Test Jigs

[M1JWR]

I have now made up a test jig, so far only for mdm 5's (pictured), the one for the 7's will probably take a little longer, i would have to probably construct it a little different to ngy's example, however it dosent seem very clear, to me anyway, how to set it up in the service manual, dont get me wrong its all there in great detail, as per the 930 thread and as i dont have a lpm all i am looking for is info on the actual iop on the robbed ex 520 laser and the health of the laser, so the future is bright, i dont really know what info that would appear on the multimeter and what to set it at, ive got a 520 down here just now to act as a test bed, its got the correct drive unit inside and is working as it should, i think it should be a different thread as it affects a variety of models. will have to have a ratch around as i only have standard multi meter probes.

[kgallen]

Looks good! That's all you need!

I must make one too some day...!

[NGY]

Nice job, congratulations. You will see it is going to be a very useful tool.

I would write on it which pin is for what, with a permanent pen. This will help you later to quickly and properly hook up your DMM.

On 10/17/2020 at 6:28 PM, M1JWR said:

i dont really know what info that would appear on the multimeter and what to set it at

You set your DMM to "mV", the range is 100 mV  (maybe 200 mV or something close, depending on your meter). Then you hook up the DMM like this (section 5-6-2 in the 520 SM): positive lead to pin 5 (="I+3V") and negative lead to pin 4 (="IOP"). When you get to “LDPWR CHECK” in service mode, you can read the actual IOP values in mA. There you go.

 

Edit: I use these cheap test hooks off ebay (for example). These fit on the standard 2mm pin DMM probes.

 

Edit 2: I just realised these linked and pictured are for soldering onto wires. But you get the idea - I will try to find another link though, for the fit-on type.

Edit 3: OK, I can't see one now, but anyhow, these ready-made hook leads are sold for peanuts too:

[NGY]

1 minute ago, kgallen said:

I must make one too some day...!

Khmmm... I thought you already had one ... ;-)

[M1JWR]

kevin, you will get a packet of pins for about 3 quid inc post, you will recieve 100 pins, the boards as its a pack of 5 ( i cut one in half) are about the same and the 6 pin connectors, again you will get 5 sets are again about 3 quid, all easily found on fleabay, as for the test hooks, now ive seen those before, dont remember if i got any with the meter originally, if not i now know where i can get them from, as for the pin outs, ive written them on a small piece of paper, red wire is rf etc and sellotaped it to the top side of the board, the black tape is for the live joints on the underside.

[M1JWR]

i have now ordered the test clips and await their arrival, meanwhile i just looked through some of these decks service menu's to see what they say at the moment, and some examples are as follows.dosent include the 930 thats currently in the "box", all below have their own correct drive units apart from 5507017 which was taken from a 520 some time ago.dont know if it tells anybody anything, i just looked for reference

jb930 serial number 604153, iop read 58.5 / 58.4, ld read 0.9mw $11, record time 3hrs, play time 7 hrs

jb930 serial number 602724, iop read 55.1 / 54.3, ld read 0.9mw $11, record time 10hrs play time 106hrs

jb920 serial number 5515468, iop read 55.6 / 56.1, ld read 0.9mw $10 record time 7hrs play time 431hrs

jb920 serial number 5507107, iop read 53.3 / 51.3, ld read 0.9mw $11 record time 1hr play time 58 hrs

[NGY]

28 minutes ago, M1JWR said:

jb930 serial number 604153, iop read 58.5 / 58.4, ld read 0.9mw $11, record time 3hrs, play time 7 hrs

jb930 serial number 602724, iop read 55.1 / 54.3, ld read 0.9mw $11, record time 10hrs play time 106hrs

jb920 serial number 5515468, iop read 55.6 / 56.1, ld read 0.9mw $10 record time 7hrs play time 431hrs

jb920 serial number 5507107, iop read 53.3 / 51.3, ld read 0.9mw $11 record time 1hr play time 58 hrs

Read laser powers all seem factory default. That's good news. Apart from the third one, others look fairly "new", hardly used. That's great news.

You may want to add the 7 mW settings ($XX) to this little table, then it will begin telling you some good pattern (for later use, w/o an LPM).

Now:  if you take your nice new jig and DMM and measure IOP values for the 7mW laser power (that's what matters anyhow, for estimating the laser's state) in LDPWR CHECK, you can compare the values you measured with the second IOP numbers above, respectively. When done, I can explain what conclusions you can draw from that data.

