Hi,

Here I have a solution for the aficionado of Aiwa Walkmans from the 90ies, who is annoyed about the use of the bulky external battery pack. With his 2V lead-acid batteries Aiwa has beaten a way, which was a dead-end street. There exists almost no more working pieces and no new to buy.

For Sony and Pansonic you still can buy even better 1.2V NiMH gumstick batteries.

But now my solution for Aiwa's PB-S5 (A) gumstick:
I got the idea when I found, that there are short 1.2V-NiMH gumstick batteries available. Two pieces of them should fit into the battery-chamber of an Aiwa Walkman. With 2.4V in series this should be still OK for the electronics. But my first try was negative, because the batteries were 35mm long - and this was to long. So it depends an every millimeter or even the tenth part of it.
The next batteries, which I found are 34mm long - and this suits.

I bought it here in Germany:
http://shop.aaaa-electronic.de...0/Products/10025-001
The plus pole of the batteries hits directly the plus contact in the battery-chamber. Only for the minus pole I had to think about.
I found the solution via a thread in this stereo2go board on a chinese page:
http://www.jd-bbs.com/viewthre...able&tid=1644473
This was the original idea, which I modified, because it is very narrow in the chamber

 
My result:

It works very good and with 600mAh the new gumstick batteries have twice the power from the old PB-S5. And they are very cheap, compared to the prices which were to pay for the last available Aiwa gumsticks.

For the charging I use a universal charging station for NiMH batteries. As the gumsticks are quite short I have a small metal distance piece.

Up to now I found no problems because of the 400mV higher battery voltage. But who is afraid, should not try it with his showpiece ;-)

best regards

kerni99

Hello Kerni99,
compliments. You were very good.
Now just add a constant current charging circuit, rated amperage of the batteries, plug it in and charging stations for Aiwa Walkman if you have it. This prevents each time to remove the batteries from the Walkman.

Very nicely done!

Amazingly, a local shop here in Singapore still stocks a box filled with nothing but new Aiwa Lead Acid batteries, quite a few models too. However, I don't think they will work anymore.

Hello,

Thanks parkashan for your reply. I do not know, if a LDO is really necessary. Up to now I had no problems with the 400mV higher voltage. But if you have a good an small enough idea, I would appreciate it. The only problem would be, if it is needed to build it into the Walkman, I would need to modify all my devices. The battery-only solution is multi-purpose.

Thanks dottor walkman for your reply. Unfortunatelly I have no charging station for the whole Walkman. For the PB-S5 battery I have only a seperate battery charger and a power supply, which I can attach to the external battery box. Maybe I can modify one of my battery boxes to charge the batteries in the Walkman. But as I'm not the electronics expert, I have no idea about the circuit. Could you propose me something?

Best regards

kerni99

I have thought of this method as I too have seen the Chinese forum page as discovered by member TheLion several months ago in another thread on this forum.

index.php?board_oid=193392314111653483&content_oid=193392314111874066

However as discussed in length the question of the extra 0.4V on the system could caused stresses on the components within, as freshly charged NiMH batteries can have voltages as high as 1.5V Up to ~2.4V would be ok, as the lead acid batteries when fully charged would have been at this voltage. Incidentally ~2.4V is about the normal working voltage for 2 NiMH batteries once they from their peak voltage.

Another point to consider is why would AIWA go to the trouble of implementing a voltage regulation circuit within the battery boxes where voltages of 1.5V would typically be seen from AAA batteries?

You are worrying unnecessarily. If you really want, you can insert a diode in series to lower the voltage of about 0.5 volts. But it's not necessary, first of all, the lead elements when they are charged, are over than 2 volts. In addition, the internal circuit of the Walkman it's can withstand higher voltages, because before you reach circuits, the current, encounters the integrated stabilizers.

That's the thing, there are no "internal stabilisers" as these are in the battery box. Well I for one would only risk this mod only in a lesser non-prized unit. The AIWA engineers allowed for the 20% tolerance over 2.0V from the sealed lead acid battery. but all the voltage regulation is done externally for the other power sources.

