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Old 25th May 2024, 7:09 am   #1
MacFZYP
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Default Sony TA 70. Capacitor replacement.

Split from this thread:-

https://www.vintage-radio.net/forum/...d.php?t=211217


Quote:
Originally Posted by JonSnell View Post
Thank you very much John Snell , I see that you are a great specialist in amplifier repairs , as I don't know anything about it and I read that all the capacitors had to be changed on this amp , would you be so kind as to give me the list of capacitors that need to be changed on this Sony amp , I would have sent it to you for repair but I live in France . Thank you very much for your help. Regards .
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Old 25th May 2024, 7:09 am   #2
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Default Re: Sony TA 70.

Quote:
Originally Posted by JonSnell View Post
Thank you very much John Snell , I see that you are a great specialist in amplifier repairs , as I don't know anything about it and I read that all the capacitors had to be changed on this amp , would you be so kind as to give me the list of capacitors that need to be changed on this Sony amp , I would have sent it to you for repair but I live in France . Thank you very much for your help. Regards .
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Old 25th May 2024, 9:41 am   #3
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Default Re: Sony TA 70.

Is it actually faulty? When I used to service these, the electrolytics were often replaced, using exactly the same values but 105°C versions in the power supply.
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Old 25th May 2024, 10:28 am   #4
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Default Re: Sony TA 70.

Don't assume that you need to change lots of capacitors in the absence of a fault. The electrolytic caps used in 1970s Sony products last very well. I have a TA-70 which is still using its original caps - even the speaker coupling caps are good.

Jon has more experience with these than I do though.
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Old 25th May 2024, 10:41 am   #5
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Default Re: Sony TA 70.

No, it works , sound comes out of both channels, except the volume potentiometer spits a bit. I saw a video on Youtube and the guy had changed 25 capacitors, is that possible? Sorry for my English, I'll go through a translator.

https://youtu.be/SOXMN2y3AWs?si=YyVo2u3wY8Ceedlh
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Old 25th May 2024, 2:39 pm   #6
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Default Re: Sony TA 70.

There is a mania in parts of the HiFi world for changing lots of electrolytic caps when they're a few years old. I've seen people advocating changing all the electrolytics every 10 years! Sometimes electrolytic caps do fail, but there's absolutely no point in changing them if there's nothing wrong with them.

The TA-70 is a stylish early 70s amplifier, but it's not a good sounding design by the standards of the 80s and 90s, by which time design engineers had worked out how to make cheap mass-market transistor amps sound really good. No sane person is going to be using a TA-70 because of the world-beating sound quality.

Your volume control probably needs to be cleaned internally with some contact cleaner spray. All the switches and potentiometers should be cleaned in this way if it hasn't been done already.

(Your English is good - better than my French )
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Old 26th May 2024, 6:02 am   #7
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Default Re: Sony TA 70.

Thank you paulsherwin . So, according to you, there's no need to change these capacitor caps. Is this video a fake ? The funniest thing about this amplifier is that I bought it in England, and thanks to Deepl for the english translation !!
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Old 26th May 2024, 10:02 am   #8
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Default Re: Sony TA 70.

Undoubtedly some owners will change all the electrolytics. My attitude is that it's pointless if the originals are still in good condition.

Of course, if a fault is present then it needs to be investigated systematically, and one or more bad electrolytics may be responsible.
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Old 27th May 2024, 7:35 pm   #9
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Default Re: Sony TA 70.

Quote:
Originally Posted by paulsherwin View Post
There is a mania in parts of the HiFi world for changing lots of electrolytic caps when they're a few years old. I've seen people advocating changing all the electrolytics every 10 years! Sometimes electrolytic caps do fail, but there's absolutely no point in changing them if there's nothing wrong with them.
Absolutely agree, and is actually detrimental to some equipment. I've seen several complaints that their Sansui amplifier has lost its characteristic smooth sound after hours spent needlessly recapping.
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Old 27th May 2024, 10:31 pm   #10
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Default Re: Sony TA 70.

