Maytag DG606 Capacitor

[jmj75]

Hi,

My vintage Maytag DG606 does not shut off after it's activated. The heat cycles correctly so I'm certain that the thermostats are working correctly. The dryer has an electronic controller in it that has a large capacitor on the outside. I was able to test the components inside the controller to make sure they work, i.e., the solenoid/reed switch, diode, and resistors (there's also a neon light in the controller box that lights up). I suspect the capacior/diode/resistor/neon light combo are part of a crude RC timer circut. I can't find the entire controller, pt #303049, and suspect that the capacitor is bad. Does anyone know what is the capacitance of the the capacitor? I was unable to tell from looking at the markings on the capacitor.

Another indication that this capacitor might be part of a timer was an article I found online that seemed to indicate that there was once a "Capacitor Kit" for these dryers that would increase the dry time by ~8 min.

Knowing the capacitance I'd be able to replace it with something equivalent, e.g., an oil/paper cap with > 120V rating.

Any help or insight would be appreciated!

BTW, the shutoff solenoid that rings the bell and resets the selector switch is also working.. So I'm pretty sure the cap is where the problem lies.

 

[kenmore71]

The original capacitor on that control was a 100 volt DC 8 uF electrolytic capacitor. It is my understanding that the electrolyte will dry out over the years and these capacitors start to leak rather badly accross the plate. The trip voltage on the neon tube is supposed to be 78 volts DC so whatever you replace it with it must be at least a 100 volt capacitor, higher voltage is fine just don't go lower than 78 volts!. When I was shopping I found the Dayton 250 volt DC audio crossover capacitors on Amazon for about $5 a piece (I think they are a film capacitor of some sort instead of electrolytic which is actually better for this application). I bought a number of them in various uF ratings so that I could experiment with what worked best. Also know that you can connect capacitors in parallel and the capacitance is the sum of the capacitors connected (i.e. an 8 uF and a 2 uF connected would give you a total of 10 uF. Hope this is somewhat helpful.

 

[jmj75]

Thanks Kenmore71! Your reply is much appreciated.

I am curious if you (or anyone else on the forum) know the operating characteristics of the dryer? That is, how the thermostats, contact sensors in the baffle (inside the drum), and the electronic timer work together in the different drying selections. The schematic on our dryer has been discolored by age and I can only see part of it. I read a post on another forum that indicated that the baffles play a part in the operation of the dryer, but I'm not sure how (esp. in a specified selection mode, i.e., perm. press, damp, etc...).

Best I can tell, there is an over temp shutoff thermostat by the gas heater. Then, there are two more inside the blower housing. One was marked L150, I can't recall what the other was. I assume these play some role in sensing how dry clothes are, i.e., dryer clothes imply a higher temp for the air passing through the blower..?.. But information on the exact way in which everything works together would be helpful.

 

[kenmore71]

The Maytag electronic dryness control was a very ingenious and relatively simply early automatic dryness control. I believe it was introduced as early as 1961 although I could be off by a year or two. It definitely pre-dated the *06 series of dryers that were produced from 1966 to 1975.

Also, there were at least three slightly different electronic control designs and 2 different drum baffle designs that were used over the production of these dryers. That said, the theory of operation was the same with all of them.

In a nutshell, the electronic control produced low voltage DC current that was routed both to one plate of the capacitor and to alternating wires (on the pre-1968 wire baffle design) or one of the bar baffles (on the 1968-1975 design). There is a copper slip-ring behind the drum that has a small carbon brush riding it (much like a simple DC motor) that connects the electronic control to the drum baffles. The other alternating wire or baffle was grounded to the cabinet. When the clothes were wet, the low voltage current was being constantly discharged to ground through the circuit that the wet clothes made across the wires or baffles. As the clothes dried, they conducted less electricity and the capacitor gradually began to take on a charge. When the charge of the capacitor reached approx. 78 volts DC, it was enough current to created a momentary flash arc in the neon tube in the electronic control. This discharge was routed through a relay that then applied a momentary 115 volt AC circuit accross the chime/shut-off solenoid. Once this happened the control was put in the "off" position. The gas valve or heating element circuit was shut off at this point. The motor, however, might or might not actually shut off depending on the temperature of the discharge air.

There are three thermostats in a Maytag electronic control dryer: Two in the blower housing and one in either the gas burner "cone" or on top of the electric element housing "halo". The thermostat on the burner cone or halo is the hi-limit stat which is I believe rated to cut-out at 210 degrees. One of the blower housing stats is the "cycling stat" which is supposed to be rated in the 150 degree range. This is the thermostat that does the main job of turning the heat on and off during the drying cycle. The other stat in the blower housing is the "cool-down" stat which is usually rated at 120 degrees. This stat is wired in such a way that it keeps the dryer motor running after the shut-off solenoid has turned off the heat. It keeps the motor running until the discharge air temp. drops to about 120 degrees.

