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BRC 1500 dropper query

 
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BRC 1500 dropper query

Post by Colourstar » Sun May 01, 2016 2:24 pm

Hi everyone

I'm working on a set with the BRC1500 chassis and as it's a keeper I'm treating it to a spanking new dropper. I note that the rather tired one I'm taking out has an additional 80 ohm fusible resistor in series with the 350 ohm HT dropper section (R125). The leg of the dropper has been cut and this resistor let in.

The original BRC service info from 1970 makes no reference to this, but the set I'm working on is a fairly late one from 1973/4 so I'm wondering if this is a later mod or if it's just been fitted by a service engineer in the past. I should add that the original section of the dropper still reads the correct 350 ohm resistance, so the additional resistor takes it over the factory spec somewhat.

Any thoughts welcome!

Steve

 
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Re: BRC 1500 dropper query

Post by nuvistor » Sun May 01, 2016 2:50 pm

No circuit to check just now but perhaps the fusible link dropper was a later mod for the BEAB regs.

 
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Re: BRC 1500 dropper query

Post by crustytv » Sun May 01, 2016 2:51 pm

Yes it was a mod , I did have the sheet somewhere

 
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Re: BRC 1500 dropper query

Post by crustytv » Sun May 01, 2016 3:01 pm

Found it, Sept 1977 12 page document covering many updates for the service manual, including the fusible resistor.

1500.jpg

 
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Re: BRC 1500 dropper query

Post by Colourstar » Sun May 01, 2016 4:18 pm

Brilliant! Thanks very much for looking.

Just goes to show you only have to ask....


Steve :aad

 
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Re: BRC 1500 dropper query

Post by Focus Diode » Sun May 01, 2016 9:50 pm

On a related matter it's worth noting variations to the dropper fitted in the earlier 1400 dual standard chassis. The 1K5 section changed to 1K7 to eliminate frame cramping.
More importantly the far end 220R section was changed to 120R with an additional 100R fusible resistor feeding the line output stage, R145 I think it was. It's clearly vital to fit the additional 100R fusible resistor if a newer dropper is fitted to an early production model.
Most already know this of course but worth noting for new members to the forum.
Brian

 
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Re: BRC 1500 dropper query

Post by crustytv » Mon May 02, 2016 3:19 pm

The discussion about the rare 1500 with solid-state field modifications has been split off here


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