This mod could take the tolerance level beyond the 20% to >40% over the nominal rated value. NiMH batteries when fully charged are closer to 1.5V per cell, which would mean you could be starting with ~2.9V.

You have a wiring diagram of the Aiwa Walkman where we can Examine the question? Usually, not Considering the circuit inserted into the socket for the AAA batteries, the input circuit of a Walkman, has transistors or ICs That Provide a filter for the excess voltage. If not (but this would be another proof of the inferiority of the project of the Aiwa Walkman compared than Sony Walkman ) you can insert a diode in series.

See page 2 for a circuit diagram.

index.php?board_oid=193392314111653483&content_oid=193392314111874066

The design used by AIWA was to have voltage regulation done externally. It is very apparent in all their models that have the AC power supply input on the battery box. This would free up space on the main board and allow for a more compact design. Such models are JX505, PX505, JX707 and so on.

It would not apply to models such as PX101, PC202 or PX410 as the AC power supply input is on the main board and all voltage regulation is done on the main board.

A small SMD stabilizer does not occupy space. However, I observed a 505 circuit. In fact, some 2 volts go directly to IC. I believe, however, that there not are big problems. At full load we would have about 2.8 volts compared with about 2.2 volts of lead-acid battery. With a diode in series with the positive solves the problem.

True, a basic SMD voltage regulator does not occupy much space, but add a few supporting components and soon precious space begins to decrease. However if there is an opportunity to off-load those components elsewhere if they are not always used (ie battery box) then it makes sense to do so which is probably what the AIWA design engineers had in mind.

Personally I would have liked the voltage regulator and AC power input on the main board for a lot of these AIWA models, as when it comes to testing them I must have to keep attaching and detaching the battery box which after a while can be tiresome.

A handful of resistors and capacitors smd would come without many problems. I know much better than the Sony Walkman. I have repaired many Aiwa (especially mechanical problems or capacitors), but only recently I am working on all their problems. I had also decided to use 2 batteries as Kerni99, but I thought to another system. I must say that I really like Kerni99 system. You just need to insert a diode in series and build a constant current charger. This way you can leave your batteries in the Walkman.

The idea by the OP is not an original one and dates back to June 2008 by someone in China called cg8858.

http://www.jd-bbs.com/thread-1644473-2-1.html

If used in non-valued AIWA units it is a partial solution, but it is by no means the ultimate flexible solution. Certainly not the first choice solution for rare or valuable models. It would also require additional components to be added to the unit if there was fear of damage due to over voltage from freshly charged batteries.

The ultimate flexible solution would be to use two NiMH batteries that are slightly shorter than a PB-S5 and build the voltage stabilsation circuitry inside a hollowed out PB-S5. With SMD components should be able to fit in the space. The NiMH batteries would be removeable and be independently rechargeable and the re-fashioned PB-S5 battery be interchangeable with any AIWA model using PB-S5 batteries without any need of additional modification. This idea could even be extended then to a PB-3/4 battery too.

This is a project I have in mind for the future, but I do not have the time to spend to execute such a project at the moment especially given the contents of a lead acid battery and its safe disposal.

No need to build a new charger. There are chargers available on the market to charge prismatic NiMH batteries. Using the original AIWA battery charger/cradle charger would not be wise as it was originally designed to charge lead acid batteries. They have a different charging profile from NiMH.

My idea is to insert a constant current generator, using an LM-317, within the charging station that accompanies the models such as the JX-2000, instead of the original circuit. We can calculate exited again so that the charging is done in 15 hours, without overheating and a long battery life.
For use: I can assure you simply insert a diode in series with the positive power smd averts any problems. There is no need for anything else. It is actually a simple problem.

I look forward to photographs of your worked solution.

Wow, what a big discussion started here. By the way, I mentioned above, that the original idea came from a chinese poster and I only modified it.

Now I have a new idea and it's completely my own

After that I found a quite easy solution to replace an Aiwa PB-S5 battery, I thought about a battery replacement for my older Aiwa Walkmans. They use the bigger PB-3 battery with different construction.

