Transformer substitution - Sanyo DP42849-01

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Would I measure the current with a clamp ammeter on the wires connecting it to the backlight? Also, I do have a few other board waiting for transformers. Maybe, since I don't have a working original at this time, I should put the transformer on a different board and see if it is the same.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

You may have to check the circuit current draws and compare it to the working original to see if the circuit is drawing too much current.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

After 24 hours of testing this, I think I may possibly have a problem. It seems like it's getting too hot. It doesn't smell hot, just feels hot. It's sitting right on the backlight with a plastic sheet as an insulator so that may be a contributing factor. I no longer have the housing for this, I wish I'd kept it now. I don't have a temp gauge and my stock board sold yesterday so I have no way to make any real comparison. What I do know is that I have 32.5 ohms resistance rather than 25.5 - 26.5 which was average on most working transformers I've encountered. Increased resistance is going to increase heat correct? Thinking about it, it's nearly 25% higher resistance than what I suspect it should be. So maybe I should use larger gauge conductor. I'm noticing too that in magnet wire, specifications seem to vary dependant upon manufacturer. I'm noticing now that if I give my caliper the slightest pinch, it reads 0.0045 instead of the 0.005 which I get from the old wire. I epoxied these things real good. I doubt I can disassemble them again. Advice?

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Thank you. I enjoy this stuff.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

You sure do have lots of patience on this project, great job.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Oh, the inductance was 36.4mh in the rebuilt, and 39.3mh in a working stock transformer. Both tested in board. The rebuilt sounds better than any I've encountered so far too. It is completely silent. A lot of the working ones I've encountered have a light buzz/squeal to them.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

I tested it briefly, just a few seconds but it was enough to see that it works. I want the epoxy to fully cure before I let this heat up.

This will be the counter I get. I'll epoxy the magnet to the handle and mount the proximity switch to the upright. I guess I won't be buying a ready made winder now. My jig works too well.
http://www.ebay.com/itm/5-Digital-Di...item4d1e220f6d

[Ltank]

Re: Transformer substitution - Sanyo DP42849-01

A inductive pickup. A simple loop of wire at end of coax on counter should work fine for checking the frequency.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

I used a caliper to gauge the wire (bare). I'm using 35 AWG triple poly nylon. They both read the same on the caliper. I'm going to get an electronic counter for my jig so I can better maintain the turn ratio. I did this slow so I wouldn't lose count though. I will test with the LCR too. I will have to pull a good transformer to get a comparison reading. I was careful to make sure I wrapped them in the right direction, which I guess would be the phase.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

It is the turn ratio that you need to maintain also, smaller gauge wire can have higher DCR compare to the the same turn using bigger gauge wire. You should also use LCR meter to test the inductance which is also important spec. The Phase of the winding should also keep that in mind.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Got the transformer wire today. Made this jig and am working on the first one. So far, so good. Resistance on the one bobbin I've completed is about 32 ohms. Working transformers I've tested were average 27 ohms. Is 5 ohms going to make a difference? Actually, I had a working transformer months ago which was 31.5 so this should be OK. Definitely could do better with a counter attached to this.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Got another one today with a bad secondary. 27 ohms on one side, 1.7k on the other. I might have found a way to get them apart. I soaked one of the broken ones in PVC pipe cleaner for 3 days and got it to come apart. So I'm soaking just the secondarys until this time Friday. I also made a pulling jig so I can evenly pull the ferrites without using pliers. Fingers are crossed. I'm still going to try to find a suitable replacement too. I'm trying to get a CRT oscilloscope, a HV differential probe, and some other stuff, from ebay.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

OK, I ordered these.

http://www.ebay.com/itm/121326345997...84.m1439.l2649

http://www.ebay.com/itm/Green-0-1MHz...item3ce27ddcb1

I'd rather have some higher quality equipment but I'll get better stuff eventually.

Now, how can I determine input voltage and power ratings? My Fluke can't read the high frequency input current.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Secondarys didn't take long. Here's a pic. Each section has 110 turns.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

I had high resistance on one of the secondarys. 1k. Good transformer was 26-27 ohms. Both were measured out of board. Plus, board worked with the good transformer which came from a board with bad PWM. I just swapped them out because the new PWM hadn't arrived yet. I did find a break in the one. The second one I didn't unwrap the bad side, it's still soaking. One I did a couple months ago burnt right at the pin but I didn't realize it until after I broke the ferrite trying to get it apart. I think I could have fixed that one.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

BTW, when you unspool all those wires, did you see any burnt wires, broken wires, if not, the transformer may not be bad then?

[stj]

Re: Transformer substitution - Sanyo DP42849-01

you counted the secondarys?


want to tell us how long that took!

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Oh, if they're parallel then the numbers would be correct.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

And I did it all twice so. Wanted to make sure I didn't miscount.

Here's the bottom view of one of the transformers. With pin out.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

Man, you sure did the details works and lots of patience.