Dansette Junior Deluxe Safety Advice

[uk_snowman]

Hi All

I'm doing some work on a Dansette Junior Deluxe.

I have noticed that the 2 Potentiometers are attached on a bracket to the negative side of the circuit board.

Is this normal for this to be attached this way as I think these could be live!!!

Thanks

[Herald1360]

Depending on the design, the chassis or negative rail on some record players is connected directly to one side of the mains. Whether live or neutral has little effect on operation.

The design of the case and fitting of knobs etc would have made access to live parts adequately unlikely by the standards of the day provided that everything was intact and undamaged. Indeed, very few users of such kit had any unfortunate experiences.

50 odd years later, standards are higher and the state of the equipment uncertain which leads both to more concern about the equipment and a higher risk element.

Be aware of the risks and treat the unit accordingly. If it is put back to original, it will be no more dangerous to use than when new.

[Michael Maurice]

You should also fit a modern two core mains cable and plug, the plug fitted with a 3A fuse. Make sure that the neutral wires does go to chassis via the switch, that will ensure it's safe.

[dazzlevision]

I'm assuming your set uses valves in the electronics.

If your set's electronics is directly connected to one side of the mains supply (when switched on), this can be tested using a test meter on its Ohms range, where there will be a very low reading between the "chassis or common" rail in the electronics and mains live or neutral plug pin, depending upon the mains plug wiring and whether any "tampering" has gone on in the set.

Another good clue is whether or not there is a mains transformer fitted, although if it is an autotransformer, there is no mains isolation.

Finally, if the valves are 100mA heater current types, such as UY85 and UL84 (the U is the clue), they may be fed from a tapping on the record deck's motor, which will therefore have three wires coming off it. That may indicate there is no mains isolation.

If your set's design is the "live chassis" type, then be very careful to ensure it has not been "bodged up" by a previous inept repair, which may compromise the safety features of the original design. The correct circuit diagram will greatly assist in this regard.

See this thread for some further guidance: https://www.vintage-radio.net/forum/...d.php?t=107005

[uk_snowman]

Originally Posted by Michael Maurice

You should also fit a modern two core mains cable and plug, the plug fitted with a 3A fuse. Make sure that the neutral wires does go to chassis via the switch, that will ensure it's safe.

Yes I always do that.

[uk_snowman]

I was thinking whether some gaffer in-between the circuit board and the metal bracket may provide some insulation

[cmjones01]

Originally Posted by uk_snowman

I was thinking whether some gaffer in-between the circuit board and the metal bracket may provide some insulation

It might provide some insulation, but it can't be considered to be improving safety. Gaffer tape is not designed as a safety insulator, or indeed any insulator. What would you do if you came across a record player that relied on gaffer tape to protect you from touching live mains? You'd curse the cowboy who did it, rip out the bodge and do the job properly.

Don't be that cowboy.

Chris

[Radio Wrangler]

I don't have any live-chassis equipment, but if i did, I'd consider fitting plugs with built-in RCD breakers, just as a last-ditch back-up. I'd still be very careful about insulation quality.

Gaffer tape is useful stuff, but I haven't come across any use for it that doesn't qualify as a bodge. The extreme case involved a radio amateur on a trip to the far North with a pal and a vintage aeroplane. A hungry bear tore the plane to shreds. They ordered up new tyres and a case of gaffer tape to stick the fabric plane back together to get it home. DXpeditions can get hairy! Risking your life to the insulating properties of a small piece on a daily basis over years could be even riskier. Then there is the possibility that someone else could get hurt.

Before taking any risk with the lives of others, just imagine the fatal accident enquiry and you'll do the right thing.

David

[uk_snowman]

I was not actually going to use gaffer tape but was wondering at the time about some sort of insulation tape.

Since looking at the chassis again iI can see insulation tape won't work but iI could change the pots to ones with plastic dial posts.

[Nickthedentist]

Pots with plastic spindles would definitely be a very good idea

[David G4EBT]

Originally Posted by uk_snowman

Is this normal for this to be attached this way as I think these could be live!

The short answer is no - the chassis, the bracket etc could not be live - the amplifier follows conventional AC only design techniques, similar for example, to an AC only radio design.

Presumably if you're working on the electronic side of the Dansette Junior De Luxe, you have the circuit for it? If not, you can download it from the top RH of the forum for £1.99. If you look at the circuit you will see that the set has a mains isolating transformer so the only way any metalwork could become live from the mains is if the mains lead on the double pole on/off switch came adrift, (or the leads to the motor, which come off the primary side of the mains transformer at the output of the mains switch). A visual examination of the mains connections, condition of the mains lead, correct strain relief in place on the mains lead etc will show up anything that looks untoward.

The single valve (EL84) plus metal rectifier circuit type MC/1961/ is common to several Dansette record players - 'Major, Major De Luxe, Minor De Luxe, Bermuda, Conquest, Celebrity', Troubadour and so on. Looking at the circuit, there's no reason as I see it that you couldn't fit a 3-core mains lead and earth the chassis for added reassurance and more in keeping with best practice, though of course, it's a deviation from how the record player was designed, in a very different time with a more relaxed view about electrical safety than exists today.

Hope that helps a bit.

[mark pirate]

I have restored three Junior Deluxe players, they do NOT have a mains transformer, they use a tap from the motor, therefore it is a live chassis amplifier.
Valve lineup is UY85 and UL41. If the correct knobs are fitted it should be safe, but make sure that the knob shafts are connected to neutral!

Mark