Sony TA-F6B PSU repair

[johnm]

Hey Mooly - sorry I haven't given any updates on this after your helpful suggestions. To be honest I am having a very hard time dragging myself away form listening to it - sounds so good now! It was good before but after recapping it it's just on another level altogether.

The only problem thus far is a VERY slight balance to the right-hand speaker. This may well have been there before the re-cap but it's just more obvious now. I only noticed this when using headphones. Even then I wasn't sure and had to use the mono button on the amp to make sure and everything then snapped into the middle perfectly. Using the reverse L+R the sound the stereo was then slightly favoring the left channel. Must try another source to see if it's unique to that one input or not.

- John

[Mooly]

Another job for a scope and generator

There can be many reasons for that effect. Seems like its not room (or ears lol) related if its the same yet correctable with headphones by switching to mono.

You can do a simple test. You need a test CD with test tones on it that are within the measurable frequency range of your meter. Most meters will be OK with up to 400hz or so.
Just play the tone starting at low volume (you don't need speakers connected as you say the effect is present on H/phones... suggesting loading isn't an issue) and measure the AC voltage at the speaker output as you turn the volume up. Output should be the same for both channels of course with fairly close limits. See what that shows.
Even if the meter were inaccurate at higher frequencies, say up to 10khz or more, as long as it showed a useful reading it would still be possible to compare left and right as the meter inaccuracy would be consistent and you are just comparing one output with the other.

Slightly more obscure could be that the inter channel separation or crosstalk (strange to say this is a topic I was considering starting anyway) might not be consistent left to right and right to left over the frequency range and so giving this imbalance effect.

[johnm]

Thanks for that Mooly - I'll try and get hold of some test tones from the internet somewhere and burn those onto a CD.

Bizarrely, the channel balance sounds OK through the speakers (though the layout of my room isn't symmetrical so the channels could still be unbalanced in absolute terms). I would therefore point the finger of blame at the headphone output, but if that were the case surely one channel would still be louder with phones when switching to mono, and this isn't the case.

I think I'm getting to the point now where I may have to get someone to look at it for me - even though it's a minor niggle. I'm getting tired of taking the lid of this thing

[Mooly]

Measurement is the only way... there are too many variables otherwise.

The headphone output is normally just the main amp output padded down with resistors.

[johnm]

Hi again Mooly!

Had other things going on, but I need to get back to sorting out those resistors for better matching the output transistors to the circuit. Rather than having to repeatedly solder on various values of resistor to the underside of the PCB (and thereby run the risk of lifting a track) would it be an idea to solder in a socket which would allow me to just quickly fit resistors in place for testing? Reckon this would be so much simpler than having to keep flipping the whole power-amp section over onto its side to fit different value resistors.

I know you can get turned sockets for op-amps and the like, but can one purchase individual pins? Something like that would be ideal for quick changing of resistors in the output stage.

Thanks,

- John

[jaycee]

Yeah you can get turned pin single in-line sockets which you can cut as needed. See for example Rapid Electronics - Cables & Connectors

[johnm]

Ah that's great - many thanks for that

They have them on Ebay dirt cheap - I'll get a couple of those ordered right now.

Cheers!

[Mooly]

Hi John... I still watching

Pleased it's all working OK

[johnm]

Originally Posted by Mooly

Hi John... I still watching

Pleased it's all working OK

Thanks Mooly

Hopefully I'll get around to try out different resistor values in the outputs within the next few weeks.

- John

[pmpants]

Hi John, Mooly, Jaycee and everyone else who contributed to this subject, I've just sat and read all 54 pages tonight! Fantastic team work from some seriously skilled, knowledgeable techs.
I'm just starting out recapping amps (Quad 405s, 303s etc) and fault finding after tinkering with hifi for years and years.
I was bought a 2nd had Sony TA-F60 Sony TA-F60 on thevintageknob.org when I was 12 (I'm 40 now!) as a Christmas present, the power supply failed and was repaired and failed (twice) by a local tech, I was ever so fond of it so bought another when it came up for sale locally, it failed 1 week after buying it! The private seller admitted it had just been repaired and actually sent it back to be repaired again, it lasted a few months this time! My dream is to gain enough knowledge to tackle these amps, hopefully get one going reliably, fingers crossed!
I use a Luxman LX33 integrated valve amp as as my main hifi amp but have a system for music production and it would be wonderful to see the vu leds of the TA-F60 working again while I play!!
Anyway I'm rambling, I definitely learnt a lot reading these posts and you've spurred me on to get the Sonys out the loft and at least try to assess them.
Thanks ever so much
Paul