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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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22nd Mar 2018, 10:51 am | #101 |
Octode
Join Date: Aug 2015
Location: Glasgow, UK.
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Re: Dansette "Monarch"
For the avoidance of doubt, here is a picture of the Mullard Mustard caps - the smaller one is C4 the 0.01μF audio coupling capacitor while the larger one is the undocumented coupling capacitor 0.047μF.
I think the consensus now is that they can stay put. The blue electrolytic capacitor (C3) has been replaced - this is the cathode bypass capacitor connected to the triode section cathode, Pin 8 of the valve. I think I'm now satisfied that the electronics associated with the main circuit board are working as expected, including the replacements I've made. Still pondering this hum which seems to vary from day to day? There is a general instability with some associated microphony when parts of the record player are touched or tapped?? Next step is to look carefully at the Tone/Volume controls and the On/Off switch, notwithstanding the need to properly route the guddle of cables. I'll also investigate the never to be used sockets at the back as well as it seems a somewhat circuitous route to connect the speakers in parallel??
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BVWS Member Last edited by DonaldStott; 22nd Mar 2018 at 10:59 am. Reason: Typos |
22nd Mar 2018, 12:58 pm | #102 |
Dekatron
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Re: Dansette "Monarch"
Hey Donald, as I and others have noted , there are very real limitations to what you can do about him in this set - just setting expectations in a friendly way, so you don’t over-invest your time fruitlessly.
Also ,not sure what output bottle your Dansette features , but Ed Dinning has just pointed out that an over-worked UL84 can be an additional rogue hum source - there’s a thread down there in Homebrew equipment and a four valve amplifier. These are normally very pleasant sets to fix as they are intrinsically simple and the chassis and layout is very accessible. Hope you get there soon!
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Al |
22nd Mar 2018, 1:33 pm | #103 |
Octode
Join Date: Aug 2015
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Re: Dansette "Monarch"
Thanks Al - I agree that this is an easy record player to work on for the reasons you outline. I'm getting this restored/repaired for a work colleague so I'm spending a bit more time than usual on it. I'm also using this as a learning experience as its the first record player I've tackled - hence the numerous Posts.
I appreciate that this Dansette will never be hum-free but it would be good to find out the source of the problem and, if possible, to reduce the hum to a background level. The Dansette I have features an ECL82 which, as you know, is a triode/pentode - the triode being the pre-amp and the pentode being the output amp. I'll have look at the Tone/Volume controls and the On/Off switch, the guddle of cables and the rear sockets, but after that I think I'm done. Not forgetting of course that I have a BSR X5M cartridge to fit. Thanks to everyone again for their ongoing support and patience.
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22nd Mar 2018, 3:42 pm | #104 |
Octode
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Re: Dansette "Monarch"
Moving on quickly here is a photograph of the Tone/Volume controls and the On/Off switch: -
The ceramic capacitors C1 and C2 (200pF) should be ok while the resistors are within 20% tolerance (measured in circuit). I don't like the look of this dodgy earth connection and not sure where it connects to?
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22nd Mar 2018, 5:28 pm | #105 |
Retired Dormant Member
Join Date: Mar 2018
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Re: Dansette "Monarch"
Hi Donald,
the end of the spring does not attach to anything.The spring is taken out of the slot and moved to adjust the tension of the arm. You would be better fitting a new stereo headshell and cartridge such as Audio Technica AT95E. To clean the vinyl try Servisol Excel polish or any decent silicone polish. Cheers Tony Kal |
22nd Mar 2018, 6:05 pm | #106 |
Dekatron
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Re: Dansette "Monarch"
Even with all of the mods/tweaks suggested in my Post #82, I still got an interactive hum whenever my hand went to use the volume and tone controls. An option would have been to make a thin aluminuin earthed screen boxed over these controls, but as the hum reduced when the hand was moved away, I never did bother.
Given this player featueres 2 large speakers, it's certainly worth persevering with. Ideally it should have had an ECL86 based amplifier!
