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RXRBILL

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Reply with quote  #1 
I am having trouble with assembling a K126 Sound activated Relay Board. I have been very careful in verifying the correct parts in the right places and all soldering has been done very carefully also. The kit worked briefly then quit. I have re-checked everything several times and re-heated all solder joints to make sure none of them were cold joints with the chip removed of course. Any advice, is there anything about this board to re-check such as was the case with the defect on my K188?

Bill Dwyer
av8rdad@aol.com

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #2 
No PCB defect on K126 as far as I know.

What do you mean 'worked briefly'? Did the relay operate momentarily when power was applied? Is that what you mean?

I assume you have tried adjusting the sensitivity via the trimpot?

Remove the IC from its socket and check that none of the IC leads are bent up underneath the IC body (common fault with ICs in sockets).

What are you using to power the kit?
RXRBILL

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Reply with quote  #3 
Finally I am able to reply.

I have tried everything you listed at least twice.

I did adjust the sensitivity both ways.

I am using the power supply I bought with the kit from Electronic Kits.

I also tried using a 9VDC Battery.

The circuit did work briefly then just quit working.

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #4 
When it 'worked briefly' what did it do? Did the relay operate in response to sound via the microphone?

About the microphone:
If you look at the bottom of the microphone you will see that one pin is connected to the case. This pin should be connected to the '-' pad on the PCB.
RXRBILL

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Reply with quote  #5 
Yes the circuit operated as it should.

The relay operated when I spoke into the Mic and the LED came on.

The Mic is wired correctly the minus terminal connected to the case.

It is not working now.

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #6 
Have looked at schematic and thought about it - nothing obvious jumps out at me. I have no idea what the problem may be.

I would need to have the kit here to fault find. So of the things I would do are:
1. Remove the IC and apply a positive voltage onto pin 7 of the IC socket. That should turn on transistor Q1 and therefore operate the relay and LED.
2. Check the voltage at pin 6 of the IC socket. It should be roughly one fifth (1/5) of the supply voltage (set by R3 and R4 voltage divider).
3. Replace the IC and apply a positive voltage to junction of D2 and D3. Relay and LED should operate.
4. Use an oscilloscope on pin 1 of the IC to check if any sound picked up by the microphone is being amplified. Verify that the output level changes as you vary the trimpot.

I would think that one of these tests would give some clue as to the problem.

RXRBILL

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Reply with quote  #7 
Frank:

I purchased 4 of these kits and I have only 1 that works.

I have found the problem with the circuit boards.

In soldering the componets to the boards what is happening is that a few of the printed circuit pads have disappeared under the solder joint resulting in an open.
I had to put the boards under a magnefying glass to see this. I am using a high quality soldering iron with a needle point and only applying the solder momentarilly so I am surprised that this is happening.

So I have 3 defective circuit boards and Electronic Kits says they do not have any replacements available.

Are any replacements available from you?

Or do I need to keep buying more kits until I can get one to work.

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #8 
Never heard of solder pads disappearing when soldered.

Please send me photos of both sides of the boards in question. Certainly if there is an issue with the PCBs then DIY will replace them.
RXRBILL

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Reply with quote  #9 
Frank:

I will try to take some photos and figure out how attach them.

I just found the "attach" button above.

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #10 
Or you can email me direct.
RXRBILL

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Reply with quote  #11 
Frank:

I sent you an e-mail with a photo attached of the defective boards and the power supply I am using to ladde@kitsrus.com.

This was the e-mail address that came up when I clicked on reply to sender.

Did you get my e-mail?

RXRBILL

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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #12 
No.

I monitor the forum so DIY would have no idea what that email is about.

Please email me direct. Click on 'Frank' - another window will open up with a link to email me.
RXRBILL

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Reply with quote  #13 
Frank:

I just figured out how to reduce the file size so I can attach the photo of my power supply and the circuit boards.

RXRBILL IMG_0312.jpg 


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Bill Dwyer
RXRBILL
Frank

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Reply with quote  #14 
The photos are not clear enough for me to see any problems with the PCB and/or soldering.

I do see some black spots in places - normally that indicates excessive heat applied when soldering. If so then that would explain 'disappearing' pads. Nor disappearing really - the pads will have fractured away from the track and is actually attached underneath the solder 'blob'.
RXRBILL

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Reply with quote  #15 
Frank:

So back to my original request, are replacement boards available.

As I said before, I purchased 4 of these kits from Electronic Kits and have only 1 that works. They say that they do not have any replacement boards.

My question is if any replacement boards are available, or do I need to just keep buying these until I can get another to work as I need 2 working circuits.

I find it hard to understand how your kits do not have any assembly instructions other than component placement. If there are things that the assembler needs to know such as soldering wattage to use, type of solder to use, if rosin is required, then that should be included in the instructions.

So, are replacement boards available?



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Bill Dwyer
RXRBILL
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