How electrically efficient are these gridseed pods when used as a space heater?
I know they are not an "efficient" heater so I am not arguing for that use.  Please assume for this question that all other heat in the house is electric and that heat is required for 9 months of the year.  Also, please ignore purchase cost of the pods versus buying an actual heater.  This info could influence miners who live in cold climates when considering a voltage mod.

My guess is that 75% of the electricity used ends up as heat.  Do you think my guess is high or low or about right?  Probable less waste heat ratio at low wattage (stock LTC) compared to high wattage (dual mode).

Well I found the dummy load.  Actually it found me ...... 

I think Gridseed numbers the chips 1,2,3,4,5
Cpuminer numbers the chips 0,1,2,3,4
Anyway, using cpuminer numbering this morning chips 2,3 & 4 were working. Chips 0 and 1 were not working.  Wattage was too high at 34w.
Chip 1 (M2 in the center I assume) is no more.  I removed what was left of it after it went up in smoke.

Now chips 0 and 4 are working. Watts are much reduced, only 14.5w at 1000MHz with the two chips working.  I feel more confident about it with the low watts. Around 170 kh/s reported by cpuminer and the pool after several hours. Very stable.

I'm assuming chip 1 connections to the board permitted chips 2 & 3 to work this morning but also prevented chip 0 from working.  Removing chip 1 allowed chip 0 to work but now prevents chips 2 & 3 from working. A 2 chip expected wattage pod is ok after that meltdown but a 4 chip pod would be better!  I need to figure out if there is some way to bring chips 2 & 3 back online. Maybe a bridge of some sort?

I will try to.  Thanks for the suggestion.  I'll keep posting what I find as clues for anyone that can help me.  For example I've found that with the 3 working chips at 1000MHz single mode mining the damaged pod is drawing 34 watts with a 47.5k resistor in the R139 spot.  I think that is high so I did not let it run unattended overnight.  I ran it this morning and it still finds 3 chips.  I'll work on it this afternoon.

Thank you J4bberwock - got it downloading.
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re: only one chip working after volt mod attempt

I posted photos of the solder that came out from under a gridchip on my pod here: https://bitcointalk.org/index.php?topic=519112.msg6432641#msg6432641  The cleanup went pretty good but still only one chip working after that.  No mods, back to stock using the untouched 33k.



I tried to mine Bitcoin to see if that part of the chips worked and it mine for a few minutes and quit.  I thought it was done for.  It wouldn't mine anything after that.  So I've been practicing my soldering on it and got it back mining on 1 chip using the stock resistor.   I put a 47.5k resistor in the R52 spot like Wolfey does his 49.9k and to my surprise now chips 2, 3 & 4 are working ! ! !   I might end up with a 275+ kh/s pod.  



Electrically, what is going on here? Why would two more chips start working by replacing the 33k resistor with a 47.5k?  I had tried it again just minutes before changing that resistor and only one chip worked.

Any ideas to help me get the other two chips working?

re: troubleshooting 1 out of 5 chips working after voltage mod attempt

Is there anyway to trace things back from chip 4?  Chip four is either the last or the first.  0,1,2,3,4  depending how things are connected.

How can I tell if power is getting to chip 3 for example?  How can I tell it is getting a signal to start?

Cpuminer shows it is sending the command to set the frequency for all chips and start mining but maybe that is more of a com chip function.  Maybe the other chips aren't even on.  I can't figure out what to look for from the pdf schematic.

Could a break after chip 4 stop the other chips from working?  Chip 4 is closest to the 12v power jack I think. Chip 2 is in the center.  Chip 2 had the solder oozing out from under. I've been mopping that up but might need a better magnifying glass or even a microscope to inspect.

Are there any test points on the board to check for general working condition?

I want to work on it but I don't know what to do next.  

gtraah - they are the same according to the docs https://github.com/gridseed/usb-miner/tree/master/hardware and assuming they are right.



Should be 4 in that general area.

FB27, FB28, FB23, FB24
FERRITE BEAD_R1206_300OHM@100MH
Value: 300ohm@100MHz,3A

Anyone know of a free dsn viewer? I can't open that file from the github docs.



