Replacing Plessey electrolytic 100uf - UK Vintage Radio Repair and Restoration Discussion Forum

astro63 · 2nd Feb 2018, 10:09 pm

I have a Dansette Prefect battery record player 1963-64. On the motor side is a tag strip with 2 resistors? and 2 Plessey 12v 100uf electrolytics. When switched on there is a hiss via the amp, which comes from the motor. I replaced both Plesseys with 16v 100uf, this cut the hiss quite a bit. I had a couple of 16v 1000uf so temporarily put them in, and the hiss is totally gone.

My question is will the 1000uf cause damage to the set if I leave them in? I have to admit it's so nice to not have a constant background hiss.

Thanks in advance.

'LIVEWIRE?' · 2nd Feb 2018, 11:38 pm

To the best of my knowledge, based on working with electronics for over 40 years, the use of higher value electrolytics will not cause any damage to transistorised equipment. Presumably the capacitors in question are supply line decoupling components. As you will be aware modern electrolytic capacitors are smaller that those made over 50 years ago, and, in real terms, most likely cheaper, too. Today's 1000uf Caps, are probably no larger than those old 100uf ones - they may even be smaller.

turretslug · 3rd Feb 2018, 11:17 am

I recall as a kid having a French-made late-'sixties battery record player (clad in tasteful blue mock crocodile) that had a pi-filter in the motor power feed with a dinky laminate-core choke- so DC motor noise was evidently an issue with these things. As said, higher capacity electrolytics won't be an issue (within rational limits....) and modern ones are likely to have better ESR and over a wider frequency range. 1000uF or so wouldn't be at all unusual across the rails in many battery-operated devices- the internal resistance of batteries goes up as they wear out, and source impedance needs to be kept low down to low frequencies to ward off instability like motor-boating.

astro63 · 3rd Feb 2018, 5:53 pm

attached of what was on the the motor and what i want to replace with, hoping this is correct

'LIVEWIRE?' · 3rd Feb 2018, 7:21 pm

Two of those 1000uf 16v caps. should be perfectly alright. Just make certain that you connect them with the correct polarity - positives to the LH end of that tagstrip in your first picture. Generally speaking I, and other forum members tend to regard those red & yellow Plessey electrolytics as 'replace on sight'. In fairness neither those nor any component of that vintage was expected to last more than 5 decades.

astro63 · 3rd Feb 2018, 9:20 pm

Many thanks for your help, will get 'em soldered on tomorrow when I can see better

2nd Feb 2018, 10:09 pm	#1
astro63 Pentode Join Date: Mar 2013 Location: Norfolk, UK. Posts: 248	Replacing Plessey electrolytic 100uf I have a Dansette Prefect battery record player 1963-64. On the motor side is a tag strip with 2 resistors? and 2 Plessey 12v 100uf electrolytics. When switched on there is a hiss via the amp, which comes from the motor. I replaced both Plesseys with 16v 100uf, this cut the hiss quite a bit. I had a couple of 16v 1000uf so temporarily put them in, and the hiss is totally gone. My question is will the 1000uf cause damage to the set if I leave them in? I have to admit it's so nice to not have a constant background hiss. Thanks in advance.

2nd Feb 2018, 11:38 pm	#2
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: replacing plessey electrolytic 100uf To the best of my knowledge, based on working with electronics for over 40 years, the use of higher value electrolytics will not cause any damage to transistorised equipment. Presumably the capacitors in question are supply line decoupling components. As you will be aware modern electrolytic capacitors are smaller that those made over 50 years ago, and, in real terms, most likely cheaper, too. Today's 1000uf Caps, are probably no larger than those old 100uf ones - they may even be smaller.

3rd Feb 2018, 11:17 am	#3
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,396	Re: Replacing Plessey electrolytic 100uf I recall as a kid having a French-made late-'sixties battery record player (clad in tasteful blue mock crocodile) that had a pi-filter in the motor power feed with a dinky laminate-core choke- so DC motor noise was evidently an issue with these things. As said, higher capacity electrolytics won't be an issue (within rational limits....) and modern ones are likely to have better ESR and over a wider frequency range. 1000uF or so wouldn't be at all unusual across the rails in many battery-operated devices- the internal resistance of batteries goes up as they wear out, and source impedance needs to be kept low down to low frequencies to ward off instability like motor-boating.

3rd Feb 2018, 5:53 pm	#4
astro63 Pentode Join Date: Mar 2013 Location: Norfolk, UK. Posts: 248	Re: Replacing Plessey electrolytic 100uf attached of what was on the the motor and what i want to replace with, hoping this is correct Attached Thumbnails

3rd Feb 2018, 7:21 pm	#5
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Replacing Plessey electrolytic 100uf Two of those 1000uf 16v caps. should be perfectly alright. Just make certain that you connect them with the correct polarity - positives to the LH end of that tagstrip in your first picture. Generally speaking I, and other forum members tend to regard those red & yellow Plessey electrolytics as 'replace on sight'. In fairness neither those nor any component of that vintage was expected to last more than 5 decades.

3rd Feb 2018, 9:20 pm	#6
astro63 Pentode Join Date: Mar 2013 Location: Norfolk, UK. Posts: 248	Re: Replacing Plessey electrolytic 100uf Many thanks for your help, will get 'em soldered on tomorrow when I can see better