9 volt battery eliminator hum

[roffe]

The white and red leads soldered to the PCB are transposed!
Do both radios use the same polarity?

[ssnjimb]

I Never noticed that.

If i put positive on neg and neg on positive it still hums.

Could it be an internal fault. RT7 ?

James

[ssnjimb]

Originally Posted by roffe

The white and red leads soldered to the PCB are transposed!
Do both radios use the same polarity?

what do you mean transposed

They are the same in both radio's as well

my r500 is the same too

Iam confused

James

[Tim]

The RT7 isn’t connected up backwards( reverse polarity) is it?

[ajgriff]

Again I'm assuming that it's the eliminator that's humming and that the radio itself is completely lifeless using the eliminator but works fine with the PP9 in which case I'm at a loss in terms understanding what's going on.

Alan

[ssnjimb]

If roffee is right. the power adaptor lead has been connected wrong.

[ssnjimb]

Originally Posted by ajgriff

Again I'm assuming that it's the eliminator that's humming and that the radio itself is completely lifeless using the eliminator but works fine with the PP9 in which case I'm at a loss in terms understanding what's going on.

I agree Ajgriff its very weird

James

[ajgriff]

Surely if the R200 works the eliminator wiring is ok as you can't inadvertently connect PP9 clips the wrong way round and the RT7 works with a battery. Still puzzled.

Alan

[ssnjimb]

Hi

are any of you near cheltenham anytime soon ?

Reason for asking. see for yourself. :P

James

[ms660]

Just my observation, the female connector on the PSU unit has a red wire connected to it and the male connector has a black wire connected to it, if the red was +ve and the black was -ve that would mean the male connector would only fit the female connector in the receiver.....the female connector in the receiver is battery +ve……

If that's the case then wrong way round me thinks.

Lawrence.

[ajgriff]

So why does the eliminator work with the R200 and a battery works in the RT7?

.... unless the battery wiring of the R200 is transposed in which case the R200 wouldn't work with a battery which I assume it does.

Alan

[ms660]

I have no idea as to why but my observation regarding the colour of the wires and what they are connected to still stands.

Lawrence.

[ssnjimb]

Both radio's work on battery

R200 works on mains
rt7 refuses to

i dont get it

/i agree with your observation about the colour of the wires

James

[Cobaltblue]

I suspect the snaps were pre wired with the red and black wires.

These would normally be connected to the radio and not pretend to be the battery.

In that case the colour of the wire to the snaps would be correct.

I suspect you can ignore the colour to the snaps and assume that the seller knew what he was doing.

What interest me is that there is a hum with the radio on or off

Perhaps the switch doesn't actually switch the set off due to some fault and the RT7 is just more fussy about its supply.

The decouplers on this set if original would be the red/black yellow Plessey caps probably very low in value by now.

I would still expect the set to work though

Cheers


Mike T

[HamishBoxer]

Maybe the power supply is not rated high enough current wise for the other set??

[ssnjimb]

Hamish

I suspect you are right.

The seller did offer a refund if i sent it back.

Does he know something ?

grrr

Do Any of you make a battery eliminator that you sell in the buy and sell section ?

James

[ms660]

Polarity aside connecting a black to red and red to black goes against normal convention, If I was making those supplies up myself and flogging them to members on here I'd soon get some grief.

Lawrence.

[Cobaltblue]

I agree that its bad practice, but he needs insulated snaps, and they need to be cheap.

I think I would have sleeved them at the very least.

If it just worked no one would be any the wiser

Cheers

Mike T

[ssnjimb]

Iam sending it back for a refund.

oh well. Long Live The PP9 (PowerPack 9)

Originally Posted by Cobaltblue

I suspect the snaps were pre wired with the red and black wires.

These would normally be connected to the radio and not pretend to be the battery.

In that case the colour of the wire to the snaps would be correct.

I suspect you can ignore the colour to the snaps and assume that the seller knew what he was doing.

What interest me is that there is a hum with the radio on or off

Perhaps the switch doesn't actually switch the set off due to some fault and the RT7 is just more fussy about its supply.

The decouplers on this set if original would be the red/black yellow Plessey caps probably very low in value by now.

I would still expect the set to work though

So basically the electrolytic caps are probably fussy due to age etc etc making the set very very fussy about how much power it can handle before it cripples itself

James

[Cobaltblue]

Not quite.

Capacitors are used for coupling and decoupling (as well as other related things).

When they age they can leak (fail to block DC) and the can go low in value.

The Plessey Red/Yellow/Black capacitors have aged worse than some.

If the decoupler for the early stages of the radio had gone low in value then Hum and ripple would get onto the earlier stages of the radio making hum and other problems like motor boating more of an issue.

These normally occur when the battery is getting close to end of life or when fed from a mains adaptor supply with poor smoothing and regulation.

Not saying this what's wrong here just another possibility.

Cheers

Mike T