Need help with an vintage air exchange controller... - Page 1
Forum section: electronics / repair

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 09:19:34 am
content: hey all you experts out there!!so a friend bought a house and it has this enerex air exchange controller unit. it appears that this unit drives 2 fans. It didnt work.when i took it apart, i noticed a very burnt 4.3k 5w resistor that had literally melted its solder joints and was literally loose on the board. I tried replacing it with the same specs and that appeared to "fix" the circuit in the sense that the 2 ouput lines (a set of 2 red and 2 black lines that appear to power the 2 fans) i was getting 17vac on one side and like 20 vac on the other. However , the resistor was getting extremely, extremely hot.so, i swapped it out for a 7watt and it seems to be not so hot, but i only had a 10k, so i know its not the right one, funnly thing is, i was getting the same output readings.the circuit has 3 400v 8a traics, a zero voltage switch, and then a 555 timers and what appears to be an optoisolator for the dc side.basically its not outputting enough current or voltage i am assuming. when i reconnect the unit, both fans appear to be trying to start but its as if they dont have enough juice, both fans are big 115vac rated fans, so surely this circuit is not working as it should be.there is zero information like schematics, or anything for that matter on the net.does anyone out there know what this circuit is, and how it should be preforming? am I supposed to be getting 120VAC on both of those red and black outputs? any idea how to test this thing, or rewire it or any advice at all?i have replace all 3 triacs, i have replace the 3059ca zero voltage switch, and i have tried several different resistors in place of the really hot 5w ceramic.any advice appreciated.thankschrisp.s the pics just show the controller, and the bottom of the circuit board. hopefully you get the idea, i can post better pics if needed.

author: tautech
author_rank: Super Contributor
timestamp: October 27, 2015, 10:09:22 am
content: Quote from: Electronic Federation on October 27, 2015, 09:19:34 amWelcome to the forum.Please do, PCB top side.

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 10:26:13 am
content: here you go!you can see the big 7w 10k resistor i whacked in there. i have tried a 4.3k 5w which is what was in there, but it gets way to hot. not sure if that is the spec resistor or if someone else tried to replace it, etc.also, i had to wire it in because the pads were toally blown and burnt off, and on the zero voltage switch the 3059ca, pin 4 which is current boost, has no pad, I am not sure if this is supposed to be connected somewhere without the schematic its hard to tell, there appears to be no trace going anywhere.urgh....any help would be appreciated.

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 10:29:24 am
content: also,you can see on the top left of the board, the 4 pin connector. thats where 120 vac comes in, and it connects to a fuse, and the power switch as well.fwiw.also the red and black wires i have assume are the 2 output pairs for the 2 fans? maybe i am wrong in thinking this? if i measure one red and one black i get a voltage, however one odd thing if i measure just a black wire on its own, i also get a voltage? i thought this was weird. So am i correct in how i am wiring the fans? one red and black wire to each fan?im lost with this thing. i need help!!

author: tautech
author_rank: Super Contributor
timestamp: October 27, 2015, 10:37:59 am
content: How's your reverse engineering skills?That's what I would do, it'll help you understand how the circuit works.You'll need a good few sheets of paper, an eraser and pencil.You'll get some tips from this thread:https://www.eevblog.com/forum/eda/pcb-reverse-engineering/

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 10:52:42 am
content: i could reverse engineer with some tips i suppose. my issue with this circuit is the use of the triacs.so where do i start ?

