The introduction

The JX707 as we all know has a standard shaped amorphous head. As a top end player, it really ought to have been equipped with AIWA's hyperbolic shaped HX head. Anyway I had a brainstorm. How about putting in a HX head. Follow me on this journey of converting a regular JX707 to one with the HX head.

Okay this is highly experimental and is a proof of concept to myself that it is achievable with my limited technical skills and tools. I don't really recommend that anyone does this modification. This isn't meant to be a guided walkthrough or shining endorsement. Not that I would prevent you from doing so. Just saying so to keep the lawyers off my back if someone copies and screws up.

The back story

I was fed up with how badly one of my JX707s sounded compared to a few others (I know I have too much time and JX707s to think this). So I got the magnifying glass out and closely examine the head on the crap sounding JX707.

On close inspection it is clear to see that there is wear on one side of the head. There was me thinking amorphous heads were extremely hard wearing. Guess not, there was the proof. To dispel any probability that I was playing back a recording I made a recording on the JX707 and played it back. Ugh - Just as bad. Dull and totally void in any treble. Worn heads it is then.

Worn patch to the left of centre from the JX707

Nice shiny uniform head from a JX929

The walkman that just keeps giving

So I knew I needed a replacement head, but from where? Most of the 0ZM-4 based AIWAs I knew were just standard head units. But then I stumbled upon the PX610. This unassuming walkman seems to have been cobbled together by someone from AIWA with

bits from the spares bin. It even sports a narrow gap HX head. Not that you'd ever guess because AIWA forget to mention this anywhere. But if you look at the picture below you can clearly see it.

I picked one up for an extremely reasonable 100 Japanese Yen (less than 1GBP). Others seem to go from 200 to 400 Yen. I suppose no one wants them. But why not? They are full of parts for repairing more worthier walkmans such as the JX70 series and PX1000. Parts such as the solenoid (the one that melts like butter), the hinge that often breaks, pinch rollers, cogs etc. Even the battery box can be used for the JX70 series and PX1000. At no more than 400 Yen a bargain to raid for parts!

When you open it up, the first thing that greets you is the part number on the PC board - HS-PL77. Another useful spare part. Truly a walkman that just keeps on giving.

Heads off

Okay down to business. I desolder the flexible PCB attached to the heads from the main PC board on the PX610 and I repeat the process on the JX707 as well. This then allows the removal of the entire head assembly block on the units.

On close inspection, the PX610 connector has 5 traces and the JX707 has 6 traces. This is a slight issue.This was not the only issue. At this point, a major decision had to be made which ultimately would affect the overall success of this modification. Do I do a full head strip down and replace or just swap over the head assemblies? I opt for the latter. Some of you may think I am cheating here. But there was one major hurdle preventing me from performing the former. The PX610 head is fitted onto the head assembly using regular cross head screws, and easy to remove. However the JX707 because of it's magnets for tape erasure has custom shaped bolts. I did not have the tool required to remove the bolts from the head assembly. This is why I opted for the latter approach of swapping the entire head assembly. I reasoned also that I was unlikely to ever record from the JX707 following this mod (that's what I have a D6C for) so not having the magnetic heads was not going to be an issue. The purists here may all be waving your arms and tutting in disgust, but I have plenty of JX707 that I intend to keep in default configuration to keep you happy. This is an experimental project afterall. Who knows one day I might even figure out a way of removing those custom bolts from the head assembly and revisit this mod.

HX head attachment

Back to the flexible PCB (or ribbon). Checking the pinouts and the ribbon layout there is a mismatch here too. The sixth connection is not really required on the JX707, so we are now down to five connections. However they are ordered differently. Nothing a bit of conformal from a solder mask pen and a rewire won't fix.

I mask off pin one and one half of pin four with the conformal on the head connection traces on the JX707. I also mask off a corner from contact two and contact five on the ribbon. Ignoring contact one for the moment, I solder contacts two to five on the ribbon to contacts two, three, five and six respectively. I then with a very fine enameled wire jumper contact one on the ribbon to the exposed top half of contact four on the main board. I test the solder joints with a continuity meter to ensure that there are no shorts through the conformal or across any of the contacts.

