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Dacor RV36 vent not working (again)

Tim K

Premium Member
Joined
Jul 3, 2007
Messages
58
Location
Philadelphia, PA
Model Number
RV36
Brand
Age
6-10 years
So we have a Dacor RV36 raised vent (downdraft) that isn't working. It stopped working once before during a power outage a couple of years ago, but then started working again after another power outage (weird).

Anyway, about a year ago it stopped working and the service guy said it isn't worth repairing as it would cost as much as a new unit. That may be true, if I pay his service rates, but if I do it myself it may be worthwhile. Also, we thought we'd be replacing our kitchen by now but that isn't happening either. I'm trying to revisit the unit again as cooking without it is just becoming a mess for our house.

So back to the unit itself. When I reconnected the power, the lights were all blinking randomly and nothing seemed to do anything. Eventually they all went out. I've tried some of the troubleshooting tips and haven't found a solution.

Here is what I found online...

If the fuse is good check for continuity between the fuse and L3 (drive motor terminal)​
- If this circuit is open the PCB is bad and must be replaced.

If this is not the issue then it is very possible that there is poor electrical contact between the Touch Pad and the Contact Board.
Before replacing the Keypad Assembly check for a foreign material between the Touch Pad and the Contact Board. Examples of foreign material include grease, cooking residue, moisture, or residue from cleaning agents. Circuit board cleaner or equivalent (available from electronic supply stores) should be used to clean the keypad assembly.
To diagnose the keypad:
1. Disconnect the Keypad Molex plug at the Main PCB and attach leads of an Ohm meter to pins #12 and #13.

2. Push the UP/DOWN button. This must show a closed circuit
If the above test does not show a closed circuit, perform the following.
- Check for grease or any foreign material between the Touch Buttons and the contact board. Clean with an electronic contact cleaner as described above.
- Repeat test above.
- If the contacts are clear, replace the keypad assembly.
- If the circuit is closed, check for 120VAC between contacts N3 and L3 on the main PCB. If voltage is not present, replace the main PCB.


A. The fuse itself looks good. I tested for continuity between the fuse and L3 (assuming L3 is the unmarked line wire opposite L1 and L2) and it appeared closed (reading hovered around 0)
B. Disconnected the molex plug for the keyboard and checked continuity on pins 12 and 13 on the plug itself while the wife pressed the up/down button. No difference, the reading stayed at 1 either way.
C. I tried to access the keypad, but no dice. I can't manually raise the vent more than 2". Something is physically preventing it. Not sure if it is the motor arm, or something snagged, but I'm stuck...

If anyone can post more specific troubleshooting or offer any suggestions at this point I would appreciate it.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
37,664
Location
Murray, Utah 84107, United States
You probably need the control board. You need to find out what's holding it so you can check the voltage on the board.
 

Tim K

Premium Member
Joined
Jul 3, 2007
Messages
58
Location
Philadelphia, PA
Yeah, I'm going to have to deal with trying to pull out all the ductwork and the blower assembly to get in there. It won't be easy.
 

Goot

Premium Member
Joined
Jan 9, 2020
Messages
17
Location
Washington
Late to this thread ... but I recently had issues with my Dacor RV36 as well and decided to track down the root cause and share it here.

Symptom: Sometimes the buttons on the keyboard were totally unresponsive, other times they would sporadically work. Although "work" in this case means the vent may raise and lower somewhat and typically very slowly, but overall operation was erratic at best. Often the keyboard lights would flicker when the units was first plugged in.

The suspect electronic control board is behind a metal cover down in the lower right corner of the unit. After taking a close look at the control board I found the integrated DC power supply on the board (that supplies power to the control electronics) was defective. The rectifier circuit wasn't cleaning up the rectified AC voltage so there's was about 2 volts of ripple on the 5V power supply causing the electronics to act erratically.

The power supply is a simple half-wave rectifier design which uses rectifier diodes (D1, D2), a 28V zener diode (D3?), and a single 100uF capacitor (C2) to generate a 28V DC input to a 5V voltage regulator (7805A) which provides the 5 volts to the electronics on the board that make everything work. In this case, capacitor C2 (100uF, 50V) was defective allowing for the excessive ripple at the input to the 5V voltage regulator which then propagates to all the control circuitry.

You'll notice that the control board is discolored around these components. This is mostly due to the 28V zener diode running pretty hot in this particular design. But since C2 sits in close proximity to this heat, that's likely what caused its demise.

If you're any good with a soldering iron, it's fairly easy to replace any of these parts. I replaced C1 and C2 since both were being baked by the zener and the unit works perfectly now.

My searches online found replacement control boards in the $250.00 range ... so the few cents a couple of capacitors costs was worth the effort.

