hifi engine

AGI 511 Preamp burnt resistor question

Hi There,
I have an AGI 511 Preamp and a power supply resistor is fried and I cannot read the color code. Its the resistor on the 120v input next to the 4 diode bridge. It looks like 33 or 330 ohms. Any help would be very much appreciated.

Thanks



Ivy Caudieus's picture

Re: AGI 511 Preamp burnt resistor question

From the Schematic, It should be 3,3 Ohms ( R72 and R74 )

Re: AGI 511 Preamp burnt resistor question

Thanks for your response Ivy,
I don't think those are the correct resistors. I only have the factory AGI schematics for the phono and amp circuits, not the power supply. This is the single resistor after the incoming power from the transformer forming the little RC circuit. I see the other two 3.3 ohm resistors on my board. If you have the Power Supply schematic could you please send me one. I have the other two I could send you if you need them.

Thanks again for you time and trouble.

Re: AGI 511 Preamp burnt resistor question

you have probably solved problem by now but in any case the RC ctrcuit across trans secondary (not 120v primary) is R70 330 ohm and C70 0.1 uF. If R70 is burnt C70 may also be shorted.

Re: AGI 511 Preamp burnt resistor question

If R70 is burnt, the only reason for that would be if C70 IS shorted, no doubt about it.
By the way, it's listed as being .01uf, not .1uf.

Re: AGI 511 Preamp burnt resistor question

1977 revised schematic shows .1uF, do not have actual unit for visual check.

Re: AGI 511 Preamp burnt resistor question

Thanks for the reply,

The 511's I have came equipped with a 0.1 cap for C70 however I have an AGI factory schematic from 1986 for a 511A that shows a 0.01uf cap. Not a big difference for this application and AGI changed things from time to time. The resistor R70 is 330 ohms. I would really like to see your schematic from 1977. I recently posted a question on AudioKarma for my latest 511 that is really different from any ones I have seen. Take a look if you like.

http://audiokarma.org/forums/index.php?threads/agi-511-preamplifier.796397/

Thanks again!