Hmmm Midibox stopped working Please Help.

Testing/Troubleshooting
1

Hi,

I made a midibox late last year and it worked great for many months.  However one day I sat down to get a mix going and it wouldn’t turn on.  I checked all the connections and soldering points, everything was good.  After a little bit I decided to check the power and it turns out my power supply (all of a sudden, as it was not doing this before) was sending out too much voltage, So my guess is that it fried something.  Now I am not as handy with electronics as most of you are, so I’m wondering if you guys will tell me which component is most likely broken.  I believe it has to be in first few steps of power entering the core module.  Also, any help on how to test the parts is welcome. 

Thanks for your help in advance.

Ryan

2

I’d look at the regulator, caps and rectifier… A multimeter might help here.

3

Yea I’ve got a multimeter, i would most probably have to de solder some of these components to correctly meter them right?

4

anyone have any good links on how to test these particular components?

5

So in using this link http://www.ucapps.de/howtodebug/mbhp_core_extract_measuring_vdd.gif I have found that I’m no longer getting +5v at any location.  It seems to be all over the place, I have seen .2v a few times.  Would this possibly be due to the voltage regulator being damaged?  If so how do I check that it is doing its job correctly.

At the input to the system (J1) I am receiving the voltage that my wall adapter is giving out (10.17 v).  I can follow it a little ways into the rest of the system but I’m just not sure what the values should be at every step of the way.  I am going to remove the cap to test its capacitance.

6

your 7805 or rectifier is broken I think, too. The black round thing (first part after j1) is the rectifier. 2 pins are input, 2 are output. Check the output voltage of it. Should be same as the input. Then it goes to your 7805 which makes 5V from it. The lower pin of the 7805 is input, the middle is ground and the upper one is your 5V output voltage. All the parts and 5V pins of the core are supplied from this pin. You can measure the resistance of your caps like this: very high or endless ===> ok … low or no resistance ===> damaged.

greetz

7

thanks a lot! I will try all the things you have mentioned.

8

I don’t think it’s the cap, I did a resistance test of it out of the circuit and it was showing readings as high as 39 mega ohms, but it would shoot up very fast and say O.L often so that makes me think it is functioning correctly.

The rectifier appeared to have two pins around 9v, and the voltage regulator is definitely not outputting 5v, it receives the correct voltage but doesn’t output correctly.  Therefore I am going down to the store soon to replace these two components.  Then we shall see if it functions!.

Thanks for the help you guys, I will be back with results.

9

np :smiley: perhaps this helps you a little bit to understand the power supply better: NO troubleshooting but you see the components and what they do. http://www.avishowtech.com/mbhp/ps/

10

Slightly OT, but if you’re in the mood for having a laugh at my expense… Talking of regulators …

you know the metal plate on the back of the regulator? I have one of those f*ckers branded into my right thumb at the moment. It’s a perfect outline, a red rectangle with a white blister where the hole is! hehehehe

while testing timing with a scope, my core stopped responding…when the core wouldn’t respond after I power cycled it, I got concerned, first thing I did was stick my thumb on the regulator - sizzle! :cry: Guess I shorted something! Naturally I powered it all off, and noticed that I’d knocked a power lead loose.

Miraculously my thumb is sore as hell, but the vreg, the core, the PIC, and the scope are all OK!  :smiley:

11

lol, the first “midibox branding”

12

I got concerned, first thing I did was stick my thumb on the regulator

rofl.

ouuups, I guess I should think about my “testing” methods, too ;D

13

Hehe…some parts get a bit rowdy right before they release the magic smoke.  :wink:

I wore an almost ledgible part number on my finger for a while…from a 16 pin dip that got so hot it split down the face of the chip. 

Gotta love those early array logic chips, great way to heat a building. :wink:

I was 12 or 13 at the time, but I still remember it every time I feel up a board looking for thermal clues.

Best

Smash

14

lol apparently I’m not alone :slight_smile:

15

right ^^

16

lolll

Well thanks a lot! I switched out the regulator and it works fine again! Hoorraay.  But yea I did some research on the the power supply section and I have a much better understanding now.

That brand must look pretty sweet! I have a perfect circle branded into my arm from a vaporizer bowl that shot out of the heating mechanism directly onto my forearm, the chicks dig it… lol.  As I am sure they will dig yours. 

Did yours hurt like all hell? man I was in some serious pain for a whole day or two.

Thanks guys.  now back to making music.

17

That brand must look pretty sweet! I have a perfect circle branded into my arm from a vaporizer bowl that shot out of the heating mechanism directly onto my forearm, the chicks dig it… lol.  As I am sure they will dig yours. 

