Topic: Dead Classic -- internal power supply issue?

I bought a used Classic about a week ago.  It has seemed to work OK for the most part, except that the screen did feel a lot warmer than my two C1s.

Today it went silent and dark.  I have tried it with four different AC adapters with no success.

One adapter (rated 7.5VDC output) produced a very dim backlight when I pressed the rear power button.

The other adapters (rated 9.0, 10.0, and 12.0 VDC) produced nothing at all when I pressed the power button.

There is a faint smell of "hot resistor" noticeable at the back vent holes.

I've had 50+ years of component-level repair experience (along with design and construction) and got my FCC First Class license 45+ years ago.  I'm sure if I could get to the board, I could take a good stab at fixing it.  Especially if I had a schematic.

So, two questions:

1.) How do I get past the leather to get to the electronics?

2.) Is a schematic available?

Thanks in advance!

Re: Dead Classic -- internal power supply issue?

1) The hard plastic bezel is glued to the softer plastic surround.  What you'll want to do is use a sharp knife to slice through the glue and pull the soft plastic away.  The glue isn't perfect - you may be able to pull parts of the softer part away without having to cut the glue.  Start with an area where the soft plastic can already be pulled away.  if you do it carefully, you can separate the two parts without tearing the soft plastic.  I've done it successfully dozens of times.

At that point you can remove the front section, and gain access to the screws for the back section.

2) Here are the schematics for the chumby Classic V3.7.  I think the power circuitry in 3.8 devices is similar.

http://files.chumby.com/hdwedocs/hardware_v3_7.pdf

CC devices generally feel like they're running hotter than C1 - the heat from the wifi dongle is dissipated through the screen on the CC (can't remove the heat through the stuffing and leather), instead of convection in the C1.  The actual heat is about the same.

Re: Dead Classic -- internal power supply issue?

some more info:

http://wiki.chumby.com/index.php?title= … classic.3F

would gentle heat help to soften the glue?

Cleaning up any loose bits and bytes.

4 (edited by gminpa 2017-03-29 08:42:54)

Re: Dead Classic -- internal power supply issue?

Duane, thanks for sending the schematics and giving me the teardown info so quickly!

(diamaunt, thanks for the info you provided, also.)

- - - - - - - - - - UPDATE - - - - - - - - - -
Upon comparing my actual motherboard to the CAD drawings you provided, my board appears to be somewhat different. 

• If you look at P.9 of the docs you provided, that board has one tab (4.0mm x 4.17mm) that protrudes out from the right side of the board.  My board has two such tabs at that end.

• P.9 also shows a 20-pin connector (for ribbon cable?) in the lower right corner of the board.  My board has no connector in that location. 

• However, my board has a 26-pin connector (for the ribbon cable) at the opposite end of the board (the end at the left side of P.9).  No such connector is shown on your drawings.

So I think my board does not correspond to your drawings.

- - - - - - - - - - END OF UPDATE - - - - - - - - - -


The schematics do not clearly indicate the physical location of the various components ... i.e. whether a given part is on the motherboard or on the rear board (with the connectors).

When I first got it apart and looked at the construction, I was hoping that the power circuitry was located on the rear board, which would be easier to access.  However I find at least some of the regulators (U300, U301...) on the motherboard.

If "chumbilical" actually refers to the ribbon cable, then it appears that the protection circuitry is also on the motherboard.  (I don't seem to find a schematic of that small rear board.)

I was hoping that perhaps the fuse in the RAW PWR circuit had opened (or a diode or choke had gone open).  So I tried to power the device using a fresh 9V battery in the battery clip.  Upon pushing the power button, still nothing.  So, unfortunately, I don't think the problem is in the protection circuitry.

Interestingly, if I connect 9V to the battery clip (through a DMM) I see 0.18 A of current.  I see that reading as soon as I connect the battery, and it does not change if I push the CC's power button.

At a quick glance over all the schematics, it appears DC IN PROTECTED goes only to the +5v regulator.  However the schematic says "BATTERY signal goes to TS/codec chip..."  so that 180mA could be going one of two places.

To narrow it down, I applied the same 9V battery to the rear panel coaxial power connector.  Again I see 180mA.  So I think that rules out the TS/codec chip. 

