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Sony TA-F3A amp....cool or what?

anderslober

anderslober

Yikes...not again!
I found this little Sony integrated amp....does anybody know anything about. Seems like pretty fine build quality. Very understated 'purist' design.....nice big machined aluminum knobs.....quality 'feel'......looks very nice inside too.

Check pictures.

Its a TA-F3A......got it wrong in the title.
 

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Raccoon1400 said:
I have the TA-F3A. Almost the same. Make sure you replace those "death diodes" in the bias circuit.
Click to expand...

What "death diodes" might those be?

I have a TA-F4A and a TA-F5A, both similar to the TA-F3A but don't know if they are also similar internally. I recently lost one channel on the 5A for no apparent reason and although I haven't opened it up yet for a look I would like to check those diodes when I do. Any other suggestions as to why one channel might just quit on the 5A, some known inherent weakness perhaps, would be appreciated.

I too appreciate the funky look of this series with the large centrally located volume knob.
 
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Racoon......man.....you cant just throw something like that out there without a bit more info.......what diodes are they? Please elaborate....thanks.
 
The black gumdrop ones. Many sony amps were smoked because of them. There is one per channel, right between the two outputs.
They'll go wonky, and the bias will go too high and smoke the outputs. Though they will probably test good.

Ok, that should be better.

That is the TA-F3A you have.
 

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I have it's elder sibling the TAF-6B and a thoroughly good amplifier it is too, your baby TAF comes from good stock!
 
Coastsider, can you PLEASE post or send me a pic of the insides of your TA-F5A? I have one that I've had for a while, but a couple of resistors look like they are missing-like they've been cut off. I made a post a while back, but didn't get the help I'd hoped for. I've looked at the schematics and the problem with that, there are different versions of the same amp and the parts don't match up. I would be forever grateful. I specifically need to see the amp board back by the output transistors.
 
backinthelou said:
Coastsider, can you PLEASE post or send me a pic of the insides of your TA-F5A? I have one that I've had for a while, but a couple of resistors look like they are missing-like they've been cut off. I made a post a while back, but didn't get the help I'd hoped for. I've looked at the schematics and the problem with that, there are different versions of the same amp and the parts don't match up. I would be forever grateful. I specifically need to see the amp board back by the output transistors.
Click to expand...

I just saw your post this morning and can definitely take some photo's and post them later today if you still need them.

EDIT: Here are a couple of shots of the amp board in full and closeups of both sides. I hope they help.
 

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Anyway.....I have re-capped and serviced the whole unit. All caps, even the main caps have been changed and a couple of resistors. There weren't many caps and the unit comes apart quite easily. The amp works fine now. BUT, I have a very low level hum....and when I engage the lowfilter it gets a little stronger. Any ideas?

Also.....this amp runs HOT! I had it on for about 10 minutes.......the heatsink got HOT....is this normal?

I could not find a service manual on the 'net......can someone point me in the direction of one? Thanks. I need to know how to set the bias and dc-offset.

Otherwise, it is a great little performer......pretty CLEAR sound too.

Edit.....found a manual at eletktrotanya.......I'll look into it)
 
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The manual says nothing about HOW to adjust the bias/dc-offset..........HELP.

Thanks. I don't think the amp should run THAT hot.
 
anderslober said:
The manual says nothing about HOW to adjust the bias/dc-offset..........HELP.

Thanks. I don't think the amp should run THAT hot.
Click to expand...

Set it for 16mV between the emitters of the outputs. Or 8mV across an emitter resistor. Gives 40mA of bias. Experiment if you want.
Replaced with two 1N4148 in series.
Mine had taken quite a bit of heat too, and was blown.

Two pots per channel, the one closest to the outputs is bias, the one near the input stage is offset. The schematic tells you that much.

Wasn't too hot once biased.

Come to think of it I am not entirely sure those are the problem diodes. But I see Coastsider posted pictures of his, I see the VD1212 diodes in the bias circuit. Those are definitely problem causers.
 
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Ok...that was the bias. I'll try and see what I can do. Where do you have your numbers from? How do you set the dc-offset? Is it set to '0v' with dmm hooked up to speaker outputs?
 
Ok.....great info. I guess the 'emitter resistors' are the big white ones near the outputs. I'll hook-up a dmm across one of them and set 8mV.

I'll do the dc-offset on the speaker outputs...'0v'.
Hopefully , it'll run a bit cooler.
Any idea on the hum? Ground loop???
 
anderslober said:
Ok.....great info. I guess the 'emitter resistors' are the big white ones near the outputs. I'll hook-up a dmm across one of them and set 8mV.

I'll do the dc-offset on the speaker outputs...'0v'.
Hopefully , it'll run a bit cooler.
Any idea on the hum? Ground loop???
Click to expand...

Was the hum there before you recapped it?

You try flipping the plug?
 
I actually didn't have it ON before I recapped(for the fear of blowing something or making a possible problem worse).
The cable on my unit is completely detachable from the unit. It uses a standard computer/printer cable for power....three pronged. It can only sit in one way.
The sound is crystal clear and powerful........you can't hear the hum when music is playing. Only when there is no music and you are close to the speakers.
 
WOW.......I measured 131mV(R) and 110mV(L) across the emitter resistors! Yikes...no wonder it ran hot! Anyway...I adjusted the bias to just around 8mV. The dc-offset is as close to '0'V as possible. The amp runs cooler now...phew!
Racoon....do you think the hum could have something to do with the low-filter switch? When I engage the LF-switch, the hum gets a little louder. Again, once music is playing you can't hear it.
 
anderslober said:
WOW.......I measured 131mV(R) and 110mV(L) across the emitter resistors! Yikes...no wonder it ran hot! Anyway...I adjusted the bias to just around 8mV. The dc-offset is as close to '0'V as possible. The amp runs cooler now...phew!
Racoon....do you think the hum could have something to do with the low-filter switch? When I engage the LF-switch, the hum gets a little louder. Again, once music is playing you can't hear it.
Click to expand...

hmm. You cleaned all the switches?
 
Switches are clean....de-oxited and fader-lubed. The low filter switch is kinda' a closed unit........ditto high filter switch.........I'll fiddle with it some more. It has been playing now for more than an hour at medium volume....the heatsinks are nice and warm....not HOT!
 
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