Bush SRP51 and AU51 - DIN socket pinouts info wanted

[dazzlevision]

Hello,

I am (at a distance) making up a connection lead to allow the AU51 to reproduce the LH channel output of an SRP51. So, I don't have access to the equipment itself, but I do have the manufacturer's circuit diagrams for the two units.

I'm unsure of the pinout numbering of the "special" 4 pin DIN socket on the SRP51 and the standard 180 degree 5 pin DIN socket on the AU51. There is a spigot on the 4 pin plug that breaks a contact pair in the SRP51's "stereo" socket, thereby separating the LH and RH outputs of the cartridge. The LH output then goes to the AU51 and the RH stay in the SRP51.

The circuit has drawings of the sockets "viewed on the pins", but it isn't clear to me whether this means looking at the front (where the plug connects) or the solder tags at the rear of them...??

Does anyone have a definitive answer to this, please? The circuit is shown in post 3 of this thread: https://www.vintage-radio.net/forum/...ad.php?t=83895

Many thanks,

Dazzle vision

[AndiiT]

Hi,
I'm not certain that the information on the trader sheet circuit diagram is fully correct at least for the amplifier connections to the internal circuitry, however as far as I can remember from making a lead up for my own SRP51 and looking at the circuit again is that the left hand output, which is the one required to feed the additional amplifier of the player, is on the right hand pins when viewing the plug from the soldering side.

On the 4 pin plug Ground/screen is the pin closest to the locating notch and hot is the left side pin of the two that are closest together and either side of the switch operating spigot. Looking at the socket on the player, or wiring side of the 4 pin plug count clockwise from the pin at the bottom left closest to the locating keyway A, B, D, C to match up with the circuit diagram.

A 5 pin plug will be required at the amplifier end, I suspect wired to pins 2 (ground) and 5 (hot), it wouldn't hurt to link Pins 3 and 5 of the plug at the amplifier end though, in case the socket has been wired to pin 3 and not pin 5.

5 pin DIN socket numbering is 1.4.2.5.3 counting clockwise from the left/pin closest to the locating keyway.

Hope this helps

Regards

Andrew

[dazzlevision]

Hello Andrew,

Thanks for the advice/info.

Regards,

Dazzlevision

[GeoffK]

This is the diagram of the input/output of the SRP51 and AU51. Looking from the top panel of the SRP51 the right and left connections should correspond to the right and left pins as viewed from the top. B&D live with screens going to A&C. Connec tion B live, A Screen go to the AU51 for left channel.

[TonyDuell]

Since the 5 pin sockets in that diagram are drawn from the wiring side of the socket (which to me is what "viewed on the pins" would mean -- that is looking at the pins side (not the wiring side) of the plug), my first guess is that the 4 pin socket is drawn similarly.

Good luck in finding the special 4 pin DIN plug. I have to admit I did have one, but modified it to make the even rarer 2 pin version some months back. The pin spacing is not the same as the more normal 4 pin plug. But it does seem to be the same as the appropriate 4 pins of the 5 pin B (240 degree) or 6 pin plug. You might be able to start with one of those, cut off the redundant pins (or heat them and pull them out) and make some plastic peg to fit there to separate the contacts in the socket.

[dazzlevision]

Hello,

Thanks for the contributions so far, but I feel more confused now than when I first asked about this!

I feel the only way to be sure about making the lead up is for someone to do a "hum" test on the two sockets ("stereo" on the SRP41 and "amp" on the AU51).

If I had both units to hand (which I do not), I would insert a slice of matchstick or other thin insulation, between the 4 pin DIN sockets switching contacts, in order to break them. I would then use a straightened out paper clip (or similar) inserted into contacts B and D in turn, to check which on the two contacts produces a hum in the SRP51's speaker (with volume control turned up). The one that does must be D, so the other must be B (the cartridges LH output, for the AU51).

Just to be sure, I'd do the same for the 5 pin DIN 180 degree "amp" socket on the AU51, to see which contact is the LH channel input from the SRP51's "stereo" socket. The one that hums in the AU51's speaker (with volume control turned up) must be the correct contact.

If some kind soul who has both of these unit could check this out, I'd be very grateful!


I do have a 4 pin DIN plug, with the switch operating spigot, although the four contact pins are arranged on the four corners of a square - they are all the same distance apart from each other, unlike the "standard" 4 pin DIN plug without the spigot. However, I also have some 4 pin DIN chassis sockets with the switch contacts, and the plug mates with it correctly. I think these came from Thorn/Ferguson 1960s tape recorders that used this for the mike, with pause switch.

Dazzlevision

[GeoffK]

This is how the connections are made.

[kirstyd]

heres the inside of the plug on mine .A bit bright but you can clearly see where the red pick up lead is attached

[GeoffK]

Although not relevant to wiring the stereo plug, in post#7 the 'Tape' and 'Amp' labelled output should read input, this is pin 5 on each socket going to the right-hand channel.

[dazzlevision]

Originally Posted by kirstyd

heres the inside of the plug on mine .A bit bright but you can clearly see where the red pick up lead is attached

Thanks for this photo. It confirms that the Rank Bush Murphy issued circuit diagram for these units, which shows the pin allocations for these DIN sockets ("view on pins"), is viewed from the INTERNAL (wiring side).

So, I have wired my connecting lead accordingly. It ought to work!

Many thanks for all your contributions.

Regards,

Dazzlevision