Rational Blues

[fixbear]

I fully understand that, as I also have signed my life away on some items.  I’m thinking the relay on the I-O board for the steam generator may be sticking. as a possible overtire cause. That or a input is not correct.and calling for generator heat.

[fixbear]

Then the ignition module has to get a control feed from some where. Gas ignition modules are built as fail safes.  It would have to have a signal from the blower that it is correct and a signal from the main control via the IO to fire, Is that correct?  RJ-45’s are notorious for getting damaged.  I’ve had to make a lot of them up over the years and have a Ideal cable tester just for that reason.  Displacement connectors are never good.  But a open should lock out fire, not lock in. 

 

The location of the ignition control is not in a stable area to stay cool. A minor moisture seepage with the burner heat is never good,  but much worse with the compactness of this design.

 

I like a challenge, but more important is a full understanding of what does what to be able to troubleshoot a machine,  Big or small.  Compound that with langage conversions and we go to a whole other level.  Unfortunately the only ovens I see here of this type are Baxters

[ectofix]

So here I go, rico,

 

I started to write out something very detailed, but that was getting too complicated.  Believe it or not, here’s my short version:

 

While I DO know that the boiler safety temp. limiter (F3) kills everything, I do NOT know what symptoms arise when just the control transformer fuse (F5) blows.  So how do you know that fuse is blown?  The schematic doesn’t illustrate that.

Nonetheless, undoubtedly I think that the fuse and the hi-limit are working as designed.

 

Although I don’t know what all can blow F5, I’m certain that it’s intended to protect the control transformer from problems on I/O board (A1) or the sensory components to that board.  The sensory components appear to be the door switch, drain-valve end-switch or the CDS sensor.  There’s also communication connections through that board via the BUS cables.

 

You’ve probably noticed that the I/O board (A1) happens to have fuses on IT.  In their case, I’m certain that those were put into the 208v feed through the board to protect IT from problems with the drain valve, solenoid valves, pumps, interior light circuit or the optional UltraVent hood.

 

The I/O board (A1) appears to command 208v output for operation of everything EXCEPT the burner assemblies.  But again, the BUS cables to or from those burners passes through I/O board (A1).  So the I/O board (A1) does have some role (however small that might be) in operating the burners too.

 

So the I/O board (A1) is central to nearly all oven functions.  It’s obviously very intricate in its design, handling the smallest communication signals…and up to operating mechanical things like valves and pumps.

 

YET – in that oven, the I/O board (A1) is cubby-holed into a place which makes it vulnerable to damage from a chemical or water leak – given its proximity to the care pump, hand shower, water lines and solenoid valves.  If none those aren’t found to be a problem, then look for…bugs.  YES, I mean INSECTS on the board.

(I’ve had both happen).

 

Water, chemicals or BUGS can make things happen on control boards that you’d never expect were possible. 

 

Anyway, so my thinking is that the fuse is going first.  If the board’s circuitry is jumbled due to moisture (or such), a possibly skewed signal might be keeping the boiler burner running when it’s not supposed to, which could ultimately run the boiler dry and trip the hi-limit.  When IT trips, that’s when everything goes dead.  Then they call you.

 

For that matter, I recommend looking over all your other boards as well. ANY signs of moisture (or any signs of its former presence of it thereof…like spatters of white chalky film) may mean you have a moisture intrusion problem to the boards.

I also suggest pulling and inspecting ALL connectors to all of them.  ANY corrosion in them or on the connecting points of the boards will be a hint to moisture intrusion as well.

 

Whichever board it might be (CPU, operator panel or I/O), if you find it’s been damaged -fixed whatever damaged it and replace the board.

[ectofix]

fixbear, that was my initial thought as well.  However, I looked at the schematic and was reminded that NO burner functions pass through any relays on the I/O board (A1).  I realized that because the schematic shows 208v feeds directly to the burner assembly component array.  Namely, 208v goes directly to:

An ignition control module

The burner blower motor’s board (motor is brush-less DC)

 

Communication for operating the burner(s) is through RJ45-type BUS cables.  Here’s a snapshot of that setup on the schematic:

 

This YouTube video further verifies that the I/O board (A1) only serves as a junction for the BUS connections (at least with respect to burner function), since I/O board (A1) is not included in this bench test:

Burner blower motor bench test

From left to right in the vid:

Operator PCB…with the Main CPU underneath (not visible) Ignition control board (usually encased in a protective, black shell) Burner blower motor assembly (also usually encased in a protective, black shell)

In addition to the I/O board, the video also lacks a burner, igniter, gas valve and air/fuel mixing chamber.  He’s simulated that flame current – as is read on the operator panel (labeled “FC”).

 

In an actual oven, the BUS line (if you will) starts at the operator PCB, into and out of I/O board (A1), then to BUS connectors for the burners and convection blowers.

 

Now…for your entertainment pleasure, here’s another video this guy made.  This the OTHER oven component that doesn’t rely on the I/O board (A1) in order to operate:

Convection blower motor bench test

The video is looking at the rear of the motor, which is actually laying sideways compared to how it looks in the oven.  Looks like the operator control panel he’s using is for a CM (combi-master) oven instead of a SCC (self-cooking center).  The CM is simply a more basic oven without all the bell-‘n-whistles of the SCC.  Both ovens use the same motor.

