Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. - Page 5 - UK Vintage Radio Repair and Restoration Discussion Forum

theredhouseinn · 27th Oct 2021, 4:08 pm

You are working on a home brew lashup with exposed mains wiring, if you are not very careful you will get a nasty shock which may kill you.
You have also added an earth wire to the metalwork which increases the risk whilst you have your hands in the works.
John.

peter_sol · 27th Oct 2021, 4:39 pm

I think that someone with more knowledge is going need to sit with you and help out. Even with the amp working it's unlikely to produce sound with the original Acos Hi G cartridge.

Edward Huggins · 27th Oct 2021, 4:46 pm

This is very sound advice. I normally will try to persevere over many Posts, as I did earlier, but in this case I have now withdrawn due to the risks involved.

Bigears · 27th Oct 2021, 5:22 pm

There looks to be 3 pins of the IC that are not soldered to the PCB. Shown in photo of solder side in post 41. good observation taking a good look at that I can see 6 pins that need attention

Bigears · 27th Oct 2021, 5:24 pm

I never work on it with the mains on, but I heed your concern

Bigears · 27th Oct 2021, 5:36 pm

Yes Lawrence, on taking a good look at the PCB I see about 6 that need attention, one of the members is concerned about my wellbeing, I am taking precautions I am not working on it live, I also know that it has a 1000 uF Cap close by

Bigears · 27th Oct 2021, 6:07 pm

As I am trying to understand how this works, it would help me if someone view this picture and tell me the names of the four main components, I can see one is a transformer and one is a choke I know that the transformer reduces voltage and the choke filters out AC current , I think so what do the other two do, any reply would help me understand what's going on, this record player is just something I picked at a market, something to give me hands on experience

Its just like I am interest in electronics I just wish I came into it earlier

Regards Ken

Cobaltblue · 27th Oct 2021, 6:14 pm

This Help?

Forgive the finger trouble typing Reservoir

DMcMahon · 27th Oct 2021, 6:42 pm

The mains transformer is an RS filament transformer, so its original intended purpose was to power the heaters (filaments) of valves that require 6.3V, as Laurence has previously explained this transformer has 2 separate 6.3V secondary windings and it looks like they are wired in series to provide a nominal 12.6V output.

Transformers depending upon their design can increase voltage (step up), decrease voltage (step down) or keep the input and output voltages the same like a 1:1 isolation transformer. In this case it is a step down transformer.

The AC output from the Mains transformer goes to the bridge rectifier (which effectively is 4 rectifier diodes connected in bridge rectifier configuration encapsulated in the black module). This rectifies the AC voltage to produce a DC voltage, but it is not a clean DC, it has an AC component called ripple.

To remove/reduce the AC voltage ripple, the output of the Bridge Rectifier has to be filtered/smoothed by the Choke and the large grey reservoir electrolytic capacitor.

There may also be further filtering/de-coupling capacitors at the amplifier PCB to further clean up the DC supply.

David

jamesperrett · 27th Oct 2021, 10:29 pm

Quote:

Originally Posted by Bigears

OK I did the test again 7.90 volts thats with the red lead of the millimetre going to the red lead red lead of the smoothing capacitor and the black to the black

If the two secondary windings are in series (as others have said) then that voltage is far too low. It is even a little low for the windings in parallel as I'd expect to see roughly 9V unless the transformer was heavily loaded.

Bigears · 28th Oct 2021, 9:54 am

Yes, thank you that's a big help regards Ken

Bigears · 28th Oct 2021, 10:01 am

Thanks Dave I have saved it in word, its a big help Regards Ken

Bigears · 28th Oct 2021, 10:04 am

thanks Lawrence

DMcMahon · 28th Oct 2021, 3:12 pm

Quote:

Originally Posted by jamesperrett

If the two secondary windings are in series (as others have said) then that voltage is far too low. It is even a little low for the windings in parallel as I'd expect to see roughly 9V unless the transformer was heavily loaded.

Important point this in terms of fault finding. Would be useful Ken if you could take a close up photo of the secondary windings side of the mains transformer to be 100% sure the 2 windings are connected in series. Also would be good to get a photo of the primary winding side of the transformer to make sure it is connected correctly, i.e. one side of the mains should connect to the 245V tap and the other side of the mains to the 0V tap.

David

Bigears · 28th Oct 2021, 5:33 pm

I tested it again today the smoothing capacitor and it showed 9.80 volts

Bigears · 28th Oct 2021, 6:10 pm

Trace the red and black? wires from the power supply area to the amplifier. what voltage do you see on the amplifier end of the leads? Is the polarity correct? 5.42 Volts

Is the polarity correct? yes regards Ken

Station X · 28th Oct 2021, 6:19 pm

9.80V-5.42V=4.38V which is one helluva volt drop.

Do the wires lead directly from the smoothing cap to the amplifier?

It might help if you drew out the circuit of the PSU section ie mains transformer, bridge rectifier, choke and smoothing capacitor.

Refugee · 29th Oct 2021, 2:06 am

That valve amp smoothing choke looks like a misguided addition. It is not needed for a transistor/IC amplifier.
The measured voltages show that the primary of the mains transformer is right but the secondary are in parallel. Once the transformer is right and the choke is out of the way the amplifier can be got going. You should get about 15 to 18 volts.
The deck can be put to one side until the amp is working.
There is also a transformer of unknown heritage between the pickup and amplifier most likely added because the pickup was duff.

Station X · 29th Oct 2021, 5:13 am

Quote:

Originally Posted by Refugee

There is also a transformer of unknown heritage between the pickup and amplifier most likely added because the pickup was duff.