This battery has its contacts small and countersunk on front side and additional on upper side. As the PB-3 battery is bigger then PB-S5, I used again the Sanyo batteries and invented an adapter. In total this solution has the same size as PB-3 and the same contact options. Some Walkmans use front side contacts and some the upper side contacts.

The adapter is made of a thin (or thin polished) perforated PCB with conductive paths and some pieces of copper plate, which I soldered to PCB:

Firstly in use with HS-PC202 MkIII, which needs the upper side contacts:

And then in use with HS-JX303, whichs needs the front side contacts:

For that I needed to add some insulation tape to avoid short circuit.

The adapter is not that nice, but it works like a charm with both Walkmans.

So - please feel free to rebuild this solution (with shapelier appearance).

In next step I will try to connect a diode in series for the PB-S5 solution. I know, that a standard silicon diode has a voltage drop of around 0.7V. Is this not to much (2.4V - 0.7V = 1.7V)?

And do I need a diode for PB-3 Aiwa's or is it not necessary as they have the voltage regulation built in?

Best regards

kerni99

That is a very good mod for a PB3 Love it

With this design, it should be easy enough to incorporate a voltage regulator for the PB4 contacts for most models that do not have internal voltage regulation.

As you've already realised, for your PC202 you should not need a voltage regulator for your mod. It is only those AIWA without the AC power input built-in which will require a voltage regulator to be 100% safe.

Regarding the PB3, a minor point is to note that in its current configuration you should not plug the AC adapter into the PC202 at the same time as you use this mod. I notice that the two copper traces are the same length. This is because on the PC202 there are 2 pins next to each other. One is to input power from the battery, but the other pin is used to output power back into the lead acid battery. Not sure how well the NiMH batteries would react to having voltage pushed back to them like this.

Assuming you have the AAA battery holder, then referring to that should help you select the correct length and orientation for that contact which will avoid accidental charging of the NiMH if you use a AC adapter too.

Parkashan, exactly, you can also select the diode voltage drop, to select the most suitable. Taking advantage of manufacturing tolerances.

If you were making a custom battery setup with a voltage regulator couldn't you use a 1-cell LiPo battery? I've seen some very tiny ones for RC planes.

Hello Kerni99, with respect to the tape, I venture to suggest:
to unite and isolate the two batteries and your adapter, use heat-shrink sheath. If you do it carefully you will get a good result. You can also insert a diode in series with SMD battery or inside the Walkman. In this way you will not have problems. Then you just get a charger with constant current, preferably adjusted to a slow charge. When even I will address this work, I will pictures of everything.
Hello Teamstress, the system is not very good with lithium batteries. Their greater ability and their smaller footprint, are outweighed by the trouble of plugging in a step-down transformer (from about 4.2 volts to about 2.2 volts, there is a difference of 2 volts less than the drop-out should be at least 3 volts, also its bulk would be problematic) and also from the charging system, because more complex pulse, otherwise the battery may explode.

Hello dottor walkman, thanks for your suggestion, I will try it.

At the moment I would like to built a charging station for my JX707, so that I do not need to change the internal batteries every time. Checking with a multimeter the external battery box I would say, I need to apply at the Walkman the plus pole to contact #3 and minus pole to #2 (see picture). I want to use for charging my universal charger for NiMH batteries (with an adapter for the Walkman).

One question, is the charging circuit for the Walkman built into the player itself or also into the external battery box? If it is built into the external battery box, it should be possible to apply the universal charger direct to the Walkman's battery contacts. If the charging circuit is in the player, this probably will not be possible?

Another question. If I use a diode to decrease the battery voltage, is it then not in blocking direction, when I apply an external charger?

Consulting the owner's manual for the JX707, it states that there are two ways to charge the sealed lead acid battery. 1) via the external battery charger. 2) via the battery when an AC adapter is used.

Are you suggesting to use the original AIWA battery charger modified (original circuitry removed) with a means to connect to a universal NiMH charger? This would be a good way to charge it. The universal charger would then manage correct charging of the battery with the appropriate charging profile for NiMH chemistry (constant current), with a by pass for the diode.

