mosa ts200

[TiN]

OK Great Memmeddu, i will check this well noted, and i come back to you. Thanks a lot.
Nota : the LM348 becomes now giving a different voltage that's increase up by the potentiometer adjusting; but the strange is the pin q2 of TCA785P n°15 is at 0v and the q1 14 is having 3,6V 5KHZ the thing that i couldn't understand why this q1 output is connected to anypoint is working and the one who is used supplying the signal to the ZTX455 is at 0V, what could be blocking this output ?
i upload for you the back side of the pcb.

 

[Memmeddu]

Try to refresh all these solderings that semes very ugly
About your question I'm not an electronic engineer but I'm only an electrician ,my experience says that there's a short circuit and something went very bad because the back side of the PCB is kind of totally burned up ,so I guess that the main power came into the low power circuit and that can be caused by a capacitor an inductor or also a varistor that failed allowing the current to pass through and made this
I think that is something more of a little component failed .
Is your engine controlled by a manual throttle?

 

[TiN]

Thanks Memmeddu for your response, i come back to you for my next result. for the engine is an automatic accleration.

 

[Memmeddu]

I have an engine driven too
My genset is manual throttle (autoregulation)
My outputs are controlled by the throttle
So more rpm =more out put current and more out voltage ,if you can not find the failure on the PCB you always hack your welder to be manual controlled
So you have to find the wiring diagram as we can look at him and know if is possible do this modification that is absolutely bomb proof because if we can remove all the Elettronic we can run the welder and have an out put
That's an idea ,not totally sure if we can do it (spoke plural because I think that you need help to do this)
My engine driven work's this way
8Hp gasoline engine makes spin a three phase alternator
This alternator have 3 windings , each one is divided in 3 sections .
These 3 windings are connected in Y configuration ,the center of the star is the neutral knob
So at the very end of the winding we have the live conductor
Live to neutral we have 120V or 230V (my welder have not 120V)
Live to live 240V or 400V
Now you're thinking
Where does the welding current come from?
Easy you remember I talked about windings
They are 3 series windings on each phase so we a total of 9 windings in parallel at the diodes
3 of them are in series with inductors
3 of them are high output
3 of them are low output
The three phases are connected to a capacitor battery (3 capacitor 500uF connected in Y configuration)
When you drain ac power the windings works in series (more ohms less current but at the same moment more voltage)
When you drain welding current they works in parallel so we have high current put and almost 120 OCV DC or 96V something in this lines
Capacitors are needed to start and repeat this process
Any and I mean any conductor that come out from the alternator goes to 2 diodes (+ and -)

This is how this thing works
It's not difficult but if we put works this by a PCB is something of absolutely hackward to understand
This board provides to have a costant and totally clear output
That is good but not completely needed
What this do ?
Easy ,
1 it reads how much output do you have
2 it tell to the engine the speed
3 if low it makes the engine rpm get up
If high make the engine slow down
4 open circuit it automatically puts the engine to idle
If you take AC power the board increase the rpm as you can use the AC power
If you take welding current it increases the rpm but the quantity that you need for an exapexa 100A

Removing electronics you have to go to the welder and read a voltmeter ,and manually throttle the engine to the power that need
Little bit boring but nothing can go wrong you have only to remember if you need 230V and the welder is giving more than that value because is max up to slow down the engine

 

[TiN]

very interesting, but it concerns more the generators made for only voltages distribution 220V 50hz and 380Vac, therfore if there is a welding obligatory you need electronic regulation with all devices (board+pot+Shunt+mixed bridge).

For the generator with only voltages it has a board called AVR.
i am concentrating with my problem to fix it, when i have a news i will let you know.
My Respect and good continuation.

 

[Memmeddu]

very interesting, but it concerns more the generators made for only voltages distribution 220V 50hz and 380Vac, therfore if there is a welding obligatory you need electronic regulation with all devices (board+pot+Shunt+mixed bridge).

For the generator with only voltages it has a board called AVR.
i am concentrating with my problem to fix it, when i have a news i will let you know.
My Respect and good continuation.