My conclusion is that both sides of the protection circuitry are OK, the DC is getting to the +5v regulator and to a few other places, as shown on the various pages of schematics. 

And something, somewhere, is drawing 180mA.  Would a CC normally draw that much in "resting" state, with no backlight, no display, no audio?

To do any further analysis, I'd have to start disassembling boards at the very least.  However, I don't have a stereo microscope and micro soldering tools that I'd need to work on these boards.  So I'm not sure there is any practical benefit in my going any further.

I'd appreciate your feedback on what I've done up to this point, and any other suggestions you might care to make.

Thanks again for your help!

Re: Dead Classic -- internal power supply issue?

It sounds like you have the 3.8 version of the chumby Classic.

In both the 3.7 and 3.8 devices, with power applied, a small secondary ARM processor is always powered.  The "power switch" on a chumby is actually a switch on the GPIO for that processor, it in turn powers on the main device.  This allows the capability of having a timer power on the device, and/or have the secondary processor keep track of time while the main device is off.

There are a couple of differences between the 3.7 and 3.8 versions of the board:

1) the 3.8 powers on when power is applied, a 3.7 requires pressing the button.
2) the 3.8 uses a different touchscreen panel (the source for the 3.7 panel stopped making them just after we started production)
3) the 3.8 has variable screen brightness, 3.7 only supports "on", "dim" and "off".

As you saw, there were some layout changes.

6 (edited by gminpa 2017-03-29 11:07:13)

Re: Dead Classic -- internal power supply issue?

Thanks, Duane.

I definitely have a 3.8, because it has slider controls for day and night screen brightness.

That being given, is any of the power circuitry for the 3.8 on the rear connector board? Or is it still on the motherboard like the 3.7?

Do you have a set of docs for the 3.8?  Or did those vanish with the demise of Chumby Inc.?

I'm pretty sure the failure was caused by an overvoltage power adapter.  Is there any "normal" failure mode of the internal PS components?  Is it realistic to hope this can be restored?

(I'm torn here.  Based on a few days of listening, I thought the sound from the CC speakers was a lot nicer than the sound from the C1.  But with my background in commercial & broadcast gear, I have to admit that the "works in a bag" concept of the CC doesn't thrill me.)

Thanks again!

Re: Dead Classic -- internal power supply issue?

The board in the back is the same for both 3.7 and 3.8 devices.  The back board is to hold the speakers and top switch, provide the external connectors, and a small bit of non-volatile memory that holds some configuration data.

I'll see what I can dig up as far as schematics for the 3.8 devices - I'm not completely sure I have that in my archives.

The CC in general is the most robust chumby device when it comes to power issues.  The C1 was basically a cost-reduction device, and some of that cost came from simplifying the power subsystem.  Normalized by volume and age, the CC exhibits less failures of the main board than any of the other devices.

As to audio, the CC uses two speakers with soundbox enclosures integrated by the speaker manufacturer.  The C1 has a single speaker with a soundbox built into the plastics of the internal bracket that also holds the top switch, the rotate encoder and the Wifi dongle.

Personally, I also prefer the CC audio if using only the device, however the devices I have at home used for music all have external powered speakers, in which case they're comparable.

Re: Dead Classic -- internal power supply issue?

I always used my C1s with external amplified speakers.  But that takes up a lot of counter space and is of course non-portable.  The CC wasn't hi-fi, but it was a lot more bearable than that C1s.  I could stand listening to it bareback for a few hours.

It's too bad Chumby never made a truly portable unit, the size of a portable radio or small boombox, with two decent speakers and room for a battery that would provide a few hours of playing time.  Personally, I would find that form factor much more practical than a soft amorphous lump.

This has probably been asked and answered, but I've never read it.  What was the original history behind the lumpy leather concept?

Re: Dead Classic -- internal power supply issue?

The leather design was an explicit rejection of the then-dominant featureless and stark white iPod design aesthetic.

We talked to several designers, we eventually went with Thomas Meyerhoffer who totally got that we were trying to make something friendly, accessible and invitingly touchable.  He was getting pretty tired of *everyone* coming to him to design yet-another-iPod, and proposed the leather/plastic combination that somewhat invoked a motorcycle glove.

From our side, we also liked it because it generated interest.  Some people, of course, hated it, but at least they talked about it.

