1290 questions

[Rob Flinn]

I`m in the process of hooking up a pair of 1290`s using TK`s boards & have a question:

Between the 2nd voltage amp & the output stage there is a 4K7 pot. Presumably a log pot since it is a gain control. The top of the pot is conected to the output of the 2nd voltage stage & the wiper to the input of the output amp. The lower side of the pot is marked on the hook up diagram as J. My question is where do you connect J to ? I looked at the diagram & made an educated guess that it would be ground, but this seems to produce a mechanical clicking sound from the mic amp at about 0.5 second intervals. Can anyone shed any light on this for me?

 

[dukasound]

[quote author="Rob Flinn"]I`m in the process of hooking up a pair of 1290`s using TK`s boards & have a question:

Between the 2nd voltage amp & the output stage there is a 4K7 pot. Presumably a log pot since it is a gain control. The top of the pot is conected to the output of the 2nd voltage stage & the wiper to the input of the output amp. The lower side of the pot is marked on the hook up diagram as J. My question is where do you connect J to ? I looked at the diagram & made an educated guess that it would be ground, but this seems to produce a mechanical clicking sound from the mic amp at about 0.5 second intervals. Can anyone shed any light on this for me?[/quote]
Hi Rob
J is connected to A (common) if you are talking about pin J on BA283
Duka

 

[dukasound]

Here is very readable schematics of 1290 or 1073 without EQ.
I redrawed it and add, phantom, pad and H.P.Filter.
http://www.cankar.net/duka/Neve_1073_T&D.GIF
Thanks Thomas for suggestions.
Duka

 

[Rob Flinn]

Duka

Thanks, but I think this is different. I`m using the diagram for the 1290, which I got from the old places website. On it pin A is the + mic input, so I trhink its not the same as the BA283. Thanks anyway !

 

[dukasound]

[quote author="Rob Flinn"]Duka

Thanks, but I think this is different. I`m using the diagram for the 1290, which I got from the old places website. On it pin A is the + mic input, so I trhink its not the same as the BA283. Thanks anyway ![/quote]
Hi
I am looking 1290, like I said J is connected to ground in this schematic E.
Also circuit B189 and B183 is the same like BA283.
Duka

 

[Rob Flinn]

This is the diagram I`m going from

http://www.robflinn.eurobell.co.uk/1290-EN10041.pdf

as you can see pin A is the + mic input & J is specified as not being connected.

 

[dukasound]

[quote author="Rob Flinn"]This is the diagram I`m going from

http://www.robflinn.eurobell.co.uk/1290-EN10041.pdf

as you can see pin A is the + mic input & J is specified as not being connected.[/quote]
Probably my english is bad :? .
I am not talking about A in 1290.
I saw same pdf. Pin J is pin of pot. That pin you can connect to ground. If you look all schematics that pot pin is connected to ground.
Duka

 

[Rob Flinn]

Sorry I can`t see that pot on your diagram. Can you point it out to me?

 

[Klaus Mogensen]

Hi Rob,

I have wired the pot excatly as you describe (to ground on the pcb) and haven't seen any peculiar behavior on the scope.

I hope you solve your problem soon.

Best, Klaus

 

[Rob Flinn]

Klaus

Are you talking about the gain pot & not the trim pot for the output stage. I think the 2 pots aren`t getting confused in these some of these posts.

 

[Klaus Mogensen]

Rob

I'm talking about the off board attenuator pot (to sit on the front panel), that acts as a voltage divider (attenuator), where you can couple a fraction of the signal to ground, so less signal goes to the fixed gain output amp.

I connected it to B- (ground) , just as in Duka's and Joe's schematic. This pot in Duka's schematic is drawn just after the BA182C HPF board.

Hope this helps. Good luck with the wirering.

Klaus

 

[Rob Flinn]

Klaus

I managed to get the pot working last night. I still have some hum issues that need sorting out though.

 

[hitchhiker]

hey Duka, That's a very nice drawing. Makes the 1290 a ready to go

for easy connection. :thumb:

Lance

 

[Rob Flinn]

I got rid of the hum, & tried at at a friends studio tonight. What a great sound, & loads of gain !!!

MANY THANKS to TEKAY for this boards design.

Its still a bit messy inside & I haven`t got the relay phantom side of it working just yet. I`ll post some pics when its finished.