FFT4ME: I think you should reflow both boards, so best to remove the second board as well. The differences in measure pre and post reflow seem to indicate a soldering issue that is likely to exist in both.
Okay,
I dug a couple old boards and the measurement across C3 all read 375K ohms [335k (R10) + 40k (R12)] so something amiss there.
My fets read about 35 or 36 ohms D to S, but it's hard to make sensible tests without a proper transistor tester.
I think you need to remove C3 from one board and measure ground to R10(g) again. If nothing has changed, then again with Q4 out...
I dug a couple old boards and the measurement across C3 all read 375K ohms [335k (R10) + 40k (R12)] so something amiss there.
My fets read about 35 or 36 ohms D to S, but it's hard to make sensible tests without a proper transistor tester.
I think you need to remove C3 from one board and measure ground to R10(g) again. If nothing has changed, then again with Q4 out...
Agreed! I know this is a long thread, but if you were to read through it all, 98% of the problems reported were because of bad solder joints, (including my own). Redoing BOTH boards and taking the time to make sure they are done right usually will solve the problem(s).
well the spite got into me because of how much solder leaked through the holes and gooped up the cap on the other side. Suffice it to say i'll have to get another cap before this board works again.
my frustration level is getting higher. with C3 out I measured again the first time I got 23.3k ohm then i checked again and got 61k ohm then checked a 3rd time and got 18.6k ohm (edit - measured again and got 19.2 kohm).
I agree that a lot of it is bad solder joints, but i went through the board and tried to reflow everything. The numbers got better but a few values were still off. I dont have any caps to fit in the board and there's an annoying piece of lead I can't get out of the hole where the cap was.
The instructions made it look so easy. I took my time and measured all my resistors and labelled them before stuffing. I checked each value a few times before stuffing it and all my values made sense along the way. I just don't know where to go now.
my frustration level is getting higher. with C3 out I measured again the first time I got 23.3k ohm then i checked again and got 61k ohm then checked a 3rd time and got 18.6k ohm (edit - measured again and got 19.2 kohm).
I agree that a lot of it is bad solder joints, but i went through the board and tried to reflow everything. The numbers got better but a few values were still off. I dont have any caps to fit in the board and there's an annoying piece of lead I can't get out of the hole where the cap was.
The instructions made it look so easy. I took my time and measured all my resistors and labelled them before stuffing. I checked each value a few times before stuffing it and all my values made sense along the way. I just don't know where to go now.
Checking your capacitor by measuring its DC resistance is not reliable. Does your meter measure capacitance? My guess is that your capacitor is OK. It is likely that your problem is with your Q4 (2SK170).
You can remove it and test it. Be careful when desoldering it. Use a needle nose plier and hold onto the leads between the Q4 body and PC board to act as a heat sink while desoldering. Then test it:
How to Test an N-Channel JFET - YouTube
As I mentioned previously the Q3 (ZTX450) is likely damaged too.
How to Test an NPN Transistor - YouTube
You can remove it and test it. Be careful when desoldering it. Use a needle nose plier and hold onto the leads between the Q4 body and PC board to act as a heat sink while desoldering. Then test it:
How to Test an N-Channel JFET - YouTube
As I mentioned previously the Q3 (ZTX450) is likely damaged too.
How to Test an NPN Transistor - YouTube
@Ben Mah thanks. I might return to it later tonight or perhaps tomorrow. I'm kind of frustrated right now and, as evidenced by a cap I now have to replace (and have none on hand) good decisions arent made when you're frustrated.
To be honest, there's so much excess solder I'm not quite sure how to handle it. I have solder braid on order as I cant seem to get the solder sucker to get into some of the nooks and crannies. If a sufficient number of components are toast, I may just go ahead and buy another parts kit and start again, this time being less heavy handed with the solder so there isn't so much goop on the other side of the PCB from where I soldered, and I can be extra careful about heat when soldering some components.
To be honest, there's so much excess solder I'm not quite sure how to handle it. I have solder braid on order as I cant seem to get the solder sucker to get into some of the nooks and crannies. If a sufficient number of components are toast, I may just go ahead and buy another parts kit and start again, this time being less heavy handed with the solder so there isn't so much goop on the other side of the PCB from where I soldered, and I can be extra careful about heat when soldering some components.
Desoldering braid with flux on it will easily remove the solder.
