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When you do highly processional work, by 99% chances are that success this is on the way.  ;)
By this post reply, my new recorded log entry this is that at 14 December 2017  my AIWA AW-DX 888 this is restored to factory condition regarding electrical motors.

I did also install new belts, but I am not 100% satisfied, Belt Circumference this is correct but thickness this is only 0.6mm and they are only 4mm wide.
While this machine it is now functional, I will keep looking to find better belts.

AIWA AW-DX 888 this hides one secret, when A or B  cassette deck this is in use, both DC motors of both mechanism they do spinning.     
When non of both mechanism are in actual use, both motors are stopped too, and this translates that both belts (A & B ) they would have identical run-time no matter of actual number of cassettes these played at its one port. 

I am now a bit sentimentally charged  :)  many memories has awaken from the past.
Originally this tape deck were purchased from me as bright new (at price extreme for my wallet back then) , so this to serve at my highest quality hobby studio and this was serving for FM radio broadcast.
Back then there was a local race of whom will deliver best possible sound quality ON AIR.
No more than few months later, CD disk revolution started and specific AIWA AW-DX 888 was not having a heavy work load.
Condition of most parts in it, they seem having run for 1/3 of expected life-cycle (heads, rollers, etc).
Therefore this restoration it did helped one winner model of the past this to stay in activity.
I bet that engineers worked in AIWA, they also take pride by reading such information's over the WEB in our times.

Back then I did skip getting an AIWA AW-DX 999 because I did not care for remote control, and brother model AIWA AW-DX 888 this never ever disappointed me.
One last word of my about DC electric motors, some people in their desperation they spent money getting Mabuchi Motor, well Mabuchi brand at 80s - 90s was Low-end brand, most cheap Hi-Fi and boombox cassette players and even car cassette players, was coming with Mabuchi Motor as standard.
Their DC motors life-cycle was limited to 2~4 years, and personally I have replace many at my repairs shop.

AIWA , SONY and YAMAHA & Panasonic they was a totally higher class of such equipment, with legendary Nakamichi to be famous but a dream for most of us, and AIWA to be a branding that were closest behind Nakamichi, than all other brands.
Therefore in our times, it is worth trying to properly maintenance such quality-made DC motors, because they where made with out planed obsolesce in mind.  ;)       
MMI-6H2LWCI inside world !!!    :)
In favor of all times and in order to help technically trained owners of AIWA (japan) AIWA AW-DX 888  & AIWA AW-DX 999 ( Both for professional use Tape-Deck equipment), I am posting these pictures bellow.

MMI-6H2LWCI or similar MMI-6H2LW they do have identical construction.
When such a DC motor starts making motor squeal sound this translates to lots of metallic particles in to both copper bushings.

For such motors there is no quick-fix, motor construction this is close to airtight and dust-proof.

For reliable maintenance it is required complete disassembly.
Both copper bushings should have a bath with WD40 (for several seconds - minutes).
Motor axle cleaning , motor brush cleaning, should be made with fiber glass pencil & corroded contact terminals
New lubrication with Grease, this must be placed from inside to outside at both copper bushings.

If maintenance become with 100% focus on what you are doing and quality work, then motor axle surface will heal (up to a point) after this working for an hour.
MMI-6H2LWCI motor operation will restores to 100% and sound of motor this will restore to normal.

Other details ..........
AIWA AW-DX 888 and similar, they requiring belts of 5mm width and 1mm thickness (original SONY-AIWA belt).
Mechanical issues ( mechanism blockage when selecting PLAY at reverse direction) these could be due dry ed lubrication over plastic sprockets, and also due incompatible belt dimensions.
If you are unable to find the issue, then by pressing rewind button momentarily, the mechanism it does return to synchronization, and reverse side PLAY this will operate.

Yes original SONY-AIWA belt this is not available anywhere ( AIWA this is no more, and SONY does not produce such parts).
Belt inner diameter: 690 mm  ( 6,9 Centimeter) 
Belt Circumference : 216.77
Flat belt thickness: 1mm
Flat belt width:  5mm    (AIWA part 3-9: Flip Disk assy ( black roller) inner wall width this is 5.8mm )
Belt length (side to side when this is positioned flat-down) 108 ~109 mm
(Belt life-cycle 12 years)

At my AIWA AW-DX 888 both motors started making squeal sounds, in the beginning I started suspecting plastic sprockets, but this is a FALSE impression.
I got my AIWA AW-DX 888 when this was best seller product  at 90s ...  this up to date it counts 27 years of life,  and I am now assuming that after such reliable DC motor maintenance, I am going to enjoy it for another 15 years or so.  ;)

If you get helped by this information, then feel free to donate 10€ at my Blog due PayPal donation Links.

At 2012 I did test such mini solar panels (single unit) at 6V application  Mini project by Kiriakos : Solar powered Agilent U1272A & U1273A and I was aware of what to expect.

This time I did one step forwards by making a theoretical  24V configuration ( 23,600 DCV open voltage).
Today I did confirm for another one time that specific modules peak current this is 60mA.

While entire circuit of solar panel this it did deliver max of it potential, my project about charging the motorcycle battery this failed because minimum required current for this task this must be over 200mA.

Solar panel permanent installation over such type of motorcycle this is BIG challenge because of limited space.
After my last experience today, I am now aware of such concept limitations, and that one 15x9 centimeter (solar surface ) this can not produce usable results as charger of  7Ah 12V battery.