Thanks for your help amix - time for me get get working on that pod.

gtraah - could be power related.  Volt x amps = watts.  If you have a significant amount of voltage drop then the amps will go way up.  You used a 49.9k right?  Are you allowing 30 watts per pod on your power supplies?  That should provide a good safety margin.

I think the part in the photo is:
Device Type:  FERRITE BEAD_R1206_300OHM@100MH
Value:   300ohm@100MHz,3A

Someone else should confirm it for you.

I could screw up any mod   I bet.  Sorry ZiG - I'm not blaming you at all.  I did the first pod and it has run for several days.
Re: C35 - the clicking came before accidentally bridging that.  I took photos and planned to post them. It looked good from several angles.
I suspect the clicking has to do with me making a poor solder connection, maybe even up at con3.  The bridge to C35 came at a later attempt.  I was so surprised that I did it and even more surprised that I didn't notice it before testing the pod.

Looking at the brd file:
R46 Pin 1  goes something referenced N31930727 on the board
R46 Pin 2 goes to DGND

C35 Pin 1 goes to N31930727
C35 Pin 2 goes to N31930664

It looked like the short went from pin 1 to pin 1. The components are tiny so maybe I shorted C35 itself.

I also started the pod at 1200MHz - I feel kind of dumb admitting that.
I had to post my failure.  I want to focus on fixing it if I can.  Turn a negative into a positive.

ZiG - Can we put a resistor between Con3 pin3 and C38 pin1 or C40 pin1 or C41 pin1 or C43 pin1?  

Thank Amix for the helpful advice.  I'll focus on cleaning the pins for now.  The underside is clean.  

Any, all suggestions, tips, advice for what to do and what to check are welcome.

I tried rmod on a second gridseed today after having it working well on another gridseed for several days.  This one already had vmod1 and I was adding 15k.  Actual measured numbers were 35.83k + 14.92k = 50.75 tested on board.  That is on the high side I know.  
I got the clicking noise and tried to redo a few times but couldn't solve it.  I'm not good at soldering but thought I did an ok job. Voltage was low on first try 1.3 something.  Second try had the voltage at 1.63v.  I removed vmod1 but the clicking was still there.  You can actually feel the clicking.  The first pod I did had a higher value large silver capacitor 16v 330.  This pod has 16v 220.

I screwed something up though on one of the later tries. I may have bridged to that 20nf capacitor.  It got hot quickly ..... some solder has actually come out from under one of the gc3355 chips on two sides!     These little things are pretty tough.  One chip of the five is still working so hopefully I can fix it up.





Summary:
rmod removed, bridge replaced, no clicking sound
It powers up and miner software sees it.  cpuminer reports 5 chips and sets the frequency.
Only one chip does any mining and those shares are accepted by pool. (only chip #4 works)
Red light blinks very very slow.  It can be off for a long time or on for a long time. This might be caused because only one chip is actually mining.
Solder is visible on two sides of the center Gridchip (one of the mining chips).  See photo.  It covers four or five pins on one side and maybe three on another side.  I did not drop solder there and I know it wasn't there earlier because I took a photo of the new resistor in place before trying it.  I think it has come out from under the chip if that is possible. How do I remove that?  

I need some advice or suggestions on what to check / what to do so I can try to recover it or at least get a few more chips working.  Any help will be greatly appreciated.

All the docs that I've looked at on Github show 20nf



Reference Designator: C35
Package Symbol: C0402
Component Class: IC
Device Type: C0603_C0402_20NF
Value: 20nF

Some multimeters have "CAP" on the selector switch.  Not all do though.

I hope you can fix it.  It all looks so big in the photos but really most of it so incredibly tiny.  At a minimum for me is to inspect with a good magnifying glass just to see it and even then it can be hard to see if something is bridged or not.  For me ZiG's rmod is "easier" but all the mods are really difficult including ZiG's rmod if you do not have experience.  There have been a few posts about accidentally removing component near what you are working on. 

Wolfey - stick with what you know how to do.  Don't you already have the best solution for you?  Why would you want to change now?

