Sony WM F707: Worth the investment?

I am considering investing in an almost mint Sony WM F707 recording Walkman. Apparently, many of these exhibit the same "no power"-problem upon insertion of both internal and external batteries and there seems to be almost no information on successful repairs here or elsewhere.

Does anyone of you have experience in repairing an F707, possibly even with this problem?

Many thanks.

 

These are relatively rare, and when you can buy the unit (preferably with accessories) for a decent price, I would buy it. I’ve been looking for these but they almost never seem to be offered 2nd hand here in the Netherlands.

 

Thanks Emiel, I’m certainly considering that. Have you ever taken one apart?

 

I unfortunately have not, I first need to get my hands on one for non eBay prices.
I am looking for one of the 700 series as a swap, see the relevant threads in classifieds and gear you want.
(Willing to trade amongst others a DD33, etc.)
However, since there are YouTube videos available, it would not be too hard to take it a part with a bit of patience and care.
The F707 is the most complex of the 700 series, with FM and AM radio, recording functionality and Dolby for playback.
It will for sure benefit from the modern higher capacity gumstick batteries.
Back in the day when I bought my EX618 new, the lower capacity gumsticks meant you could only really use it with the external battery holder attached.
By the way, the service manual you can find here: https://elektrotanya.com/sony_wm-f707.pdf/download.html#dl

 

I am somewhat more cautious. I dread "no power/dead on arrival"-issues because they force you to do the power tracing all over the place which is really a hit-or-miss thing. I have heard there are some leaky SMDs on the main board, so maybe that's the issue here.

I am not sure about complexity either. I've refurbished a 701c down to the motor itself and it really feels cobbled together with the mainboard being split into two and additional flex boards. Compared to that, miniaturisation seems to have advanced by the time the 707 came around and there seems to be only one monolithic mainboard plus the usual flexes.

I know of the YouTube videos but did not find them so useful, aside from the instructive internal views of the R707.

Well, I might just have to do a moon shot here and give it a try...

 

Given what you say, it's clear that you have enough experience and skills to repair such a walkman properly. Although the walkman is one of the complex ones (I've looked on the schematic), the problems are likely specific and likely related to leaky SMD electrolytics.
There are a couple of those in the DC-DC converter section, so those going leaky can explain a possible no power situation.
These small units are usually powered by batteries only, so the chance of someone powering it with reverse polarity or higher voltage is extremely low.

Not to mention there is the opportunity to take pictures and make a tutorial yourself about repairing/refurbishing the WM-F707, as there is none available to date and there are some common problems on most/all of these units.
Good luck with your purchase ! I'm looking forward to a repair tutorial.

 

That's a great point, thanks. Alright, I'll give it a shot and let you know how things go once I've had some time fiddling with my latest toy (when it gets here).

 

Did you get the F707 in the end?

 

Yes, I did. And it does look good with only minimal wear. I have also already done the recap and documented it. It seems that it went well as I checked and it does draw power and at least some buttons are working. I did not find time to proceed with the repairs as I am working on several projects in parallel at the moment. It will be a few weeks before there'll be more progress.

I am considering putting up a repair tutorial "Part 1" for the moment, though...

 

I hope to see it. It could help me with F701C repair.

 

I looked into a few details of the 700 series, since I really like the appearance of the units.

Sony engineers further optimized these thin Walkmans in terms of energy efficiency, culminating in the EX9oo series.
For instance the EX910 (EX921 nearly identical), the total current draw is unbelievably low: 24mA in playback (both ways), and 35mA ff & 32 mA rew.

Compare that to for instance the 701C: 210mA (!) in playback, 120 mA ff & rew.
That playback value, almost a 9 fold decrease going from the 701C to the EX910!
Ff & rew of the EX910 are only a 1/3 of the 701C value, nevertheless a great result since most of the time the device is in playback mode.

To stay on topic, the F707 values are: 130mA playback, 100mA ff & rew.

Although the EX910 does not feature Dolby C, this is still an amazing achievement.

 

Construction-wise the F707 is entirely different beast than the F701C, I am afraid. I have worked on both and the F707 is *much* easier to work on as it is pretty much constructed around a single, very miniaturised PCB. By comparison, the F701C feels almost cobbled together as there are multiple PCBs linked through flex cables and boards, for instance.

If you have any specific questions regarding repairing the F701C, ask away.

 

Sony WM F707: Worth the investment? the answer is NO

 

I finally got around to doing the repair tutorial. Sorry that it took so long. You may find it here: http://stereo2go.com/forums/threads/sony-wm-f707-repair-tutorial.7755/
Any hints on how to improve it are appreciated.

