hot trafo

Hi,I am first on this forum,and a new restorer.I have a schaub lorenz goldy 3133 radio,my problem the radio is no working , only it has flament lights.another problem, trafo is very hot, I have replacemend C98 and C99(4700pf 1600V), after I have measuremend voltages on EZ80 tube and results;

pin1  zero VAC

pin7 235VAC

pin3 zero VDC

interesting thing is that;when EZ80 on socket,pin1 connect to ground but when there is no on socket, it is no connect to ground. EZ 80 is faulty? or trafo

To thank the Author because you find the post helpful or well done.

With no EZ80 plugged in and Radio not plugged in:

A) Resistance pin 1 to chassis / negative common

B) Resistance pin 7 to chassis / negative common

C) Resistance pin 1 to pin 7

C should equal A + B

A & B should not quite match, but be similar (same number of turns, but usually one winding is inside the other, so less length of wire.

If one measurement is A or B is much less then there is a short. If one is very high, it's open.

Remove ALL valves (tubes) and lamps.

Plug in to Electricity and see if Transformer gets hot. (slightly warm is OK). If hot, it's got a short and faulty

To thank the Author because you find the post helpful or well done.

I measuremend resistance and the results;

pin1 to chassis 213 ohm

pin7 to chassis 224 ohm

pin1 to pin7  437 ohm

To thank the Author because you find the post helpful or well done.

Hello Mr. Watterson.

Maybe this give you an additional information. Post 13

regards from  HansM. Knoll

To thank the Author because you find the post helpful or well done.

Thanks Hans!

However şaban özyazgan

The resistances sounds as expected. The small difference is the difference in length of wire for same number of turns but outer vs inner layers. Of course a single shorted turn will not show up in a resistance check. That is why Part 2 of test is to see temperature rise with NOTHING taking current.

So now power the transformer WITH NO tubes or lamps or EZ80 connected. No load at all.

Then report how hot does it get in degrees C (with no load at all it should not be too hot to touch).

However make sure you are on the correct mains tap and your line voltage isn't too high, because even 10% too high the core can be close to saturating and iron losses rise rapidly.

If the transformer has a shorted turn it will get very hot and may eventually smoke. If the transformer FED WITH CORRECT volltage and no load (not even bulbs or filaments) only gets warm but you can touch it without burning, then the fault is elsewhere, not the transformer.

To thank the Author because you find the post helpful or well done.

Mr.Watterson

I checked your step 2 and There is no much hot on the trafo and no smoke.

To thank the Author because you find the post helpful or well done.

The problem is less expensive. It's not the Transformer.

Make sure the HT electrolytic capacitors are OK. I use a current limited bench PSU. So witn no EZ80 and power off measure HT current as you increase up to 30V. If Current is under a couple of mA, then perhaps you have a faulty EZ80 or wiring. The EZ80 anodes should only connect to transformer. The Cathode to + of 1st HT Electrolytic.  The transformer centre tap to the Electrolytic - or case etc.

A pair of 1N4007 each with 47 Ohms in series can be temporarily used instead of an EZ80 till you get a replacement. This does stress the Electrolytics more as the voltage is very high instantly until the output tube  is running. Do make sure the capacitor feeding the output EL84 grid is not leaky or the EL84 takes too much power and transformer is hot also EZ80 gets damaged.

To thank the Author because you find the post helpful or well done.

Mr.Watterson,

tomorrow I will try your recomments.thanks

To thank the Author because you find the post helpful or well done.

Hi,Mr. Watterson

I have replacemend electrolitic capacitors and EZ80 tube and just the radio is working and no hot trafo.thanks for all of your interests but now I have a new problem; I need a schema for dial scala cord,because the dial cord is missing for LW,MW,Sw bands.

To thank the Author because you find the post helpful or well done.

Go to model (this all should be under the model)

Scroll down to about 4th last photo of the front view of chassis  and drive cord.

General Tips:

1. Make tuning capacitor fully closed / meshed.
2. Check which is Low frequency  / big wavelength of scale.
3. About 2.5 turns round drive spindle with tuning knob.
4. Arrange direction of turns on drive knob shaft such that clockwise moves scale pointer to left (anti-clockwise to right).
5. Cord on more than 180 degrees of drum such that pulling it will open tuning capacitor.

To thank the Author because you find the post helpful or well done.