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Vintage Audio (record players, hi-fi etc) Amplifiers, speakers, gramophones and other audio equipment. |
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20th Jun 2018, 12:14 pm | #1 |
Diode
Join Date: May 2016
Location: Falkirk, Stirlingshire, Scotland, UK.
Posts: 7
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BSR C123R - Loud pop/bang
Hi, recently acquired a Thron Ultra 6339, with a BSR C123R deck. We’ve managed to sort the seized platter and the cartridge being held on with blu tac, but the big issue that I am finding hard to solve is the loud bang/pop sound the speakers make when the auto stop kicks in at the end of a record or when you switch it to start or to stop. The pop is really quite loud even when the volume is turned almost off, and I can’t hear buzzing or anything so I’m stuck.
The main knobs that control volume, tone, what radio wavelength, etc, also make noise, but this is nowhere near as loud or concerning, it is more of a crackly sound. Is there anyway this can be sorted? Sorry for all the (probably silly) questions, hope you can help!! |
20th Jun 2018, 2:11 pm | #2 |
Octode
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,577
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Re: BSR C123R - Loud pop/bang
Check the switch under the deck that turns the motor on and off. Follow the wires back, there it is. Check that the mechanism that operates it moves quickly and easily, if that's OK have a look at the contacts. Clean up any pitting or burning and make sure they close cleanly and tightly when the motor is supposed to be on. Finally, you could add a 100nF capacitor (X2 class only!) across the switch contacts, that should calm it down.
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20th Jun 2018, 2:34 pm | #3 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,335
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Re: BSR C123R - Loud pop/bang
If those switching contacts are dirty/carbonised, turning the unit on and off will cause an electrical arc to be created. This will be amplified resulting in a loud pop/bang.
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Edward. |
20th Jun 2018, 5:20 pm | #4 |
Nonode
Join Date: Jun 2014
Location: Bristol, UK.
Posts: 2,074
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Re: BSR C123R - Loud pop/bang
The volume/ tone controls probably just need cleaning. Take a look at the potentiometers behind the controls - there is a little gap where the wires are soldered on - squirt a little Servisol (contact cleaner) in there and work the controls back and forth. Usually works wonders.
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'....don't go mistaking Paradise for that home across the road!' (Bob Dylan) |
20th Jun 2018, 5:44 pm | #5 |
Dekatron
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,554
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Re: BSR C123R - Loud pop/bang
If it is a live chassis amplifier it may be a missing deck earthing capacitor.
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20th Jun 2018, 6:00 pm | #6 |
Dekatron
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,335
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Re: BSR C123R - Loud pop/bang
Not a live chassis, this is an early 1970s, mid-range Stereo Radiogram.
This used a near standardised chassis which appeared in a number of branded permutations - HMV, Marconi, Ultra - usually accompanied by the ubiquitious BSR C series autochanger and two 8" x 5" speakers.
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Edward. |
20th Jun 2018, 6:58 pm | #7 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: BSR C123R - Loud pop/bang
It's unlikely to have a live chassis if the motor is being switched on and off. Record players with a live chassis used a tapping on the motor stator as an autotransformer to supply the valve heaters, so would have left the motor running full-time and just disengaged the idler at the end of the record.
Also, a C123 sounds just a bit modern for anything with valves anyway, unless it's a retro-fit. And nearly everything transistorised has an isolating transformer.
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21st Jun 2018, 12:06 am | #8 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 5,000
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Re: BSR C123R - Loud pop/bang
Lucy - have a look at the this recent thread linked to below, where someone else has just had same problem and fixed it, with advice from members:-
https://www.vintage-radio.net/forum/...d.php?t=147275 |