[M1JWR]

i will get back to you on that when i get the clips, never thought about the 7mw setting, however i can give you two as the other players are put away for the time being

jb930 s/n 602724 is 7mw $90

jb980 iop read 54.6 / 53.5, ld read 0.93mw $11, record time  24hrs / play time 166hrs, 7.25mw $90

its just as these two are the ones i use, so accessable, however also apart from 940 did some lesser models yesterday, again not 7mw settings though, if i dont put the play/ record hours on its because they are 1hr each so must have either lost memory or been reset at some point.

jb940 s/n 5503208 (not uk special) iop read 52.5 / 50.9, ld read 0.9mw $10

je 470 s/n 6606247 iop read 54.4 / 53.3 ld read 0.9mw $10

je 470 s/n 5516667 iop read 54.4 / 53.8 ld read 0.9mw $10

je 470 s/n 5502169 iop read 49.7/49.7 ld read 0.9mw $10

je 480 s/n 6682482 iop read 50.1 / 49.1, ld read 0.9mw $11 rec time 25mins/ play time 239hrs

je440 s/n 6601065 iop read 50.5 / 50.9, ld read 0.9mw $11 that had the bd board swap

je440 s/n 6602565 iop read 53.7 / 53.9 ld read 0.9mw $10

je520 s/n 6613980 iop read 53.5 / 54.1 ld read 0.9mw $11 rec time 8 hrs/ play time 945hrs

i havent got any more..... honest !!!

[NGY]

On 10/19/2020 at 11:09 PM, M1JWR said:

jb930 s/n 602724 is 7mw $90

jb980 iop read 54.6 / 53.5, ld read 0.93mw $11, record time  24hrs / play time 166hrs, 7.25mw $90

Both are factory defaults for the 7mW laser power. Good.

On 10/19/2020 at 11:09 PM, M1JWR said:

if i dont put the play/ record hours on its because they are 1hr each so must have either lost memory or been reset at some point

In fact, the x40 families (as well as other models that use the very same MDM-7 flavour, like the PC3 and the S50, and possibly others too) have a glitch in their firmware. The odometers will never begin counting (see more about this here). Too bad, because these very four are my machines I use the most on daily basis: 640, 940, PC3 and S50. I will never know, how far they got ... :-(

[M1JWR]

980 is also mdm 7 varient and it reads ok, must've changed it with the 80 series play/record

[NGY]

Indeed. It also already worked in the x70 decks, so they fixed it with the new generations coming out.

[M1JWR]

I have done some checks, i used the 520 first, as above its done quite a few hours 945, it came out as follows, 200mw range ld pwr check, on menu 0.9mw $11 came up as 96.8 on meter and 7mw came to around 46.5, it started a little less than that and rose slowly to that figure and began to steady.

this 930 is not on the above lists, s/n 602837, 0.9mw $11, 7mw $90, iop read is 51.8/ 55.8, 51.8 is what i put it at from when i had the 940's laser in to start with that diddent work out, total record 120hrs and play time is 1005hrs, dosent really pay relevence to the laser thats in it now i would think, possibly explains what was wrong with the original, not an expert on that.

the 0.9mw setting came out at 103.2 and the 7mw came out at around 76.2, it started at 72'ish and rose to that and slowed at the 76 area, quite different to the 520's readings, i can check another 930 if needed for comparison

[kgallen]

2 hours ago, M1JWR said:

I have done some checks, i used the 520 first, as above its done quite a few hours 945, it came out as follows, 200mw range ld pwr check, on menu 0.9mw $11 came up as 96.8 on meter and 7mw came to around 46.5, it started a little less than that and rose slowly to that figure and began to steady.

I'm not really comprehending these measurements :-(

So you're measuring Iop using a digital voltmeter attached to your jig board? The DVM is on a voltage mode (not on a current mode).

It's not clear to me from the SM how the DVM voltage reading relates to the actual Iop current. Page 37 does say the Iop in milli-amps is equal to the DVM voltage reading in milli-volts when measuring across 1 ohm. Well you're not going to put a 1 ohm load across the Iop terminals, that's a recipe for blowing up the driver chip. Maybe NGY knows how the setup works...

[kgallen]

Ah right I see...

