Jumping in, the documentation suggests only one 6.3V winding. But there are 3 Transformers.

18-32 (HT 250VAC); 18-1 (HT 275VAC) 18-27 (HT 325VAC) and they interchanged two of them resulting in a change to the back bias resistor. So we do need specific info. as this pings which one it probably is.

Marc

Yes Marc
I was very much of two minds on removal of the transformer and party the grommets & condition is why I was thinking of that.

I wanted to really see what condition those wires were in were they were under the heater wire... see how pliable they are and (hopefully) had not gone brittle and breaking off insulation at this point..... they seem ok

The grommet thought dirty with I think wax (maybe fat) seems not to be crumbling away .. I was kinda of expecting that it would be hard and flaky

the wires there are covered in, Iam fairly sure its wax
but seem OK (just checking the heater wire to be sure & mains wires to be sure..its rather messy and since you say a point to watch out for...then definitely check as best I can without pulling tranny)

I'll see if I can find a type number...I haven't cleaned it apart from brushing some dust off the tranny

I wouldn't be so concerned but as you know this does have secondary that could run 500 ~ 750 odd volts (fully) on the secondary (scary for shorts)

I do regard your experience & knowledge here with this very highly...i just like to be sure thats all and well...

Just the state of this thing scares me I guess

for safety's sake I'd rather sleeve and extent (if I have too) the HT secondary anyway

the rest of the wiring is mush and has to go

So the secondary HT could be any of the following
250 V (per side of the CT )
275V or 325V

Humm Thanks
I'll see if I can spot a number but didnt notice any before

its still possible to test as is so I will leave it as is and test
in place

OH and yes VERY MUCH AGREE and APPRECIATE your comment on the "Primary side "
Most important not to get that mixed up!!!!

I will do a completely different post in this thread on all testing and details of the Transformer when I get a chance to properly check it

Sadly I dont have whats needed for a full test but hopefully what I do will be enough

On that solder joint
you are right it looks dicky looking for sure

but does test solid to ground at about 0.3 ohms

It has pin 7 of the rectifier, one side of the Volume control
(I will rework it thought)

pin (used by rec Valve) unused 6... is being used as a termination point for a few things and its linked via a wire to pin 4 of the 6V6..if I go that right

Monochrome625

the 6V3 and HT windings are separate windings, yes... as far as I can tell

OK guess at this point till I test the tranny not much I can really do
well make a component list

Thanks again for all the great Help... really its good to get solid knowledge from everybody's expertise

Cheers

EDIT

That 275 Ohm resistor is Open Circuit by the looks of it
I take it from parts its a 1W ?....wow big
(since it seems to be R 138 if I got it right and listed as 400 ohm on schematic..50 ohm is ok)

Time I started getting some old resistor ID photos in place I think...

Transformer & Testing

This post will be edited for additional and information as needed on, condition general information & testing

This in formation is in relation to the transformer in this particular unit

it may or may not be functional (looks like it might be)

This transformer did suffer at the very least a partial short circuit on the 6V3 winding

This is fact: charred heater wire was found between 6X5 and 6V6 (under lower Electro Cap, beside choke)

Details so far

The Transformer has one tapped primary N, 220V 240V

White N
Dark Blue 220V
White 240V *
(* maybe marked with green pant on block)

N = Neutral.... for the sake of Clarity
(in ref to termination block used)


**Please ensure you "never" mix the taps up as being the full primary winding**

measured DC resistance from N to 240V is 55 Ohms
to Tap is 50 Ohms

The secondary is of 2 separates winding

One at this point "unknown Voltage" centre tap secondary for High Voltage supply
*** tentatively 250 AC per side of CT ***

Red... White CT.... Red

Resistance total of winding 715 Ohms
350 & 370 Ohms to either side from CT (white)

The Second Secondary is the 6V3 heater winding

The colours per say are a little harder to tell but whitish and black
I think they may have bee cloth covered? but age & probably heat) has discoloured them

DC wise Measure about 0.6 Ohms

==============================

At this point as best I can tell the wiring insulation for all leads except maybe the heater is OK back to termination point on transformer

the heater wires are exposed a bit on the side of the transformer have move them gently out of the way to check there was no damage to the mains primary leads..all looks good there YAY


More to come after testing is done
when I find my work bench again...that is ...

UPDATE

Tentatively good news

measured 7 VAC on heater winding

measured 257 VAC on either side of CT for HT winding

These are Unloaded Voltage measurements

---------------------
Thank you all
Hope you had a good Anzac Day

Only by remembering those that suffered the reality of War may we hopefully prevent things like that ever happening again..

******UPDATE 2*****

Let Transformer run for 2 ~ 3 Hrs, it got Luke warm

check it against true mains Voltage measured 245VAC so says meter
Measure 6V9 Heater and 250 VAC both side of CT

I know under true load this should drop a few volts

Warming the Transformer I suppose wouldn't be a bad idea anyway to get rid of any moisture its been sitting for years.