I should add that although the repair went smoothly, my own F707 is not currently working properly. I am seeing power distribution issues: while the 1,5V directly from the board are there, the 3,6V and 2,4V rails are not. I'll have to look into this at a later time, but it's likely unrelated to the repair.

 

I'm glad to hear you did the tutorial. Given you have asked, I have a few suggestions about the thread:
- I would use the "Upload a file" button instead of attaching images from the gallery for a couple of reasons: the blue text below image will not be there anymore (it's distracting and not relevant in my opinion).
You can use the full size option if you want to maintain the format with bullet points and picture below. If you put just a thumbnail, there will be a lot of empty space left on the right.
You can upload all pictures (seen there are more in the gallery) and not attach all of them (they will still appear as very small thumbnails at bottom of post). Of course, you can keep the pictures in the gallery
as well if you consider them to be relevant there.
- the second picture needs some red (could be other color) circles pointing those 2 plastic prongs (which are barely visible), so newbies avoid breaking them;
- Mention SMD tantalum capacitors can be used instead of SMD electrolytics (which can be hard to find in that 4V voltage rating/small footprint);
- A link for purchasing the belt (fixyouraudio or similar) can be put, so people can order more easily;
- When you do have the time to investigate that DC-DC coverter, post that also (it will likely be capacitors or transistor/transistors);

As for THT electrolytics, I do agree with you if they're not leaky, don't replace. Other people have a different opinion about this and that's ok. Mine is based on measurement on the LCR meter which indicate most old caps that are not leaky are still in spec.
Those that I can see in pictures (an R inside a rectangle, don't know what brand it is) are good capacitors. They are used in the D6C and I have never seen leaky capacitors in a D6C.
Of course, anyone can proceed as they like in this aspect, but they do have to keep in mind electrolytics are used less and less in modern electronics (especially those very small ones), that's why they have become pretty hard to find nowadays.
SMD ceramics and tantalums are the go-to solution for most modern devices. It is to be noted only SMD tantalums are a replacement for SMD electrolytics (they are in fact better than electrolytics, but significantly more expensive), while ceramics are not because of very high ESR.

 

Thanks!

I found the image insertion function extremely unintuitive. It always asks me for URLs. I'll give it a try the way you say.

I'll also add some markers to some images.

I did not mention the tantalums because procuring the SMD versions was no problem where I live (Germany) and as I am not a trained electrician, I was unsure with the technical details. But I am aware that you may use them, too.

I'll let you know about the DC-DC-converter. I am currently seeing some ICs being supplied with the correct 1,2V while other IC's don't receive the proper voltage. I need to dig a little deeper first to figure out why there seems to be a break in the circuit somewhere.

 

I agree, the image insertion function is not intuitive at all. When I posted my first tutorials here, I got into the same issue. One of the problems seems to be image resolution, it typically needs to be 2000 x 2000 pixels maximum, but the interface will accept higher and compress it.
Sometimes that renders an infinite progress bar, but usually they are uploaded even if not shown and will appear after you save (in case of edit) or post.

Where do you buy those capacitors in Germany ? Do they ship internationally ? TME (tme.eu) has very few of these smaller caps in stock. I wanted to buy a batch of 220uF@4V (very common in walkmans) and was surprised the stock was zero.
That's because I just finished the batch that I already had. Opted for tantalums instead and ordered just a few more than necessary. And in their case, when the stock is zero, it usually remains that way.

As for the DC-DC converter, you're lucky if it's just a break in the circuit, it's even simpler in this case. Probably some vias/traces that got damaged by the leaky caps I assume.

 

If I can buy in bulk, I buy from Mouser. Mouser is uneconomical for smaller quantities, though. Then I order from Conrad Elektronik. They have comparably small inventory (and not a great reputation), but tend to run 90% of what I need and from the big brands. Had not heard from TME yet, but shall give it a try when I order again.

Concerning the DC-DC converter, I need to check if the 3 rails are actually supplied by the converter itself, first. I would dread having to repair another trace as they are extremely small in the F707 and since the vias do not actually go through the board in the form of holes, drilling would be required – something I can do, but it's always risky. Let's see.

 

I think I have one of these models. I'm having to go dig for one
Also, let me add that I searched the internet to images for this model to remember what it is because there wasn't any other images in the most recent thread. So this is now thread revival. Yay

Hey, this is one of those models that takes a little button cell battery inside as well as a regular battery or a gumsick or an external AA battery in the little compartment thing.

Guess I got to go find batteries and take some time to test this but I'll do that another time. Right now I'm working on another boombox. I found this. I'm here