Dansette Prince

[Minster97]

After having my failed attempt to restore my Black Box thank fully rescued by one of you for which I remain extremely grateful I thought I would go for something simpler. Sorted the seized auto changer the easy bit of course.
Volume very crackly and intermittent which hopefully will go in time with switch cleaner?
Amplifier is quiet as a mouse until the motor starts to turn when you get an annoying hum, the volume proportional to the volume setting. Have checked the deck is seated and the four leads to the cartridge seem ok.
Any ideas as to how to sort this out please?
On a different note I stumbled on a dealer website who will have absolutely nothing to do with this mode of machine and a list of others. Quite put the wind up me.
The deck and motor are earth bonded. The incoming three core first goes to the amp chassis which is earthed but that’s as far as the earth goes. I thought these live chassis were not earthed. Removing the knobs I was pleased to see plastic covered shafts so may be Dansette wasn’t trying to kill every teenager off!
Thank you

[Michael Maurice]

It sounds like its a transistorised machine where the motor acts as the mains transformer.

How many wires going to the motor?

[simpsons]

From previous threads on this site, there are 2 versions of this record player.

Distinguished by the number of controls, those with 5 are Dansette's own valved designed audio amplifier using AC/DC UCL 82 valves and those with 4 uses a Rank Bush Murphy transistorised circuit firmly AC design.

Both have an earth lead but with the valve version, you need to keep "one hand in your pocket" when touching the chassis and your feet dry!

Which one is yours?

Chris

[Cobaltblue]

There was a thread about the Transistorised version of the Prince a couple of years back: https://www.vintage-radio.net/forum/...d.php?t=147845

Is this the same type of machine ?

I would not get over worried about what people will and won't repair If I were trying to earn a living there are things I would give a wide berth as well.

I had a Fidelity live chassis record player when I was 10 till 13, I never got a shock and I was pretty careless with it

Cheers

Mike T

[ms660]

Circuit is the same as a Bush SRP52 if I remember:

https://www.service-data.com/product...44/9593/m17044

Lawrence.

[Minster97]

All, It is the valved version

[Minster97]

It is Transistor version, not valve. Sorry

[Edward Huggins]

I'm a bit concerned that the OP can't seem to tell the difference. The Dansette made PRINCE is valved with an UCL82 and a UY85. So if he is planning to work on this, be aware of the live chassis. The later RBM made Prince is transistorised.

[Minster97]

I had had a valve one alongside and just had mental blip! Won't work on it while turned on.

[simpsons]

OK Now we know what we are dealing with, how do we get Minster's record player working.

The first thing to know is that it is also known as a Bush SRP 52. There are a number of posts on this site which will help familiarise the OP on his model.

The second thing to know is that the Bush AU 52 is also the same amplifier.

The snag is only parts of the circuit are shown, the front end is missing.


Chris

[ms660]

Bush SRP52 schematic in the link in Post#12 here:

https://www.vintage-radio.net/forum/...d.php?t=118777

Lawrence.

[Minster97]

I have ordered the DVD’s from this site also so will study them.I have the amp out now and will check the capacitors when I have the circuit diagram. Visually so far all looks pristine, no signs of overheating or swellings .As I said only hums when motor running, the hum increasing as you turn the volume control up. Otherwise a nice sounding record player.

[simpsons]

First of all, to repair anything an engineer needs to both understand enough of how the workings of the job in question following which, the "grey matter" must be switched on.

In this instance, the hum happens only when the motor starts and most importantly the hum is controlled by the volume control. This is the clue you are looking for; changing capacitors willy-nilly is a recipe for disaster.

The volume control precedes all else which means that the problem must be before the control.

There are screened cables between the pick up and sockets which might now no longer be earthed or the deck. You will need to either use a test meter to check this out or, using a flying lead, ground to the chassis connections prior to the volume control until you can eliminate something which has come adrift.

The hum level described by AWC is not the same problem you have described.

If you are unsure how to follow a schematic or how a record player cartridge is connected to the amplifier, don't apologise, that is how we all started.

Chris

[Minster97]

Thank you for the help, seems very sensible. The deck itself does not appear to be earthed. The only earth bond is between motor and deck themselves. The amplifier chassis only has an earth connection. I will certainly check everything but am I correct in saying that I shouldn’t earth anything that wasn’t already earthed?

Gary

[Boulevardier]

I can't work out what's going on here. In his posts, Minster says that the amplifier chassis is connected to mains earth through the three-core mains supply lead. Yet I think it's being said that the unit is of the "live chassis" type, without a mains transformer.

I haven't seen the circuit diagram, but something's seriously not right, surely.

Mike

[Cobaltblue]

There was some confusion earlier in the thread (The OP has two different versions it seems) but it looks as if this is the transistorised version we are dealing with here:

Lawrence pointed to the service info in Post #11

Cheers

Mike T

[simpsons]

Hi Gary

The way an amplifier and connections to it are earthed is carefully chosen by the engineer who designed the record player. This is to minimise hum being introduced by what are known as earth loops.

In the case of your record player, the record deck is most likely to be earthed through the leads connecting the amplifier to the cartridge and this is typically via a tag strip located on the record player deck. This is also the tag strip which the pick up leads are are wired. From the circuit diagram, the amplifier connection is via 2 sockets.

They are: Stereo out and Tape In.

This means the amplifier connection to the pick up goes via these sockets not, as in simpler models, straight to the tag strip.

You need to trace the connecting wires and make sure that the outer or screened earth connection is soldered correctly either by using the test meter or, as suggested, a simple length of wire which you connect from the chassis to the earth connection.

Interestingly, the tape in socket when used disconnects the pick up cartridge and so, should you have the right lead, you could see if the hum is present when used.

Because there are no high voltages which you could inadvertently connect accidently to where they don't belong, I am confident that my suggestion can be followed with little risk.

Let us know how you get on or if in doubt, take some photos of the tag strip and wiring to and from the amplifier.

Chris

[ms660]

I must be on a different planet

Lawrence.

[simpsons]

Lawrence, should I have got something wrong do let me know as I would be happy to defer to those with greater knowledge.

Chris

[ms660]

I have two schematics, one for the valve version and one which is supposedly for the transistor version, the schematic I have for the transistor version is for the Bush SRP52/ AU52/ Murphy A856G which so far as I know is the same as the transistor version of the Dansette, and in that one, nothing is switched out of circuit when the tape socket is used so far as I can see, the only thing that's switched out of circuit is the cartridge's LH channel when the stereo lead is plugged in for connecting to an external amplifier.

I don't have the full manual, just a schematic.

In post #7 the OP says it's the transistorised version he's referring to.

Lawrence.