We also experimented a lot with packaging - the device came in a set of nested cloth bags, which people tended to reuse rather than throw away.

I think we accomplished what we wanted from a positioning and marketing standpoint, and I personally still have a fondness for the CC over the C1 - all of the several devices I have deployed in my house are CCs, I have a C1 on my desk at work.

Re: Dead Classic -- internal power supply issue?

This device seems a bit like what you're looking for.

I posted them as an April Fool's joke a couple of years back, however, they're real working prototype devices we just didn't take into production.

Re: Dead Classic -- internal power supply issue?

Aha, I can relate to it as an anti- iThing statement.  I have always been displeased by the starkness of the iWorld ... not to mention being appalled at the huge ripoff being perpetrated by those overpriced electronics.

It's probably some psychological defect, but I am somewhat bothered (for example) by electronics that look asymmetrical.  For example, I find this radio rather upsetting.  Aluratek AIRMM01F
(I am also bothered by the fact that most of the controls are on top, which makes use difficult for someone lying in bed, with eye level at or below the device.)

The CC is at least nicely symmetrical ;-) and, for that matter, my symmetry bias is overridden by my practicality bias:  I prefer the C1 because it has an always-accessible rotary volume knob (even 'though it slightly upsets the symmetry).

At least a nice new CC looks plump and happy.  But I see some used ones on eBay that look as if they've been abused, or perhaps stored jammed into a too-small space.  They look lumpy and pained.  (I guess that CCs, like cats, need to have considerate caring owners.)  When they reach that stage, what can you to to plump them up again?  Obviously you can't toss them in the clothes dryer with a few tennis balls, as you can with an old pillow.

Anyway, the April 1 prototypes are interesting.  I kind of like the triangular cross-section.  I like the concept of multiple buttons to get to the various screens quickly without going through a touch-screen menu.  I would still like a quickly-grabbable rotary volume knob.

Back to OT :: I haven't done anything with my CC in the past day.  I hate to start dismantling and then blindly probing around on the MOBO without a schematic and layout.  Too bad Howard Sams never published a repair manual for these, with test points identified and expected voltages specified.

Did Chumby ever have any board-level repair options?  Or were these considered to be mostly disposable?

Thanks again for the insight and historically interesting photos.  (And, of course, thanks for keeping the Chumbysphere alive.)

Re: Dead Classic -- internal power supply issue?

I am still trying to put my order in for one of those C3s. There must be a very long waiting list.

13 (edited by gminpa 2017-04-04 08:52:35)

Re: Dead Classic -- internal power supply issue?

Duane wrote:

3) the 3.8 has variable screen brightness, 3.7 only supports "on", "dim" and "off".

Duane, someone sent me photos of a CC screen that says "Screen brightness" at the top.  Below that are two "sunshine" icons.  The bigger "sunshine" has the words "Full brightness."  The smaller "sunshine" has the words "Low brightness."  That sounds especially inconvenient because no way to turn it off for nighttime.

This certainly does not match what I saw on my CC 3.8 (?) model.  It also does not seem to match your description of the CC 3.7 version.

They list HW: 3.7,   SW: 1.7.1,  FW: 1830.

Any thoughts about this?

Thanks again!

Re: Dead Classic -- internal power supply issue?

Right - the 3.7 *hardware* supports "full on", "dim" and "off".  The Control Panel screen for brightness exposes this as the two buttons and the "off" button appearing on the Night Mode screen.

The 3.8 hardware supports variable level brightness, as well as on/off, displayed as two sliders on the brightness screen (one for normal use, and one for Night Mode) and the same "off" button in Night Mode.

Re: Dead Classic -- internal power supply issue?

OK we found the schematics and gerbers for the 3.8 hardware:

Schematic: http://files.blueocty.com/hdwedocs/IRON … _FINAL.pdf

Gerbers: http://files.blueocty.com/hdwedocs/gerb … _FINAL.zip

Re: Dead Classic -- internal power supply issue?

Duane, thank you very much!  That's excellent.

These docs definitely appear to correspond to the HW that I have here.  At least I'll be able to start checking a few supply voltages to see if something obvious has fried.

That said, this will still be nearly impossible to work on IMHO.  I have done a small amount of SMT work, but nothing that is nearly this small and compact.  It will be an interesting challenge.

Thanks again for the great support!