Yeah, you'd only reverse to stock or maybe VMOD1 if a SHA coin was regularly at the top of the profitability lists.  It seems unlikely but my guess is that there is a lot of older Bitcoin hardware that might be used to mine other SHA-256 coins as Bitcoin difficulty rises and makes the old equipment obsolete.  Just a guess.

btw, VMOD1 is pretty impressive for the low watts used.  413 kH/s 48hr average Scrypt only using sandor's cpuminer.

C42 in photo here: https://bitcointalk.org/index.php?topic=519112.msg6359210#msg6359210 upper left of center on photo of PCB.  I measured 1.75v there when I added a 15k rmod.

Emu05  - what is, where is R128?

Ahh, right, for all 3 values you'd need to add a physical switch or jumper. Thanks for catching that Xer0 ...
So, your idea of using a 20k spindle-pot as the resistor is ZiG's rmod would allow all values from 33k to 53k right?

Is this summary correct?
Bridge R333 to allow "voltage=0" or "voltage=1" to be used via some software.
ZiG's rmod ups everything by adding the resistor chosen.
So, if you picked rmod 14k then you get 50k with "voltage=1" or 47k with "voltage=0".
Short this use of Zig's rmod with a jumper or switch then you'd get 36k with "voltage=1" and stock 33k with "voltage=0"

Without software options you'd bridge R333 and also bridge R337 to force "voltage=1" via hardware.
So, if you picked rmod 14k then you get 50k. Short this use of Zig's rmod with a jumper or switch then you'd get 36k.

Without software options and no additional bridges if you picked rmod 14k then you'd get 47k. Short Zig's rmod with a jumper or switch then you'd get 33k.

Bridge R333 to allow use of software voltage switches.
Bridge R333 and R337 to force use of R66 (36k).
Cut  R46 to allow adding resistance in series aka rmod.
Adding a resistor between R46 points will add to R139 (36k) and/or R66 (33k) dependent on your choice of bridges used or bridge and software used.

Thanks for catching that!

I like those ideas.  I think only cgminer has the software voltage switch though.
I get it.  Just adding 1 bridge, cutting 1 bridge and adding one resistor, a 14k Rmod plus the 2 software switches would give us 36k or 47k or 50k options all controlled by software. Can't ask for more than that!

No, I don't have photos of method 1.  I did method 2.  I'm still waiting for my resistors to come in the mail.  I want to do method 1 and will take a photo.

ZiG's rmod works.  Mine has been running for several days now https://bitcointalk.org/index.php?topic=519112.msg6364716#msg6364716 non stop.

I think it is easier to do but you still need to make good solder connections.

ZiG's rmod is adding a resistor in series and can be done at least 2 ways.

1. Cut the bridge at R46 and add a resistor between those two points.  To undue just re-bridge R46.  Removing the resistor is optional as it would be bypassed by the bridge.

OR

2. Cut the bridge at R46 and add a resistor between the outer point of R46 and CON3 pin 3 (DGND). To undue remove the resistor.

method 2 is a bit easier because you have lots of room to work at both points
method 1 is easier to undue

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I think that ZiG's discovery has additional uses. (I'll try to confirm tomorrow)
VMOD1 = 36k + ZiG's idea but using a 13k resistor (for example) would give you 49k. (not tested yet)
VMOD3 = 47K + ZiG's idea but using a 2k resistor (for example) would give you 49k. (not tested yet)
It looks useful for anyone who has done other mods but now want to try a higher resistor value.  It's possible you won't have to undue the other mod if this works.

nemercry or ZiG would know if the second part of what I posted is correct or not.  
For now, stick to the first part of my post (above the dotted line) as being ZiG's rmod.

(edit - I see ZiG posted as I was typing)

Jess85 - Step B needs clarification as it has merged two separate mods.  ZiG's rmod requires that you cut the bridge at R46 then one method is to solder the resistor as described.  To reverse ZiG's rmod you would remove the resistor and re-solder the bridge at R46. Then you could do VMOD1 if you want but vmod1 has nothing to do with ZiG's rmod.  

I wonder if the clicking sound is the result of not cutting the R46 bridge or accidentally bridging it again when soldering?
Emu05 - are you trying Zig mod or a different mod like vmod1?