Reassemble and test

The JX707 was then reassembled and tested.

The first thing I hear is an abundance of treble and perfect tracking. The JX707 has been given a new lease of life with this new head. Comparing it with the JX929 and there is probably slightly more mid range from the JX929, but the JX707 has very good treble and equally good bass. With BBE activated the JX707 is very bright and clear. DSL, well I am biased against using DSL on the JX707 but it is bassy nonetheless.

This was a worthy but very difficult modification, but not without improvement. The magnetic erasers could have been added. May be it would revisited in a future post.

A creative experiment! I have several Aiwas with that head but never mention that it is a HX/Amorphous head anywhere either. Parts Bin raid! I don't really care for recording on any walkman except a D6C either.

How many JX707s do you have? And between your new "HX" 707 and your other 707 variants, which one sounds the best?

Hi bub,

A rough count suggests that I have over half a dozen from the JX70 series. A few of them are non-working. However with the aid of the PX610, I should be able to get at least one and be a step closer to getting another working too. The rest either work or have some issues with the tape transport.

I'd say it is a very even tie between the JX929 and the modified HX JX707. I like the mids the JX929 gives, but the modded JX707 has spades full of treble. So ultimately it would depend on my mood and the type of music I'd want to listen to.

Before you rush off and tear all your AIWAs apart for a parts raid, be sure the one you are selecting is based on the same tape transport as the JX707. It makes trying to shoe horn the HX head in heck of a lot easier.

Great subject as usual Plop! I have a PX610 coming up soon but I won't be suing it for parts since it is basically NIB. Sadly, there is no BBE but I think it's a sleeper and potentially a very good sounding player. It is interesting that it has an HX head. It cost 80GPB back in the 1992 while the PX1000 cost 200GPB.

Excellent work Plop as always

A rough count suggests that I have over half a dozen from the JX70 series.

This reminds me of myself and the G08 which I Have to buy them all when i see them listed anywhere.

why won't you buy working units instead of just repairing them?

When I get a working one I sell a broken one. I think it's just easier that way.

keep up the good work

Cheers,

TheLion

@TheLion

I actually own a JX707 from new all the way back since 1992 when they first came out. I used that walkman practically every day I owned it, until that fateful day... Sadly the flexible circuit board split across the door hinge from too much use and it was impossible to control the unit anymore. Also the hinge got broke when it got knocked about in my college bag. So you could say I did once buy a working one brand new in the box!

Barely decent condition AIWA JX707 very rarely come up for sale. When they do, they are always sought after. Sometimes you just have to grab what you can. Virtually all of them I have bought have had mushy belts. Some I bought have had attempts to carry out a belt replacement and the person doing the repair ended up damaging the delicate parts inside. Some seller's descriptions are dubious to say the least, and of course they usually use the old excuse - "no battery therefore not tested", so you have to take a chance and bid with a low price.

Anyway I have enough JX707s (and scrap units) now to keep me going for a while. Maybe when I have most of them all fixed, I will put a couple of them back on the market for sale fully restored and serviced with new capacitors, belt, and memory battery. It would be interesting to see if in that condition what price they fetch then.

Dear friend - BOUGHT BELTS that were previously 'ORIGINAIS''MAS NOT THE SAME RAN VERY WELL .... OR SKATING OR NOT HAVE POWER TO REWIND ..... CAN BE ANY ELECTRICAL PROBLEM? I have 02 AIWAS THAT HAVE THAT SAME PROBLEM: JX810 and JX707 - WAIT HELP. THANK YOU

Sounds like your original belts may be too old now and are hard and/or glazed and they are slipping on the pulleys. I don't think it would be an electrical problem, since you have the issue on two different units. I would suspect the belt as the issue. See if you can purchase new belts (actually manufactured in the last 2 years) and see if that helps. If the belts you purchased were actually manufactured more than a few years ago, they may not work well as you are finding out.

Xenawise