[HELP!] AC Voltage leakage in TEAC A3340 Tape deck

[kidsreturn]

Hi everyone, hope you are doing well.

I have recently bought a TEAC A3340 tape deck (ungrounded), and noticed that when I was connecting the GND electrode at the back of the chassis to earth, I got an instant power outage.
When I am probing the chassis with my digital voltmeter while the unit is running, I have noticed that there was a non negligible AC Voltage between the chassis and my rug for instance, of approx. 5 VAC.
I am suspecting a dead electrolytic capacitor causing this voltage leakage, but I am not yet sure which one, and don't want to cut every wire before realising I did not replace the good one.

I have uploaded here the schematics of 1) the whole tape transport section 2) the voltage rectifier 3) the control relay board.

My current guess is that either C1, C2 or C3 is to be replaced. Do you think it's a good guess?
What other experiments can I run to make sure my diagnosis is accurate? I would love to know more from you guys.

Thanks a lot in advance, really appreciate your help!

Have a great day,

Max

 

[cademan]

I believe that ground on the tape deck is to go to the amplifier to prevent ground loop hum but if there is no hum, why worry about using it?

 

[avionic]

I got an instant power outage.

What do you mean by " power outage" .. Blown fuse ? Tripped circuit breaker ?

Try -- reversing the AC plug 180° --

 

[kidsreturn]

I believe that ground on the tape deck is to go to the amplifier to prevent ground loop hum but if there is no hum, why worry about using it?

Yes, I agree. The machine works fine when not connected to a grounded device. However, last time I connected the outputs of my TEAC to my active monitors through my soundcard, it just burnt the fuse inside the left speaker and blew a fuse in my house.
Another time, as I was going to connect the output RCA connectors to my soundcard to record something, I accidentally touched the Left connector with my left hand and right connector with my right hand and felt a shock. So I guess it's not safe to use as is for the moment. Don't wanna die using a tape deck .

 

[kidsreturn]

What do you mean by " power outage" .. Blown fuse ? Tripped circuit breaker ?

Try -- reversing the AC plug 180° --

Sorry, yes I meant blown fuse. I am french so I didn't know the exact wording for this.
I am going to try reversing the AC plug and monitor the AC voltage on the chassis and see if it changes anything. Thanks for the recommandation.

 

[avionic]

Sounds like you have a pretty high AC potential on the metal chassis...That's not good..

1. Check each AC motor for windings shorted to the metal case.

2. Check each solenoid for windings shorted to the case.

 

[kidsreturn]

What do you mean by " power outage" .. Blown fuse ? Tripped circuit breaker ?

Try -- reversing the AC plug 180° --

So i have just tried reverting the plug 180° and if one sides gives me a smaller AC voltage, I still measure around 10-15 VAC Voltage on the chassis no matter how I plug the tape deck.

 

[kidsreturn]

Sounds like you have a pretty high AC potential on the metal chassis...That's not good..

1. Check each AC motor for windings shorted to the metal case.

2. Check each solenoid for windings shorted to the case.

Have tried both: no trace of any shorts!

 

[petehall347]

i have this trouble with a tape deck . it turned out to be an electrically leaky switch . cant remember the deck now but it was an omron switch . but this one had a 3 core mains cable from new .

 

[kidsreturn]

Update:
When I probe the AC voltage between the GND pin on the chassis and the phase in the socket, i measure 208 VAC, whereas I measure 28VAC between the neutral in the socket and the GND. I guess it should be 230 and 0 VAC instead (i'm in europe ), right?

 

[petehall347]

yes neutral should be same potential as ground . have your wiring checked .

 

[kidsreturn]

So, I was able to do a couple of measurements today so I thought I would share some of them with you.

To sum up:
When machine is turned off:
230VAC between Phase and GND (chassis)
0VAC between Neutral and GND

When machine is turned on:
108VAC between Phase and GND (chassis)
122VAC between Neutral and GND

As the GND of the chassis is connected to the 0V located on the output of the transformer, there is a 108VAC offset between the GND of the machine and earth.
Even if there's a huge offset on the tape deck, it still operates OK unless it is connected to a device connected to earth. In that case, blown fuse.

I have attached to this message the schematic of the input and output of the transformer.

I am pretty sure now that the transformer is faulty.

What do you think?

Thanks a lot!!!