Bellow there is some pictures of my tests,  and test results this is a good souvenir for me,   and one reminder for you about spending more into such projects if you expect usable results.  :) 
This time I did a new discovery,  partially damaged DPDT miniature horizontal button, this could cause issue at ammeter this not functioning at low current.

While I did proceed with cleaning and temporarily restoration, I did find new buttons (this was not easy) and I will order them and replace then in a later time.  ;)

Because of this opportunity about taking apart my power supply, I took several pictures from internals.
This is a huge opportunity so especially young people to see how a true quality build PSU this looks like.
Even me as an expert I did get further impressed by looking details at my pictures.
Entire number of components they are of supreme specifications, internal capacitors inspection shown no damage even after two decades.
Pin headers look silver plated, and there is no corrosion over the PCB or over components.
I got this PSU as used at 1997 and all these years I was unaware that this PSU it got wet due possibly an accident.
Bottom plate was having signs of rust which I did clean and remove due this opportunity of taking it apart.  :)
Beginning of 2018 it is scheduled one small upgrade  for my Ansmann Energy 16 charger  :)

I am going to replace entire amount of these ( Red -Green ) LED, mostly because over the years their luminosity it is degraded.
Green LED color this has higher number of hours in usage due to trickle charge mode.
Additionally not entire number of charging channels has equal hours of operation, and some LED they now fade more than others.

Therefore soon I am going to have a fresh opportunity, so this freshly reconditioned charger, to also look as NEW !!!  ;)
This is another update relative to charging potentials.
Over time I did manage to get a special cable this is just 35cm long USB to micro USB 3.0,  this is high power cable that came accidentally when I shopped for one USB 3.0 real hub, and this cable came with it.

While I have build my own gadget of Volts/Ampere meter (USB charging monitor), and because my older USB capacity tester this had an accident (display smashed),  I did recently purchased the very fresh UNI-T UT658 USB capacity tester.
My new benchmarks this is another one confirmation of everything that I wrote so far.

Naturally when such capacity tester this is plugged directly to the charger and the charging cable this is powerful and sort, what you get this is highest possible voltage and current that phone circuit this can tolerate due minimal electrical losses at power transfer.       

New UNI-T UT658 USB capacity tester within 2017 Mini Review
Finally after 30 Days of waiting  :)  I did manage to double the quantity of these solar panels.

Theoretically  I am having here 4x panels of 5.5V at 60mA ( or also listed as 6.8V 90mA).
I did some testing but I had cloudy weather all day long, and I could not get even 3% of output.

Originally I thought to get just another one panel, but last minute decision was to get two instead so to gain more flexibility and to avoid disappointment.
Either way in few hours I will be able to test my new solar panel, and I will discover it limits.  ;)
Today I can confirm my suspicion (conspiracy theory)   :P ,  that UNI-T UT658 it can steal 100mAh from capacity total value, if you do disrupt charging when Ampere value this seems to be 0.00A .

In my case I did benchmark 2800mAh battery, if I was not a good observer and by me insisting to leave overnight the phone connected to the charger,  I would have 100mAh less.
Older generation of mobile phones these using 650 ~ 800 mAh Lithium cells,  at such lower capacity 100 mAh lesser this is an significant number.

Final thoughts ... 
According to UNI-T specifications,  voltage measurement this can introduce 1% Error,  additionally and current measurement this can introduce another 1% of Error.
Therefore in capacity measurement combined error this can be as 2%.
Sum of capacity measured after full charge and overnight (balancing period ) this is 2179 mAh, by now calculating  Plus/Minus  2% Error real capacity could be :
Lower end=  2.136 mAh
Higher end=  2.222 mAh

And here we have again roughly 95 mAh difference at  again roughly 2200 mAh total.
And now I can safely assume that introduced error to 1000mAh cell this would be 50 mAh,  and also error at 650 mAh capacity this could be 30 mAh. 
Now, in case that under benchmark there is a power bank of 4.400 mAh or 5000 mAh, then you may expect an estimate of 200 mAh (Plus/Minus) as theoretical measuring error.

Product behavior & volts accuracy tests made by ITTSB Blog.
Believing it or not ..  UNI-T UT658 this is not an  Plug&Play meter.
When I did connect UT658 directly to laboratory power supply and compared input voltage with a 50.000 counts multimeter, UNI-T UT658 this was measuring half volt less when this tested at 3~9V DC.

UNI-T UT658 started measuring correctly DC Volts after this be powered for 10~15 minutes (warm-up period).

I did record input voltage - measured voltage &  Milli-ampere which UT658 this required from DC power supply. 

Input DCV  .......  measured DCV ......... mA

9,005  .......  9,02  ......  6.5 mA   =  DCV - Accuracy Error approximately +0,3% 
8,002  .......  8,02  ......  6.4 mA
7,003  .......  7,01  ......  6.2 mA
6,008  .......  6,02  ......  6.0 mA   
5,009  .......  5,01  ......  5.7 mA  =  DCV - Accuracy Error approximately +0,3%
4,008  .......  4.00  ......  5.5 mA
3,004  .......  3,00  ......  4.0 mA  =  DCV - Accuracy Error approximately -0,3%

Input DCA .......  measured DCA

1,009 A     ....... 1.00 A =  DCA - Accuracy Error cannot be calculated due limited LCD display resolution
2,006 A     ....... 2.03 A  =  DCA - Accuracy Error approximately +1,5%

According my measurements I can now estimate total of +1.8%  Error in the measurement of mAh (capacity measured) by my very own UNI-T UT658. 
Voltage measurements was taken by BRYMEN BM869 and Current measurements was taken by U1272A HH multimeter. 

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