Dear Technical Manager,

I introduce myself as the managing director of Fanavarane Partow Danesh (FPD) Co. which is an Iranian engineering company with various fields of activity.
Though it's a young company but honored to have a seasoned technical team with engineers who have many years of experience in their career. Our main field of activity is repair, overhaul, maintenance and providing electrical systems as UPS, rectifier, inverter, frequency converter etc.

Recently we've been contacted by an Iranian glass company which uses Italcarrelli machines and the machines are equipped with Zapi drivers in turn. Italcarrelli machine type is TPEN and Zapi type is Dual-SEM3. As we're reported, the MTBF of Zapi drivers is very short. In some cases their life span is 1 month or even shorter!
At the moment we aren't seeking the reason of their failure but we've been asked to repair them. The system given to us has the following sticker:

F78008 – CHOP .Dual-SEM3 00/700
MAT: 05 45 300972131

At first step we checked the power boards and found them healthy, then changed some of the ICs of the controller board. The customer has an instrument that connects to the system and sets the parameters. When the customer engineer tried to connect to the system, that instrument showed no connection and the engineer told that its micro controller (SAF-C517A-LN) has been failed, so he used the control board of another system which its microcontroller was SMD type. Unfortunately after connecting battery to the system and starting the machine, the Mosfets of one of the power boards exploded. We think the problem related to the control board so we switched to the first control board.
What we did next was repairing the power boards completely and got a SAF-C517A-LN from the customer which they'd bought some for repair purpose from Italy. We Installed it on the board and substituted almost all ICs though there was no sign of burn on the control board. We also checked the diodes, capacitors and resistors and all were ok. The ICs which remained intact were U15(MM74HC244N), U16(MM74HC373N), U17(MX27C512), U10(93C46W), U6(ST62T25C6), U5(UC2843), U4(MM74HC14N) and U1(CNY17-3), because from our point of view they were all ok.
Last week we went to the customer factory and loaded the system on the Italcarrelli machine, connected the battery and started the machine. The wheels started running but after some seconds stopped working. The instrument which set parameters was connected to the system and it gave the alarm R V FIELD NOT OK. Then we tried back motion, the wheels rolled backward but again after some seconds stopped again. What I should note is that as soon as the system was energized its LED started blinking 7 times then after a short stop the period repeated again. What we did was substituting U17(MX27C512) and U6(ST62T25C6) with the ICs of another board and started the system. This time the wheels didn't move and we faced a new alarm CHOPPER NOT CONFIG, so we removed the 2 ICs and installed the origin ICs. It's strange to say that the status didn't change, that is, the wheels didn't move and the alarm was again CHOPPER NOT CONFIG. Of course we were lucky that during this series of tests the power boards faced no damage.

Now we hope to get a useful solution from you to be able to remove the problem.
We appreciate your reply in advance.

Best Regards

Abbas Ghoreishi
Managing Director

Fanavarane Partow Danesh Co.

Suite A1, No:1140, Satarkhan St.,
Tehran, Iran
Phone: +9821 44 268 690
Fax: +9821 44 260 580
Email: Ghoreishi@fpd-eng.ir