# Flyback Transformer Pin Identification

#### Richard Trump

Joined Jan 17, 2016
5
I know this is an old topic, but I've tried many of the old ideas with no luck. This is a 10 pin transformer from an old Magnavox color tv and I'm wondering if there is something wrong with it because my readings seem odd.

First, I tried to find the 0V pin on the secondary by running 15V DC through the HV red wire and checking each pin for voltage. I found 0.54V on pins 2,3,5,6,& 9. A quick continuity check showed continuity between all of these pins and each other. This confused me at the start, because I expected to only find 1 pin for the 0V on the secondary so I don't know what to make of this. I tried reversing the polarity of the DC source and got no voltage that way so the polarity seemed correct.

Secondly, I looked for the primary by measuring the resistance between all of the various pin combinations and found 12 combinations with resistance between 0.8-1.3 ohm. I had read that the primary pins are usually adjacent, the only ones meeting that criteria were pins 5-6 which had 0.7 ohm (but both of those seemed to be associated with the secondary circuit...possibly). Several other combos had resistances around .5 or less.

Since I didn't know what to make of all this I thought I would try the brute force approach. I have an 11 volt AC source, so I ran that through every possible combination of pins that had shown resistance or continuity, and checked for any output from the red HV wire with each unoccupied pin as a possible 0V pin. From this I got about 16 combinations that produced an AC output, but none that were over 2 volts. This also confused me because I had expected a significantly higher voltage from at least one of these.

This is the first flyback transformer I've tried to salvage, so I'm either missing something glaringly obvious to everyone, or I got a very strange/bad one here. The transformer itself is from Mexico, I googled all the numbers on it and found some documents in Spanish but they weren't very useful (I don't even know if they were about anything electronic). It also has a thick white wire coming from the top attached to focus/screen controls and a thinner white wire coming from the base ending in a single connector.

Any suggestions appreciated. I just have my multimeter, 11V AC, and 0-15V DC sources for testing purposes.

Richard

#### Dodgydave

Joined Jun 22, 2012
9,307
Pictures of it would help, also what model tv was it from?

Also Lopt are tuned to 15.6Khz, and dont work well at low frequencies like 50/60hz.

#### Richard Trump

Joined Jan 17, 2016
5
It's a 19" Magnvox from 1992, Model given is RR1937 W122

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#### Dodgydave

Joined Jun 22, 2012
9,307
Ok, what are you trying to achieve, repair the tv or use the transformer for another purpose?

#### Richard Trump

Joined Jan 17, 2016
5
I'm just salvaging this for hobby HV purposes. AFAIK the tv was functional, just not wanted, but I never plugged it in to check.

#### Dodgydave

Joined Jun 22, 2012
9,307
Ok, well to test the transformer you need to find the primary winding, and pulse it at 15khz with around 100v dc, but i assume thats the question you're asking, whats the pinout....

#### ian field

Joined Oct 27, 2012
6,539
Ok, well to test the transformer you need to find the primary winding, and pulse it at 15khz with around 100v dc, but i assume thats the question you're asking, whats the pinout....
Its not that simple - to start with, its 5th harmonic tuned, secondly the horizontal scan yoke forms a significant part of the inductance in that tuned circuit.

That's why many TVs have an interlock link on the deflection plug.