That would suggest 18-32 transformer. You could leave it idle for a bit & see if it gets hot. At this point it looks positive.

Just watch it, if you measure plate to plate across the HV secondary, not plate to CT: Many modern meters will not handle the volts. (A message for all)

You can always split a new grommet & feed it in, unless you have removed wires & can slip in a new one.

Octal tubes read: Wiring side, clockwise left of spigot is 1 Right of spigot is 8.

Only one heater pin will have a floating wire, it is possible that either pin 7, or 2, and they interchange, will be grounded and what is on pin 7 from the volume is a common ground.

Marc

Thanks Marc

Yeah I was so use to looking at the bottom I nearly missed the top side rotation

18-32 seem like it might be the one

Question thought


Strike Out "bias" below...questions still valid though in regard to what to do about it

just found you comment
-----------------------------------------------------------
Filter is a capacitive input filter with trap for the unwary. The first filter cap is not earthed as the set is back biased via R157 & R102. The centre tap is floating and the first cap neg goes to it: Beware.

**Actually were are those two resistors? **
R157 & R102


Read more: http://vintage-radio.com.au/default.asp?f=2&th=448&offset=3#ixzz300YVEGjV
--------------------------------------------------------------------
If R138 is the Bias resistor ? monochrome was talking about

This one is 275 Ohm (which is open circuit)

The specs say for the 18-32 as per original circuit 400 ohms
which I think might have had monochrome scratching his head

There is listed in the PDF in the 4GZ section a "type 18-6" which has a 220 V to CT Transformer, it listed as 250 ohms

The 275 R seems to be an original ...green paint on Valve connection looks still intact

If I got that right..... got any thoughts ? & should that be replace with a 400 ohm (or near, 390 ohm) ?
(maybe I should wait till I load the transformer a bit)

while I am at it ...should I just replace most all I need to, resistor wise with 2 Watt modern day resistors ?
(easier to handle and Voltage safety)

Are there any that should definitely Be of the 3 Watt variety that you remember off hand

Just getting a parts list together and for the price of a few resistors I'll buy them all Just in case..spares are always good

Oh on the transformer yes I will give it a soak test and them put it on a light load (if I can find something to load it with)

there was no growling at all... in fact it was perhaps a little too quite...but no load at all...then again I am deaf these days

I've calculated out roughly the 6V3 winding will need to supply about 2 Amps...4 Valves plus Lamp
(anything I missed?)

Seem on heater pin they stuck to pin 2 as wired link and 7 to chassis.. as a return (thought yes I know its AC)

BTW Earthing the Chassis will tie the heater winding to true earth ....how does that go with Hum? just carious...

Seems with HI FI and Guitar Amps they are alway fighting the hum factor

I just found the heater arrangement here rather interesting to start with..I know it saves on wire & probably time, after a few thousand thats probably a few bucks in costs


No idea on the HT currents thought (thinking wet finger in the air 30~60 mA possibly)

I'll shut up for the moment... my posts must be a pain to read ...but thank you for spending so much time with me on this.... so nice of you

Cheers

PS yes I am aware of that with meters 600V...I kinda miss my old analogue ones

I am using a Fluke 73 (old version) but have a few others
Valve and old radios are new territory for me..

PPS it just a common point of the rec valve pin 7 and the volume to GND (chassis)

Seems with HI FI and Guitar Amps they are alway fighting the hum factor

Yes, because their inputs, such as pickup coils, are great hum collectors.

GTC Very true Thanks

yes thats major a point ...sensitive areas and your right were most problems with hum are likely to arise anyway

just, thinking about heater wiring lead me to that train of thought in how this is different
Side thought really

just, thinking about heater wiring lead me to that train of thought

I haven't read every post in this long thread, but I guess you already know that heater wiring is twisted to nullify mains hum.

Actually GTC this is why the question...normally thats what you'd expect to see & Agree with you
(Edit.. lest wise in guitar amps and I assumed most everything)

in this thought, its only one wire jumped from pin 2 to pin to 2
in a slightly star fashion Transformer to pin 2 of 6v6 then over to 6X5 but also from 6V6 off to 6G8 then from 6G8 to EK32

Pin 7 of the Valve sockets just goes to Chassis near each Valve socket by the looks of it... as does one side transformer

So quite a strange arrangement...I can see how it could save money and a bit of time thought

Marc said to Earth the chassis which would also take advantage of the transformer shield.. this would tie one of the heater lines to true earth that shouldn't really matter
(Except in the case if you separate your heater and Cathode by too much voltage..so I understand..which I believe causes cathode heater break down ..)

anyway as I am learning it seems a lot of things with Valves isn't voltages set at fixed points but rather voltages relative to each other..thats the important thing