If you're having similar issues, replacing the board is straightforward (if you don't want to actually repair it). Just take pictures of the wiring, yank the board, stick the new one in and then put the wiring back together. If you can reach the board without pulling the entire unit out of the counter it should take less than 1hr to replace it.

Good luck!
 

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mwolfod

Member
Joined
Jan 19, 2020
Messages
1
Location
US
Late to this thread ... but I recently had issues with my Dacor RV36 as well and decided to track down the root cause and share it here.

Symptom: Sometimes the buttons on the keyboard were totally unresponsive, other times they would sporadically work. Although "work" in this case means the vent may raise and lower somewhat and typically very slowly, but overall operation was erratic at best. Often the keyboard lights would flicker when the units was first plugged in.

The suspect electronic control board is behind a metal cover down in the lower right corner of the unit. After taking a close look at the control board I found the integrated DC power supply on the board (that supplies power to the control electronics) was defective. The rectifier circuit wasn't cleaning up the rectified AC voltage so there's was about 2 volts of ripple on the 5V power supply causing the electronics to act erratically.

The power supply is a simple half-wave rectifier design which uses rectifier diodes (D1, D2), a 28V zener diode (D3?), and a single 100uF capacitor (C2) to generate a 28V DC input to a 5V voltage regulator (7805A) which provides the 5 volts to the electronics on the board that make everything work. In this case, capacitor C2 (100uF, 50V) was defective allowing for the excessive ripple at the input to the 5V voltage regulator which then propagates to all the control circuitry.

You'll notice that the control board is discolored around these components. This is mostly due to the 28V zener diode running pretty hot in this particular design. But since C2 sits in close proximity to this heat, that's likely what caused its demise.

If you're any good with a soldering iron, it's fairly easy to replace any of these parts. I replaced C1 and C2 since both were being baked by the zener and the unit works perfectly now.

My searches online found replacement control boards in the $250.00 range ... so the few cents a couple of capacitors costs was worth the effort.

If you're having similar issues, replacing the board is straightforward (if you don't want to actually repair it). Just take pictures of the wiring, yank the board, stick the new one in and then put the wiring back together. If you can reach the board without pulling the entire unit out of the counter it should take less than 1hr to replace it.

Good luck!
That is some impressive troubleshooting sir. I wish I had your electronics knowledge (working on it.......).

Mine is discolored as well in the same (apparently) troublesome area. Thus, I suspect I have the same problem.

Well, I can't solder too well and removing the darn board was troublesome enough, so I will just replace the entire Board.

Thank you for the highly educational and inspirational Post.
 

Retired Gman

Premium Member
Joined
Aug 23, 2018
Messages
25
Location
CA
MWOLF:

Love the detail here. I am handy with a soldering iron and am a retired Gov Engineer (PE). Mechanical. Only need a bit of guidance on which components to replace the board. Could you post a pic with arrows showing which ones to replace? BTW when I hit the up switch the board hums for a time then shuts off. Motor good. I do have heat discoloration on back side of board.

Retired Gman
 

Goot

Premium Member
Joined
Jan 9, 2020
Messages
17
Location
Washington
I've attached another version of the RV36 board pic below with some pointers locating the critical components for the issue described previously.

The yellow pointers are the two capacitors I replaced. The larger one is a 100uF, 50V electrolytic capacitor and the smaller is a 10uF, 50V. The 100uF cap was actually defective causing the issue. I replaced the smaller simply because it was so close to the hot zener diode. You can order these online through Amazon or any number of sellers for cheap, but they'll make you buy them in packages of 5 or more.

The red arrow points out the zener diode that is discoloring the board. If this part is bad your unit likely won't do anything at all. So if you're getting any lights, noises or movement, then the zener diode is probably okay. To be clear, the discolored board is normal so don't assume the board is toast just because its ugly! If the board is actually burned and/or the zener is physically burned (black and crunchy) then you're gonna need a new board.

The green arrow points to the 5V voltage regulator. The output from the zener feeds into the voltage regulator that then generates a 5 volt output the runs most of the circuitry on the board. Once again, if this part is bad you're not going to get any lights, sounds or movement out of the unit. If you have a volt meter you can check the three legs on the regulator (don't short them together accidentally when probing) and see if you have around 28 volts on one of the legs and 5 volts on another (the third leg won't have any voltage on it). If you have that then there shouldn't be anything wrong with any of the components mentioned above.

One other thing to mention, if the lights and controls on the panel seem to work okay, but the blower simply buzzes or struggles to start then you may have a bad start capacitor. The start capacitor is housed inside the metal enclosure that's holding the blower itself. It's a fist-sized "metal can" sitting inside the enclosure wired directly to the blower.

Hope this helps!
 

