cosser record player/radio

[robert.copley1]

hi all , new to this site , for a few years now have been interested in battery powered record players , I'm not an electronics type , but take my time and work my way through getting them working , but I'm stumped on a cosser radiogram type 545 it reqs 2 4.5 v batteries on 2 plugs 1 plug has a yellow wire to speaker and red to on off switch the other has only 1 wire to the switch but the other wire is missing I need to know where this missing wire runs to also the grey twin cable is disconnected at the pcb end can anyone help me ? bob

[pwdrive]

I think this was discussed on the UKVRR forum, the two battery plugs should be connected in series via a link wire.

If I remember correctly from the other forum the grey cable is a screened cable from the pickup cartridge, you will probably have to consult the schematic to see where it should be connected to on the PCB.

Lawrence.

[tiv48]

Hi bob

I have found some service info in red book (r&tvs) 1958/9.
the missing battery wire also goes to the same speaker connection be aware that one battery to speaker is positive the other is negative.
as for the grey wires a photo would help
As my scanner is not working i have tried to take a photo of the relevant part of the circuit  

Rob T

[ppppenguin]

The twin 4.5V batteries (as compared to a single 9V battery) saved the cost of an output coupling capacitor. It was used in a few radios too. You could probably use a single 9V battery if you added a large (100uF+) capacitor in series with the speaker.

[pwdrive]

Looks like the last IF transistor doubles up as an emitter follower for the pickup?

Lawrence.

[tiv48]

There is a scan of the AD28 battery here if you fancy making your own
http://www.the-thompson-brown-family.co....s/ad28.htm
Rob t

[Mike Watterson]

The twin 4.5V batteries (as compared to a single 9V battery) saved the cost of an output coupling capacitor. It was used in a few radios too. You could probably use a single 9V battery if you added a large (100uF+) capacitor in series with the speaker.

I'm not sure why, as a PP9 is very expensive and very much shorter life than two sets of generic Alkaline D cells in suitable replica case.
Especially if i the 4.5V packs run the record player motor?
I have half a dozen PP9 packs that take 6 x Alkaline AA cells, about 1/4 running cost of the hard to find PP9 packs.

If the original was 2 x AD28, those are VERY much lower internal resistance than PP9, Alkaline D cells would be similar.

[tiv48]

Looks like the last IF transistor doubles up as an emitter follower for the pickup?

Lawrence.

I had not noticed that  but you are right
Rob T

[ppppenguin]

I wonder if the original battery was a PP11:
http://mw0gkx.co.uk/batteries/batts/pp11.htm

Amazingly you can still get AD28 batteries. Just google them. The 1289 (also known as 3R12) is another 4.5V battery that's readily available.

For test purposes 2 sets of 3x AA cells in suitable holders should work fine. Or 6 in one holder as Mike suggests, with the centre point brought out on a wire.

[Refugee]

I would avoid using a single 9 volt battery and a capacitor as it may well affect biasing.