Just looked at the schematics. So there is already a 1 ohm resistor in the circuit, R169 (1 ohm 1%) that is between the +3V terminal and Iop terminal of the jig board.

So yes, Iop (in mA) is equal to the DVM voltage reading (in mV).

Carry on Sergeant!!

[M1JWR]

i am taking it the higher the figure the healthier the laser, had a look at s/n 604153 its 7mw reading is 84.5, again started a bit lower than that and came up to settle at that figure, and as can be seen in a post above its very low milage !!!

you can test your 530 now kevin, bit of a pain getting the connector in, its in a awkward spot, you have to remove drive and tilt it so as you can get it in then put it back in place, getting it out again is easy though.

[kgallen]

Higher the number the more current is required to drive the laser to achieve the required light output. This is not a good thing. The higher current will likely result in more heating which is what degrades the lasers faster.

However there is manufacturing spread in characteristics (as with any manufactured object). This means some laser diodes will need more drive current from new. Similarly some will require less. However as the manufacturing process will be tightly controlled the current spreads seen across laser diodes (at new) should be relatively small.

Needing to increase the drive current as the laser ages is a downward slope to an expired laser. 

[NGY]

Can I make a few corrections/comments here:

10 hours ago, M1JWR said:

I have done some checks, i used the 520 first, as above its done quite a few hours 945, it came out as follows, 200mw range ld pwr check, on menu 0.9mw $11 came up as 96.8 on meter and 7mw came to around 46.5, it started a little less than that and rose slowly to that figure and began to steady.

this 930 is not on the above lists, s/n 602837, 0.9mw $11, 7mw $90, iop read is 51.8/ 55.8, 51.8 is what i put it at from when i had the 940's laser in to start with that diddent work out, total record 120hrs and play time is 1005hrs, dosent really pay relevence to the laser thats in it now i would think, possibly explains what was wrong with the original, not an expert on that.

the 0.9mw setting came out at 103.2 and the 7mw came out at around 76.2, it started at 72'ish and rose to that and slowed at the 76 area, quite different to the 520's readings, i can check another 930 if needed for comparison

- "200mw range ld pwr check" - I trust you meant 200 mV range on your multimeter, didn't you? mV = milli Volt, that is a unit of  voltage (voltage = electric potential difference), while mW = milli Watt is a unit of power (power = rate of energy transfer). In this case, none of them have anything to do with the OP laser power, that is related to (laser) light energy.

- "on menu 0.9mw $11 came up as 96.8" - this figure calls for some clarification from your side. Normally, the IOP of an MD laser diode in read mode (at 0.9mW) is around 18...20 mA, that should read on your multimeter as 18..20 mV. Your "96.8" is something massively different, and I cannot imagine, what it could be. Same for the 103.2 on the 930.

- "iop read is 51.8/ 55.8, 51.8 is what i put it at from when i had the 940's laser in to start with that diddent work out" - please get back to my posts here and here, for IOP values explanation. Especially to this sentence: "Ultimately, you can write ANY numbers there, it will NOT impact the behaviour of the laser AT ALL."

- "the 7mw came out at around 76.2, it started at 72'ish and rose to that and slowed at the 76 area" - yes, as the laser heats up, begins drifting. That's exactly why the SM explicitly states DO NOT stay in that mode for more than 15 seconds. Because you can hurt your laser diode big time. The 76.0 mA (if it's a true reading) is a very bad number when the nonimal IOP was 51.8 mA.

When I see such a big discrepancy (while the $XX values seem factory default) I normally do another check on the OP (that I won't detail right here and right now, until we conclude how to properly measure IOP and how to properly interpret that data), because it is a sign that the OP has already been tinkered by someone "incompetent".

 

3 hours ago, M1JWR said:

i am taking it the higher the figure the healthier the laser, had a look at s/n 604153 its 7mw reading is 84.5,

- "s/n 604153 its 7mw reading is 84.5" - what is the nominal IOP of that OP? What do we compare the measured value to?

- "i am taking it the higher the figure the healthier the laser" - please DON'T. Wrong way! Again, please see my posts linked above. And also Kevin's post:

3 hours ago, kgallen said:

Higher the number the more current is required to drive the laser to achieve the required light output. This is not a good thing. The higher current will likely result in more heating which is what degrades the lasers faster.

