Static on select? and crosstalk

i played with the Shearne last night and it seems to have a problem. The source select knob seems to suffer from static, this isnt the sound of a dirty pot. If i just touch the knob there are crackles, pushing or wiggling it produces more noise.

Also there seems to be a fair amount of crosstalk comeing from the tuner into other channels. I had some of thos RCA plugs that are meant to cut out RFI hanging around so i stuck them on and it seems better. So could the cross talk be caused by the ariel lead at the back of the rack?

And to cap it all off the phono stage only works on one channel, but i think that it may just need the board seating right. The phono stage is on an extra board that sits on some well naff looking 5 pin connecter.

Hmm, so all in not the most impressive of Ebay purchases.
In its favour ill say that it has midrange to die for, maybe slightly coloured but still very nice. It excels at female vocals and less heavy music. It doesnt seem to do bass tho, thats not to say its thin just that it lacks somewhat for trance/tecno type stuff. Im willing to accept that a 2hour run is probably not enough and hopefully it will improve with further use

 

A spray of a suitable switch cleaner should clear the problem... of the switch... but not the xtalk.

Regards

 

so would that sort the static and crosstalk probelms?

Also i want to remove the phono card to work out if it that causing the 1 channel problem.
The card sits on a 5pin riser and on the PCB it says to revert back to Aux link outer pairs
would that be link pin 1 to pin2 and pin 3 to pin 4?
Im fairly sure i can trace the PCB tracks to work it out, just wondered if anyone had any experiance of it

 

Sounds more like a dry joint....easily fixed or tested. Just put the hot iron on all the switch connection and remelt the solder and allow to cool.

 

Cross talk is a more difficult problem.......

The only true way is cut the link between units that are not being used. I designed a preamp with relays that switched to the appropriate input when the selector was moved. Its not impossible to retro fit several relays on vero board to do this, a voltage is thenfeedthrough the switch and then to the required relay. Disadvantages are that the audio signal has to pass through the relay.

If the signal is getting in to the ground screen and hence on to another input. There may be away of solving this by increaseing the resisance of the connection to ground of the audio signal, but I don't like the sound of it.

 

hmm
well if its going to take that much i feel i would rather pass it on as an amp that didnt suit me

 

Has the pack arrived ?

sorry to hear the amps dodgy....It got good reviews.

There are other solutions .....but I need to research them ! I think.

 

post arrives after i leave home in the mornings, hoipefully there tonight
Ill see how hard it looks to remove the board when i get home, if its not to bad ill redo the solder joints and keep my fingers crossed, i also need to test the phono stage tonight.

 

Keep us posted [ha ha]

 

wilco

 

arse
due to me soldering the new speaker trminals in the amp lsat night i could remove the board without cutting the terminals, wich i didnt fancy doing.
so i took pot luck and put a wire from the selecter switch to earth
Tada
a lot less noise
still got the cross talk tho

 

That sounds like a dry joint on the ground of the selector.

The cross talk if its a real problem find which input is worst and make certain that you don't use it !

Alternatively a real world solution, keep the other source switch off or unplugged.

Do you know if the cross talk is a proximity thing of if its on the ground plane?

If it the first you may be able to use shorting plugs to eliviate the problem, and RCA thats connected to its self, or through a 1m res and see pluged into an unused socket.

Another though Check the grounding of the amp, you could try the old trick of running a wire to the earth binding post of the amp to a three pin plug connected to the earth pin only, and see if that makes a difference.

 

I used shorting plugs and it helped, so seems it must be proximity?
How would i overcome that as a permanent fix?
Ill try the earth trick tonight, the amp has a 4mm banana socket for earth so it will be easy to do.
The phono stage is sorted now, it wasnt seated properly. Not the best stage ive heard but it's competant and will suffice until i build the cornet stage.

I tried to PM you last night Pete but it was bounced due to a full inbox.
I recieved the parcel yesterday. Its a better kit than ive seen from commercial sources Instructions are exemplary. Many thanks for doing that, i owe you a favour

 

Blush ....thanks

 

your welcome

 

I hope the finished mod lives up to expectations.

Remember a good aerial is key [if you haven't got one].

 

hopeing to get an ariel in the roof space soon