author: tautech
author_rank: Super Contributor
timestamp: October 27, 2015, 11:12:31 am
content: Quote from: Electronic Federation on October 27, 2015, 10:52:42 amIdentify all the IC's and active components and get their datasheets.Where IC's have multiple parts (logic gates etc) use those datasheet symbols (gate parts) and draw the connectivity pin to resistor/cap/bipolar/connector etc.Just correct errors as you go and even put it on multiple sheets until you can make sense of it.Use some symbol/identifier for off PCB items and condense it down once you've got it correct.Remember to mark polarities and pin #'s of components that need them.Study some simple schematics for guides on layout and symbols used.Circuit flow should be from left to right with signal inputs or sensors on the left.Lastly fill in passive device values.Others will have a different order to do this, I'm just trying to get you thinking of a path/process.It will take several attempts to get it neat and tidy.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 27, 2015, 11:28:53 am
content: For a 4.3k resistor to dissipate 5W, it must have at least 146V across it.That would be a normal operating voltage if this resistor is the limiter between high and low voltage circuits - which seems to be, given it is connected to pin 12 (or pin 5) of the 14-pin IC (which one is it, BTW?).Also, given you replaced the resistor and everything is working fine, I would assume the resistor was underrated by the manufacturer - I just ran into this when repairing a pool timer I have here: 3W where it should have been 5W. I blame this on planned obsolescence.Also, is the red wire on top of the DSC0002.JPG picture a jumper? If so, there is no reason (from a PCB standpoint) for it to be there, unless the manufacturer did not populate a proper fuse.

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 11:35:55 am
content: the red and black wires, i assumed were outputs to conecct the fans. well, its the only spot where the fans can be connected.yes, on the 14 pin dip zero voltage switch (3059ca) its pin 5 where the input ac voltage goes. the resistor in question obvious worked for many years and got real dang hot, which is why the board is charred, and the pads are destroyed.again, the red pair and the black pair of wires that the 2 fans hook up to. they seem to be twisted together in pairs, its it possible that one fan gets wired to black and the other to red? i had assumed that it was one red and one black to each fan?

author: Electronic Federation
author_rank: Contributor
timestamp: October 27, 2015, 03:51:29 pm
content: Quote from: rsjsouza on October 27, 2015, 11:28:53 amsorry, it actually goes to pin 3, the resistor, it goes to pin 3 of the 14pin dip zero voltage switch.my thinking is however, that my outputs (on the red and black lines) are no where near high enough to drive these fans. without the schematic, i have no way of knowing that the bloody output voltage is supposed to be. im not familiar with these types of circuits and using triacs. or if these are in fact the actual outputs for the fans, and IF they are one black and one red for each fan, or if its black and black and red and red, etc.anyone have any ideas on this?

author: rsjsouza
author_rank: Super Contributor
timestamp: October 27, 2015, 07:06:28 pm
content: Quote from: Electronic Federation on October 27, 2015, 03:51:29 pmI beg to differ; due to the way the DIP package is configured, the resistor is either connected to pin 5 or pin 12 (the third pin from the outside of the board towards the transformer). Also, theCA3059 datasheetindicates the power resistor should be connected to pin 5 - it even gives some details on the implementation that will greatly help you with the schematic capture.Quote from: Electronic Federation on October 27, 2015, 03:51:29 pmLook at the fans themselves and see if they have a voltage rating - this will help you determine if the output voltage of the circuit is compatible. You will have to connect a load to the outputs to get a voltage.Quote from: Electronic Federation on October 27, 2015, 03:51:29 pmThink of TRIAC as a switche electrically controlled by a pin (called Gate). In your DSC0002.jpg picture, the Gate is the pin closer to the small red/orange glass device (a DIAC, which helps trigger the TRIAC), which in turn is driven by a simple dimmer circuit (where the speed is set by the two 100K trimpots). There is a third TRIAC that is controlled by a small transistor (which in turn is connected to pin 4 of the IC).Search around on the internet for "dimmer with triac" and you should find some common topologies.Quote from: Electronic Federation on October 27, 2015, 03:51:29 pmThe PCB wiring indicates each fan is a pair of likewise wires (red-red for fan 1, black-black for fan 2).

author: Electronic Federation
author_rank: Contributor
timestamp: October 28, 2015, 06:57:21 am
content: Quote from: rsjsouza on October 27, 2015, 07:06:28 pmthis also now makes total sense. very awesome information. thank you very much, if you could answer the questions i asked here i think i should be able to revisit this and get somewhere. adding a load to the circuit is what im really wondering about.thanks for taking the time!

