Dansette Bermuda MkII - volume hum - UK Vintage Radio Repair and Restoration Discussion Forum

markkelsall · 23rd Nov 2018, 2:19 pm

Hello all

Yes another Dansette hum related question!

I'm resurrecting this Bermuda MkII for a friend and have so far repaired the X3M cartridge and done a full mechanical clean and re-lube incl the motor. All works sweetly there.

However, whilst the background hum (with volume turned down) is negligible, which I believe means the smoothing can caps are OK, as I increase the volume so does the hum.

Note: I have also fitted a new ceramic cartridge which does the same (one of those cheapo black and red jobs) so I'm happy it's not the cart.

I appreciate that these things are a bit rubbish so do hum a bit, but I think this is excessive. You can't hear it with the music playing but it's still a bit loud to my ears.

Are there a few checks/readings I can make to try and trace the fault? e.g. cathode biasing, gate or anode voltages etc. And if so what sort of readings should I be expecting? Also what would be the check points for my multimeter?

I've read that the 0.047 uf capacitor (diagram below) almost always needs replacing. Would this cause my hum problem?

Please also note that the diagram is not exactly like the Bermuda I have. e.g the tone control pot on 'mine' is 1 mega ohm!

Many thanks.

Station X · 23rd Nov 2018, 2:27 pm

Quote:

Originally Posted by markkelsall

You can't hear it with the music playing but it's still a bit loud to my ears.

That sounds perfectly normal to me.

If the smoothing caps are OK, then any hum will be down to stray pickup by the wires leading from the cart to the amplifier. You could try rerouting them.

DonaldStott · 23rd Nov 2018, 2:36 pm

Have a look at this and other similar Threads on Dansette hum: -

https://www.vintage-radio.net/forum/...d.php?t=151618

As Chris (Herald1360) noted in Post #11: -

"Some hum is endemic in basic old valve record players. To get rid of it, you may well have actually to improve the design and wiring layout from the original. Knowing what's original sin (and therefore presumably acceptable) and what isn't is where it gets interesting."

It's also where it gets expensive going way beyond the value of these old valve record players. Most of us have just accepted the hum as a "feature" and moved on...

23rd Nov 2018, 2:36 pm	#3
DonaldStott Octode Join Date: Aug 2015 Location: Glasgow, UK. Posts: 1,850	Re: Dansette Bermuda MkII - volume hum Have a look at this and other similar Threads on Dansette hum: - https://www.vintage-radio.net/forum/...d.php?t=151618 As Chris (Herald1360) noted in Post #11: - "Some hum is endemic in basic old valve record players. To get rid of it, you may well have actually to improve the design and wiring layout from the original. Knowing what's original sin (and therefore presumably acceptable) and what isn't is where it gets interesting." It's also where it gets expensive going way beyond the value of these old valve record players. Most of us have just accepted the hum as a "feature" and moved on... __________________ BVWS Member

23rd Nov 2018, 2:19 pm	#1
markkelsall Triode Join Date: Jan 2015 Location: Stoke-on-Trent, Staffordshire, UK. Posts: 18	Dansette Bermuda MkII - volume hum Hello all Yes another Dansette hum related question! I'm resurrecting this Bermuda MkII for a friend and have so far repaired the X3M cartridge and done a full mechanical clean and re-lube incl the motor. All works sweetly there. However, whilst the background hum (with volume turned down) is negligible, which I believe means the smoothing can caps are OK, as I increase the volume so does the hum. Note: I have also fitted a new ceramic cartridge which does the same (one of those cheapo black and red jobs) so I'm happy it's not the cart. I appreciate that these things are a bit rubbish so do hum a bit, but I think this is excessive. You can't hear it with the music playing but it's still a bit loud to my ears. Are there a few checks/readings I can make to try and trace the fault? e.g. cathode biasing, gate or anode voltages etc. And if so what sort of readings should I be expecting? Also what would be the check points for my multimeter? I've read that the 0.047 uf capacitor (diagram below) almost always needs replacing. Would this cause my hum problem? Please also note that the diagram is not exactly like the Bermuda I have. e.g the tone control pot on 'mine' is 1 mega ohm! Many thanks. Attached Thumbnails