Electrolytic capacitors contain a water-based electrically-conductive jelly. Over time it dries out via vapour leaking past rubber seals.

When this gets bad, the capacitor commences to look resistive... its Equivalent Series Resistance, ESR increases.

There are small hand-held ESR meters which allow you to measure the remaining life expectancy of a capacitor. Think of a fuel gauge! Some of these ESR meters work quite well with capacitors still in-circuit.

Electrolytic capacitors are available in different grades rated for different temperatures and sometimes for longer probable lives (in thousands of hours) at those temperatures. The difference is really better quality seals which can better resist the vapour pressure.

So one approach is to go around the equipment with an ESR meter, looking up the specification of the capacitors you find, or the specification of common makes and types to see if any look to have gone higher. These are the capacitors needing replacing.

Unfortunately, the re-capping cult drives inexperienced people to change lots of parts, making lots of solder joints, sometimes buying unsuitable parts, sometimes fitting them the wrong way around, sometimes making dry solder joints, sometimes leaving solder splashes shorting things etc etc. Unless their workmanship is very good, they introduce more faults than they cure and are left with a non-working set with multiple faults scattered throughout it.

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Old 28th May 2024, 12:19 am   #11
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Default Re: Sony TA 70.

Wholesale recapping may be justified if you are dealing with a studio desk or racked equipment which has been run hot 24/7 for years, but domestic kit rarely, if ever, gets that kind of use. Better to establish what is wrong with the unit by ordinary fault-finding and take it from there.

There are some cases, frequently where surface mount capacitors are involved, where physical deterioration is so obvious that the lot has to be done - DAT transport electronics tend to need this approach - but, in general, electrolytics are much more durable than many "content creators" assert.

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Old 30th May 2024, 6:54 am   #12
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Default Re: Sony TA 70. Capacitor replacement.

OK, thank you very much for your advice, so I'm going to trust your experience and not change anything. I should point out that I don't know anything about electronics and I wouldn't know how to use an ESR meter. It's strange that this video on YouTube recommends changing everything!

https://youtu.be/SOXMN2y3AWs?si=YyVo2u3wY8Ceedlh
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Old 30th May 2024, 11:10 am   #13
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Default Re: Sony TA 70. Capacitor replacement.

If you have no experience of electronics, that is a good reason to avoid doing unnecessary work. You will probably make a poor job of the soldering, and may damage tracks or introduce other faults.
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Old 30th May 2024, 11:37 am   #14
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Default Re: Sony TA 70. Capacitor replacement.

Quote:
Originally Posted by MacFZYP View Post
It's strange that this video on YouTube recommends changing everything!
There are lots and lots of videos and websites telling you to do that.

There are also lots and lots of amplifiers and radios dumped in landfill because they couldn't be got going again afterwards. Not only is the equipment lost, but also the person suffers a blow to his confidence and may never attempt repairing anything electronic again.

Most of the people following the 'recapping' advice are relative beginners. They don't yet know the differences between similar appearing types of capacitors, how to buy new ones without risking getting fakes, and their soldering skills are at a beginner level.

Consequently, in changing a lot of capacitors all at once, there is a high probability of introducing more new faults than there were old ones to begin with. Beginners also haven't yet developed skills and experience in fault-finding so the set is often beyond their capabilities.

One way out with a set which is partially working, is to replace one at a time and try the set between each replacement action. This way, if things get worse, it's obvious which component to look at.

Changing parts in groups depends on how much confidence you have in your skills. The probability of trouble increases as the difficulty of fixing the error increases.

Sometimes you come across a piece of equipment which has run for long times in a hot environment and it's worth replacing all the electrolytics. I have a Revox FM tuner which was used by the BBC for monitoring and re-broadcast purposes. It lived in a hot transmitter rack for 20 years running 24 hours per day, 365.25 days per year. about 3/4 of all the electrolytic capacitors in it had gone high resistance. It really was worth changing the lot of them. So I did.