author: Electronic Federation
author_rank: Contributor
timestamp: October 28, 2015, 07:00:55 am
content: hey rsjsouza, one more question also.on the zero voltage dip, the current boost pin, isnt connected to anything. the pad was gone when i got the circuit, since the old zero voltage switch had crapped out.pin 3 current boost pin. i cannot see anywhere that it was connected to. based on your expiernce should this be connected somewhere in this circuit?i guess I will know once i fiqure out how to get a load accross those 2 outputs.thanks again.

author: rsjsouza
author_rank: Super Contributor
timestamp: October 28, 2015, 11:37:52 am
content: According to the datasheet pin 3 does not necessarily need to be connected to anything.The load can be anything, really. Just for testing I would connect some 115V lightbulbs and perform some measurements on the output of the TRIACs. Keep in mind the following details:- As I don't know your level of experience I have to say this: play it safe with outlet voltages. Use a somewhat small fuse (1~2A, for example) when connecting this whole thing to the mains (to protect the equipment and the wiring) and connect everything to a GFCI outlet (to protect YOU). Don't skimp on any of these (I know this frommy own experience). Also, before connecting everything, clean your workspace from these rolling screws, small blobs of solder, small round all-metal precision screwdrivers, etc.- When measuring the output voltage with a multimeter, you should see a voltage lower than the regular 115Vac - this is due to the speed control adjusted by the trimpots. Mark the original position with a pen and twist it around to see if the voltage increases and decreases. This will be a good indicator of the normal operation of the TRIAC.- If you have an oscilloscope and probes that are able to withstand the rated voltages, you can see the waveform of the TRIAC and compare to waveform references that you probably found by performing the internet search I suggested before.- If the voltages measure ok but the fans still don't spin, then you can suspect the fans are the problem.

author: Electronic Federation
author_rank: Contributor
timestamp: October 28, 2015, 07:28:17 pm
content: Quote from: rsjsouza on October 28, 2015, 11:37:52 amagain, excellent advice all around that i will follow. i have experience I work on arcade stuff, monitors and the like so I am familar with a variac, and being safe around 30kv on a 2nd anode of a crt. never really ran into triacs and motors before and your excellent advice has taught me a ton. just what i needed a push in the right direction.thank you and i will report my result I have a lecroy 9310 300mhz scope. ill use it and post results.thanks so much.

author: Electronic Federation
author_rank: Contributor
timestamp: October 30, 2015, 04:45:43 pm
content: update.ok, so when I tried to attached 2 lights, for a load on this thing, I get nothing. On the 2 sets of outputs, when there is nothing connected as a load, i get about 12vac on the 2 outputs. when I connect the loads, (just 2 basic light bulbs, 60watts) i get nothing, not even the 12vac thats normally on there.am i using the wrong type of load? when you said, 115v light, maybe i am using the wrong load?thanks!!!

author: zoltan
author_rank: Contributor
timestamp: November 08, 2015, 06:52:44 pm
content: Hi there!Others made a lot of good suggestions. I will notI've been in HVAC/controls industry for almost 10 years now. If this thing was in my house, i'll throw this thing out ASAP, even if its 100% working.What I'd suggest to you, is the following:- find out what type/rating the vents are- check how they are connected to ducts, maybe there is something that opens/closes the in&out-take, probably two on/off air dampers on intake/exhaust (the third triac).- when you know exactly what is going on, take a seat, a favorite microcontroller, some power outputs (triacs, relays, ...) and do it from scratch.You can then incorporate free cooling on summer nights, shut down or start the ventillation based on RTC or temperature, etc...That last step would probably take no more than a hour to design, solder and program the thing for basic functionality.Or, buy a new/used controller. The basic types are dirt cheap.