Making new AC DC transformer for La Z Boy chair

[Jonawald]

I have tried applying DC14V to the actuator terminals. There was no movement. Though I suspect there is circuitry inside the actuator that would stop and start movement according to signals from remote. It does have a round female 5 pin connector besides the 24V connector. I'm guessing there is a relay or a transistor hidden away in there somewhere.

 

[Jonawald]

I took apart the actuator. There is no circuitry inside there other than two limit switches. One for fully extended the other for fully retracted. There must be something wrong with the remote itself. The control board is in the remote itself. I will have to take a look at it sometime after I finish my current project over in the repair section.

Jonathan

 

[Jonawald]

So after dropping this and then finally coming back now that I have a bit of time to look at it I got everything working with the exception of one relay to get the actuator working. While I wait for the relay to come in, I temporarily set it up with a 3 pole toggle switch on a separate remote. This way I can get all functions of the chair to work. Vibrate and heat on original remote and recline/restore on separate stick with toggle switch.

One problem. The transformer I used seems to be a bit weak. The recline and restore are very slow. Getting it to go all the way up so that it brings you to a stand is torture indeed. Takes forever.

I have a stronger 24V 15VA transformer. The problem with this is that when I connected my board with this transformer, the remote got hot near the bottom. Where there is a 5V regulator. And one of the transistors that turns the vibrators on/off shorted out and until I replaced it that one vibrator was always on.

Power going to the remote is AC straight from the transformer. I suspect there is too much Voltage or Amps. I think I should be able to fix this by putting a resistor in on the AC side on my board to get voltage down. But since the chair already asks for 24V, I am not sure what value of resistor I should use.

Can any body help me with that. I know I could use ohms law to figure it out, but what's my target voltage?

Currently I get 27.5V form the transformer with only my DMM as a load.

 

[73's de Edd]

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Sir jonawald. . . . . .

Looking at the spec plate on that linear actuator /screw drive/ "Deltadrive" it sez it will be consuming 24 VDC @ 2.2 amps.

Dropping down to your #23 post you say:

One problem. The transformer I used seems to be a bit weak. The recline and restore are very slow. Getting it to go all the way up so that it brings you to a stand is torture indeed. Takes forever.

Is this the same transformer that you used before with the 4 diodes to make a DC supply ?
If so it must be quite puny in its current capabilities.

You next say in this entry
:
I have a stronger 24V 15VA transformer.

Now if you didn't make a typo on that 15VA spec, that "new" transformer would be WOEFULLY deficient and unusable for your power supply needs for that units 24VDC @ 2.2 A motor..
You need to be considering one up in the 60VA vicinity after leeway in considering losses...

How about going back to the activator and hook up the original power supply that you built up and have been testing the actuator with and measure what the power supply's DC supply voltage pulls
down to, when the linear actuators screw is running after about 10 seconds or so.

Then open one leg of the PS to DC activator motor and insert your DVM, set to its DC 10 amp range, and then do another quick test to see the motors amperage pull just after it has started moving the screw.

Thassit . . . . .

73's de Edd

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[Jonawald]

THanks de Edd. The transformer I use now is smaller than this 15VA transformer. I have a different transformer here. It is quite large by comparison, but it has a bunch of different voltages The pins directly connected to the transformer are labeled 5-12. I tested voltage on each pin. Using 6 GND here's what I got. 5 - 28V, 6 - GND, 7 - 28V, 8 ? 9 - GND, 10 13,5V, 11 - 5.2V, and 12 - 7.5V with my Digital Multi Meter. This transformer is out of an old large stereo system. Physically it looks large enough to have the amps I need, but I'm guessing some of this size is due to all the coils for different voltages in there. Am I wrong in this? or should I hook it up to a load, (the actuator) and then use my DMM on amps to see what it does?

 

[73's de Edd]

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Sir jonathon . . . . . .

