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plop - 2010-08-23 14:55

Most of you will have read my previous post regarding an Aiwa HS-JX505 needing urgent attention due to some failed capacitors and major electrolyte leakage on the circuit board.

Well following from that, this time I decided to tackle an Aiwa HS-JX707 with a seemingly wishy-washy DSL bass and a slack BBE. I'm not going to bore you with pictures on how to take it apart, that in itself deserves a thread, it is not for the faint of heart taking this model apart.

This first photo illustrates how on the face of it everything seems fine and all in order.

However ...

Using the technique of twist and pull with a pair of long nosed pliers learned from another website on circuit board repair we remove the SMD caps and their plastic separator to reveal the horrible fact that twenty years will cause even SMD capacitors to leak nicely onto a circuit board. This is bad, since we could not even tell that there was any trouble from the first photo (OK there was a bit of a tell-tale oxidisation on one of the 47uFD capacitors, but I don't think you would have seen that from the picture due to the shadow being cast.)

*** Edit ***

NOTE : Having worked on more heavily corroded boards now, I feel that caution should be exercised when using the "twist and pull" removal method especially where there is acid damage on the traces. Invariably using this method could cause the copper trace to come away from the PC board if inappropriately applied.

**********

After removing the leads from the caps, I've cleaned up the board and re-tinned the contacts. It is now ready for the new SMD caps to be fitted.

So we are going to fit like for like. I have opted for Panasonic 85 Degree 1000 hour life SMD parts sourced from Digi-Key. I have to admit the through hole Panasonic caps are slightly too tall for this, so if you are planning to emulate this task you may want to consider an alternative, or be very careful how you install them onto the board. (ie do not solder them in place until you are ready to re-fit the board back to the chassis. I have included the original caps in this picture. You can see the electrolyte has also leaked nicely out of them too. I believe these are the two caps responsible for the bass response.

Well finally all caps now fitted. To fit the SMD caps, be sure to tin them before soldering directly to the pads as per the correct orientation. It is also worth noting that applying too much solder when tinning the pads will cause some caps to sit too high. There really is bugger all spacing in this Aiwa model.

Well, it is now reassembled and when powered up I can hear the DSL bass quite clearly when the circuit is enabled. I have to note that the bass is not as heavy handed as the HS-JX505 when I replaced the caps in that model. Otherwise job done.

BBE sounds great too. Previously with the old tired caps in mode 2 BBE would sound overly exaggerated, but now it appears better at dealing with the rapid changes in the music. Personally I prefer either mode 1 or even no BBE at all as the HS-JX707 has quite a reasonable dynamic range without it.

thelion - 2010-08-23 16:45

Plop, you are the man!

This is really a great job you are doing there. I enjoy reading your repair posts.
First it was the AIWA HS-JX505 and now this one, cool.

Would you please mind to tell us, what exactly are the catalog parts numbers to order from digi-key? this is always my weak point, what exactly to order?

Keep up the good work.

Cheers,
TheLion

rerooted - 2010-08-23 20:20

why is it that the 505 i randomly bought off ebay for 20.00 sounds and works 100%? when can i expect the sound to go to hadees so i know when the end is close to coming. i mean is it like those darn geers that have about a 20 year life span. or mabey it is a matter of use or abuse. i am totally clueless on this one. all i did was open the back,,take a look at the stretched belt and put it back together. i am a 0 electronics person so belts and a few other minor things is as far as i can go. that's life

plop - 2010-08-24 03:05

quote:
Originally posted by TheLion:
Would you please mind to tell us, what exactly are the catalog parts numbers to order from digi-key? this is always my weak point, what exactly to order?

Ok, here are the parts details from Digi-Key. There was a typo in my previous post. They are in fact all 85Deg @ 1000h Panasonic capacitors.

For all orders from Digi-Key note the minimum quantity you need to buy in the price break table. So in other words if you only wanted one capacitor, you'd still need to buy ten if ten was the minimum order quantity in the price break table. This is especially the case for the 220uF through hole caps, but I needed more than a dozen, so that wasn't so bad.

Another gotcha from Digi-Key is that if you are ordering from abroad they claim that it is free delivery to your country of destination for orders from a certain amount, what they don't tell you is that they use expensive couriers who then charge you the sales tax (plus the duty) for the delivery. This is not made clear. I got a nasty bill for that too a month later after only expecting to pay the sales tax on the items only.

