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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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19th Jan 2023, 11:28 pm | #1 |
Pentode
Join Date: Jun 2020
Location: Woking, Surrey, UK.
Posts: 146
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Dansette Major (early type) Issues
Hi everyone
I'm having issues with an early Dansette Major that I can't seem to find any schematic for. The scenario is that this appears to be a UL84 variation of the later EL84 type. It has mains hum like crazy and changing the triple Mains Cap for modern equivalents has made no difference, nor has changing the .05 uF tone control cap, making every capacitor on the board new. I have valve tested the valve and it passes with no issues. The rectifier (a type 06e 11/8 ) has output of 282v ac. The valve readings (again ac) are .. Pin 1 0v (but hums like crazy when you try reading it) Pin 2 As Pin 1 Pin 3 16v Pin 4 heater negative Pin 5 heater positive 45v Pin 6 149v Pin 7 219v Pin 8 219v Pin 9 148v The only other thing done to the player is to fit a 3 core mains cable (earthed to the volume pot). The last thing of note, is that the record deck is disconnected (motor and pickup wires) The board has the numbers 157/4 and I can't seem to find any reference to that anywhere in the Dansette Schematics I have seen, hence why I can't check specs, voltages etc. Can anyone throw some light on the subject ? All answers gratefully received. Kind Regards Paul |
19th Jan 2023, 11:32 pm | #2 |
Hexode
Join Date: Dec 2020
Location: Raunds, Northamptonshire, UK.
Posts: 351
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Re: Dansette Major (early type) Issues
I would reconnect the audio lead to the deck, you may well find that this will cure the problem.
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Graham |
19th Jan 2023, 11:56 pm | #3 |
Banned
Join Date: Dec 2022
Location: Peterborough, Cambridgeshire, UK.
Posts: 418
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Re: Dansette Major (early type) Issues
I once found that if the PCB wasn't firmly soldered to the metal chassis carrier it caused this - have a look.
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20th Jan 2023, 12:01 am | #4 |
Dekatron
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 7,567
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Re: Dansette Major (early type) Issues
If this uses a UL84 it suggests a live (non-isolated) chassis and therefore should not be earthed. Is it an oddball that uses a proper mains isolation transformer? If not, the earth you have introduced could be the problem.
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There are lots of brilliant keyboard players and then there is Rick Wakeman..... |
20th Jan 2023, 12:06 am | #5 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,327
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Re: Dansette Major (early type) Issues
Your amplifier is a later and interim version of the one first found in the Dansette "Automix" which used a UL41 valve. Using the same mains TX, this later had a UL84 (same heater voltage) before the final EL84 version. With a 3 core mains lead, this amplifier should possess a fairly low hum level, hum only being noticeable over the last 25% of travel of the volume pot. Re-connect as advised above and make sure you do not introdce any earth loops.
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Edward. |
20th Jan 2023, 12:21 am | #6 | |
Pentode
Join Date: Jun 2020
Location: Woking, Surrey, UK.
Posts: 146
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Re: Dansette Major (early type) Issues
Quote:
This one does incorporate a mains transformer, rather than using a UL85 valve (from schematics) and seems exactly the same circuit at the EL84 type apart from a different rectifier. But I will disconnect the earth and see if that is the cure. If so, I owe you a pint |
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20th Jan 2023, 12:36 am | #7 | ||
Pentode
Join Date: Jun 2020
Location: Woking, Surrey, UK.
Posts: 146
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Re: Dansette Major (early type) Issues
Quote:
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20th Jan 2023, 12:42 am | #8 |
Pentode
Join Date: Jun 2020
Location: Woking, Surrey, UK.
Posts: 146
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Re: Dansette Major (early type) Issues
Many thanks for your input. I have done continuity checks and also ohms tests from board to earth and reading 0.00 on the scale. This doesn't appear to be the issue I'm afraid.
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20th Jan 2023, 1:46 am | #9 | |
Pentode
Join Date: Jun 2020
Location: Woking, Surrey, UK.
Posts: 146
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Re: Dansette Major (early type) Issues
Quote:
I removed the original wiring to the deck and fitted some co ax, connected that back to the deck and the noise levels are now back to acceptable Dansette levels. I definitely owe you a beer, unfortunately, as you are nowhere near me, will a virtual one do ? Many thanks to everyone's answers. All valid and helpful and for that ... I thank you all !!!! |
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21st Jan 2023, 12:11 am | #10 |
Hexode
Join Date: Dec 2020
Location: Raunds, Northamptonshire, UK.
Posts: 351
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Re: Dansette Major (early type) Issues
My pleasure, I shall be in Thames Ditton next Friday but alas I shall be attending an AGM until late evening so a virtual pint it will have to be!
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Graham |