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Old 25th March 2003, 12:44 PM   #1
mrdr is offline mrdr  Netherlands
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Default ta-fa3es fried resistors?

hi everyone, i hope i'm in the right forum.
i've got a sony TA-AF3ES amplifier and it started smoking recently after some static off my turntable.
i'm not sure if i can just replace the resistors. if so does anyone know where to find which ones they were as the color coding kind of scorched off
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Old 27th March 2003, 12:07 AM   #2
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They appear to be the R of an R/L Zobel circuit near the speaker protection relay. Most often, these are around 10 ohms 1W FP (flameproof) - these burn out because of excessive high frequency oscillation from the amplifier. Your turntable issues could have triggered this, I suppose.

The amp might still work without them, but replace them as soon as you can to avoid ampifier damage in case of another "meltdown".
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Old 27th March 2003, 12:22 AM   #3
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Default The burned resistors...

If the number of the resistor in the impress circuit is R525 and R625..they are 10 Ohms 1/2 W resistors!

Regards!
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Old 27th March 2003, 11:35 AM   #4
mrdr is offline mrdr  Netherlands
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you guys are the best!
thanks a lot.

my turntables aren't properly grounded. can the static that that produces be the problem?

i can't see which is which. they scorched the impress circuit pretty awfully. should i call sony for that?
or does anyone know a good way to clean the circuit board?

thanks again!
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Old 27th March 2003, 04:15 PM   #5
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Just opened my Sony and it are 10 Ohm resistors of a few Watt indeed. Clean the board with alcohol and when it is really dirty or burned try to scrape the dirt of with a flat screwdriver. Please remember that the coal conducts electricity so cleaning is important.
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Old 27th March 2003, 04:32 PM   #6
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Quote:
Originally posted by mrdr

my turntables aren't properly grounded. can the static that that produces be the problem?

i can't see which is which. they scorched the impress circuit pretty awfully. should i call sony for that?

IMO the problem you had (or still may be having) is not static. Probably an improper grounding on the wall AC, or an AC ground which is not zero.

I've never seen static burning a passive part. Static can damage an active part, particularly FETs and some ICs, but not a passive. Correct me if I'm wrong.

My first suspect would be your turntable. What brand is it? Can you see if there's some leaking there that maybe causing your problem?

You were lucky if you only burnt those resistors, which certainly can burn from oscillation, not from static. On the other side, turntables can rarely cause an oscillation, as the parts feeding into your computer are "almost passive", that is do not carry high voltages. The very small volts generated by your cartridge will only be amplified at the RIAA preamp.

Can you get a meter to measure all voltages(AC and DC), related to ground, coming from your turntable or from your Sony amp? If possible do these tests also inverting your AC plug. Be careful when you do these readings, as in your country you should have 220v or so, don't you?


Carlos
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Old 27th March 2003, 05:48 PM   #7
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Quote:
I've never seen static burning a passive part. Static can damage an active part, particularly FETs and some ICs, but not a passive.
True enough, but a sudden burst of "static" (usually consists of wide bandwidth noise) can trigger a poorly designed amplifier into ultrasonic oscillation. I would lay most Sony amplifiers in with "poorly designed" in some cases - but not all.

Checking all grounding is a good thing, but also tighten the screws attaching the speaker, RCA and chassis components. Sony uses metal straps at key points to assist in grounding throughout the chassis. If some parts are loose, the unit WILL oscillate during normal operation. I speak from repair experience....
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Old 10th April 2003, 11:41 PM   #8
mrdr is offline mrdr  Netherlands
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jean paul,
you say you'ce opened your sony, is that a ta-fa3es as well?
i've taken out the old resistors but i'm not sure which ones to put in now. should they be exactly the same as the old ones?
if i use a multimeter will they give an accurate reading (if any) or have the values changed because of the "burn out"?


envisionaudio,
i've checked all screw's they were well tightened. there is no proper ground off my wallsockets though, so it wasn't grounded before. (i was well impressed by the design of the amp though (of course i'm not an expert like you guys, but hoping to become one). it has a pretty fat gnd cable going to the pcb concerned. and it's all copper screws.

thanks guys
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Old 11th April 2003, 06:19 AM   #9
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Quote:
Originally posted by mrdr
jean paul,
you say you'ce opened your sony, is that a ta-fa3es as well?
i've taken out the old resistors but i'm not sure which ones to put in now. should they be exactly the same as the old ones?
if i use a multimeter will they give an accurate reading (if any) or have the values changed because of the "burn out"?

Yes it is the same. Buy 10 Ohm resistors of a few Watt. Avoid wirewound resistors except for low inductive types. The shops that sell parts for loudspeakers have nice quality metalfilm 2 W resistors ( for example Speakerland in the Netherlands ).

Just look at the picture and the last question will be answered. Replace them please.
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Old 11th April 2003, 11:26 AM   #10
mrdr is offline mrdr  Netherlands
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does low inductive mean "lage inductie"?
what is the alternative to wirewound resistors?
speakerland is in oss? i live near amsterdam, does a standard electronics shop like display or aurora sell those?

thanks again,
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