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Edward. |
22nd Mar 2018, 7:22 pm | #107 | |
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Re: Dansette "Monarch"
Quote:
It looks to me that a previous owner replaced the original native two core cable with a twin and earth, and soldered the end in the pic to the internally exposed metal of the tone control, either as as a safety precaution, or, more likely, just because there was nowhere else to attach it to! There's nothing wrong with that. It may not be original, but it's fine. The good thing is that the cable is nicely strain relieved.
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22nd Mar 2018, 7:27 pm | #108 |
Dekatron
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Re: Dansette "Monarch"
You can't use the AT95E in this player without adding a Pre-Amp.
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Edward. |
22nd Mar 2018, 9:08 pm | #109 | |
Octode
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Re: Dansette "Monarch"
Quote:
What are the possible sources of the hum - the AC heater perhaps, the proximity of the two transformers, the cables running to and from the controls, the controls themselves?? One quick fix could be to disconnect the speaker wires running to one of the rear sockets and just have short lengths of cable to wire the speakers in parallel - there is already one red wire in place. Another one is the grey co-axial cable that runs from the tag strip where the cartridge wires terminate to another rear socket and from there to the controls - why not just run a co-ax from that tag strip directly to the controls. There is also a white co-axial cable that runs from the tag strip to the third rear socket??
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22nd Mar 2018, 9:18 pm | #110 | |
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Re: Dansette "Monarch"
Quote:
Re: Hum, short the wiper of the treble control to the chassis and see if that affects the level of hum. Lawrence. Last edited by ms660; 22nd Mar 2018 at 9:25 pm. |
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22nd Mar 2018, 10:37 pm | #112 |
Dekatron
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Re: Dansette "Monarch"
I would check all the chassis connections both on the amplifier chassis and the control panel chassis. Another test would be to short the grid of the triode to the chassis.
Lawrence. |
22nd Mar 2018, 10:55 pm | #114 |
Dekatron
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Re: Dansette "Monarch"
Through the gaps or through the rivets if they're hollow, I wouldn't try removing the thumbwheel knobs:
https://www.vintage-radio.net/forum/...2&d=1448284336 Lawrence. Last edited by ms660; 22nd Mar 2018 at 10:58 pm. Reason: addition |
23rd Mar 2018, 10:47 am | #115 | ||
Octode
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Re: Dansette "Monarch"
Quote:
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23rd Mar 2018, 10:52 am | #116 |
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Re: Dansette "Monarch"
If this player hums excessively as opposed to normal hum levels expected from a record player, is it really going to be down to long cables which were part of the original design?
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
23rd Mar 2018, 12:07 pm | #118 |
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Re: Dansette "Monarch"
No. I'm expecting an answer from someone.
Various mods were suggested in post #82, but surely even without these being done the hum level should be in line with what was/is expected from a record player?
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
23rd Mar 2018, 12:57 pm | #119 |
Octode
Join Date: Aug 2015
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Re: Dansette "Monarch"
Understood - as a relative novice at Repair and Restoration (despite my age!) maybe I expect too much in the way of definitive answers. Lots of suggestions to try various things but I suppose what I'm looking for is advice on how to track down the source of this excessive hum? Learning as I go of course as I'm not interested in just a painting by numbers approach!
I've read countless Threads and Posts on this and other Forums on this topic but a lot of it seems to be "smoke and mirrors"? I'm not too concerned about authenticity here and do feel that in 2018 there must be changes that can be made to improve on the original design of these record payers from the early 1960s - within reason of course. I'll give the Forum a bit of a break while I try the various suggestions over the weekend - thanks again to everyone.
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BVWS Member Last edited by DonaldStott; 23rd Mar 2018 at 1:03 pm. |
23rd Mar 2018, 12:58 pm | #120 |
Heptode
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Re: Dansette "Monarch"
In post 106 it can be seen both the mains in and out leads to the mains switch are very close to the vol/tone controls. I would move them as far away as possible, this would involve repositioning the mains lead 'P' clip.
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