However there is manufacturing spread in characteristics (as with any manufactured object). This means some laser diodes will need more drive current from new. Similarly some will require less. However as the manufacturing process will be tightly controlled the current spreads seen across laser diodes (at new) should be relatively small.

Needing to increase the drive current as the laser ages is a downward slope to an expired laser. 

 

Let me summarize: a measured IOP value in itself is worth nothing. When you compare it with the nominal value for that given OP, then and only then you can make a conclusion. And that conlusion is this (as stated in the SM): if the difference between the two values is less than 10% of the nominal IOP value, or less than +/- 10 mA (whichever limit is reached first), your laser is working in the required  range.

This does not yet tell us, if the emitted laser (light) power is sufficient or not. That's when the LPM comes in. But even without an LPM we can tell if an OP has a C13 error or skips in recording/reading. Then we do the "educated guess" thingy I explained here. The good news is we can "play" with the laser power like that even without an LPM, as long as we continuously measure the IOP and make sure we do not step out of that safety range.

 

[M1JWR]

meter is uni-t ut58a set to where it says 200m just below where this one is actully pointing

 

[NGY]

17 minutes ago, M1JWR said:

meter is uni-t ut58a set to where it says 200m just below where this one is actully pointing

I get you. That's exactly the setting/range you need for measuring IOP on the jig.

[M1JWR]

would've been getting pretty close to the 15 second time when reading settled, bit strange those readings then, if thats the case, i dont understand why they are like they are, it could only mean that the 200mv setting dosent corrispond with this meter, strange they are all working players.

[NGY]

Your meter is fine, trust me.

And believe me, when I say a measured figure is "way off", or "looks bad", it is because it is way off or looks bad :-) . Don't get me wrong, it is not arrogancy, it is experience, and documented (I fill a form I designed myself, for each MD deck I get my hands on. Lot of good data, of over 100...120 decks).

Here is the thing: I have never ever seen any Sony MD decks (talking about KMS-260 A/B/E OP-s), that had nominal IOP values out of the 40...60 mA range. MDM-3 drives used to be generally around 47...49 mA, MDM-5 and up used to be around 51...55 mA. This was the pattern I observed over the years. So when you measure something over 70 mA or even 100 mA (and the latter one in read mode), then something is not round. Theoretically, that laser is not supposed to work ...

[M1JWR]

so because its working i am doing something wrong

[NGY]

I did not say anything like that! Did not even think! You are experimenting, you may want to repeat some measures if they look strange, etc.

I just feed back what practical and probable values you can expect to see in which circumstances.

[M1JWR]

9 minutes ago, NGY said:

I did not say anything like that! Did not even think! You are experimenting, you may want to repeat some measures if they look strange, etc.

i never thought you did, i am assumeing that of myself, being more mechanically minded

in the mechanics world there is an old saying,"let it develop", ha ha dosent count for electronics world though as i am finding out

[NGY]

Nothing wrong or insufficient with your mindset. I was the one who poured a bunch of information on you, without giving you enough time to digest and try in practice. I will try not to get carried away that much :-) . Regardless of that, you are doing great, and I like your enthusiasm.

[M1JWR]

i'll have another shot at it, will let you know tomorrow, this will be on player 602837 the one with the old 520 laser inside, something funny going on, will see if i can suss something out, have a good night for now

[sfbp]

"AC" on the meter???? Whoa folks....

[M1JWR]

24 minutes ago, sfbp said:

"AC" on the meter???? Whoa folks....

nah its the section below that, thats just a refrence pic from the net, its the 200m position two clicks below where that one is pointing

[sfbp]

Good, you had me really worried

[M1JWR]

cracked it now, was on the wrong pins, 0.9mw one is 19.7 and 7mw one is 62.1

[NGY]

7 hours ago, M1JWR said:

 0.9mw one is 19.7 and 7mw one is 62.1

Great, I knew you would find your way. Well done. These are the kind of realistic figures we want to see normally.

Now as you build your database, we can do our little analysis  :-) !

But I give you more time to do your tests before dumping my thoughts. That little table you already began to create will be very useful. You will essentially have these data:

- existing data: model name, serial number (to differentiate similar ones), two values from "IOP READ", [nominal IOP stated on the OP-s sticker], two $XX settings from "LDPWR CHECK" respectively, for read/write, total rec/play hours from "ERROR DP”, 

- measurements and comments: actual IOP mA values respectively (measured on the jig), [measured laser power values in mW for read/write - one day, when you get an LPM :-) ], comments on decks status ( working OK, read errors, write errors, etc.), conclusion on laser status, and "misc" (as always :-) ).