A temperature controlled soldering iron is best for delicate electronic components such as small form factor transistors. Is your 40W iron temperature controlled, or is it 40W with no control? A 40W iron with no temperature control can solder delicate components if you have good soldering technique. But the margin for error is low with delicate components such as transistors.
On the other hand, poor soldering technique with a temperature controlled soldering iron can still damage components. If this is your first electronics project and you are soldering for the first time, some online viewing of instructional videos and soldering practice may be helpful.
An iron with a small tip and small diameter solder (0.8mm/0.032") are also helpful.
A temperature controlled soldering iron is best for delicate electronic components such as small form factor transistors. Is your 40W iron temperature controlled, or is it 40W with no control? A 40W iron with no temperature control can solder delicate components if you have good soldering technique. But the margin for error is low with delicate components such as transistors.
On the other hand, poor soldering technique with a temperature controlled soldering iron can still damage components. If this is your first electronics project and you are soldering for the first time, some online viewing of instructional videos and soldering practice may be helpful.
An iron with a small tip and small diameter solder (0.8mm/0.032") are also helpful.
@Ben Mah considering the last time I held an iron was a good 25 years ago, for all intents and purposes I'm new.
I have three soldering irons but none of which I really like. The 40w is nonadjustable and I have a cheap one that is part of a kit that has a temperature dial on it which seems to work the best, and one that is part of a chinese rework station that has temperature control but the very tip of the iron doesn't seem to get as hot as a mm or 2 below the tip.
I did check out the video recommended on soldering in the build guide to get a refresher and my solder is on the small side. The issue I think is being so out of practice and not being familiar with the tools that was my downfall.
I'm going to set the project aside until I get some solder braid here and make a go at fixing the issues on the other board since I haven't touched it yet. I'll see what happens from there. That one I think isn't as bad off as it would let me bias between about 4 and 6v if memory serves. If it doesn't work out at least I've had practive (albeit expensive practice) and my next parts kit may not go so badly.
I have three soldering irons but none of which I really like. The 40w is nonadjustable and I have a cheap one that is part of a kit that has a temperature dial on it which seems to work the best, and one that is part of a chinese rework station that has temperature control but the very tip of the iron doesn't seem to get as hot as a mm or 2 below the tip.
I did check out the video recommended on soldering in the build guide to get a refresher and my solder is on the small side. The issue I think is being so out of practice and not being familiar with the tools that was my downfall.
I'm going to set the project aside until I get some solder braid here and make a go at fixing the issues on the other board since I haven't touched it yet. I'll see what happens from there. That one I think isn't as bad off as it would let me bias between about 4 and 6v if memory serves. If it doesn't work out at least I've had practive (albeit expensive practice) and my next parts kit may not go so badly.
Looking forward to building my 2nd ACA. Thank you very much. Great product !
Sorry you had trouble getting C3 out. These boards do make it hard without the tools for the job, but you have solder wick on order now and that will help a lot. You should be able to push the 'stump' out with a cocktail stick and hot iron. That will also work for holes were you cannot clear the solder with the wick or sucker.
Those fluctuating resistance figures point to Q4 being faulty. Perhaps you need to short all three (Q4) leads together for a second or two, then check the resistance again?
At some stage you will have to remove Q4, might be easier to cut it off the top of the board with side cutters and pull the remaining leads out of the board with pliers. It's difficult to unsolder three leads at at time...
Don't worry, you will get it working one way or another.
Upgraded power supply question.
I will be ordering one or possibly two kits soon. I understand that the kits come with the power adapters and they work just fine.
I'm kind of old school and I'm use to seeing big hulking power supplies. Is there an upgrade PS board or plans that would yield an improvement in performance and sound?
I will be ordering one or possibly two kits soon. I understand that the kits come with the power adapters and they work just fine.
I'm kind of old school and I'm use to seeing big hulking power supplies. Is there an upgrade PS board or plans that would yield an improvement in performance and sound?
Honestly, building a linear power supply that is at least as capable as one of the kit SMPS is a lot of work. Fortunately the ACA runs from a single power rail + ground, so it is possible to build a very good PSU with a 300VA transformer with dual 24V secondaries. Yes, after a CRCRC filter, the power rail on the ACA channel board will be about 28V or a little more. Dual mono
Done properly, this can sound better than a pair of bridged ACA with the kit SMPS. It will cost a little more, though.
Done properly, this can sound better than a pair of bridged ACA with the kit SMPS. It will cost a little more, though.