TEAC A3340 mains problem - UK Vintage Radio Repair and Restoration Discussion Forum

BrianM67 · 2nd Sep 2014, 1:55 pm

I have a Teac A3340 which, on its own, and when amplified via my Revox A77, works fine. However, I am anxious to transfer some of my 4 channel tape to my computer. When I connect the 3.5 jack plug into the computer, and switch on the A3340, this action knocks out the power at the fuseboard.

The material could be copied to the A77 direct, but the tape playback signal, when compared to the Input signal, is lacking treble.

Additionally, when the A3340 is off, but plugged in at the switched on mains, I can feel a slight tingle when the casing is touched. This goes off when the A3340 is switched on. I note that at the rear of this tape recorder is a knurlled screw with the earthing sign. Could this be the answer, or is it something more sinister? Your input would be much appreciated.

paulsherwin · 2nd Sep 2014, 2:41 pm

You probably have a slightly leaky capacitor on the mains side of the power supply. This is causing a very small current to flow to the chassis. When the chassis is unearthed you will feel a slight tingle, and if you earth it via the computer you will trip the circuit breaker in your consumer unit.

If you still had an old installation with fuses instead of breakers then there probably wouldn't be a problem.

BrianM67 · 2nd Sep 2014, 3:57 pm

Thank you, Paul, for your prompt response. I also have at my disposal a TEAC 2488 Neo mixer with in-built hard drive and recordable CD unit.

Do you think the same scenario would appear (mains outage) if I connected (via 1/4" jack plugs) the 3340 to this unit. Failing this, I am really stumped what to do next.

trsomian · 2nd Sep 2014, 8:42 pm

May I suggest plugging one unit into the mains via a mains isolating transformer; this should eliminate any earth leakage problems.

paulsherwin · 2nd Sep 2014, 9:19 pm

Your breaker will trip if you connect anything with a mains earth connection to this recorder. Only a tiny amount of earth leakage is required to do this.

A very dirty solution is to disconnect the earth wire in the computer's mains plug, though this isn't good practice. An isolating transformer would work but you're unlikely to have one. An external USB sound interface may provide the necessary isolation but there are no guarantees.

The only real solution is to identify the leaky caps and replace them with modern class Y components.

jamesperrett · 3rd Sep 2014, 1:04 pm

Another solution might be to buy a ground loop isolator that goes into the audio connection between the tape deck and computer. Cheap ones are available from Maplin or Ebay while a higher quality solution would be something like the ART Cleanbox or the Orchid Dual Isolator.

Maarten · 5th Sep 2014, 1:46 pm

The leakage might even be as designed. As long as the capacitor is Y2 class and below a certain value as to limit the current, even a double insulated set may leak mains to case... Strange as it sounds.

BrianM67 · 5th Sep 2014, 2:02 pm

Many thanks to all who contributed their answers to my problem. I think I will take up James's suggestion of an isolator from Maplins.

Will keep you informed.

2nd Sep 2014, 1:55 pm	#1
BrianM67 Retired Dormant Member Join Date: Aug 2014 Location: Brighton, East Sussex, UK. Posts: 3	TEAC A3340 mains problem I have a Teac A3340 which, on its own, and when amplified via my Revox A77, works fine. However, I am anxious to transfer some of my 4 channel tape to my computer. When I connect the 3.5 jack plug into the computer, and switch on the A3340, this action knocks out the power at the fuseboard. The material could be copied to the A77 direct, but the tape playback signal, when compared to the Input signal, is lacking treble. Additionally, when the A3340 is off, but plugged in at the switched on mains, I can feel a slight tingle when the casing is touched. This goes off when the A3340 is switched on. I note that at the rear of this tape recorder is a knurlled screw with the earthing sign. Could this be the answer, or is it something more sinister? Your input would be much appreciated.

2nd Sep 2014, 2:41 pm	#2
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: TEAC A3340 mains problem You probably have a slightly leaky capacitor on the mains side of the power supply. This is causing a very small current to flow to the chassis. When the chassis is unearthed you will feel a slight tingle, and if you earth it via the computer you will trip the circuit breaker in your consumer unit. If you still had an old installation with fuses instead of breakers then there probably wouldn't be a problem.

2nd Sep 2014, 3:57 pm	#3
BrianM67 Retired Dormant Member Join Date: Aug 2014 Location: Brighton, East Sussex, UK. Posts: 3	Re: TEAC A3340 mains problem Thank you, Paul, for your prompt response. I also have at my disposal a TEAC 2488 Neo mixer with in-built hard drive and recordable CD unit. Do you think the same scenario would appear (mains outage) if I connected (via 1/4" jack plugs) the 3340 to this unit. Failing this, I am really stumped what to do next.

2nd Sep 2014, 8:42 pm	#4
trsomian Hexode Join Date: Oct 2010 Location: Box End, Beds. UK. Posts: 271	Re: TEAC A3340 mains problem May I suggest plugging one unit into the mains via a mains isolating transformer; this should eliminate any earth leakage problems.

2nd Sep 2014, 9:19 pm	#5
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,943	Re: TEAC A3340 mains problem Your breaker will trip if you connect anything with a mains earth connection to this recorder. Only a tiny amount of earth leakage is required to do this. A very dirty solution is to disconnect the earth wire in the computer's mains plug, though this isn't good practice. An isolating transformer would work but you're unlikely to have one. An external USB sound interface may provide the necessary isolation but there are no guarantees. The only real solution is to identify the leaky caps and replace them with modern class Y components.

3rd Sep 2014, 1:04 pm	#6
jamesperrett Octode Join Date: May 2007 Location: Liss, Hampshire, UK. Posts: 1,873	Re: TEAC A3340 mains problem Another solution might be to buy a ground loop isolator that goes into the audio connection between the tape deck and computer. Cheap ones are available from Maplin or Ebay while a higher quality solution would be something like the ART Cleanbox or the Orchid Dual Isolator.

5th Sep 2014, 1:46 pm	#7
Maarten Dekatron Join Date: Dec 2007 Location: Haarlem, Netherlands Posts: 4,199	Re: TEAC A3340 mains problem The leakage might even be as designed. As long as the capacitor is Y2 class and below a certain value as to limit the current, even a double insulated set may leak mains to case... Strange as it sounds.

5th Sep 2014, 2:02 pm	#8
BrianM67 Retired Dormant Member Join Date: Aug 2014 Location: Brighton, East Sussex, UK. Posts: 3	Re: TEAC A3340 mains problem Many thanks to all who contributed their answers to my problem. I think I will take up James's suggestion of an isolator from Maplins. Will keep you informed.