Well the first thing noticed on that transformer shown is the AC line spec of having that 2.5 amp fuse on the AC primary . . . its loooooooking gooooood !
This must be from a Japonie . . . . . Matsushita family of product, being salvaged from one of those first day "big screen" tv's that used crt's that got used
by their owners down to their last bit of emission.
( Along with the crappy picture that they produced in that final poor emissive state. )

You found a string of different voltages, but don't look too hopefully in utilizing any "quasi-tandem-series--parallel -series aiding-push pull" arrangements in
order to eventually come out close to the voltage output that you now need.
The windings were for different voltages and SPECIFIC current needs in different portions of the set.
Ergo . . .having a mix-mash in the variance of wire gauges used for different windings.
HOWEVER . . . . .fortunately you have given that first pair of windings outputs as 28 VAC and that sounds like, just what you need.
Assuredly those windings were utilized for the differential +&- supply voltages for the audio power amplifier of the set, with logic of having system sound as
equally impressive as its associated "big screen".

You possibly lost me on ALL of the series of voltages to pin connections referencing that you gave in your write up, but I am just looking at your GOOD photo
of the unit and seeing that THE winding of interest is being the 5-6-7 terminal combo with those HEAVY copper foil traces associated with them.
(There IS some POWER being carried therewith !)

28 VAC --- 0 ---28 VAC would produce 56 VAC across the ends , so that would not be conducive of the use of a FWB rectifier.
So just use its equivalency, by use of a full wave rectifier configuration by letting pin 6 be the power supply's common negative ground.
Then one of two 2-3 amp rated power diodes has its anode connected to transformer terminal 5 and another, like matching diode has its anode connected to terminal 7.
The diodes cathodes are connected and your filter capacitor(s) + connection is made to them.
The filter capacitor(s) - connection is made to terminal 6.

Therewith, you then will be having a power supply which will be putting out in the order of 28 VDC, under the loading imposed by the the motor of that linear
actuator. . . . . .aka . . . . "Deltadrive"

Thasssit . . . . .

73's de Edd


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[Jonawald]

Um.... Let me take a bit to digest what you said and try to figure out if its English. Some of the words seemed familiar so there's hope. ...

 

[Jonawald]

So after re-reading - a few times, here is my best guess at what you are suggesting I do. Take out the solder in the red rectangle. Then connect pins numbered 5,6 and 7 at the arrows indicated.

 

[73's de Edd]

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Sir jonawald. . . . . .

Lets just call the situations equal . . . as I was having like difficulty in picking out ALL of the connections on that perf board construction of yours, since I only confirmed 95 % of it with another 5 % having a possible error factor at the corner Molex connectors.

Since you were not sure of my technical verbiage, as related to incorporating the utilization of a full wave rectifier circuit, a schematic is accompanying this post.

Since you used separate discrete diodes , vice a FWB potted block, you could beef up and parallel the pairs as per the dotted in option.

Howyoudoittoit:

Thassit


73's de Edd

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[Jonawald]

Thanks Edd. Your Eloquence amazes me. I have one question. Right now I have a 50V 3300uF Cap on the board. That was all that I had on hand when i build this. Should I keep using that or use a 35V 2200μF that I now have on hand? Is there an advantage of using the larger cap?

 

[Jonawald]

Well. That went well. ... .... ya I guess.

Now back to the original question I asked in #23. What to do when the AC side is too strong? The DC side works well. The actuator actually has plenty of power now.

The AC side is another story. The sticker on the chair states that it wants 24VAC. This goes straight to the remote, from there some of it must be converted to DC and used for powering transistors, LEDs and the controller. It didn't take long at all in my test this afternoon for the transistors to say to heck with being transistor i'll just be a jumper from now on.

I guess 28V is too much. But how much do I cut it down? I'm guessing ill need a resistor, but of what value? I didn't use both 5 and 7 pins, I used only 7 so half the amps that I used on the DC side if you get what i'm trying to say.

Jonathan

 

[73's de Edd]

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Sir jonawald . . . .


within Post 31
"This goes straight to the remote"

And I am interpreting "remote " as being a small unit that you press buttons on to change channels or TV volume . . .be it infrared / ultrasonic sound , or even in "olde dayes" directly wired.