If in the second case to perform in unit charging would be harder to incorporate a by-pass for the diode also it would be using the charging profile for lead acid batteries (constant voltage) which would not be favorable.

Hello Kerni99,
within the jx-707 is an exact point where to place the diode smd. In this way, the diode acts only on the power of Walkman, without interfering with the charging of the battery.
We must disconnect the point where the parallel flow into the battery positive terminal, pin 3 and the capacitors C148. Here is welded to the negative terminal of the diode SMD. The positive terminal of the diode SMD (indicated by a band) to be solder on the point, in parallel to the confluence of Q 34, R130, the positive D6 and D7, etc..
A description may seem complex, but it is not. However, as soon as possible, I can I take a picture of the inside of JX-707 and show you where to place the diode.

Hello parkashan,
we not must consider the number of batteries in series. Any charger with constant current, measured in a vacuum, can also have an output voltage very high (even higher than 12 volts). When it connects to the rechargeable battery, the voltage drops to the value of rechargeable batteries that are connected. What is important is the charge current to be one-tenth of the battery capacity. In this way, the recharging takes about 15 hours, and is not harmful to the batteries. While charging, you can continue to use the Walkman. It is fed by the voltage of the batteries that act as regulator and voltage stabilizer. By inserting the diode (to reduce the excess voltage of the batteries on the Walkman) into point that is downstream of the charge (this applies to all the Aiwa Walkman, which have the stabilization circuit in the battery holder outside) all types of power (batteries rechargeable batteries, AAA alkaline battery and external power supply) will have to pass through the diode to power the Walkman.
So you have everything you need to complete:
1 - Make the change as shown to kerni99.
2 - If you have a charging station, build a circuit with constant current charging and insert in the charging station, instead of the old circuit for lead acid batteries.
3 - Modify the circuit regulator and voltage stabilizer (in the external AAA battery case) to compensate for the voltage reduction effected by the diode and be able to recharge the new batteries, if you want to use the external power supply. In this way we can continue to use the AAA batteries and the original power supply, as before the insertion of the diode.
4 - At this point, if the voltage, of the original power supply, becomes too low, you can also change it or replace it with a slightly higher with the voltage. Also to compensate for the presence of the diode and recharger the new type of battery.
IMPORTANT:
If now we measure the output voltage of the charging station, it is approximately 2.6 volts. If we include the Walkman in it without the battery pack, do not cause damage. After entering the circuit with constant current to recharge the battery NI-CD and H-NM, its output voltage will be higher (it measured no-load, must be much higher than 2.8 volts, otherwise it will not charge batteries of Kerni99). So we should never put the Walkman in the charging station without the batteries, otherwise we risk burning the Walkman.

Hi dottor walkman, I would very appreciate to have a picture where to place the diode. Maybe also the exact type which you used.

Regarding the charging station I want to use the external battery box only as a mechanical base. For that I have a spare box. Especially I want to use the spring contacts of the box. That means the voltage regulation circuit of the box will be bypassed.

I will check, whether my universal charger will charge two batteries in series.

Hello parkashan,
- As regards the end of charge after 15 hours.
With the slow charge, do not need to be very precise. That is why the slow charge is best. It is very delicate. However, I use a timer that disconnects the 220 volts after 15 hours. This is the easiest and most secure.
- As regards your question 3. How I told my 3 and 4, we must make changes on both the stabilizer inside the external battery case, both the original power supply. Depends on what one prefers to do. For example, you could totally eliminate the original circuit inside the battery holder and use two external power supplies.
The first: a regulated power supply to 2.5 volts. It would provide exactly 2 volts stabilized downstream of the diode.
The second: if you do not have a charging station, a constant current generator that should be used only with the batteries inserted into the walkman. It also serves as a power supply while charging the batteries. If you are afraid to keep it connected over 15 hours, you can use a timer.
Hello Kerni99, yes, you're on the right track. If your charger does not work well, you should build one. I have many personal stereo to be repaired, but I promise that as soon as I have a little time, I'll open a jx-707 and I'll do the pictures to show you where to place the diode and what type.

