Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Hi all, Here we have a MONARCH BSR Black Box, but it seem to have been refitted into a kind of homemade cabinet, it powers up and all is working, but no sound from the speaker, well the speakers work but just the volume hum, I think this model war made in the 1955 with valves and it seems it has been updated with printed circuit board, can anyone tell me what steps I need to take to get the sound working, Regards Ken

Re: MONARCH BSR Black Box
 

I don't think you will find that this has anything at all to do with the Pye "Black Box". This looks like a home-made record player using a 1955 BSR UA6 autochanger (which was used in some early BBs) and some much more modern electronics. I can't see any speakers or even one speaker. What experience do you have with vintage electronics, especially in signal tracing and fault finding?

Re: MONARCH BSR Black Box
 

There is a speaker in the lid, It looks as if the amplifier uses the Plessy SL403 Audio amp chip https://www.radiomuseum.org/tubes/tube_sl403.html

I agree with Edward nothing to do with PYE this one but an interesting project just the same :thumbsup:

Cheers

Mike T

Re: MONARCH BSR Black Box
 

https://www.vintage-radio.net/forum/...d.php?p=922763

Lawrence.

Re: MONARCH BSR Black Box
 

Looks like the Radiospares stereo PCB with just half being used as a mono amp.

Re: MONARCH BSR Black Box
 

You can see the speaker, well part of the speaker in one of the pictures.

Re: MONARCH BSR Black Box
 

Thanks.

Re: MONARCH BSR Black Box
 

That's what I said in my post, its a BSR Black Box that has been relocated in to a home made Box and up- dated with PCBs it all works but no sound only a hum from the speaker, and the Question was ( How would I go about sorting out the sound)

Re: MONARCH BSR Black Box
 

OK so how would I go about sorting out the sound as the auto changer and turn table work ?

Re: MONARCH BSR Black Box
 

Depending upon your electronics fault finding experience, this may not be easy for you.

The first thing I would check is the power supply DC voltage at the large electrolytic reservoir/smoothing capacitor. This is shown as C15 on the second schematic attachment at Post 14 from the link at Laurence's Post # 4..

Do not know what voltage it should be, but at a guess at least + 15 volts. If the capacitor is bad there may be a lot of AC mains ripple present which will result in low DC voltage (and potentially hum). The decoupling capacitor C14 (0.1uF) if bad may also result in higher than normal ripple. Note - this capacitor on the PCB artwork looks to be C13 ?

If you have a scope would be good to actually quantify the ripple level.

David

Re: MONARCH BSR Black Box
 

I don't know why you keep referencing it's provenance as being from a Pye "Black Box". This may confuse other Members trying to help you. Even the BSR deck from 1955 is not the type that was ever used by Pye in any "Black Box".

I should know, I was there.....

Yes, and now you point it out, I can see the edge of a speaker. BTW if this is a 6.5" 3 ohm Goodmans speaker, please do let me know as it may throw some light on the possible provenance.

NOW - to try to help you, do you know if the cartridge in the tone arm is working? If not place a finger onto the input on the PCB to see if you get a "buzzing " sound with the volume turned up. If not, please advse us.

Re: MONARCH BSR Black Box
 

Thanks Edward, My electronics fault finding experience is nil, how ever I will check the Caps

Re: MONARCH BSR Black Box
 

Sorry Dave

Re: MONARCH BSR Black Box
 

I do not think Pye was mentioned by the OP, is Black Box specific only to Pye ?

David

Re: MONARCH BSR Black Box
 

Would be good if you could identify/close up photo the actual cartridge/stylus that is fitted, especially if it turns out to be a bad cartridge.

David

Re: MONARCH BSR Black Box
 

Yet in your previous post (No. 2 above) you say the deck was used in early versions.??????

Re: MONARCH BSR Black Box
 

I tested the speaker and it gives a reading of 1.4 on the multiimeter
Note the lead from the needle pick up arm seems to go nowhere, do you think that could be the problem? I send some pictures

Regards Ken

Re: MONARCH BSR Black Box
 

1955 was my estimate when the deck was made, thats all

Re: MONARCH BSR Black Box
 

Yes that cable should be connected to the amplifier.

If it follows the normal circuit for the SL403 then it should connect across the outer tags of the volume control.

The centre tag and another should be connected to the pcb.

The centre conductor of the screened cable should go to the tag with nothing else connected the braiding to the opposite tag leaving the centre tag also connected to the PCB if that makes sense.

Cheers

Mike T

Re: MONARCH BSR Black Box
 

I don't think the input is connected to the MB see my latest pictures

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Hi Ken

Yes I can see that the cable is not connected but it should be,

Can you show a picture of the backs of the volume and tone controls?

Cheers

Mike T

Re: MONARCH BSR Black Box
 

Thanks Mike,

it is confusing to me, so I should connect the wire to that transformer that connect to the speaker , I think its only the wire that needs to be connected, so its the inner wire to the inner wire and the outer wire to the outer , I will do that and send you a picture before I solder it,

Regards Ken

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

OK I will.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Hi Ken

Send pictures before you do anything.

Are you saying that the cable is for the speaker?