SMD

These are all supplied cut from tape reels

47uF EEE-0GA470SR

100uF EEE-0GA101SR

220uF EEE-0GA221SP

Through hole

220uF ECE-A0GKS221

plop - 2010-08-24 04:08

quote:
Originally posted by rerooted:
why is it that the 505 i randomly bought off ebay for 20.00 sounds and works 100%? when can i expect the sound to go to hadees so i know when the end is close to coming. i mean is it like those darn geers that have about a 20 year life span. or mabey it is a matter of use or abuse. i am totally clueless on this one. all i did was open the back,,take a look at the stretched belt and put it back together. i am a 0 electronics person so belts and a few other minor things is as far as i can go. that's life

It's hard to say why one twenty year old unit will be ok and another would have gone to pieces. It could be down to a number of factors.

1. Parts used. Some batches of capacitors may have been made using sub-standard parts and therefore may not have stood the test of time. Although older electrolytic capacitors are notoriously bad for leaking in general from what I have read elsewhere.
2. How the device was treated. There is some debate that a regularly used device helps keep the capacitors refreshed through the charge and dischard process (Although I think that is more to do with the caps staying within their manufactured tolerances than actual failure). On the otherhand a device previously well used that has been put into storage and since hardly used slowly decomposes. It is worth noting that the main point of failure in these electrolytic caps is the rubber bung holding all the liquid inside it. We all know how well rubber stands the test of time a la drive belts.
3. It was simply it's time to go. Parts are made with rated mean time to failure. Eg 1000 hours @ 85 degrees C.

Whatever the case above it would seem logical that given the unreliability of these older cheap electrolytic caps that Aiwa seemed to like to use, that investing in a set of newer caps is the wiser thing to do. Obviously it is not always practical to do this as identical parts are not always available and hard decisions have to be made to use an alternative equivalent part.

I have looked at various audio repair fora and the common concenus seems to be for antique amplifiers is to replace caps on boards older than 5 years. However they seem to talk mainly about replacing them for seriously expensive audio grade caps. For personal walkman the range of caps is VERY limited. For me, just replacing dodgy caps with equivalent ones is fine.

In the case of your HS-JX505, I guess you are lucky that the one you picked up is still good. I have a couple other HS-JX707 that are also good and don't require immediate action to replace the caps in them. However I do know that given time I will need to do it, as given time the sound quality will degrade and the caps will leak and risk the acid inside the caps damaging the delicate internals. Ticking time bomb springs to mind.

If you are concerned about changing the caps yourself, then I suggest you try and hook up with one of the many enthusiasts here that do repair/replace parts to do the work for you. Or entrust the work to a professional who may or may not treat it with as much care as someone on this forum.

rerooted - 2010-08-24 21:22

very interesting and sorta like the broken geers in all the DD models. every once in a while a person says they are still using the original part with no clicking at all. for me,,a good running clicker is my best hope. my wm-d3 continues clicking away as it records. on the the other hand,,my wm-f5 died bran new,in my hand after about 2 minutes of use. it was fresh out of the box. anyway,it makes a nice display or a very heavy radio. reminds me,,i may have left the batteries in it for a good long time now. everything is dead mint so it is worth saving for someone in the furure.

gregorybotha - 2010-08-24 22:04

Hi Plop,

Well done on the repair work. It's nice to know there's hope for these older Walkmans.

drmr2000 - 2010-08-30 00:02

Found it better to use a heatgun at 650-840 max degrees Fahrenheit works great, just preheat the board at 200 degrees so you don't warp the pcb with the heatgun at low temp for 5 mins and cover the plastic part and jacks with aluminum foil, so you don't melt them, you don't have to worry about breaking traces off the board this way, just don't leave the heat to long in one spot, and only take less then 30 sec.

I do a video of one later this week, when I get sometime.

dottor.walkman - 2010-10-03 05:38

Some time ago I purchased an AIWA HS-JX2000 tenth anniversary on ebay. It did not work because all the capacitors that had lost the electrolysis. This problem affects many Walkman all brands, because in those years there have been many defective capacitors. The acid had also damaged some tracks on the circuit. I repaired the broken door and I replaced the capacitors with some of the highest quality. Since I had paid a high figure I managed to get a partial refund and keep the Walkman.

steve.moore - 2011-03-22 22:16

Hi, this is a long shot but I have a 707, and I know this isn't really a reply, but I'm trying to remove the circuit board (gently lift/hinge) it out of the way. I have removed all visible screws including the ones where the tape operating buttons are... but something is still preventing it from lifting...any advice would be welcome, as I wish to enjoy this fabulous unit again! I bought it in '93 - '94. Love it!
regards, Steve.

bub - 2011-03-23 03:17

If I remember correctly, the board will need to be desoldered at some point. Mine's lying in pieces in box awaiting caps that fit and battery box/or I will install larger ones n the battery bay).