As you fill this database, you will see how the "book opens". Whenever you get hold of another deck and insert it's data to the table, you will see if that is worth to do anything with, from the laser's point of view.

I stop now :-) .

[kgallen]

Guys this is fantastic stuff. I’m learning too!

Keep up the great work and voyage of discovery!

@NGY you are a gem beyond words.

However for now the lid stays on my 530 as it’s working beautifully :-D Maybe I do some of these measurements on one of my 4xx decks...

[M1JWR]

12 hours ago, kgallen said:

However for now the lid stays on my 530 as it’s working beautifully

these work perfectly, now ive done more conclusive tests, i can give you all more definitive results, i'll leave the best one until last, had to put wires to the clips as the meter probes wouldent fit, then the wires to the probes secured with black tape, so here we go

930 s/n 602837, 0.9mw $11 - 19.7// 7mw $90 - 62.1 //play 1005hrs //rec 120hrs //iop read 51.8 / 55.8 (the drive that got the ex 920 laser, spindle motor and owh)

520 s/n 6613980, 0.9mw $11 - 17.4 // 7mw $95 - 56.1 //play 945hrs //rec 8hrs //iop read 53.5 / 54.1

930 s/n 604153, 0.9mw $11 - 20.1 // 7mw $92 - 59.5 //play 7hrs //rec 3hrs //iop read 58.5 / 58.4

920 s/n 5515468, 0.9mw $10 - 19.4 // 7mw $90 - 60.6 //play 431hrs //rec 7hrs //iop read 55.6 / 56.1

930 sn 602724, 0.9mw $11 - 18.2 // 7mw $90 - 54.5 // play 106hrs //rec 10hrs // iop read 55.1 / 54.3

theres the other 920, i'll do that one at another time, as for the 40/70 series, quite difficult finding the correct ribbon for the jig, i am still looking, its people like ngy with much more knowledge that help us, if not for people like him we would not be where we are, much appreciated, will get back on deck errors etc next

[M1JWR]

22 hours ago, M1JWR said:

these work perfectly, now ive done more conclusive tests, i can give you all more definitive results, i'll leave the best one until last, had to put wires to the clips as the meter probes wouldent fit, then the wires to the probes secured with black tape, so here we go

930 s/n 602837, 0.9mw $11 - 19.7// 7mw $90 - 62.1 //play 1005hrs //rec 120hrs //iop read 51.8 / 55.8 (the drive that got the ex 920 laser, spindle motor and owh)

520 s/n 6613980, 0.9mw $11 - 17.4 // 7mw $95 - 56.1 //play 945hrs //rec 8hrs //iop read 53.5 / 54.1

930 s/n 604153, 0.9mw $11 - 20.1 // 7mw $92 - 59.5 //play 7hrs //rec 3hrs //iop read 58.5 / 58.4

920 s/n 5515468, 0.9mw $10 - 19.4 // 7mw $90 - 60.6 //play 431hrs //rec 7hrs //iop read 55.6 / 56.1

930 sn 602724, 0.9mw $11 - 18.2 // 7mw $90 - 54.5 // play 106hrs //rec 10hrs // iop read 55.1 / 54.3

theres the other 920, i'll do that one at another time, as for the 40/70 series, quite difficult finding the correct ribbon for the jig, i am still looking, its people like ngy with much more knowledge that help us, if not for people like him we would not be where we are, much appreciated, will get back on deck errors etc next

Errors

920 / 5515468 / retry error - r/0c p/ff,/ total error - ff, / error history 00 - e04,/ temp check - t=03 (0f) ok

930 /604153 / retry error - r/01 p/00,/ total error 28,/ error history 00 - e01,/ temp check - t=ff (0d) ok

520/6613980/ retry error - r/ff  p/ff,/ total error - ff,/ error history 00 - e04,/ temp check - t =04(12) ok

930/602724/retry error - r/6d  p1/a,/ total error - ff,/ error history 00 - e07,/ temp check - t=04(13) ok

930/602837/ retry error - r/ff pa8,/total error - ff,/ error history 00 - e0a,/temp check - t=05(13) ok

diddent realise there was more in the error history until the last one so can give that which is 01 - 09 all e04, of course this is all double dutch to me so somebody else can have fun with it.