If that's the case I am surprised you were getting a hum.

It looked to me that the long cable was going to the cartridge connections on the record deck.

Cheers

Mike T

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

On that little mb, where the wire connects to the speaker, is that where I should connect the wire from the pick-up arm?

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

No the cable from the arm is going nowhere at the moment the cable from that little MB is going to the speaker.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Are there any connections on the underside of that MB?

David

Re: MONARCH BSR Black Box
 

See pictures

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

I meant the underside of Photo 2, the side that you cannot see.

David

Re: MONARCH BSR Black Box
 

Yes, it sort of was, but it was a special version of the BSR UA6 made for Pye. It had an all-metal tone arm and a Pye badge added on a moulding at the rear of the arm. The version shown in the OP's photos was the standard UA6.

Re: MONARCH BSR Black Box
 

Black Box was a generic term that came from use within the RAF during WW2 to designate a "special device", such as in-flight recorder. Also during the War Pye made a large number of special devices like IF strips (of EF50 fame) for the RAF. Therefore when Pye planned the launch of their new compact record player for home use in late 1953, they used the (familiar to them) name "Black Box". Indeed there was a Black version. Born of my Farther's WW2 avionics experience, and also my time at Pye in the 1950s, I hope this explanation helps.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Isn't that the output transformer? You can see the mounting lug.

Perhaps there's something written on the insulation covering the wiring?

Re: MONARCH BSR Black Box
 

I think we've established the provenance of this record player. Can we get round to discussing its repair please.

Anyone care to draw up a diagram showing the interconnections between the various parts? Pickup/cartridge, volume and tone controls, amplifier, output transformer, filament transformer???, rectifier, smoothing capacitor and another transformer, or perhaps a smoothing choke.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

So far as I can make out the screened cable from the pickup should connect to the volume control (which looks to be the top control in the 1st photo in the last set of photo's) I would say the signal wire (the center lead of the screened cable) goes to the top tag (as viewed in the photo) and the screen (the outer copper braiding) goes to the bottom tag (as viewed in the photo)

Lawrence.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Yes that makes a lot of sense now, I thought it was some kind of terminal board.

David

Re: MONARCH BSR Black Box
 

I thought it probably is a smoothing choke as it looks like it connects to the bridge rectifier.

David

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

There doesn't seem to be any way of turning the player OFF. The orange lawnmower? mains lead goes straight to the mains transformer and there are no connections to the double pole switch ganged with the volume control.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

The use of the wording "Stereo Amplifier" may confuse some Members who may have missed parts of this lengthening Thread. There's just a Mono amp connected to an Elac elliptical speaker (now I can see it) but constructed on a Stereo amp PCB.

Re: MONARCH BSR Black Box
 

Yes very helpful, I had to Google and read up on the EF50 very interesting.

David

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

True the only way I can turn it off is by pulling out the mains plug.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

What I have done is to connect the wire form the pick-up arm to the small MB ( the inner wire to the inner and the outer shield to the outer shield.

I don't know if this is right or wrong thing to do!

I have not tried to turn it on as I am in the very early stage of electronics , in fact I know very little.

Regards Ken

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

What you're calling the M/B (Mother Board?) is in fact the output transformer which sits, electrically between the amplifier and the speaker. You shouldn't be making any new connections there.

The cartridge/pickup needs to be wired to the volume control as described previously.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

I wonder if that transformer is an 'impedance matcher' that sits between the cartridge output and the amplifier input? I've seen that setup in the likes of the KB Tunetime radiogram.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

OMG. There's enough confusion in this thread already. The pictures show a screened lead from the speaker to the output transformer, which has the cover fitted in this picture.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

.....er, looks like Co-Ax cable? I'm just getting lost with this Thread.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Yes well spotted. Definitely recommend that the mains cable be rewired/re-routed to the on/off switch contacts on the back of volume control and then output side of the on/off switch then wired back to the same black terminal block connections where the Live (Brown) and Neutral (Blue) wires currently connect to.

I personally would go further and replace the 2 core orange (does look like lawnmower typical cable) mains cable with a modern 3 core mains cable, then will be able to connect the earth in the new mains cable either direct to the turntable metalwork or take the earth wire into a spare slot in the black terminal block and from there connect earths as required out to the turntable, PCB (for ground connection) etc.

David

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Mods permitting for voltage ID purposes only (Mains transformer):

https://picclick.co.uk/Transformer-H...html?refresh=1

Secondary = 2 x 6.3Volts @ 1.8Amps, in the player under discussion those two windings look to be connected in series so 12.6Volts AC into the bridge rectifier, from the photo's the PSU looks to me like it's connected as a choke input filter (LC) as it stands, although I could be wrong.

Lawrence.

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

Well found Lawrence, I did wonder if its original purpose was a valve filament transformer, the fact that it is called Fil trans of course being a big clue :)

Of course the original mains transformer when the unit had valve amp would have had a separate secondary winding for the filament supply.

David

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

ok I will unconnect it from the output transformer

Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.
 

I inform you that this is not my handy work, its just something that I picked up at a car-boot and just gives me something to work on in the winter nights