Try to remember me the exact model...
I check out for you to find the PCB diagram

 

[TiN]

Oh it will be great helpfull, ok it's a TS415VSX/EL-BC the pcb reference is 20801.9.800, for your information i v'e downloaded from the internet the use and maintenance manual but it is not enough to solve the problem.
Thanks another time Memmeddu

 

[Memmeddu]

Oh it will be great helpfull, ok it's a TS415VSX/EL-BC the pcb reference is 20801.9.800, for your information i v'e downloaded from the internet the use and maintenance manual but it is not enough to solve the problem.
Thanks another time Memmeddu

Yes in the service manual says
Welding current control PCB , number 65 in the parts diagram.
Taking a look a the diagram seems that the welding current is regulated by the throttle but also some switch that put more or less windings in parallel to the rectifier bridge
It's more complicated than what was thinking
So the PCB must be repaired or replaced
Have you tried to call MO.SA ?
Because I see that this welder cost something like 10.000 euro

I think that there is a shunt or an hall effect sensor
Because this thing when you are using more than 250A (or 200A) disconnect the generation section
You are running all the time to something like 400A
You must check for the switch or a fuse that allows this board to work .
But if you need only the generator function you can bypass the 400V contactor , and disconnect the power to the etxiting coil on the welding current contractor
You have something like 100A on the welding side and 12 kW I guess on the power generation side .
Can you do some photos of the internal of the machine maybe we can study an easy not electronic circuit to have some sort of regulation
We have 10 (i must recheck )knobs for the gross arrangement and the engine throttle for the fine arrangement
I think I understood how all this thing works
Holding always the same problem now
We can do step regulation off the current out put ,stop the generation side stop the welding current
Do "fine" adjustments but not fine because you can find your current but not have an idea of how much output you really have
Example we have step control at 100A , now by using the engine speed we can reduce this or increase but need an amp meter to be sure so this is a problem
You may think to have 90A and maybe they are 120A
I think that is an idea that can work but this is the plan B if the PCB is totally died (I don't think because she gives the highest output command )

 

[eddie49]

The TCA785 is a phase control chip, used to vary power by altering the time after the zero crossing point of an AC source that a firing pulse is sent to a thyristor/SCR/Triac. In an earlier post Jim Davey mentioned SCRs. So assuming this machine has them, have you checked these components for short-circuits ? If you disconnect the ( thin ) gate wires, do you still have the same fault?
Regarding your troubleshooting around the TCA785 chip, I guess that you are reverse-engineering the schematic diagram of the PCB, or do you have the diagram? If Q1 is active but Q2 is stuck low, that could be a fault in the TCA755 chip or a short at the base of the ZTX455 transistor that the chip drives. You could lift or cut Q2 pin 15, or the base of ZTX455, or the PCB track between them, to check if Q2 goes active when not under load. You could also measure the "not" pins to see if they are valid. Pin 2 is "Not Q2" and pin 4 is "Not Q1" - i.e. the inverse of the straight outputs.
Regarding the large blue electrolytic capacitor - there are 4 fat diodes near it, so probably a bridge rectifier + smoothing cap. Measure and if possible view the DC voltage across the cap, if the ripple is low it's OK.

 

[TiN]

Hi Dear
-Yes i've ask them for a diagram but they don't want.
-the welding current is regulated by the throttle. --> No. the welding current it is regulated only by pcb 65 as you said.
-You are running all the time to something like 400A . yes like the defective board it bypass the regulation and it gives around 320A.
-You must check for the switch or a fuse that allows this board to work. No there is no switch nor Fuse for, there is a dual volatge ac transformer that makes with some components a symetric power supply of +15VDC and -15VDC and GND.
-No we can not make it function with a different points of welding currents unless we have the proper electronic board.

Anyway big thanks to you for this effort, as i told you i am going to fix it and i'll resume to you all what i did, but please if u can provide to me the pcb diagram i will gain a time.

Regards

 

[TiN]

Hi Eddie Thanks for your contribution.

-Yes sure i am doing a reverse engineering for this repair.
-Yes, i 've checked the voltages all are ok offset for the ua741, the lm341 too +-15VDC. No short circuit.
-No i isolate already the board from the engine because i 've done a like a simulator in my workbench, already the 3 gates terminal are free.
already to gain a time i replace all 3 TCA785P and all ZTXs but it gives the same issue, no signal voltage at the primary pulse transformer. even i isolate the 10k resistor going from pin 15 and going to base of ZTX.

#Regarding the large blue electrolytic capacitor - there are 4 fat diodes near it, so probably a bridge rectifier + smoothing cap. Measure and if possible view the DC voltage across the cap, if the ripple is low it's OK.

-yes already checked at the first time there is a 27VDC smooth. and going to regulators +/- 15VDC to supply the ua and LM.

For THe 3 opto are used here to supply +15VDc of the TCAs this is not direct.

ok, i am right now found that the Q2 is always in low state but the Q1 is giving a square signal with 3,7V 5khz, this is the issue because this output is not connected to ZTX, the Q2 who is connected but unfortenately it is steady at 0V, so i study the tca i found that it should be a signal form of sawtooth with positive ramp if not this needed output Q2 will be sticked ever in 0V.


