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 Changing the Volume pot of a Radiogram
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 Return to top of page · Post #: 1 · Written at 8:56:25 AM on 14 February 2011.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Hi All

Since there has been a rush of no one out there with this type of pot, I am thinking of modifying the controls of the radiogram to allow me to use a normal untapped 100k log pot.

Is this possible? I dont mind modifying the whole preamp stage to suite. I have attached a link to photobucket where I have the diagram.

Can people tell me how to go about changing it to suit the 100k (LOG) pot instead of the 2M (LOG) pot.

http://i1017.photobucket.com/albums/af300/dan_flakes/Philips%20RF6-01/PhilipsRF6.jpg

Thanks

Daniel


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 2 · Written at 12:08:20 PM on 14 February 2011.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 326

I've got a dual 2 meg you can have. Shaft 1/4" wide, 7/8" long, thread 3/8". It has taps, but not sure if it's log. How do I tell?


 
 Return to top of page · Post #: 3 · Written at 3:52:33 PM on 14 February 2011.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

It will tell you on the side. it will say something like 2M ohm "A" or "C". The tapped pots are usually "C"

A Pot that says something like 2M "B" is a linear pot.

I am interested in it if you want to part with it. Contact me through the email form to let me know the details.


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 4 · Written at 11:27:21 AM on 15 February 2011.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 465

Dan,
On the circuit diagram , what are the connections with dual dashed lines and solid triangles, near the Volume and Tone controls and elsewhere???


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Cheers, Ian

 
 Return to top of page · Post #: 5 · Written at 11:47:31 AM on 15 February 2011.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Hi Ian

The dual dashed lines outside a solid line are Shielded cable.

The single dashed line means that it is a Ganged pot.

I am not sure what you mean by the solid triangles.


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 6 · Written at 12:21:09 PM on 15 February 2011.
Sue's avatar
 Sue
 Location: Daylesford, VIC
 Member since 13 January 2011
 Member #: 809
 Postcount: 326

I can spare it. The markings are: 502 DUCON 2MT900KZ5 677 2351. At the half-way point of rotation the resistance is 700K, about 30% of the total, so it's not a linear pot. As the markings suggest, the tap's at 900K.


 
 Return to top of page · Post #: 7 · Written at 12:43:29 PM on 15 February 2011.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 465

Hi Dan,

Solid triangles?? as an example ....... the cartidge connection blue wire ....the dual dashed lines (shielded cable) are connected to solid wires via ?solid triangles? (??). Simply soldered connections to shielded cables?

There are a couple of other connection symbols that I haven't seen before eg one side of each speaker ..... circle with cross inside, and nearby .....circle with a slash. ????


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Cheers, Ian

 
 Return to top of page · Post #: 8 · Written at 1:04:54 PM on 15 February 2011.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Ian

Ok I understand what you want now.

The Triangles? are a way that shielded cable was drawn manly by Philips. it shows the connection of the shield to the GND points.

The other markings:

circle with cross inside - Positive speaker Connection!

circle with a slash - Just a normal connection point. I don't know why it is like that but there is nothing special.

Another symbol you wont see much is L1 & L2. that's because it is a Permeability Tuner. This is not the standard variable cap but a variable Inductor. the Capacitance is Semi Fixed by C3 (Trimmer) and a ferrite cored slug is moved through the coil.

Another odd thing with this cct is the fact that they use the K suffix for Capacitors.
eg 4K7 400 = 4.7nF 400v

Philips Liked to do things Different to others!


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Valve radios, They just don't make them like they used to

 
 Return to top of page · Post #: 9 · Written at 1:44:32 PM on 15 February 2011.
Tinkera123's Gravatar
 Location: Melbourne, VIC
 Member since 5 October 2009
 Member #: 555
 Postcount: 465

Thanks Dan,

Nice and clear now. Sorry for highjacking the Thread re Volume Pot.


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Cheers, Ian

 
 Return to top of page · Post #: 10 · Written at 1:51:51 PM on 15 February 2011.
Flakes's avatar
 Location: Adelaide, SA
 Member since 27 February 2010
 Member #: 630
 Postcount: 392

Its ok. At least I can pass on the limited knowledge that I have.


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Valve radios, They just don't make them like they used to

 
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