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FH9HVX - Budget Conscious 100w Class AB for Lean Times

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Kokanee

Kokanee

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Joined 2010
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My adventures with smd, solder paste, and hot air. Mostly it was a success. I had the air on low and temp was about 350-360C. Soldered up the caps with no problems. To solder the wafer thin resistors, I tried a bit more heat and had a low volume of air. One of the resistors solder paste, just dried up and the resistor moved off the pads. I used excess solder paste (maybe a problem?) on the resistors. I then got out the flux and the solder iron and soldered in place.

Questions: I have an LRC meter, so after soldering, I measured the smd's, and I also turned the board over and measured the pads for the thru hole which are in ll with the smd's. Everything measured OK. Does this indicate everything is OK, or is there any other measurement technique to use? Maybe one just waits until power up time.?

Regards,
MM
 
Francois G

Francois G

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Joined 2004
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xrk971 said:
That’s a nice hunk of heatsink! Should be fine, especially with a fan to help out when needed.

Elsinores are fine speakers for either amp as they are ~92dB sensitive?
Click to expand...

Sorry X,

I missed the implied question. Yes, the Elsinores are reported to be 92 db/2.83V. I have not tested the number, but subjectively I think this is close, perhaps even better. So, do you expect I would not like the FH9-Hvx amp on those sensitive speakers?

Of course I’m going to build it and compare it to Alpha Nirvana on my speakers. I hope to report my findings in a few months. Unfortunately, my hearing is not quite up to snuff; perhaps I could arrange a wider, post-covid listening test.

Also, Konanee, very interesting about your SMD, solder paste, hot air experience. Very good to know. I hold you in no harm, so, let’s be friends.
 
Kokanee

Kokanee

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Joined 2010
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Francois, I have no problem with you. The trouble with emails is that they are not face to face encounters, and sometimes it is hard to understand the message conveyed. So lets bury the hatchet.

Do you have any answers on testing soldered components, or just wait and see once the power is hooked up.
 
pinkfloyd4ever

pinkfloyd4ever

Member
Joined 2008
youtube.com/watch?v=dQw4w9WgXcQ
Measuring components once they’re soldered into the circuit doesn’t really work. I mean, your DMM will give you values for R and C, but they’re almost never correct once soldered to the PCB. This is because the DMM is usually measuring the component you’re trying to measure, plus some other components in parallel in the circuit.

So you want to measure your Rs (and Cs if they’re chip-type SMT) before soldering them to the PCB.
 
J

jhofland

Member
Joined 2009
I would suggest that visual inspection is a reasonable thing to do. The surface mount component ought to be pretty flat to the board and most of all, the joints ought to be shiny with a small solder fillet between the pad and the component. If the joint has too much solder, you can remove some of the excess with solder wick. As others have mentioned, trying to do an electrical test after they're in place isn't very useful, particularly when there is more than one component connected to a net. As there nearly always is.
 
Mark Johnson

Mark Johnson

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Joined 2011
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In my experience, on hand-soldered SMD boards the most common failures are open circuits. The component leg does not have electrical continuity with the PCB pad. The simple way to test for this is with a DVM on continuity "buzz" test mode. One probe goes to the component lead, the other probe goes to another component lead supposedly connected to the same signal net. If it buzzes, you've got continuity. If not you've got an open circuit.
 
Kokanee

Kokanee

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Joined 2010
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Thanks for the info gentleman on testing and continuity. In my case the smd components are in parallel with the thru hole components. If the smd component was open circuited, would i expect a reading on the pads of the thru hole when testing? Is my thinking flawed?

MM
 
Kokanee

Kokanee

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Joined 2010
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Hello Mark Johnson,

I tried a continuity test with R112 & R114, the smd resistors on the bottom side of the pcb. Lets call R112 the top resistor and R114 the bottom resistor. Test results below:

1.btm tab of R112 and top tab of R114 = continuity

2. top tab of R112 and top tab of R114 = no continuity

3. top tab of R112 and btm tab of R114 = no continuity

4. btm tab of R112 and btm tab of R114 = no continuity

My thinking is that I should be able to get continuity between the resistors with any pad that is probed. Please correct me if I am wrong? If correct, I will reflow the 2 pads that are not showing continuity.

Thanks for the help,
Myles
 
A

as8912

Member
Joined 2020
If you post an image of the board/SMD joints we should be able to give a pretty accurate assessment as to whether the joints are fine or require reflow. If the SMD joints look fine then there's very rarely an issue unless you overheated the parts (which would require heat for another 30 seconds+ after the joint has been made).
 
Kokanee

Kokanee

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Joined 2010
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Hello audio forum members,

I seem to be having problems lately with 2 items.

The first item is etiquette that should be used on this forum. Maybe some helpful feedback can help me out here, as I evidently seem to be landing in hot water lately, and it seems that I do not how to phrase or respond to questions correctly.

I am a retired Engineer, like others here, and I do not like chaos in my life. If I receive information from someone, I reply to that person with what I have to offer. Excuse me, I am new to this electronics world, I have a lot of questions and sometimes I do not think the same way as others . If the way I word messages offends you or triggers some hidden emotion inside you, please do not reply to my message. No rudeness or malice intended.

The second item is the problem with continuity in my All C's pcb between R112 and R114. The results of my investigations with my DMM are shown in post 568.
The question I have is: I would like to know if I should have continuity between the 2 resistors, no matter which pads I probe on one resistor to the other.