The actual cycles on the control varied slightly according to the year that the dryer was produced. This is a general summary:

Air-fluff operated only the motor circuit and ran approx. 10 minutes +/- about 1 minute.

Damp dry was designed to do just that - clothes were supposed to be about the right moisture level for ironing without having to sprinkle them. When the dryer is empty, Damp Dry should shut the dryer off within about 15 seconds or less.

Regular Dry was designed to get lightweight fabrics (sheets, light cotton) completely dry and heavier fabrics nearly completely dry. There was much debate amongst service personell and housewives back in the day about what the right of amount of "dry" was proper. Maytag tended to err on the ever so slightly damp side. An empty drum should shut off in the 9-12 minute area.

Wash n Wear (after 1969 "Permanent Press") was designed to insure that then "modern fabrics" (resin treated) were heated to 150 degrees or higher (to release wrinkles) and then cooled down to prevent re-wrinkling. Maytag also recommended this setting for heavyweight items such as towels and jeans if there were not dry enough on "regular". An empty drum should shut off in the 12-17 minute range.

Here's a schematic of the 1966-67 "wire baffle" design.

 

[kenmore71]

And the 1968 - 1975 bar baffle design
A close examination reveals that this design is quite radically different from the previous design and considerably more complex. I'm not sure of the resons for this. The theory of operation, however, remains unchanged.

 

[jmj75]

Fantastic! Thank you for sharing your detailed knowledge and taking the time to post schematics.  This dryer is a great appliance and built like a tank.

BTW, I ordered a replacement capacitor from Mouser Electronics, www.mouser.com. I went with one that was non-polar, http://goo.gl/8UZLu. I also replaced all of the electrical crimp connectors in my unit after I noticed that many were heavily corroded and brittle. So, now I just have to wait for the replacement capacitor to arrive.

Thanks again!

 

[kenmore71]

A footnote for the archives....

The later more complex design that debuted with the "bar baffles" in 1968 eliminated the need for the 120 volt input current polarity to be correct on a gas dryer in order to make the electronic control work properly.

 

[combo52]

DG606 Dryer Not Shutting Off

Pull the yellow wire off the EC box [ the same wire that goes down to the sensor ring ] and run the damp-dry setting, the dryer should shut off within 10-30 seconds, if it does your EC and capacitor are likely in good shape. At this point you have a shorted sensor sensor circuit.

 

As a service tech I have never seen a bad Cap on one of these dryers, but I sure it can and has happened.

 

The really common problem with these dryers [ especially the gas ones ] as they age are bad connections on the little circuit board where the wires plug on the edge, the best thing to fix this problem is to clean the connections and then solder the little terminals directly to the board.

 

[lowefficiency]

>> Here's a schematic of the 1966-67 "wire baffle" design.
>> ...
>> And the 1968 - 1975 bar baffle design
>> A close examination reveals that this design is quite radically different from the previous design and considerably
>> more complex. I'm not sure of the resons for this. The theory of operation, however, remains unchanged.

For the record, there was a third version of the schematic as well, with an altered electronic control circuit when Maytag switched from the reed switch to an SCR.

My 1975 documentation identifies the three electric variants as:
* MODELS DE806-906 WITH REED SWITCH & WIRE BAFFLE
* MODELS DE806-906 WITH REED SWITCH & BAR BAFFLE
* MODELS DE806-906 WITH (SCR) AND BAR BAFFLE

and the gas equivalents as:
* MODELS DG806, 906 WITH REED SWITCH AND WIRE BAFFLE
* MODELS DG806, 906 WITH REED SWITCH AND BAR BAFFLE
* MODELS DG806, 906 WITH (SCR) AND BAR BAFFLE

I don't have any information on when this change occurred, but my DE806 from August of 1975 is of the SCR variety, and has the SCR schematic glued to the back of the control panel cover. My understanding is that the revised control circuit carried the same part number (3-3049), as evidenced by this photo from member 'duke', so Maytag must have considered them to be functionally identical.
(From thread "Maytag DE806 Thanks", https://www.automaticwasher.org/cgi-bin/TD/TD-VIEWTHREAD.cgi?68522)

 

[daveamkrayoguy]

So sorry I'd missed out on seeing this in MINE!

Neat circuitry... Whereabouts in the actual dryer does this go?

-- Dave