[Joe / APP Team]

Originally Posted by acser

From page 9 of
http://www.dacorservice.com/PartsCat...s/Links/14.pdf

"-F1- Alarm “System Watchdog Circuit”
ERC Self-Diagnostic circuitry has detected a failure in the bake/broil system. Any portion of the ERC, relay board, touch pad, heating elements and related wiring may be at fault.
How to diagnose/repair potential cause:
Step 1: Disconnect membrane from ERC. If an F-1 alarm is not activated within 30 seconds, check membrane function test points with an OHM meter. (refer to page 20 of the Diagnostic Test Manual) If the membrane test switch fails, replace membrane. If membrane test is good, continue to step 2.

Step 2: At ERC check for 24 VDC between J2 pins 1 and 3 for upper/single ovens or J5 pins 7 and 10 for lower ovens (when lower oven is not in a cooking/clean mode) **Note: F-1 must be showing in the ERC/Clock Display. I you read 24 VDC at those test points, replace ERC"

My issue seems to be resolved at Step 1, which means that only the keyboard pad is shorted somewhere.

There are two alternative ways to fix this:
a) Check the front bezel. If it's NOT broken, cracked, etc.chances you can get away with just a new keypad. Order and replace just the keypad, which for RSD30S (black) is part number 86063B.
OR
b) If the front bezel is chipped, broken, cracked, I'd recommend replacing the front bezel, which also comes bundled with a keypad built into it. The part number for the bezel for an RDS30S (black) is 76480B.

I'd also recommend checking this web url as well:

http://www.smythies.com/~doug/misc/dacor_f1_fault.html

(Someone somewhere said that humid weather makes intermittent F1 problems appear more, this is perfectly logical with a shorted keyboard membrane.)

IMPORTANT: An appliance technician also told me that you should never use the self cleaning feature on this oven as the 800F+ temperature that self cleaning function heats the oven to almost guarantees that the keyboard membrane or control circuit/clock will be fried and you will see the F1 appear.

Acser,

Thanks for your input. It'll be of great assistance to others

[JohnGalt]

I believe the intermittent F1 beeping error I have been observing on a customer's RSD30S (and as reported in a number of other web posts) is the result of an electronic design flaw on the ERC circuitry which does not handle power line voltage fluctuations correctly.

For the record, I have about 30 year experience at troubleshooting electronic gear, especially gear with intermittent problems.

I'll give details below of why I believe this, but first here's the way I recommend to fix it:

Dacor reports to me that they can't fix this flaw at this point in the product life cycle (because the ERC is now out of production).

So the only reasonable fix that I can come up with is to add a simple 110V switch to the ERC power transformer to fully power down the ERC (the entire oven control) when the oven is not in use. This switch will have to be patched into the relay board's internal wiring.

If the cook wants to bake something they turn this switch on and do their baking and when done baking turn the switch back off.

Note that this will leave the cooktop lighters operational, but the clock will be dark unless baking.

Although several other fixes were contemplated, I think this switch will be safer and less of a hassle for the cook than having to go outside to turn the circuit breaker on and off when baking to address this problem, or to create a safety concern by overriding the malfunctioning fail-safe circuit.

I reverse engineered (i.e. drew a schematic of) the relay board and much of the ERC to arrive at this diagnosis and proposed solution.

First, there are no inputs from the relay board back into the ERC (not even one), therefore nothing that happens on the relay board could possibly be seen by the computer or cause this issue. So this error code simply can't be coming from the Relay board (as at least one other person on the internet suggested was possible.)

Second, the membrane is a rather simple device and if it is otherwise functioning correctly should not cause this problem. From my analysis the membrane does not appear in any way directly connected with the F1 error electrically.

Third, I was able to rule out the other classes of problems which can cause this sort of intermittent problem, e.g. tempature changes, broken solder joints, etc.

Fourth, we just replaced the ERC with a brand new ERC, and the symptom is the same. I think it is quite unlikely that two boards (especially with one of them brand new) have exactly the same flaw, unless it is a design flaw.

So after much study of this problem, it appears the feedback that the ERC is detecting that is setting the F1 error comes from within the ERC itself.

In particular there is a darlington transistor circuit (centered around Q11 and Q12) which enables the 3 heating elements on the relay board. Q11 grounds the 3 heating element relay coils to make them operational if they are also become powered up (on the other relay coil terminal). This happens on (J1 pin 3).

The output of Q11 is watched by the U2, the CPU (located under the clock display) via R43, D17. I'm pretty sure this must be where the F1 error code comes from. This is the only fail-safe circuit I could find on the ERC or elsewhere.

Here's how it works: If Q11 were to fail and short "on" (as transistors often do when they fail) then the CPU could detect this via R43 and D17, and set the F1 error code, start the beeping to alert the home owner that the oven might have come on on it's own, (in error), and as part of the fail-safe at that point the CPU could disable the 3 other transistors needed to turn on individual heating elements.

In other words to turn any heating element on first requires that Q11 be turned on and then in addition one or more of Q6 (bake element), Q13 (broil element) or Q14 (convect element) must be enabled.


All of this would work quite well except for two intersecting design issues:

a) The ERC has no voltage regulator. Any power line voltage fluctuations (such as an electric water heater, furnace, or well pump) turning on and causing what we commonly observe as dimming lights will also cause the ERC's internal voltages to fluctuate. I can only guess that the ERC designer thought he was saving a few bucks by not putting voltage regulators on the ERC. (It would actually have needed two of them, as the ERC has two slightly different negative power supplies.)

b) Although many circuits can tolerate this type of small power fluctuation without any glitch, the darling circuit unfortunately also employs C11 which is connected between ground and the Q11 base bias ladder.