@as8912, Thanks for the info. The joints all look OK, and I will do a little more investigating on continuity before I post any pictures.

Regards,

Myles
 
Z

zman01

Member
Joined 2011
Kokanee said:
The first item is etiquette that should be used on this forum. Maybe some helpful feedback can help me out here, as I evidently seem to be landing in hot water lately, and it seems that I do not how to phrase or respond to questions correctly.

I am a retired Engineer, like others here, and I do not like chaos in my life. If I receive information from someone, I reply to that person with what I have to offer. Excuse me, I am new to this electronics world, I have a lot of questions and sometimes I do not think the same way as others . If the way I word messages offends you or triggers some hidden emotion inside you, please do not reply to my message. No rudeness or malice intended.
Click to expand...

Myles,

I don't think you phrased your previous question in an offensive manner. And I don't think diyAudio member Mark Johnson intended to put you in any dilemmas around that. :)

MJ champions a lot of DIY efforts here. However I have noticed that he actively encourages folks to learn through reading through forum posts, participating among themselves, and doing it themselves. Seldom does he directly answer - and that is not bad in any way. :)

Some of us including me are more of the newbie types (we all start as newbies) and have a lot of well intentioned questions, and maybe we try answering ourselves through reading, discussing, and doing vs getting the answer directly from a more expert member - I think MJ was evoking that spirit only...

I also fully understand that not all of us are mentally invested in the hobby equally, and some of us would just simply prefer to follow the instructions and build something. :)

Can you please post a pic of the board that you are working on including the components that you have soldered already? Let's give it a try ourselves, and I am petty sure MJ will help out if needed. :)

Cheers,
Zia
 
Last edited:
A

as8912

Member
Joined 2020
Kokanee said:
@as8912, Thanks for the info. The joints all look OK, and I will do a little more investigating on continuity before I post any pictures.
Click to expand...


Awesome, then it's very likely good to go. I have yet to have a bad passive component without it looking bad in my 10+ years of SMD soldering. Continuity checks could just be confusing as you are unlikely to be measuring the isolated component.
 
Kokanee

Kokanee

Member
Joined 2010
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Thanks for the help Zia, I guess I am used to asking a simple question and expecting a simple answer to get me on my way. I fully understand your post and have always been impressed with MJ's knowledge of electronics. I will research this out and learn what I can about testing for continuity in parallel and series circuits. Let me post a couple of pics of the smd's. Apologies to Mark also, my bad.

MM
 
Mark Johnson

Mark Johnson

Member
Joined 2011
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Here are a couple examples of the way I would use a continuity test buzzer to look for open circuits on a surface mount PCB.

1. The schematic says that U4 pin 3 should be connected to the external I/O terminal (bolt hole donut) at top left. So I would touch one buzzer probe to the IC's pin -- NOT the PCB copper trace on the board -- and the other buzzer probe to the I/O donut. If there's no continuity then I've got an open circuit, probably the IC pin is not soldered correctly.


2. The schematic says that C4 , R3 , and U5 pin 4 should be connected together. So I would touch one buzzer probe to the top of C4 itself --- NOT the PCB copper trace on the board --- and the other buzzer probe to the top of R3 itself. If there's no continuity then I've got an open circuit. Then I'd move the second probe to the component lead of U5 pin 4 --- NOT the PCB copper trace on the board --- and check for continuity.


3. The schematic says that U5 pin 2 should be connected to the VLOWER signal trace. The schematic also says that D4 cathode should be connected to the VLOWER signal trace. Thus there should be continuity between U5 pin 2 and D4 cathode. I would touch one buzzer probe to the component lead of U5 pin 2 --- NOT the PCB copper trace on the board --- and the other buzzer probe to the cathode of D4. If there is not continuity then I've got an open circuit.

_
 

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Kokanee

Kokanee

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Joined 2010
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Thanks for this verbal and images information. In the last couple of days I began examining the schematic to find useful test points for continuity. I have tried to get closeup photo's with my old i5 phone, and they are not good. I am experimenting with soldering smd's and I think I am going to have to reflow some of the resistor's. Will know after continuity checking. All is good, and I will post photo's later. The good thing is, if the smd's do not work out, I can always revert to thru hole components.

MM
 
L

legis31

Member
Joined 2009
Questions about female counterparts for 2,3 pin headers and R- 143

Hi,

Does anyone have a part number & source for the female corresponding plugs to the 2 and 3 pin headers
used on the FH9HVX amp boards? Mouser's parametric search function only seems to work well when one knows the exact name/discription of the part in question. When I specified Molex KK 2.54 mm female I got a dizzying array of results that I couldn't narrow down! Are premade harnesses available in acceptable lengths too?

Since R-143, the 4r75 1w CMF60 is back ordered til spring of '21 I was wondering if the CPF series is an acceptable substitution? I narrowed that down to these 2;

https://www.mouser.com/ProductDetail/Vishay-Dale/CPF14R7500FKEE6?qs=NkGzlUK1gXnN2ARvjLkCGQ==

https://www.mouser.com/ProductDetail/Vishay-Dale/CPF14R7500FKE14?qs=AgiByKCM3cCDG0IsnSCufw==

Both have different temp & voltage ratings than the CMF series.

on a different note, you guys weren't kidding about soldering those inductors. What an adventure!
I cranked the temp WAY up on the iron and used copious amounts of flux to get things flowing successfully.
 
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