4001 Slow to get to good SNR?

afcwomble

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Been given a 4001 which was working (or at least does when warmed up) to have a look at. The problem is the SNR is low when cold-around 19-20dB. If I leave this on for about 10 mins or so it gardually builds up to 34-35dB which is fine-Unplug it and plug in again and away it goes-Until its unplugged again and then it does the same all over again. Is this what you would call a stuck in tune box, in which case I can try to change over the caps in the TUT or would it be a lazy tuner problem? any help or suggestions appreciated.
 

chookey

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Change the caps according to the stuck in tune guide mate. I had the same thing and this cured it.

Chookey
 

afcwomble

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Change the caps according to the stuck in tune guide mate. I had the same thing and this cured it.

Chookey

Thanks Chookey-I'll order them in and give it a go. I've done this before on a box though and it didn't work-I narrowed it down to the 35v line going to the rear tuner which was 38v when plugged in but steadily dropped. I have figured that the rear tuner needs the volts in able to pick up the netid. Would you know what would be failing on that one to cause this? I did post a thread ages ago about it but the problem never got sorted-any help would be appreciated as it still sits here as a reminder of the hours I put into the poxy thing!!!Don't you just love the 4001's
 

chookey

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Hello afcwomble. The tuning supply could be dragged down in a number of places but the best place to start is the source. I would change C12 for a start. When I had low snr gradually rising I applied some heat to the 2 caps in the stuck in tune guide,close to the card reader. The snr then rose rapidly and the nit was found. Applying freezer spray then caused the snr to drop. Its' always wise to replace all the caps anyway when you have any problem like this.

Chookey
 
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afcwomble

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When I had low snr gradually rising I applied some heat to the 2 caps in the stuck in tune guide,close to the card reader. The snr then rose rapidly and the nit was found.

Chookey[/QUOTE]

Spot on mate-Just blasted the box with hot air gun for a few seconds and up to 35dB. Your a star-I always thought it was a tuner problem. Going to order the bits so will change them over next week when they arrive. With the low volts one I see the C12 is 220uf 50v, is it OK to use these on C323/5 as well, if so i'll order all the same?

Thanks for your help - thats been doing my head in for ages trying to find out why the SNR starts low and builds up gradually as i've had a couple like that in the past-i'm hoping I stuck them in the garage or loft and didn't sling them!

:THANKS:
 

chookey

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Yes mate, use 220uf 50v for all 3 and remember to try and get the 105 degree if you can. Hope it all works out for you and thanks for helping me reach my 1000th post.

Chookey
 

afcwomble

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Cheers Chookey-Got the caps today for the box with low SNR, changed them and Bingo-burst to 34.7dB!! Thanks for the pointer mate it is much appreciated-I would never have thought of heating the caps. I can't believe how easy it was once you said-Waiting to get hold of the other box now(one that volts drop off) as i've left it in bro in laws. Will let you know if I have success with that one soon.: thanks :
 

chookey

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Glad you got it sorted mate. Its' nice when someone ends a thread with a result, seems to be a few of late who just say sorted and don't say how.

Chookey
 
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