Which transformer is that? I think you may be referring to the unnecessary output transformer which was discussed up thread.

ms660 · 29th Oct 2021, 9:23 am

Need to establish the secondary windings configuration of the mains transformer, ie: are the two windings electrically separate, connected in parallel or connected in series.

Also need to establish the filter configuration for the output of the rectifier, ie: is it CL or LC, if it's the former then I can't see that the choke is doing anything unless there's another large capacitor hidden away somewhere to make it CLC.

Lawrence.

27th Oct 2021, 4:08 pm	#81
theredhouseinn Pentode Join Date: Jan 2013 Location: Kelvedon, Essex, UK. Posts: 211	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. You are working on a home brew lashup with exposed mains wiring, if you are not very careful you will get a nasty shock which may kill you. You have also added an earth wire to the metalwork which increases the risk whilst you have your hands in the works. John.

27th Oct 2021, 4:39 pm	#82
peter_sol Octode Join Date: Aug 2003 Location: Welwyn Garden City, Herts. UK. Posts: 1,730	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. I think that someone with more knowledge is going need to sit with you and help out. Even with the amp working it's unlikely to produce sound with the original Acos Hi G cartridge.

27th Oct 2021, 4:46 pm	#83
Edward Huggins Dekatron Join Date: Sep 2015 Location: Southwold, Suffolk, UK. Posts: 7,430	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. This is very sound advice. I normally will try to persevere over many Posts, as I did earlier, but in this case I have now withdrawn due to the risks involved. __________________ Edward.

27th Oct 2021, 5:22 pm	#84
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. There looks to be 3 pins of the IC that are not soldered to the PCB. Shown in photo of solder side in post 41. good observation taking a good look at that I can see 6 pins that need attention

27th Oct 2021, 5:24 pm	#85
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. I never work on it with the mains on, but I heed your concern

27th Oct 2021, 5:36 pm	#86
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. Yes Lawrence, on taking a good look at the PCB I see about 6 that need attention, one of the members is concerned about my wellbeing, I am taking precautions I am not working on it live, I also know that it has a 1000 uF Cap close by

27th Oct 2021, 6:07 pm	#87
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. As I am trying to understand how this works, it would help me if someone view this picture and tell me the names of the four main components, I can see one is a transformer and one is a choke I know that the transformer reduces voltage and the choke filters out AC current , I think so what do the other two do, any reply would help me understand what's going on, this record player is just something I picked at a market, something to give me hands on experience Its just like I am interest in electronics I just wish I came into it earlier Regards Ken Attached Thumbnails

27th Oct 2021, 6:14 pm	#88
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 5,707	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. This Help? Forgive the finger trouble typing Reservoir Attached Thumbnails __________________ Don't care if it was a bargain why's it in my kitchen Mike T BVWS member. www.cossor.co.uk

27th Oct 2021, 6:42 pm	#89
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 4,748	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. The mains transformer is an RS filament transformer, so its original intended purpose was to power the heaters (filaments) of valves that require 6.3V, as Laurence has previously explained this transformer has 2 separate 6.3V secondary windings and it looks like they are wired in series to provide a nominal 12.6V output. Transformers depending upon their design can increase voltage (step up), decrease voltage (step down) or keep the input and output voltages the same like a 1:1 isolation transformer. In this case it is a step down transformer. The AC output from the Mains transformer goes to the bridge rectifier (which effectively is 4 rectifier diodes connected in bridge rectifier configuration encapsulated in the black module). This rectifies the AC voltage to produce a DC voltage, but it is not a clean DC, it has an AC component called ripple. To remove/reduce the AC voltage ripple, the output of the Bridge Rectifier has to be filtered/smoothed by the Choke and the large grey reservoir electrolytic capacitor. There may also be further filtering/de-coupling capacitors at the amplifier PCB to further clean up the DC supply. David

28th Oct 2021, 9:54 am	#91
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. Yes, thank you that's a big help regards Ken

28th Oct 2021, 10:01 am	#92
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. Thanks Dave I have saved it in word, its a big help Regards Ken

28th Oct 2021, 10:04 am	#93
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. thanks Lawrence

28th Oct 2021, 5:33 pm	#95
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. I tested it again today the smoothing capacitor and it showed 9.80 volts

28th Oct 2021, 6:10 pm	#96
Bigears Pentode Join Date: Nov 2017 Location: Durham, County Durham, UK. Posts: 101	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. Trace the red and black? wires from the power supply area to the amplifier. what voltage do you see on the amplifier end of the leads? Is the polarity correct? 5.42 Volts Is the polarity correct? yes regards Ken

28th Oct 2021, 6:19 pm	#97
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 19,152	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. 9.80V-5.42V=4.38V which is one helluva volt drop. Do the wires lead directly from the smoothing cap to the amplifier? It might help if you drew out the circuit of the PSU section ie mains transformer, bridge rectifier, choke and smoothing capacitor. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

29th Oct 2021, 2:06 am	#98
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,387	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. That valve amp smoothing choke looks like a misguided addition. It is not needed for a transistor/IC amplifier. The measured voltages show that the primary of the mains transformer is right but the secondary are in parallel. Once the transformer is right and the choke is out of the way the amplifier can be got going. You should get about 15 to 18 volts. The deck can be put to one side until the amp is working. There is also a transformer of unknown heritage between the pickup and amplifier most likely added because the pickup was duff.

29th Oct 2021, 9:23 am	#100
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 12,087	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. Need to establish the secondary windings configuration of the mains transformer, ie: are the two windings electrically separate, connected in parallel or connected in series. Also need to establish the filter configuration for the output of the rectifier, ie: is it CL or LC, if it's the former then I can't see that the choke is doing anything unless there's another large capacitor hidden away somewhere to make it CLC. Lawrence.