Earth continuity fault

[20%cooler]

hi all,

I have this old reel to reel tape recorder that failed it's PAT test due to an Earth continuity reading, any ideas how to fix this?

it is very old and has a few valves inside
I am fairly new to electrical work but am very determined to get this thing working

 

[Deleted member 9648]

If it's class1 then check the cpc is connected at both the plug end and at a suitable earthing point in the appliance. Possibly tested by an automated muppet though...."Computer says no....",sometimes older appliances need a little experience to decide whether or not they are safe if they dont meet current requirements.

 

[20%cooler]

whats a CPC?

If it's class1 then check the cpc is connected at both the plug end and at a suitable earthing point in the appliance. Possibly tested by an automated muppet though...."Computer says no....",sometimes older appliances need a little experience to decide whether or not they are safe if they dont meet current requirements.

 

[20%cooler]

here are some pictures of the insides of the unit for reference

 

[20%cooler]

here are some better pictures showing the internals, any ideas what to do?

 

[telectrix]

cpc... circuit protective conductor. commonly called earth wire.

 

[20%cooler]

it seems to come into the unit and connects to the center tab of the volume/power switch

 

[telectrix]

what's the case made from? looks like wood with a covering. if so, it may not need earthing.

edit: is the mains cable 2 core or 3 core?

 

[20%cooler]

it is wood with a covering (ugly looking thing), the mains cable has 3 wires black red and green
it failed PAT test due to an earth continuity fault

what's the case made from? looks like wood with a covering. if so, it may not need earthing.

edit: is the mains cable 2 core or 3 core?

 

[Lucien Nunes]

Manufacturers were often a little blase about how the green wire was connected to the metalwork. You might find that the amp chassis is earthed but the deckplate not, or vice versa. Sometimes one will be connected to the other only by the screen of an audio cable, which will provide continuity but at a rather higher resistance than you will normally expect.

Please post a close-up pic of how the incoming flex cores are connected.

On another subject, I expect it is not working its best at the moment as I can see a few components of specific types that are invariably faulty at this age and which I replace on sight (I repair vintage electronics).

On yet another subject for anyone who reads this in the future - if you have a valve radio, record player or TV that seems to be missing an earth, do not immediately assume that mains earth should or could be connected to the chassis. Some older designs specifically have the chassis connected to LINE, NEUTRAL or RECTIFIED MAINS and THE WHOLE INTERNAL METALWORK IS INTENTIONALLY LIVE WHEN IN USE. Of course, in these designs, you can't touch any of it from outside and only a 2-core flex was provided originally.

 

[20%cooler]

Manufacturers were often a little blase about how the green wire was connected to the metalwork. You might find that the amp chassis is earthed but the deckplate not, or vice versa. Sometimes one will be connected to the other only by the screen of an audio cable, which will provide continuity but at a rather higher resistance than you will normally expect.

Please post a close-up pic of how the incoming flex cores are connected.

On another subject, I expect it is not working its best at the moment as I can see a few components of specific types that are invariably faulty at this age and which I replace on sight (I repair vintage electronics).

On yet another subject for anyone who reads this in the future - if you have a valve radio, record player or TV that seems to be missing an earth, do not immediately assume that mains earth should or could be connected to the chassis. Some older designs specifically have the chassis connected to LINE, NEUTRAL or RECTIFIED MAINS and THE WHOLE INTERNAL METALWORK IS INTENTIONALLY LIVE WHEN IN USE. Of course, in these designs, you can't touch any of it from outside and only a 2-core flex was provided originally.

 

[20%cooler]

https://www.dropbox.com/s/x1n8bj7s2u5c1w7/IMG_1338.JPG?dl=0
theres the image, just in case it doesn't display

 

[DPG]

Good advice from Lucien as usual. I would definitely as a bare minimum, protect my eyes when powering up for the first time! Exploding capacitors can be nasty. Daz

 

[DPG]

Oh and good on you for getting it up and running. It's a shame when things like this get scrapped. Daz

 

[20%cooler]

need to fix this problem before I even attempt to power it up

Oh and good on you for getting it up and running. It's a shame when things like this get scrapped. Daz

 

[DPG]

need to fix this problem before I even attempt to power it up

You do indeed. Still not entirely clear that earth connection though - the image is a little cropped at the top. Does it go to the chassis, or just to a terminal? Daz

 

[Lucien Nunes]

Ah, I understood that it had been in use and working, but just failed the PAT. If not, do not power it up. You can turn a small problem (shorted capacitor) into a big one (burnt out transformer) by not doing the repair BEFORE powering up. Many of the old consumer electronics I see with major faults were OK until someone tested it after a long period of disuse, because capacitors often fail in storage. I see one capacitor (probably the output valve coupling) has been replaced not so long ago, it's the bright yellow one, how long ago do you think it was last used?

The mains lead earth (green) is soldered to the amp chassis punch tag, so you should have solid continuity there. Post the actual test result in ohms.

What is your experience with electronic repairs - can you test components, voltages etc?

 

[Noob2013]

Chuck It in the skip!

 

[20%cooler]

well, I do have a volt meter/amp meter, but it's only very basic

 

[Noob2013]

I'm kidding mate. Best of luck with the repair