 

Here’s that convection blower motor in its protective casing:

 

Here’s all that crammed into a little brother to rico‘s oven – an SCC101G:

 

 

 

Credit to PartsTOWN for the individual component pictures.

[ectofix]

A question in that other Rational thread made me realize I’d mis-spoke in THIS thread that “120v” supplies everything.  That was wrong and I’ve correct them now.

 

It so happens that, although our Rational gas ovens can INDEED be powered from a standard 120v 15a outlet, the oven’s SYSTEM COMPONENTS are actually 208v (or I think it might actually be 230v).

Rational products are made in Germany, but sold internationally.  So they adapt each oven to their respective markets.  For the U.S. and Canada, there’s a step-up torroidal transformer added into the oven for us.  Our 120v powers that transformer, then primary oven power is from that transformer.

[rationaltechnician]

I know this is an old post and problem was probably solved by now.  But I see an opportunity to learn here and wanted to provide what I know.

 

To answer question about F5 1.6A fuse of T1 control transformer, this fuse is on the 11.5V secondary circuit.

The 11.5V circuit has only 1 purpose, the halogen lights inside the unit.

This is good so that a short on your light circuit does not take the whole unit out of commission.

 

Some may ask, what are all the secondary voltages on the T1 Control transformer?

2.5V-0V-2.5V – This simply is your A2 Display PCB touch display lights.  You’ll notice if you unplug this connection on X10 of PCB, you can still touch and operate your PCB.  You just can’t see what you are touching.

12V – This goes to the I/O PCB on X21.  The I/O PCB uses this voltage for the low voltage side of the board.  It also amplifies this voltage to 16V and sends it to the PCB through the RJ45 “bus cable”.  This is the operating power supply for the A2 Display PCB.  So you see, the bus cables are not just a communication, it also carries power.  Now that you know this, take care with these bus cables around the unit.  Damage to cables such as pinching behind a steam generator can short all connected components (PCB, I/O, Motor and ignition modules).

11.5V – Already mentioned above.  But notice only one line is fused.  This is the only supply that has a fuse on the secondary side of the T1 transformer.

 

T1 transformer – located behind front panel and square in shape.

T3 transformer – donut shaped.  Near front of 201 and 202 models (floor models as per Rational) and accessed from left side panel.  Under cooking cabinet on index E units (hand shower panel removed to access) but moved to left side back on Index G units due to introduction of Carecontrol.

 

What about the F7 1.6A fuse on the T3 “special transformer”?

This transformer, I believe, is specific to 120V North America.  It takes our 120V to 230V so that the rest of the unit can use all the same components for Rational built around the world.  So, you have 230V solenoids and pumps.  It supplies your 230V to the A1 I/O board on X21 for the high voltage side of that board (solenoids and pumps).  Note the onboard relays on the I/O board also operate with the high voltage (not the 12V as many would suspect).

So the F7 “inline” fuse on the secondary side of the T3 transformer kills everything if it goes. (No display).

 

So what can blow the F7 fuse?  You guessed it, everything that does not have a smaller fuse between it and this fuse (there are no smaller fuses).

 

Gas units:

On a gas unit, you will notice the F6 fuses on the A1 I/O PCB is after this fuse and are rated 2A time delay.  This always confused me.  If a solenoid or pump shorts, it is the F7 fuse the blows, not the F6. 

Electric units:

On an electric model, the absence of the T3 transformer and F7 fuse meant that the F6 fuses now play a role.  Instead of unit shutting off, you get no water and pump function and the get the energy optimizing symbol in manual cook modes (right side of second display looks like a E with a line going across.  Some people mistake it for an F due to the dot matrix display).  Why, because without 230V to the I/O board, the energy optimizing link is no longer linked (another topic).  Exact same symptom as auxiliary not closing on an electric model. 

 

All Units

If you suspect your K1 coil, unplug X21 on I/O, the T1 transformer, ignition modules and burner blowers and the cooling fans.  Replace fuse, switch on unit.  If it blows again, you got a bad coil most likely unless you missed a short on your wire harnesses.

Common on the 202G units to have water on Cleanjet pump because door gasket not changed (watch that lower left corner behind door gasket).  But also something dripping on cooling fan transformer (hose leak steam generator water supply possible).

As Rational always recommended, use a paper towel and run it around until you find your leak.  Seems so simply but effective.

 

Possible scenarios for your problem

If F7 fuse is blowing and the steam high limit is tripping at same time…I’m confused but intrigued. 

That high limit trips on high temperature while the fuse protects the transformer and wiring from electrical issues downstream.

But the power through the high limit is after this fuse so something must be related.  I’m guessing a loose or bad connection somewhere.  I would remove the wire ties and start running my fingers across those wires to look for nicks.

[ectofix]

Thanks for your explanation.  I’m going to copy & save that. 

 

Although it’s probably in the training manual and the schematics, I’ve rarely had a reason to break all that down.  Besides, you write English allot better than whoever translates German-to-English for Rational.  I WILL say though that they’ve gotten better.  I have manuals dating all the way back to the C-Line ovens because we still have some of those (built in the mid-nineties).  Those and (lesser so) the CPC-line manuals are hard to read.