JV33 Bad TP8 HELP?

[kjbarrett]

Hey all, been into this machine for many years, story short, wont boot, TP8 had no signal, the rest did. Around 17.5k.

Caused two transistors to blow, Top row, (3rd and 4th from left), 1741 and 4550. Got them replaced. And got into Download/Upload fine to save parameters,

Tried to boot normally and once it got to the main menu (Local) it tripped off, COM-H or TP8 reads 0 again, yes, there was a burning smell after the transistor blew.

Does anyone know what circuit is attached to each Test Point, more specifically TP8? Am I looking at a slider issue, heater issue or something else.

Can anyone shed some light, many thanks.

 

[Neil]

I had a look in the Service manual for you. It looks like it's connected to the head. TP8 on Slider board is different nozzle channel to TP8 on main board, but both from the head.
I'd check your head cable for damage or ink drops

 

[netsol]

i have no mimaki experience, but 35 years of other wide format.
(techjet & the like, before roland and the others joined the industry.)

SINCE THERE WAS NO BURNING SMELL before you changed the transistors
i would guess:
you mounted them improperly (?) lost te mylar insulator sheet or nylon washer (?)
mixed the transistors up? they are a complimentary pair (1) PNP (1) NPN
a solder splash across a ground?

it might be time to have someone who does electronic repairs (tv repair shop, if there is such a thing anymore)
look at the board. they will be able to check for an obvious short & compare resistance readings to ground

a little bit of experienced help can still salvage this project, before it becomes, "where can i get a replacement board?"

 

[kjbarrett]

yes, it would seem it is connected to head based on the manual. When I first changed the transistors they lasted about a week, even did a test print. Using a different working head.

turned it on to schedule auto cleaning and then later that day I smelled the burning smell. Has new head cables and known working head. If I disconnect the head ad slider cables from the mainboard I was able to boot into upload/Download and save my printer parameters. But then I tried to boot it normally and it will give a head warning as the cables are disconnected.

Once I reconnect cables and try a new boot, burning instantly even with new cables and working head. slider seems to test good at all tests. Its as though TP8 controls the head, should I try booting with head disconnected from slider board. maybe try the original head. its a 2007 jv33 with resettable fuse (not removable)

each try i have to replace transistors to give it a new try. burning through them pretty quickly at this rate. lots of soldering and replacing for each attempt. thermal pads insulators are in place and transistors in the correct order.

I may have to run it to an electronics place, could I just have a simple short or are there a few more tests I can try at the office. I have another jv33 that runs so this one is just a backup. of I get it backup and running

 

[netsol]

a couple things:
are the transistors original? exact number
are you replacing all insulators? nylon washers, mica (thin plastic)
are you using thermal heat sink compound?

have you ever done this type of thing before?

we probably need to compare resistence readings, channel to channel
i will see if i can get an exact service manual (these circuits are all the same BUT...)

i need to see exactly how this is connected, before i have a real suggestion

 

[kjbarrett]

they are all original with exception of the ones im replacing them with. But one is the 1742 and the other the 4550.

When I repaired it the first time all TP read about 17.5 ohms and tp8 was like 16.9 almost 17. so i figured that was close enough. Second time they blew the reading was more like 12ohms, i didnt even try booting with the number that low.

transistors read good, continuity on pins 1 and 3, and readings around the circuit seem to be ok, tested caps, resistors. I will try and replace the transistors tonight and see if I can start by leabing the slider unhooked. If its like before I should be able to get into paramaters, I dont think it will boot past the head error, I could be wrong

 

[netsol]

i need to look at a real schematic, or, at least one of mimaki's boards
SOMETHING is shorted now, by the sound of it, and you will only do further damage

 

[Smoke_Jaguar]

Electronics troubleshooting over text is near impossible. Most boards can be saved with time, expertise and a bit of luck. That said, look for things that move, connectors, ribbon cables, stuff like that. Seen a wonky ribbon cable kill a board on quite a few occasions where it wasn't seated correctly, and it shorted out a circuit. That said, finding the cause of the failure is only a fraction of the overall solution.

