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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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16th Oct 2020, 6:47 pm | #1 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Dansette Major capacitor
Hello, just a quick one. Bad hum problems on this amp and I think as it has so few components I'm just going to replace all the caps while I've got it apart.The tone control cap, 0.05uF is a waxy-looking thing which, curiously has a black stripe at one end but is not shown on the schematic as polarised. Could anyone enlighten? I was going to replace it with a polyester but would something else be more suitable? Thanks, MD
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16th Oct 2020, 7:01 pm | #2 |
Dekatron
Join Date: Aug 2013
Location: Wigan, Greater Manchester, UK.
Posts: 9,427
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Re: Dansette Major capacitor
The black line is the outer foil and in this position it can be ignored. Polyester will be fine, I would use a 630vw minimum, may as well use 1000vdc.
Before doing major work check the cartridge, it requires a high out type which are virtually impossible to get or very expensive.
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Frank |
16th Oct 2020, 7:40 pm | #3 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Thanks Frank, yes that had crossed my mind, I've been asked to make one working model from two existing units plus a spare deck, so 3 cartridges, maybe one of them will be OK!
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16th Oct 2020, 7:49 pm | #4 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
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Re: Dansette Major capacitor
Is that the EL84 model? If so it is likely to be the triple electrolytic and be aware the case of the electrolytic forms part of the circuit!
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17th Oct 2020, 9:38 am | #5 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
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Re: Dansette Major capacitor
You will most likely need to replace the 3 in 1 can with discrete components. Don't forget when you have used the other player and the separate deck for spares, these in their own right, will be sellable. Also suggest you add a 3 core mains lead. BTW Even a dud cartridge can sell in order for it to be rebuilt.
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Edward. |
17th Oct 2020, 11:39 am | #6 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Yes it's the single EL84 with a metal (selenium?) rectifier. As usual, what I thought may be an hour or so's job gets a bit trickier.. the PCB is riveted to the chassis and the mains transformer prevents access to most of the bottom of the board, so have to decide whether to drill out the rivets and replace with nuts and bolts, or remove the transformer, which is bolted down and then covered with a liberal amount of wax or epoxy of some kind but.. in post-France quarantine so lots of spare time..!
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17th Oct 2020, 1:35 pm | #7 | |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Quote:
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17th Oct 2020, 2:48 pm | #8 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
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Re: Dansette Major capacitor
It certainly would be simpler - you are unlikely to be able to stuff new caps into that very small can! The high-output cartridge might make or break this project. Mono-only BSR TC8H clones can still be bought in the UK for £35-00.
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Edward. |
17th Oct 2020, 8:59 pm | #9 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Just wondering about the 2 HT caps, which are 32uF and 16uF; I'm sure I've seen other EL84 circuits where they are both the same value and wondered if anything would suffer if I used a dual can 32+32?
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17th Oct 2020, 9:54 pm | #10 |
Hexode
Join Date: Jan 2013
Location: Wigan, Lancashire, UK.
Posts: 372
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Re: Dansette Major capacitor
I too have seen other EL84 valve amplifiers using a dual 32+32uF can. It won't do any harm and may reduce the hum. They may have used 32+16uF to keep costs down. Fidelity did the same on their later UY85 - UL84 amplifiers.
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18th Oct 2020, 8:25 am | #11 | ||
Hexode
Join Date: Jun 2012
Location: Chester, Cheshire, UK.
Posts: 420
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Re: Dansette Major capacitor
Quote:
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18th Oct 2020, 11:41 am | #12 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,527
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Re: Dansette Major capacitor
Is this a problem? The chassis on most radios with isolating transformers is HT- too. No problem with earthing those. Most even had a specific connector for just that. Helpfully labelled "E" usually.
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26th Oct 2020, 11:23 pm | #13 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Thanks for all replies so far. I've replaced the smoothing caps and the tone control cap and the amp now runs well. I did order some 1N4007s and 150R 5W resistors, but it seems that the original metal rectifier works fine, so is it worth replacing it just for the sake of it? Also good news, all 3 cartridges work fine with a good clean output. One mechanical problem I have is that the motor is running slow. Definitely the motor - I've cleaned the jockey wheel, set the correct height, cleaned turntable inside rim, cleaned and re-greased the central ball race, etc, and have removed the cam so the auto-mechanism is not in play; turntable spins freely when disengaged, so I think dismantling the motor and cleaning inside it may be the next step. Incidentally, as I previously mentioned, I actually have 3 decks and all of them run with varying degrees of "slowness" so I'm concluding that years of inactivity have caused this...