With you probably REALLY referring to a controller circuit board.
Soooooo . . . . . for saving my look up time . . . . refer me to the / any post #(s) that are showing me that board, in order to evaluate and see what connector receives that 24VAC DC ??? supply.
In that manner, we might then realize that maybe "90%" of that 24 . ..now 28+ . . .supply is only intermittently needed for the minimally and infrequently utilized linear actuator motor, while we
are constantly in need of a true 24 V . .AC or DC ??? at the "remote" (Circuit board) at a possible 10% capacity of that power supply.
Then we figure how to get a reduced 24 V . .AC or DC ??? on that board.

73's de Edd
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[Jonawald]

Ok. Sorry about that. I guess I should have done this right away. Anyway here are pictures of the remote (Which I think, maybe erroneously, of any device that controls something else tethered or tethered.) I'll post pictures of the circuitry on the perfboard I hacked to get my DC and AC to the chair.

In the picture with the control board CS exposed, there are three transistors right under the bundle of wires. For sure two maybe all three of them are fried right now. There is a 5V regulator near the bottom of the controller.

I got to run, hopefully the pictures are good enough for now. Didn't take a lot of time with them I have got to run off to work.

Jonathan

 

[Jonawald]

just in case a closer look would help

 

[73's de Edd]

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Sir Jonawald . . . . . .


Well at least we can see that part or all of this hand unit is supposed to be running on 5VDC, supplied by the 7805 regulator on the end.
And if you have popped transistors, I might suspicion them to be the larger Q407, Q403 and the hidden one under the hook up wire matrix is
probably also being the same type.

I can see that one IC is a 74LS32 which is a standard quad nor gate . . . .but its not looking good for the other IC, since its having 18 pins and that is
not going to be a conventional logic chip . . .HOPE . . .that it was not damaged.

Was this hand unit working in earlier times. ****?

What are the voltage specs on the two electroltytics on the board.***?

Am I correct that the blue wire is the one that brings the raw . . .supposed to be 24VDC . . . to the left terminal of the 7805 on the board.***?

I would just take an educated guess that when you were running the linear actuator as a load on that supply, it would be loading down to
about a 29 volt level, but as soon as it was stopped the supply voltage would shoot on up to approx 39 volts, with it not being loaded.

So you are saying that this new power supply is wired to this hand unit, but are other boards being tied into this power supply also? ( I HOPE not )

For 65 + years I have always had a Variac . . . .eventually accumulating 5 of them . . .and I would have had it supplying the primary of that transformer
and adjust it to set the power supplys DC outputted voltage at 24VDC and tested the actuator, to see how much its loading would then drop that voltage under load .
Then bring up the AC to get 24 again while running the actuator, and bring back down just before turning the actuator off.

This remote board might be working with two supply voltages, the 5VDC, from the 7805 which we can see present at the end of the board, and a lower
voltage or possibly the full 24V. (++ In your case) to some of the transistors.
Your minor, small sized TO-92 cased transistors are probably LED drivers being interfaced with that 18 pin mystery IC's outputs.
I couldn't make out any ID #'ing on it from your photo.

Your far right terminal of the Regulator is the 5VDC output, in a power down state, how about ohmmming between that pin and the pin 14 of the 74LS32 to detect a
short and thereby confirm that they are running that IC at 5VDC.
Then probe all of the pins of the 18 pin to see what might be shorted to the 5V regulator output for being its supply line, to confirm that it was also running at 5VDC.

The top spec for the 7805 is 35VDC input voltage I SURE hope that this unit was beefy enough, that it held up to a bit more than that max voltage input spec .

Waiting for feedback . . . . whenever you're being able.


73's de Edd

No graphics references were utilized in this post.
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[Jonawald]

So it was as I expected. Two of the C238A transistors are kaput. Yes they were the big ones. One hidden under wires. I ordered new ones. at $3 for 50 I should have a few spare kicking around after everything is said and done. Now I wait for them to come. I don't expect anything else to be burned up. Still don't know what I'll do about the voltage being too high.

Jonathan

 

[73's de Edd]

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Sir Jonathan . . . . . .


Questions only this go around.

Are any other boards, in addition to this wired remote, being wired into this DC supply that you just assembled ?

Do you have acquaintances in the electronics field that might have a variac that they can loan you, and if not,
confirm that those friends might know of other friends that might have one.

It's being an item that usually only gets occassional use during power up testing..


73's de Edd


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