gary o

V72 Mic Pre problems any ideas ??
« on: March 18, 2006, 01:20:44 PM »
Hi there couple years ago I made my self a V72 mic pre, my knowledge is very patchy I just soldered this thing together point to point, got trans plus choke from Sowter and with some tweaks it worked great, but now it makes white noise sound and crackles still passes audio, I thought it could be tube bases needed cleaning but no, swapped all capacitors still no havent got any other tubes to sub sadly, it runs off power supply that I use on my other home creations and they are all ok, anyone have any ideas remember im not that technical.

Thanks Gary O.


q2audio

V72
« Reply #1 on: March 18, 2006, 02:15:24 PM »
Noisy cathode resistor? Failing tube? I've had resistors go open in original units as well as numerous caps fail - mostly the large output coupling cap.

ciminosound

V72 Mic Pre problems any ideas ??
« Reply #2 on: March 18, 2006, 02:17:45 PM »
Besides checking the tubes, check the resistors in the HV path.

Hiss and crackle is a very common complaint with vintage Fender guitar amps and many times it turns out to be the 100K 1/2 watt carbon comp plate  resistors Fender used. I always like to use 1 watt when replacing those.

What did you use in the V72, carbon or metal film?

gary o

V72 Mic Pre problems any ideas ??
« Reply #3 on: March 19, 2006, 11:56:01 AM »
Thanks guys, I been poking the birds nest [sounds bit rude] with lolly stick technical stuff I know and bit scarey, and it seems to be a dry joint havent had time to resolder yet but will do soon thanks once again for your time and thoughts.

CJ

V72 Mic Pre problems any ideas ??
« Reply #4 on: March 20, 2006, 01:39:44 PM »
Its the tubes-- my guess.

Pull them and see.
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

gary o

V72 Mic Pre problems any ideas ??
« Reply #5 on: March 20, 2006, 05:24:41 PM »
Thanks CJ it was dry joint, good thing cheaper than a tube.

Cheers Gary O.

CJ

V72 Mic Pre problems any ideas ??
« Reply #6 on: March 20, 2006, 05:30:53 PM »
Good good good!
How dare me accuse the EF804s.
30 days in the cooler!
If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html


 

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