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27th Oct 2020, 12:08 am | #14 |
Dekatron
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 7,484
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Re: Dansette Major capacitor
You will need to dismantle the motor lower bearing and clean and add some light oil. That should cure the speed fault. Give the pulley a good yank after reassembly to ensure it's all centred!
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Regards, Ben. |
26th Nov 2020, 1:27 pm | #15 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Hello, just an update on the Dansette, which is proving far trickier than the original "quick job" I envisaged! I repaired the amp and as far as I can tell, it's working fine - except the only thing I can try it with is the cartridge... where another problem occurs: I tested the original cartridge with a separate amp and it seemed to perform well.. so I married up the deck with the repaired amp and... very low volume! I think the mistake I've made, which is staring me in the face in retrospect, is that the other amp I used to test the cartridge is obviously a modern one with a much higher gain than the single EL84 one, and it's hidden the fact that the old cartridge has in fact deteriorated and is giving a good tone but with a much reduced output.. does this make sense? Further strange goings-on... I ordered a new cartridge online and it's giving a 2-3V output as you'd expect but it sounds very distorted... supplier replaced it and the second one sounds the same. Bit of a chicken-and-egg thing, I don 't know for certain that the newly-restored EL84 amp is definitely OK and I don't know for certain that the new cartridge(s) are faulty or OK. I don't have an oscilloscope so the only way of testing the amp would be by ear really. What kind of input could I feed into the EL84 amp to verify its sound quality in order to do a process of elimination? I was thinking maybe the output from a portable radio, through a coupling capacitor, but this would be a low impedance signal into a high impedance input so probably would be inconclusive - any ideas? Thanks
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26th Nov 2020, 1:47 pm | #16 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Dansette Major capacitor
Feeding a signal from a low impedance source into a high impedance input is no problem, eg: imagine what difference connecting a 1meg resistor across a loudspeaker in a loudspeaker circuit will do....not a lot.
Lawrence. |
26th Nov 2020, 2:26 pm | #17 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
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Re: Dansette Major capacitor
The issue is that your player was designed to work with an (orange bodied) BSR TC8H Mono cartridge. You can (still) buy a replacement for £35-00 - but do remember this will not be suitable for playing Stereo records and most of your LPs will be Stereo. What type of cartridge have you bought as no cartridge that I know of can give as much as 2-3 volts output, except on occasional highly modulated peaks? Your assumption of why it may sound "loud" on a much higher gain amplifier is quite correct.
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Edward. |
26th Nov 2020, 2:51 pm | #18 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
It is an orange-bodied TC8H, identical to the old one, for £35.00.. yes I get everything re stereo etc, the new cartridge sounds very distorted both playing a 78 and a mono 45, not just an "overloaded input" type of distortion but an unpleasant uneven distortion.. I was prepared to accept that it could have been a faulty new cartridge but when the replacement item also sounded the same I had to re-think things. Re the output voltage, I understood that these cartridges could deliver up to 3V. I've measured the output while a record is playing, probably not a very scientific method, with a DMM set on AC, and it's reading between 2 and 3V using this method. Both the new cartridges sound much worse than the 60-year old one which had been fitted when it arrived. Thanks for the bit about impedances; I can see that perfectly as you put it like that; I think I'll try to eliminate amplifier problems first. Ironically I've got a big collection of working vintage gear but I just don't have another record player with the EL84 / crystal cart combo that I could use to compare various parts...
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26th Nov 2020, 11:01 pm | #19 |
Hexode
Join Date: Aug 2014
Location: Wigston, Leicester, UK.
Posts: 348
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Re: Dansette Major capacitor
Hi, could it just be that the selenium rectifier is showing its age and you haven't got enough HT now?
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26th Nov 2020, 11:16 pm | #20 |
Pentode
Join Date: Jan 2019
Location: Liverpool, Merseyside, UK.
Posts: 121
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Re: Dansette Major capacitor
Yes, good point, that was an avenue I was going to explore, the HT seems OK and have replaced filter caps but I think I'm going to try a 1N4007 with a 150R resistor and see if that improves things
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