Ouch!! Well fortunately my lab is about a metre from my kitchen, and I iced it immediately - so it’s fading already :slight_smile: But I have a floating point thumb, with a nice little decimal point :wink:

Did yours hurt like all hell? man I was in some serious pain for a whole day or two.

OMG yeh! I made the mistake of forgetting about it and used my cigarette lighter once. OW. Do not do that.

18

Hehe…some parts get a bit rowdy right before they release the magic smoke.  :wink:

I wore an almost ledgible part number on my finger for a while…from a 16 pin dip that got so hot it split down the face of the chip. 

Gotta love those early array logic chips, great way to heat a building. :wink:

I was 12 or 13 at the time, but I still remember it every time I feel up a board looking for thermal clues.

lol apparently I’m not alone

Shall we start a club?

T shirt or tie?

In my case it was complete lack of knowledge of how hot ECL gets. Put my hand on the board just to see it was ok - it stuck to my hand. Whilst swearing over the pain, I was more worried I’d somehow fried the ECL chips (expensive!). It was fine - it just runs that hot! Which is why that cute looking Cray1, ate about 115KW, (correct figure, checked, it had poly phase 400Hz secondary power distribution to the final supplies under the ‘love seat’ bit.)

For those who din’t do old style logic, work ECL, Emitter Coupled Logic, was for years the fastest logic chip type you could buy. Some types ran up to 1GHz. The Cray 1, the worlds first real ‘supercomputer’ was built using 1000’s of ECL chips. Cray 1’s were like the SR71 Blackbird, (or Bugatti Veyron or whatever),  of the computer world: hand made, mind blowingly expensive, and requiring serious maintainance, massive amounts of electricity and cooling, but delivering ultimate performance. See:

http://www.nasm.si.edu/imagedetail.cfm?imageID=1118

I think my “favourite” power repair was the faulty transformer that blew the black plastic parts right off a set of 78/79 series regulators. An inter-winding short had produced about 3 times the secondary voltage, and guy at the knitiing factory where it was, had put a bigger fuse in, ‘just in case’. I had to replace every chip on two double euro cards. I added a ‘crow bar’ circuit,  ‘just in case’.

Mike

19

LMAO!!

I am so jealous that you got to play with a cray 1 !!! Even if it did take a few layers of your palm as an entry fee :wink: I notice you were kind enough to spare us a graphic recollection of tearing your hand off the board :wink: :cry:

it took me 5 reads to decide which was the funniest part, and I think I have a winner:

put a bigger fuse in, ‘just in case’.

;D

20

I am so jealous that you got to play with a cray 1 !!! Even if it did take a few layers of your palm as an entry fee :wink: I notice you were kind enough to spare us a graphic recollection of tearing your hand off the board :wink: :cry:

I think I left the wrong impression here - I was citing the Cray as an example - I have actually been in the machine room at World Weather Centre in Reading, but they were later Crays. I used it an an example of high end ECL, and why they ate so many Amps. I researched the machine very thoroughly for company that wanted a model building. A local retired engineer built it, as a break from his steam engines. The company had a long discussion (they are all tecchies) about whether it would be possible to make a 1/12 model Cray 1 that actually works, using modern parts. The answer seems to be "yes if you can afford about £2K worth of high end FPGA and fast static RAM (the main RAM was 50nS static 64 bits wide plus parity, the main clock ran a real 80MHz - actual cycle time, the registers have to cycle in 6nS!). I’m worried they might decide to ask me to do it, and whilst i have a lot of the system documented, the design of some kind of I/O for the thing would be a killer on it’s own.

By the way, the Cray used vector processing. The length of a vector is often known as it’s … ‘Stride’. 

The guy who runs Armari has a couple of rescued Crays

http://www.hexus.net/content/item.php?item=903&page=3

and these guys in Germany have real ones you can log on and use

http://www.cray-cyber.org/general/start.php

My board was a eurocard sized multiply and accumulator, board, for early sort of DSP, part of a project inspired by something in Strawn and Roads’ “Foundations of Computer Music”. It was connected with one of IRCAM’s multivarious projects. We got it running very nicely, then those nice people at TRW came out with a single large chip that did roughly the same job. . . .

I think I’d successfully supressed the memory of the thing dropping back to the bench with a thin layer of my skin barbequing on top of the chips. After your comment I’m going to have to do some more therapy. Fortunately I’ve got a very good Russian therapist called ‘Stolichnya’…

Mike