the 25V caps are still in spec for mains fluctuations up to somewhere north of 130V / 260V which should be out of statutory limits and even more rare.
I thought the above worth commenting so that builders in 115V or 230V supply areas or areas where distributor's supply regulation goes lower than nominal can make an informed choice.
If Owen is okay with that Suggestion 2 alternative spec I could help dig up some resistor values and part numbers, I haven't gone searching yet.
Regards,
Chris
I just wanted to put a note in here for people using AnTek transformers in areas with EU-derived mains voltage standards. (I'm not familiar with NA mains voltage standards, someone else can comment perhaps on how relevant this is in Northern America).
The below is based on the following conditions:
AnTek AS-0515 transformer
Output current 1.41Amps (8*(0.25/sqrt(2))
Mains voltage drops to 230 or 115V or below
With the above conditions, the 15V AnTek transformers are likely to starve the regs of volts with the BOM specified 18.17V regulator output voltage when the mains drop even 3% from 120V (or 240V) [NB AnTek transformers have no load voltage specified at 115V and full load ratings with 120V input which is .... odd, but it is clearly documented].
For EU-based mains voltage standards this might cause some problems, because at 230V nominal we're already outside the -3% and at nominal mains voltage the regulators are potentially going to see voltage dropout during full current peaks. (filtered voltage drops to 18.4V and is about 0.4V below dropout assuming 1.4A is roughly the peak current)
This isn't a big problem for me in Australia because we're in this odd transition from 240V standard to 230V standard but with high residential PV adoption here in residential areas and the fact that the distributors haven't changed the way they do distribution transformer tap settings ... it is exceedingly rare to see 230V in a domestic environment.
Suggestion 1
- select a different transformer specified for 15V @ 230V
Seggestion 2
- drop the regulator voltage to 17V [R7, R35]
- reduce gain to 14.5dB. [R6] (for SE - I haven't looked at the BAL BOM)
This will keep the SE input ~2V RMS input voltage clipping level, continuous power drops to 14W and regulators don't see any dropouts until ~111V or 222V mains. Which is only 3.5% below nominal supply voltage for 115/230V areas. As noted above in Australia at least I'd be reasonably confident with this configuration outside of rural settings. Others might comment on how things go for mains regulation in different parts of the world?
NB checking capacitor voltage rating, the 25V caps are still in spec for mains fluctuations up to somewhere north of 130V / 260V which should be out of statutory limits and even more rare.
I thought the above worth commenting so that builders in 115V or 230V supply areas or areas where distributor's supply regulation goes lower than nominal can make an informed choice.
If Owen is okay with that Suggestion 2 alternative spec I could help dig up some resistor values and part numbers, I haven't gone searching yet.
Regards,
Chris
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Hi Mattias,
You could certainly get away with sharing one 50VA transformer between a stereo pair of amps, but you would want to have quad secondaries so each rail of each amp has its own winding.
As you would basically need a custom transformer for that, I would suggest using a dedicated 50VA per channel. If chassis space is an issue, then you can safely go as low as 30VA per channel, and stack the toroids one on top of the other to reduce footprint.
You should also give Hochopeper's post above a good read, as it outlines the requirements more carefully for 50Hz use and 220-240V mains. You really need to consider your use case scenario (do you really need maximum continuous power?), your local mains voltage, and the quality/specs of the transformer you intend to use.
Cheers,
Owen
You could certainly get away with sharing one 50VA transformer between a stereo pair of amps, but you would want to have quad secondaries so each rail of each amp has its own winding.
As you would basically need a custom transformer for that, I would suggest using a dedicated 50VA per channel. If chassis space is an issue, then you can safely go as low as 30VA per channel, and stack the toroids one on top of the other to reduce footprint.
You should also give Hochopeper's post above a good read, as it outlines the requirements more carefully for 50Hz use and 220-240V mains. You really need to consider your use case scenario (do you really need maximum continuous power?), your local mains voltage, and the quality/specs of the transformer you intend to use.
Cheers,
Owen
Hi guys,
the transformer is a good point.
Did anybody have success to connect two amps to one transfomer with only two windings? I know Owen simulated this and it was right, but in fact the combination doesn't work... at least not with my amps. I'd like to avoid using two transformers
Regards,
Stammheim
the transformer is a good point.
Did anybody have success to connect two amps to one transfomer with only two windings? I know Owen simulated this and it was right, but in fact the combination doesn't work... at least not with my amps. I'd like to avoid using two transformers
Regards,
Stammheim
Stammheim, do you get hum? I measured 300mv of 120hz hum/buzz when connecting a source.
I was very carefull to colour code the AC wires going to the amp boards from the transformer. I made sure evry connection was the same on both boards. I tried reversing the phase of one winding, no help.
On my setup the buzz/hum only occurs when a source is connected. I was able to reduce the hum/buzz to <10mv by connecting a heavy wire from the G speaker terminal on one board to the G speaker terminal on the other board and using the centre of that heavy wire as the speaker return for both channels.
I will try to connect the signal grounds to that same point tomorrow and see what happens.
I also have a problem with one of the positive regulators. One channel produces 100 mv of ripple the other channel doesn't. I don't have any spare regulators. I will play with it some more tomorrow.
I was very carefull to colour code the AC wires going to the amp boards from the transformer. I made sure evry connection was the same on both boards. I tried reversing the phase of one winding, no help.
On my setup the buzz/hum only occurs when a source is connected. I was able to reduce the hum/buzz to <10mv by connecting a heavy wire from the G speaker terminal on one board to the G speaker terminal on the other board and using the centre of that heavy wire as the speaker return for both channels.
I will try to connect the signal grounds to that same point tomorrow and see what happens.
I also have a problem with one of the positive regulators. One channel produces 100 mv of ripple the other channel doesn't. I don't have any spare regulators. I will play with it some more tomorrow.
What is happening is that one of the regulators is getting hot immediatelly, when both amps are connected to one transformer. When I separate one amp, everything is fine. So both amps are ok for themself.
I thought about separating the power supply from the output stage and build a linear ps for both amps. Not really nice and I'd like to know what happens with the THD then...
I thought about separating the power supply from the output stage and build a linear ps for both amps. Not really nice and I'd like to know what happens with the THD then...
If the transformer wires are marked a b c d and the terminals on the boards are called 1 2 3 4 did you connect a to 1, b to 2, c to 3, and d to 4 on both boards in the same sequence exactly? I am using 0-20V , 0-20V windings and the regulators are not hot at all, not even warm. And yes I did change the capcitors to 35V types.