Access meant that it was worth doing one board at a time and I had enough confidence in my workmanship to not keep refitting boards to try it out. But I've had a lot of experience designing things and building prototypes my workmanship is pretty good when I'm going slowly and taking care. My fault finding skills were developed in handling prototypes of my own designs, diagnosing problems in hardware which had never been made before.

So even the experienced experience trepidation when changing things en masse.

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Old 30th May 2024, 11:56 am   #15
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Default Re: Sony TA 70. Capacitor replacement.

You can imagine a similar attitude towards other objects: "My camera is 30 years old, so I'd better completely disassemble the lens and replace the glass", or "my car is making a funny noise, so I'll get new seats and repaint it". Sounds ridiculous, right?

Enjoy your amplifier and ignore the dissatisfaction merchants who encourage you to change things for the sake of it. Say in a year's time you notice a crackle on one channel, then that's a legitimate fault that can be investigated and the relevant components replaced, rather than a scattergun approach that isn't aimed at fixing a fault, and runs the risk of 'fixing it until it breaks'.

Some elements in a very old piece of equipment or one with a peculiar design will require preventative maintenance, which the experienced will know about because certain parts are known to fail in a particular way. There's a certain capacitor in many valve radios that has a tendency to fail, and the way it fails can cause expensive damage to valves and transformers. Replacement with a modern type of capacitor here is a good idea even without testing it, but that's a very specific case.

There is no shame in not knowing what you're doing, as you haven't done it before. I spend most of my time not knowing what I'm doing, able to fix some things because of the good offices of members here who gently tell me when I'm suggesting something idiotic, and gradually I learn.

One great piece of advice I have received is 'listen to the music, not the components'.

Enjoy the music!
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Old 31st May 2024, 6:32 am   #16
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Default Re: Sony TA 70. Capacitor replacement.

Thanks again for your advice, I'm going to connect my Sony TA 70 amplifier with a Lenco L80 turntable that I've just restored, the motor was dead and I found one on Ebay, (not easy to find) now it works properly . Have a good weekend ! Regards !
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Old 31st May 2024, 9:18 am   #17
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Default Re: Sony TA 70. Capacitor replacement.

I often find it difficult to suppress a chuckle when I read a thread on a forum along the lines of "I re-capped my XXXXX and now it doesn't work".

I realise this makes me a terrible person and I'm undoubtedly going to hell as a result but I really can't help it...
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Old 31st May 2024, 9:49 am   #18
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Default Re: Sony TA 70. Capacitor replacement.

Indeed. Threads which start like that often run to hundreds of posts without the item being returned to working order. If ALL the caps have been changed including the ones concerned with RF, LO and IF tuning you might as well give up.

There's a misconception that any set can be fixed by changing all the caps, all the out of spec resistors and giving the pots and switches a squirt of Servisol.
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Old 31st May 2024, 2:06 pm   #19
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Default Re: Sony TA 70. Capacitor replacement.

Hello,

Regards capacitors…, and going at a tangent, I’m working on one of the Cage amplifiers I got from Redditch via Guy, and as part of the exercise I want to keep as many of the original components as possible. Reliability isn’t a major factor in this exercise.

Its 54 years old (1970) and the blue axial Mullard capacitors still read OK with negligible leakage current.

I measured them using an Atlas LCR/ESD meter after running them at roughly 75% of their working voltage via 2K7 series resistor for an hour or so.

The two 64uF 25V measured 78.8 and 77uF - ESR 0.24 and 0.25 Ohm respectfully.

The two 64uF 64V measured 69.2 and 70.7uF – ESR 0.32 and 0.4 Ohm respectfully.

These are acceptable for cathode bypass duties.

I won’t comment on the Erie non insulated 8A solid carbon resistors though

Edit... I hasten to add I removed the capacitors from the unit.

Terry

Last edited by Valvepower; 31st May 2024 at 2:12 pm.
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