Did you try to back to life original battery? Lead -acid a specific and dont like a full disharge as Ni-Mh accums. I red a lot of literature about lead-acid batteries without liquid electrolite (this type used in Aiwa, sorry i could not translate it correctly in english)/ If somebody read russiuan i will send links to articles. 

Briefly:

Do not try to charge old battery directly in the Aiwa device. It will destroy battery 100%. Too many gas H2 will be emmissed and safety (??? do not know english word) will be opened. 

There are two ways to restore battery from bad condition:

1) Charge by special impulce current. Positive impulse with 2,2V  with special fronts of impulse and negative impulses with low voltage. Required to develope spesial charging device. In the internet there are Diagrams for 12V batteries but I did not find for 2V small batteries. If somebody want to create special charging device - write me exchanger@inbox.ru I will give you additional info

2) Charge by 0,1-0,05 current. For example, for PB-5S with 600mAhg capacity charge by 30 mA in 20 Hours. Then make a breake in 20 hours and measure voltage.  Less then 1,8 - charge again by same current. 2V and more - charge in Aiva playr as usual. This method prevent emission of H2 gas and solve sulfates (? english word?) in the battery.

How to charge? A lot of diagrams in internet for power adapters with stabilized current (not stabilized voltage!) LM317 for example could be used.

I have a new PB-4S new but produced in 121995 . It could be used for my JX-707 and I will try to restory it soon. Now the voltage is 0,125V - so looks fully died. Viktor

0.125V although a reasonably high voltage is probably still too low to try and resurrect with normal methods.

I recently received two old PB-4 batteries through some walkmans I acquired. One was temporarily flat at 1.8V and was simply recharged back to nominal working voltage of 2.2V. The second one had a voltage of 1.0V it was left to charge overnight in the standard AIWA desk stand charger in a PL505 and has since recovered back to 2.2V as well.

Lead acid batteries can reverse polarity if they become too discharged. I have one PB-4 with reversed polarity of 0.01V.

I have yet to find a good PB-S5 in the wild and I have quite a few.

Well it seems the link to the battery is now broken. Anyone have any idea where else I could get these?

Knowing how highly you rate your PX610, if I were you I wouldn't bother with the mod from within post #1. The reasons for not doing so have all been discussed at length above and in other similar AIWA lead acid battery posts.

Here is the current link, batteries are still available:

http://www.aaaa-electronic.de/products.php?SANYO-Akku-Ni-MH-Prismatische-Z-1-2V-600mAh-2-Stueck-&cPath=22&osCsid=aqu2medvg88n0uhqltlk4oiu74

Thanks for the update! I thought the entire store has been shut down because both links I tried redirected me to the host's default ad page. Bit weird...

By the way, I don't rate my unit particularly highly, I guess wording in the past has suggested that unfortunately. The amp has just died in it (transport still works though, strangely). The only thing I do like about it is the look and feel of the metal chassis.

The DC coupling capacitors have probably dried out, giving the impression that the amp is dead.

I posted my solution in 2011. Meanwhile we have 2014 and I still use it that way. None of my highly rated AIWA's had a problem with it. It works.

Well I haven't touched the PX610 since I got a replacement model that uses the older transport and has mechanical controls, and should be easier to repair if I get into cassettes again. It probably uses a different battery model though so I'll stick with standard cells for now.

Hi everyone, I too have had this issue with some aiwa players, I have used the 2 ni-mh mini cells and all is well, but I take the point about wear & tear, and so I got to thinking if I used a mini step up voltage regulator powered by 1 of these mini cells it could produce the 2 volts needed for the player, its just an idea but I had not read anyone else suggesting it, so more food for thought then! one thing I would be mindfull of with such a system/ device is generated noise, now chances are it would be well above audible range but it could modulate within the amp or cause splurious signals within the logic ic circuits, so it's just an idea but would need testing, but if all proved well 1 of the ni-mh cells has a 500 mA capacity, which is well in excess of the original lead acid aiwa cell, any thoughts

I have been searching eBay for months to see if anybody sell the appropriate battery for Aiwa PB-S5 and so far no luck.

anybody has any update ?