Defiant MP4 with AT6 Turntable refurbish

[Station X]

Yes.

[ggg1234]

My analogue meter shows around 25vac on transformer tag
Graham

[Station X]

Something literally doesn't add up here.

The valves (which light up) both have 38V heaters, a total of 76V, so you should see at least 76VAC on pin 9.

EDIT. I see that back in post #11 you measured 80V on pin 4 of the UY85 which is near enough correct.

Is the "bottom" end of the secondary winding correctly connected to chassis? What voltages do you see on the other secondary tags?

Is your meter reliable?

[ggg1234]

Pin 4 reading earlier was in fact my error it was pin 5 (heater). The blue (B) and yellow (Y) cable from pins 5(B) and 9 (Y) have the following readings.

Pin 9 Anode (but no valve in) about 25 vac
Pin 5 Heater (but no valve in) about 80 vac
the tag on the transformer (all connectors on top as shown in pic) 25vac

Regards
Graham

[Station X]

Looks like a problem with the transformer.

POWER OFF

Remove at least one valve and measure the resistance from chassis to each of the secondary winding tags. The "bottom" one should read close to zero ohms. The readings should increase as you measure at the heater tap and then at the "top" tag which goes to pin 9.

Also check the resistance between the heater tap and the tag which is wired to pin 9.

[ggg1234]

here is pic of transformer and board
Graham

[ggg1234]

It appears to read 'open' (nothing).
Graham

[ggg1234]

I'm not too sure what you mean by 'bottom' all the tags are on the top of the transformer?

[Station X]

The Red and Black wires are the mains connection to the primary, with a parallel connection to the turntable.

The twisted Blue and Yellow wires fed the heater and anode of the UY85.

I'll guess that the solitary Black wire is an earth connection to the chassis.

[Station X]

Originally Posted by ggg1234

I'm not too sure what you mean by 'bottom' all the tags are on the top of the transformer?

I mean that it's the bottom tag on the circuit diagram. It's wired to chassis.

[Station X]

Originally Posted by ggg1234

It appears to read 'open' (nothing).
Graham

What does?

[ggg1234]

Transformer does run quite hot (almost too hot to touch) after 3 or 4 mins is that OK?
Graham

[ggg1234]

The heater tap and pin 9 (post #24)

[Station X]

Does it get hot with no valve in?

Can you clarify the resistance readings please.

[Station X]

Originally Posted by ggg1234

The heater tap and pin 9 (post #24)

If you're certain about that, the transformer has had it.

Forum member Ed Dinning may be able to rewind it for you.

[Station X]

Just so we can be certain that the diagnosis is correct, can you tell us where the wires from the mains transformer go to.

[ggg1234]

Unfortunately it takes a while to cool down to test right away but the valves have been out for the last couple of hours and when I do turn it on it get quite warm very quickly. It not red hot but would be a little uncomfortable to hold for long.
Graham

[ggg1234]

Mains transformer wiring routing is as follows:

Two yellows to mains lamp indicator
Two blacks and two reds from mains and too Turntable motor
Blue to Heater pin 5
Yellow to anode

Regards
Graham

[ggg1234]

If it is the transformer as it appears . . could I buy a new one and do you know what the spec I will need would be?
Graham

[Station X]

Looking at your second picture in post #38.

Number the tags from 1 to 6 starting at the bottom of the picture.

Does tag 1 go to chassis?

Measure the resistance from chassis to pins 1, 2, 3 and 6, then post the results here.