Need help with Ground Loop Isolator

Deziel0495 · Apr 1, 2015

I purchased a ground loop isolator from Scannermaster (Isolator Cable Male To Male) to try and help with a hum and general background noise on my feed. However, when I plug it in, it silences the feed completely. Even if I turn all my volume levels all the way up, you can barely hear anything. Is that how it's suppose to work, or am I doing something wrong?

Thanks

n0nhp · Apr 1, 2015

I am not sure how those are made. however the audio should definitely pass from one end to the other. If they are transformer style (that is what it appears in the illustration) you should be able to take your multimeter and measure a near DC short at each end of the wire. The wire end-to -end will appear open.
My guess would be that you have a defective cable and it needs to be replaced.
At minimum, if you are handy with a soldering iron and have some signal tracing experience, cutting off the heat shrink and looking for where the signal disappears would be an option. Better because it is brand new would just be paying for the shipping and getting a replacement.

Bruce

Deziel0495 · Apr 1, 2015

The picture on ScannerMaster does not do it justice. I've attached some pictures of what the item actually looks like. It comes with 2 stereo cables, nothing fancy. Tried it with them and some I had, even tried mono cables but all had the same results. I've contacted ScannerMaster, just waiting for a reply.

n0nhp · Apr 2, 2015

Well I see a transformer and possibly the top of a capacitor. Don't know what might be lurking under the sticker and lower on the board.
From the description and what I can see, they may have decoupled the input and output with non-polarized caps and maybe put a zener or the like in there. Very hard to troubleshoot without opening it up and seeing what the signal path is supposed to be.
Hope ScannerMaster does the right thing and you get it worked out.

Bruce

ak4fn · Apr 2, 2015

Just for giggles try hooking it up in reverse. Could be a transformer with different primary and secondaries. A step up or step down. Just a thought.

Deziel0495 · Apr 2, 2015

ak4fn said:
Just for giggles try hooking it up in reverse. Could be a transformer with different primary and secondaries. A step up or step down. Just a thought.

Tried that. same thing unfortunately.

FKimble · Apr 2, 2015

Here it is on the makers website and some more info.
ComTekk Software

Deziel0495 · Apr 5, 2015

Still waiting for a reply from ScannerMaster.....

K9DAK · Apr 5, 2015

Wonder if you got the one designed for MIC input rather than LINE input...

"May be ordered with Male/Male connectors or 16dB attenuation to reduce audio level when used with computer's MIC input. "

Deziel0495 · Apr 5, 2015

K9DAK said:
Wonder if you got the one designed for MIC input rather than LINE input...

"May be ordered with Male/Male connectors or 16dB attenuation to reduce audio level when used with computer's MIC input. "

I didn't think there was much difference (if any) between mic and input. Guess I will try mic, and report back.

jim202 · Apr 5, 2015

The cap is there to block any DC bias that may be coming from the source. I would also check with an Ohm meter that you have a good connection on the non cap input side. If your 1/8 inch connector is making a good connection, you should see a low resistance.

Is there some chance your using a stereo cable with both tip and ring rather than just a 2 wire connection with just tip and sleeve? If so, you may not be getting the correct connection to make it work.

I didn't see any indication if you need to use just a mono jack. Look inside the female connector and try to see how many fingers are there trying to make a connection with the male 1/8 connector.

Deziel0495 · Apr 5, 2015

jim202 said:
The cap is there to block any DC bias that may be coming from the source. I would also check with an Ohm meter that you have a good connection on the non cap input side. If your 1/8 inch connector is making a good connection, you should see a low resistance.

Is there some chance your using a stereo cable with both tip and ring rather than just a 2 wire connection with just tip and sleeve? If so, you may not be getting the correct connection to make it work.

I didn't see any indication if you need to use just a mono jack. Look inside the female connector and try to see how many fingers are there trying to make a connection with the male 1/8 connector.

Two 1/8 inch stereo cables are included for each side of the unit. I tried them, some I had, and mono cables but all got the same result. Also tried reversing the connection incase they labelled it wrong. That didn't work. I did not try using MIC input, but will give it a shot. Looking inside the female connectors, looks like 1 finger but I can't be sure. Whole device is only about the size of my thumb so it's hard to tell.

n0nhp · Apr 5, 2015

Most modern mono 1/8" jacks have enough distance between the tip and the ground contact that it will miss the ring. The ad says works on either stereo or mono, that would indicate to me that they have the tip and ring tied together as there is only one transformer.
If I had it, I would cut the heat-shrink off and look for a bad solder joint before using my old radio-shack signal tracer (amplified speaker) to follow the audio through the path. Also possible is the transformer has gone open on either the primary or secondary. that would give the symptoms he is describing of absolutely no audio getting through.
Of course, I have been a consumer-audio/ RF tech for 40 or so years and am not afraid of voiding warranties.
If ScannerMaster won't do anything for you, we can make arrangements to ship it to me to trouble shoot and possibly repair. I won't charge and will even pay shipping back.

Address at QRZ is good if you are interested.

Bruce

Deziel0495 · Apr 5, 2015

n0nhp said:
Most modern mono 1/8" jacks have enough distance between the tip and the ground contact that it will miss the ring. The ad says works on either stereo or mono, that would indicate to me that they have the tip and ring tied together as there is only one transformer.
If I had it, I would cut the heat-shrink off and look for a bad solder joint before using my old radio-shack signal tracer (amplified speaker) to follow the audio through the path. Also possible is the transformer has gone open on either the primary or secondary. that would give the symptoms he is describing of absolutely no audio getting through.
Of course, I have been a consumer-audio/ RF tech for 40 or so years and am not afraid of voiding warranties.
If ScannerMaster won't do anything for you, we can make arrangements to ship it to me to trouble shoot and possibly repair. I won't charge and will even pay shipping back.

Address at QRZ is good if you are interested.

Bruce

Audio gets through, but just barely. Crank the scanner volume, line-in volume and computer speaker volume and you get a faint preview of very unintelligible audio (because it's so loud). I'm assuming there is something wrong with the unit itself, because the cables that came with it work perfect on anything else.

I really appreciate your generosity. If I don't hear back from ScannerMaster, I just may take you up on that offer. I'm not one for tearing things apart. I leave that up to people that know what their doing!

Deziel0495 · Apr 8, 2015

ScannerMaster is usually pretty good with customer service. In the past I always got a reply within 48 hours.

Emails sent Wednesday 4/1/15 and Monday 4/6/15. No response from both.

This experience certainly changes whether or not I buy another product from them.

Need help with Ground Loop Isolator

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