The result is that when the power line rapidly fluctuates, the voltage across this capacitor does not, and the result is that the darlington may be briefly turned on, and this could be caught by the CUP as a F1 error.

Interestingly, my customer's home, is located at the end of a road and long power line. It's miles to the nearest substation so I can easily imagine that this line gets voltage fluctuations. Any heavy power load on that line will cause a voltage drop and then spike when the load is removed, once again: electric water heater, electric furnace, or well pump cycling. The water pump would be a natural at this as it's start up load is quite heavy. It's sort of a rural issue for power not to be as stable as it is in cities where power lines are designed in more of a grid to keep the voltage stable.

Finally, although it might be technically possible to fool the ERC into ignoring the error prone faill-safe input (by disconnecting R43), I don't think this is a good idea for safety reasons.

[Joe / APP Team]

Originally Posted by JohnGalt

I believe the intermittent F1 beeping error I have been observing on a customer's RSD30S (and as reported in a number of other web posts) is the result of an electronic design flaw on the ERC circuitry which does not handle power line voltage fluctuations correctly.

For the record, I have about 30 year experience at troubleshooting electronic gear, especially gear with intermittent problems.

I'll give details below of why I believe this, but first here's the way I recommend to fix it:

Dacor reports to me that they can't fix this flaw at this point in the product life cycle (because the ERC is now out of production).

So the only reasonable fix that I can come up with is to add a simple 110V switch to the ERC power transformer to fully power down the ERC (the entire oven control) when the oven is not in use. This switch will have to be patched into the relay board's internal wiring.

If the cook wants to bake something they turn this switch on and do their baking and when done baking turn the switch back off.

Note that this will leave the cooktop lighters operational, but the clock will be dark unless baking.

Although several other fixes were contemplated, I think this switch will be safer and less of a hassle for the cook than having to go outside to turn the circuit breaker on and off when baking to address this problem, or to create a safety concern by overriding the malfunctioning fail-safe circuit.

I reverse engineered (i.e. drew a schematic of) the relay board and much of the ERC to arrive at this diagnosis and proposed solution.

First, there are no inputs from the relay board back into the ERC (not even one), therefore nothing that happens on the relay board could possibly be seen by the computer or cause this issue. So this error code simply can't be coming from the Relay board (as at least one other person on the internet suggested was possible.)

Second, the membrane is a rather simple device and if it is otherwise functioning correctly should not cause this problem. From my analysis the membrane does not appear in any way directly connected with the F1 error electrically.

Third, I was able to rule out the other classes of problems which can cause this sort of intermittent problem, e.g. tempature changes, broken solder joints, etc.

Fourth, we just replaced the ERC with a brand new ERC, and the symptom is the same. I think it is quite unlikely that two boards (especially with one of them brand new) have exactly the same flaw, unless it is a design flaw.

So after much study of this problem, it appears the feedback that the ERC is detecting that is setting the F1 error comes from within the ERC itself.

In particular there is a darlington transistor circuit (centered around Q11 and Q12) which enables the 3 heating elements on the relay board. Q11 grounds the 3 heating element relay coils to make them operational if they are also become powered up (on the other relay coil terminal). This happens on (J1 pin 3).

The output of Q11 is watched by the U2, the CPU (located under the clock display) via R43, D17. I'm pretty sure this must be where the F1 error code comes from. This is the only fail-safe circuit I could find on the ERC or elsewhere.

Here's how it works: If Q11 were to fail and short "on" (as transistors often do when they fail) then the CPU could detect this via R43 and D17, and set the F1 error code, start the beeping to alert the home owner that the oven might have come on on it's own, (in error), and as part of the fail-safe at that point the CPU could disable the 3 other transistors needed to turn on individual heating elements.

In other words to turn any heating element on first requires that Q11 be turned on and then in addition one or more of Q6 (bake element), Q13 (broil element) or Q14 (convect element) must be enabled.


All of this would work quite well except for two intersecting design issues:

a) The ERC has no voltage regulator. Any power line voltage fluctuations (such as an electric water heater, furnace, or well pump) turning on and causing what we commonly observe as dimming lights will also cause the ERC's internal voltages to fluctuate. I can only guess that the ERC designer thought he was saving a few bucks by not putting voltage regulators on the ERC. (It would actually have needed two of them, as the ERC has two slightly different negative power supplies.)

b) Although many circuits can tolerate this type of small power fluctuation without any glitch, the darling circuit unfortunately also employs C11 which is connected between ground and the Q11 base bias ladder.

The result is that when the power line rapidly fluctuates, the voltage across this capacitor does not, and the result is that the darlington may be briefly turned on, and this could be caught by the CUP as a F1 error.

Interestingly, my customer's home, is located at the end of a road and long power line. It's miles to the nearest substation so I can easily imagine that this line gets voltage fluctuations. Any heavy power load on that line will cause a voltage drop and then spike when the load is removed, once again: electric water heater, electric furnace, or well pump cycling. The water pump would be a natural at this as it's start up load is quite heavy. It's sort of a rural issue for power not to be as stable as it is in cities where power lines are designed in more of a grid to keep the voltage stable.

Finally, although it might be technically possible to fool the ERC into ignoring the error prone faill-safe input (by disconnecting R43), I don't think this is a good idea for safety reasons.

John, Thanks for the input. A little involved for the basic do it yourselfer, but very informative, and specific. As you stated, it would be nice f engineers would include regulators on the control boards, but that's not realistic in todays economy and market. If the issue can't be traced back to the control board or key pad assembly then the issue is an electrical problem ( fluctuating supply) and that becomes a different issue and is not or cannot be resolved by an appliance technician.
With some time, effort, and experimentation most servicers have discoverred that a faulty key pad assembly can produce an F1 error code on most cooking products.