[kgallen]

These codes from the "Error History" are documented in the Service Manual. May not be of use to you immediately but they may be of interest in conjunction with reading other parts of the SM.

• UTOC - User Table Of Contents - the area of the disc that holds track information - positions (addresses) on the disc, titles and other track-specific information
• PTOC - An area of the TOC that is created when the disc is manufactured and cannot be changed, holding information like the length of the disc (60/74/80 mins)
• Address - the entire length of the recordable track is manufactured with a "wobble" in the pregroove that encodes an address (number) that the deck reads to work out where it is on the disc

See the Minidisc Tutorial.

Get some of these on occasion is to be expected. Sometime the deck has to "retry" - bad spot on a disc or the deck got knocked for example.

[M1JWR]

interesting, though dont see ff on there, that appears quite a lot, had a look through sm, diddent see reference to that there either.

[kgallen]

Total Error = ff

ff is not a code, it's a count.

It's the number 255. Your homework is to tell me how ff = 255 :-)

[kgallen]

Those "E" error codes only relate to the Error History which is a chronological list of the last 10 abnormal conditions that the deck detected.

[M1JWR]

14 minutes ago, kgallen said:

Total Error = ff

ff is not a code, it's a count.

It's the number 255. Your homework is to tell me how ff = 255 :-)

understood the first line kevin, ff = 255, looked that up, way over my head, on a lighter note i do know about 42 though !!!!

[kgallen]

MD decks are computers at heart and as such use binary counting in their digital electronics, 0=low voltage 1=high voltage (well 5V or 3.3V). With 8 binary digits (bits) you can count from 0 to 255 in the same way as with decimal with say 3 digits you can count to 999.

Hexadecimal (base 16) is an easier way for humans to work with binary numbers because writing out strings of 0s and 1s is tedious and error prone. So instead of writing binary we often use hexadecimal.

In decimal, we have 10 "symbols" we use to make any number: 0,1,2,3...,9. When we run out (i.e. we get to 9), we increment the next column along (the 10's column). So the number ten in decimal is one-ten plus no-units, so we write 10. So when we count up 0,1,2,3,4,5,6,7,8,9, then we go 10 then 11,12,etc until we get to 19 then we count 20 (two tens plus no units).

All number bases work the same way. Hexadecimal is base 16, so we need 16 "symbols" to count with. We already have 0,1,2...9 we can use for the same purpose as in decimal, but we need 6 more, so we use the letters a,b,c,d,e,f.

So in hexadecimal, we count 0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f but then, as in decimal we've run out of symbols so we increment the next column along, and write 10. But this is not ten as in decimal. The number 10 in hex (we write 0x in front usually so we know it's hex, so we write 0x10). Well 0x10 means one-sixteen plus no units, or sixteen in decimal. So then we just count units again as we do in decimal, so 0x11, 0x12, ... 0x19, 0x1a, 0x1b, ... 0x1f, then as with decimal we roll again and get to 0x20. This is two-sixteens plus no-units, so 0x20 (twenty hex) is 32 decimal.

Keep going and when you get to 0xff you have "f"-sixteens plus "f" units. f in hex is 15 decimal, so we have 15-sixteens plus 15 which is 255 decimal.

Hexadecimal is useful for binary because you can take 4-bit chunks of binary and convert to one hex digit. Computers tend to be "8-bit" or "16-bit" or "32-bit" etc, so the numbers involved can be written using 2, 4, or 8 hex digits respectively.

Converting binary to decimal is a pain which is why hexadecimal (or octal - base 8) is used commonly in computing and digital electronics.

As humans we're naturally tied up with the decimal system, but there is nothing special about decimal (or base 10). You can have a number system of any base.

In decimal the "columns" are the ones, the tens, the hundreds, the thousands etc. They are ten-to-the-power numbers.

In hexadecimal the "columns" are the ones, the sixteens, the 256's, the 4096's etc. They are sixteen-to-the-power numbers.

In binary, the "columns" are the ones, the twos, the fours, the eights etc. They are two-to-the-power numbers. So in binary, 1011 (going R to L) is one plus two (no four) plus eight, or 11 (eleven) in decimal, or b in hexadecimal.

Hope that helps :-)