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Goot

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Jan 9, 2020
Messages
17
Location
Washington
Gman, is the control panel working correctly?
Does the lift motor do anything when you try to activate it?
 

Retired Gman

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Joined
Aug 23, 2018
Messages
25
Location
CA
Hmmm here are the pics of board around the components you replaced and one overall pic. That Zener area is slightly discolored as you can see.
In answer to your first question, the panel lights come sporadically on but do nothing when they are on.
 

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Retired Gman

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Aug 23, 2018
Messages
25
Location
CA
Yes every third or fourth push it clicks. It ran a bit on one of those. It’s a 110 VAC motor and it runs and moves the gears when I hook it up to house power. I don’t get 110 on the spades when I push the up button. Just a few volts AC.
 

Retired Gman

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Messages
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Location
CA
Hey Goot, not sure this means anything but with the board out and in my hand I get no continuity between the fuse and L3 spade.
 

Goot

Premium Member
Joined
Jan 9, 2020
Messages
17
Location
Washington
If you're seeing sporadic operation of the control panel, my guess would be you have the same problem with the regulator circuit. Your board layout is a little different, but the components seem to be the same from your picture.
That light blue capacitor just to the right of the transistor labeled "U5" is probably equivalent to the one that failed on mine. If it's labeled 100uF I can almost guarantee it. And the fact that it's still sitting right next to the damned zener makes it suspect as well.
Do you have a volt meter to check the pins on that voltage regulator that looks like its labeled "U2" as I described above.
Anyway, if you're comfortable soldering its pretty quick to just change that capacitor and see what happens. Be sure it has a 100uF and 50V rating and it does have polarity ... so make sure you place the new one with the black "----" marking in the same place as the original. And be nice when you're desoldering that thing so you don't damage the pads/traces.
If you want a little more confidence that cap is your problem, as an experiment you can temporarily solder the new cap onto the back of the board to the same pins without removing the original. If that part is your problem, just having the new one tacked on the back will fix it (remember to get the polarity right).

Good luck!
 

Retired Gman

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Messages
25
Location
CA
Wow thanks for the rundown. I’ve worked on circuit boards before I have the dishonoring suction tool and some of that mesh. I also have a Weller iron set up on my workbench for just this kind of thing. Will check all that out and let you know. Which of the tests you mention have to be done with the unit back hooked up to power and the motor? My guess is all of them correct? Oh and yes I have a VOM with which to make those measurements.
 

Goot

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Jan 9, 2020
Messages
17
Location
Washington
To make sure you're chasing the right problem, take the VOM (with power applied to the circuit board; the motors do NOT need to be connected) and check the voltage on pins 1 and 3 on the voltage regulator (designated "U2" on the board) It's at the top of your picture and labeled "7805CT" on the package.
Place the ground probe of the VOM on the case of the 7805CT voltage regulator (the case is the metal part of the regulator with the screw through it) and then place the other probe on Pin 1 (see picture below of the regulators pinout). Pin 1 should read about 28 volts DC. Then check Pin 3; it should read 5 volts DC. If that capacitor is bad both of those pins will read about 30% lower voltages they're supposed to be (ie. Pin 1 will be about 3.5 volts and Pin 3 will be about 20 volts.)
If that's what you see, then change that light blue 100uF, 50V capacitor right below the regulator.
Remember to observe component polarity if you replace it. Don't pull the old one out until you're ready to put the new one in ... and then place the component markings (the bold "------" lines on the side of the package) in the same position.

By the way the soldering setup you have is sweeeeeet for this!!
 

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Goot

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Yeah, and I hate tossing a $2,500 appliance when it just has a bad $0.35 capacitor. ;)
Good luck to you ..... and don't forget NOT to accidentally short the regulator pins together when you're probing them!!! It wouldn't like that. 😩
 

Retired Gman

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Messages
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Ok up here in Cali, after watching the market plunge, I think I’ll cheer myself up by saving big on the capacitor replacement. No worries on the shorting. Might buy it locally at Frys cuz I’m gonna need it operational by tomorrow. Stand by.
Gman
 

Retired Gman

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Aug 23, 2018
Messages
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OK test results: pin one 1.16 vac, center 0.0 vac, pin three 7.31 vac. See setup in pics. Fluke not hooked up in pic cuz I didn’t have 2 extra hands. Also can’t source locally cuz Frys is out of stock. Had to get from eBay see pic. 20 for three dollars. Gee now I can go into business!

Gman
 

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Goot

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Setup your VOM for DC and see what you get. I'm not sure what to make of your AC readings. Are you sure you're identifying the pins correctly. I'd expect the reverse of what you're reporting.
Anyway let me know what the DC readings look like and we can go from there.
 
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