Look over the board, scan with your eyes, side to side, top to bottom. Look for cracks, scorch marks, swollen components, anything that looks potentially problematic. Heck, when something burns, I will even sniff the board, smells like utter ass when you pick up the scent of a burned component. Sounds crazy, but I've used it to surprisingly good effect. Also, take pics, the more visual of us looking to help always benefit from more information.

 

[netsol]

Electronics troubleshooting over text is near impossible. Most boards can be saved with time, expertise and a bit of luck. That said, look for things that move, connectors, ribbon cables, stuff like that. Seen a wonky ribbon cable kill a board on quite a few occasions where it wasn't seated correctly, and it shorted out a circuit. That said, finding the cause of the failure is only a fraction of the overall solution.

Look over the board, scan with your eyes, side to side, top to bottom. Look for cracks, scorch marks, swollen components, anything that looks potentially problematic. Heck, when something burns, I will even sniff the board, smells like utter ass when you pick up the scent of a burned component. Sounds crazy, but I've used it to surprisingly good effect. Also, take pics, the more visual of us looking to help always benefit from more information.

mimaki's are different
the rolands and mutohs are much easier.
i have almost no experience with mimaki & they have quite a bit of circuitry you don't see on the other brands

i would like him to have someone local to have a look at it, even a tv repair shop, if they still exist
much like when accountants are frantically searching for a minor error, you can look at your own work for hours, whereas, a fresh set of eyes will spot what is wrong in a few minutess

 

[Smoke_Jaguar]

High skill means less time, low skill means more time. But yeah, definitely worth having a pro look at it. Last thing you want is a bad repair taking out a printhead or other stuff.

And yeah, Mimaki does weird things. Never seen so many Altera Cyclone FPGAs in a printer in my life before. It's like their design mantra is based around complexity and expense.

 

[netsol]

there are lots of disreputable people in the semiconductor business
decades ago we had a supplier who would restamp cheap power transistors, with a number compatible with the commercial line sony monitors.
(selling a $3. part for $25. except they "smoked" in a day or two)
i haven't seen anything making player in that end of the business more trustworthy lately...

 

[Smoke_Jaguar]

Counterfeits are an absurd issue these days, all sorts of clones, copies and such. Tend to shop Mouser and Digikey where I can.

 

[netsol]

it appears to me, that although amazon tries to convince you that they are just the logistics end of this, they are often the guilty party when i order "the real thing" & get Chinese
garbage

 

[kjbarrett]

put transistors back in, getting good at it now.

picture attached. my repair looks rough but there are no shorts or bridges in the soldier.

Removed the 220 resistor and measured on and off board, 22.5ohm. Could there be a short possibly in the IC driver chip?

Any thing in this circut I shouyld check first. The TP8 test now doesnt read anything, numbers jumping all around, assuming no resistance? baffled.

Transistors are from CHINA

 

[Smoke_Jaguar]

Look where the arrow pointing at Q53 is, the component left of that mark looks pretty toasted. Might just be due to the camera however.

 

[kjbarrett]

poor solder job, had that small transistor off to test. swapped from one on the good circuit and no difference

 

[netsol]

first, take a tooth brush & flux remover or 91% alcohol & do a bit of cleanup
there is no resistance, because whatever was smoking is open circuit now
hopefully a small choke or micto inductor & it is not the printhead winding that smoked

 

[netsol]

it is damn near impossible to NOT DAMAGE those shitty little surface mount devices.
i know itt is a pain in the ass, but, i would not reuse one, unless you have access to a hot air rework station (and someone with a little experience using it. at my age, i simply can't do it any more. this is not a criticism of your work, just a real world assessment of the task in front of you.

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its really time to check the pins on those ribbon cables again