To be continued....

Regards

 

[eddie49]

Thank you for your description of your work so far.

It is perhaps still more likely for high-power and high-stress components to fail, rather than control logic, so I would check the SCRs for short-circuits ( and also the other power diodes, assuming this is a half-controlled bridge ).

There are three trigger circuits, all with TCA785's and pulse transformers. It is unlikely that all three have failed. Do the signals and voltages on all three circuits behave in the same way? All three Q1 have signals and all three Q2 are permanently at 0v ? If so, the fault must be earlier in the circuit.

Often optocouplers are used to send the gate trigger pulses to SCRs, or pulse transformers are used. This provides electrical isolation between low-voltage control electronics and the high-power/high-voltage components. In this circuit, there are both optocouplers and transformers?

According to the Siemens datasheet for the TCA785, the sawtooth ramp voltage develops across a capacitor at pin 10. It is compared with the control voltage at pin 11 ( perhaps from the potentiometer ), and this determines at what point in each 180 degree half-cycle the trigger pulse for the SCR is generated.

The Mosa generator may run at 50Hz, 60Hz, or perhaps a higher frequency ( e.g. 400 Hz ? ). However, the datasheet states the maximum operating frequency for the TCA785 chips is 500 Hz, so I don't understand why you are seeing a 5 KHz squarewave on pin 14.

 

[TiN]

Thanks to you too.

Ok, in fact this welder engine the first status was the potentiometer defective and the mixed bridge thyristor and diodes was out of order, and i noticed that a power resistor near a second bridge diodes was broken i think by the maximum current.

so i have repaired the bridge and i replaced with other power resistor even i don't knew the exact value anyway i have replaced the 5k potentiometer.

After that i checked the welder after all this intervention it gives the same, then i resume that a question of a board malfunction, i was thinking immediately on amp op because there is no reaction between the regulation and pot position, the two i v'e changed them but the same result; thus i go far and i found those TCAs no output on pin15.

Yesterday i made more analysis about the problem, sure i'll give you a feed back for the next task.
thanks for You MR MEMMEDU and Eddie49 for your reactivity and all my thanks to mig-welding co uk is a geat forum.

Mr MEMMEDU what do you think if i remove i mean i bypass this spiral power resistor who is in the side ? because i 've heard a lot of people they remove and no problem!!!

 

[Memmeddu]

Mr MEMMEDU what do you think if i remove i mean i bypass this spiral power resistor who is in the side ? because i 've heard a lot of people they remove and no problem!!!

Generally speaking a power resistor is mainly used as current limiting device
So I think that if you remove it and bypass using a wire you'll probably cause the totally loss of the PCB
But you can remove it and check the continuity if is open circuit you must replace it if is into the rated range is ok and you can reinstall it .
If they use this resistor there's a reason surely so PCB needs it to work

 

[TiN]

i mean the power spiral resistor not 10W mounted on the PCB. Please sir can you share with me the pcb diagram if you have?

 

[Memmeddu]

Oh sure now I understood , answer is not .
It seems more like an inductor but if they said that is a resistor I think that it is
So look the start and the end of the lead where is attached
Y point of the windings is the start ,then is mounted onto the rectifier bridge then goes to PE plug
Now I think that is some sort of filter or safety features or even a part of a bigger apparatus to allow a better start when using a Tig torch or E6010
I suggest you to try to completely unhook it without bypassing it
Then try to check what this causes
I have your same diagram
Ps please I'm to young to be named sir

 

[Memmeddu]

Ok is maybe something that is related to
arc force?
Cellulosic mod?
Costant voltage mode?
68V/72V?
There is a contactor between the positive side of that circuit connected to a switch
So that circuit can be related not to current regulations but only related to somesort of welding settings

The problem is on the other side of the circuit so or in the triristors (very plausible) or in the board
Have you some kind of setting on the machine over then current settings?
Many questions are because the owner manual is too poor ....

 

[bwservices]

its arc force
the machine probably has a on/off switch for it,instead of a potentiometer

 

[TiN]

I see the community here is in a deep sleep, what happens no help no assistance from the skilled and pro members, only Mr Memmeddu who is talking in his electricity level!!!
Anyway i am in succefull real progress in my repair.

 

[Memmeddu]

I see the community here is in a deep sleep, what happens no help no assistance from the skilled and pro members, only Mr Memmeddu who is talking in his electricity level!!!
Anyway i am in succefull real progress in my repair.

We need to know
don't leave us alone waiting to know if it works or not