Sometimes I find it easier to desolder connections on a walkman I am not familiar with in case I rip a cable.

steve.moore - 2011-03-23 03:50

Hey thanks for that information, i might do it, ..... while i was waiting for a reply I found a website with a service manual (PDF) for the 707, I'm just awaiting the download now.... I'll leave mine alone until i can find out more, the manual is at "Manualzone.com", do you know the website? it seems very very good.

plop - 2011-03-23 06:00

Having taken a good number of the HS-JX707 models apart. There are three areas to de-solder before you can remove the PCB.

1. Four points on the motor. This part is a walk in the park.
2. Two points on the recording solenoid (seen through hole in the hinge flexible PCB). It is possible to manipulate the ribbon carefully to get access to the contacts without scorching the ribbon.
3. Two points on the playback mechanism solenoid. These are quite hard to spot if you don't know what you are looking for (If you look at the first picture in this post you will see the line of the holes where the solenoid passes through are straight across the middle of the headphone and mic jacks on the left over to the internal battery contacts), there are two relatively flat circular solder points about 2.5mm in diameter spaced roughly 15mm apart. WARNING : Work quickly to remove solder and ensure all solder is removed before lifting the PCB. Extended heat applied to the pins on the solenoid WILL cause them to come away from and damage the solenoid most likely beyond repair if you don't. I've seen a few units where this has been a failed attempt.

It is not necessary to remove any of the flexible PCB, but do be aware they are very fragile and have a tendency to tear. Nor is it necessary to desolder the solder blobs bridging the tape controls PCB to the main PCB, but you will need to remove the two screws that are attached to it.

You will need very good flux impregnated solder wick or have a very good solder vac, and have to work very quickly with the solenoids, and once again do not dwell too long on the points as the solenoids have a habit of melting and you end up destroying the solenoid or lifting the tracks from the PCB.

plop - 2011-03-23 08:19

Originally Posted by Steve Moore:

Hmm. Manualzone charge nearly $20 USD for a scan. If you have money for a manual you could get a better deal and get them from getmanual.com at least they are only $10USD and you basically get the same thing. For that price you'd nearly have change for a second manual. Or better still for $50 USD they'd throw in the whole Aiwa CD with 275 service manuals.

steve.moore - 2011-03-23 12:58

Thanks immensely plop, I shall heed your words and forge ahead with the greatest care, I am a jeweler by trade, and my speciality is making very small complex parts...so i have the patience and hopefully the ability to de-solder this little masterpiece successfully.....but yes photos would help, and would be most appreciated!....... now I have another source for manuals...thanks :-)

kerni99 - 2011-08-03 04:17

Hi plop,

I just completed the change of capacitors and the memory battery for one of my JX707. Furthermore it got a new belt (thanks DocP). Wow, what a sound it has now. For the position of through hole capacitors I used the SMD types with cut legs and an insulation sheet below. The through hole caps were a little bit to high for my feeling (as you described above). It was hard to place back the PCB.

Together with the replacement batteries for PB-S5 (see my other post) the cassette player is now like new and it is a big pleasure to use it.

Thank you so much for all of your tutorials. Without this I never had a chance to do that.

Best regards

kerni99

bub - 2011-08-03 04:19

Yup, I too used SMD caps for through hole.

I also learned the twist method of removing caps from this thread, great stuff.

plop - 2011-08-03 06:28

In actuality care should be heeded when using the "twist and pull" method, especially where there is chronic corrosion due to leaky capacitors. Traces can be weakened by the acid corrosion and come away easier in such cases.

I now desolder the capacitor instead if there is bad corrosion, and would recommend others to do so too instead of risking the removal of traces.

kerni99 - 2011-08-03 07:03

Hi,

My experience was the opposite. I at first tried to remove the caps by desoldering with a small SMD soldering iron. The solder was hardly melting and at the end I ripped off some of the traces from PCB. Then I tried the "twist and pull" method and the caps could be removed very easy. And all the traces were fine and I could desolder the remaining legs.

plop - 2011-08-03 07:10

Yes if there is bad corrosion, then the tin in the solder reacts with the acid leaving only the lead. This lead on it's own is a lot harder to melt, but it is possible to melt it. Although seemingly counter-intuitive since you want to remove solder, the trick is to add fresh solder to the oxidised joint. This is usually enough to help melt the lead and then free up the component.

Another point to note is that too much heat can also cause the glue holding the copper trace to the PC board to soften, which also allows that to lift away.

bub - 2011-08-03 07:24

Here's what I try now:

Twist, but not pulling. I hold the plastic base with pliers and turn the cap until the legs snap off. The plastic base helps counter some of the fore applied to the board I guess. It's easier on caps where corrosion is so bad the legs are very weak.

Plop, what better methods do you recommend for desoldering? I've heard of applying indirect heat and such...

plop - 2011-08-03 08:55

The best method for desoldering is a dedicated desoldering station, but since I am not a professional I don't have a budget that would stretch to that. Some people prefer the use of hand pumped solder siphons but due the presence of small parts such as SMD resistors and ceramic capacitors I don't like using them. I once had a tiny resistor get sucked straight inside one. It was a pain to fish out of the hand pump. Plus they are awkward to use in tight spaces. I prefer to use desolder braid. My preference is the ultrafine stuff preloaded with roisin for working with SMD components. I also have a flux pen handy to help the solder along with the melting process, especially for removing old oxidised stubborn solder when cleaning solder pads. For bigger lumps of solder I use thicker graded desolder braid. It's not just the tools but also the technique, so sometimes fresh solder applied to an old oxidised joint and mixed in well, is needed to remove all traces of the old solder too.

If I cannot de-solder a corroded SMD cap for whatever reason, I'd favour levering a thin screwdriver between the plastic base and cap at one of the four sides where there is a solder connection and then rocking gently with pliers to try and force that leg of the cap away from the can. Then I'd repeat the same for the other side. The down force of the screwdriver against the plastic base would prevent the trace from lifting away from the PC board.

cosmos99 - 2011-09-07 14:30

So all those caps exist in 4 volts ?? The Replacement caps thread made me buy 6,3 volts.... Should be updated no ?

plop - 2011-09-08 00:20

Originally Posted by cosmos99:

So all those caps exist in 4 volts ?? The Replacement caps thread made me buy 6,3 volts.... Should be updated no ?

The original capacitors in the JX707 are indeed 4V, but technology moves on, and there is no harm specifying higher voltage rated capacitors with equal (or slightly higher) capacitance. If you have read the AIWA Capacitor Replacement Guide, you will have noted that the following comment was added following discussion with S2G member Bub...

"These are all 6.3V values, but they are shorter and have higher endurance than the 4V Panasonic previously suggested. Thanks to Bub for suggesting these instead."

The JX707 article was written over a year ago, and of course information in that is out of date. Where appropriate you should refer to the capacitor guide first as I will be updating that in the first instance over any individual post. If you choose to replace with 4V rated values there will be no major detriment to the function of the unit either.

cosmos99 - 2011-09-08 05:27

Sure , so you confirm the 6,3 volt range are shorter ? Did you encountered problems with the 4 v range in your 707 ? Where they small enough or little too tall ? Thanks. By the way , how do you regrease ? Do you dismantle it all or not ?

plop - 2011-09-08 06:08

I did not encounter any sizing issues with the Panasonic 4V SMD capacitors even in the JX707. The Chemicon are shorter by about 0.5mm. Not a great saving in height, but can be useful if you choose to install them in place of the Panasonic hole radial capacitors (which are longer than specified). The real benefits of the Chemicon capacitors are that they are a higher rated endurance than the Panasonic and that they were also marginally cheaper too.

How to re-grease? Well best to apply grease for the all the plastic and metal moving parts. If applying small quantities you can apply small amounts using an interdental pick. Do not over grease otherwise it can leak through into the cassette compartment.

cosmos99 - 2011-09-08 06:37

What is endurance ? Life span ?

plop - 2011-09-08 07:32

Panasonic PCE3848CT-ND - 1000 hours @ 85°C

Chemicon 565-2058-1-ND - 2000 hours @ 85°C

I've just checked the prices on Digikey and for 220uF the price of the Chemicon seems to have gone up and are now about 9 cents more per capacitor than the Panasonic (46 cents + taxes). Still for double the endurance I'd be happy to pay the extra 9 cents.