Edcor and Trafomatic Output Thread (was Meet my Amp...)

[EWBrown]

Hi Prasad,

I'll check my PT data sheet at home and post it tomorrow.

I suspect that if customs x-rayed or opened the box, they would probably wonder just what this thing is, and yes, it would look "suspicious" to the non-technically inclined... :o

I'll post a guess for now, but it's best to wait for the actual connections, just to be safe...

4 orange wires labelled 1,2,3 and 4. two 115VAC primaries, connect in series for 220-240VAC line voltage.
I presume that the AC line voltage on India is 220-240 @ 50 Hz ?


2 windings - green pairs with white center tap. 6.3VAC filament windings

Pair of Yellow wires 5VAC filament

Pairs of red and blue, one grey tap, One yellow wire labelled "0"

This is the HV secondary with taps for 360-325--55-0-325-360 VAC, 55VAC is the "bias" tap. Red and blue pairs are the HV(360 and 325VAC)
gray would be the 55VAC bias tap and the yellow "Zero" wire is the centre tap.

A Yellow wire with green (or perhaps blue) stripes. Internal shield, connects to chassis ground.

/ed B in NH

[Quad]

Yep, we are at 220V, 50 Hz here in India. At least, thats the theory.
In practice, there is a lot of voltage fluctuation on the mains.

( mesherm suggested using the 325V tap since I plan to use SS
rectification. This might also be a good protection against high voltage
on the mains.)

My guess on the windings is exactly as yours.
Anyways, documenting the info on this thread might be a good idea.

They should have used 2 different colors on the primary windings.
If those little clips are lost, it's easy to make a mistake wiring
the dual primaries in phase.

[EWBrown]

It's a good idea to run a simple DC resistance check on all the windings, at least that allows you to get a rough idea as to what leads go to which winding.

Frr SS rectifiers, the 325V windings are probably the safest bet, I'd use some pretty hefty rated rectifiers, like UF5408s (3A, 1000V) or some HEXFREDs, and definitely NOT uF4007s, those would probably not stand up to ST70 usage with "uncertain" AC line voltages. I would expect that in a warm or tropical climate, that thunderstorms are a major factor, and AC line spikes, dips and surges are just a part of every day life.

The 360VAC taps could be used for KT88s, but the PSU caps would have to be at least 600VDC rated, or use pairs of 300 to 450VDC caps in series with 470K, 1W "equalizing" resistors. That is an "old school" technique for higher voltage DC power supplies.

That is the approach I'm eventually going to use with my Trafomatic "STA-100" set-up. These trannies are quite conservatively rated, so they should not heat up like the PA060s do.

/ed B in NH

[EWBrown]

I checked my Trafomatic Power Trannie, and the wiring scheme is TOTALLY different... (hence Murphy's Law has been invoked)

It has a single 115VAC primary, and is rated at 300VA capacity.

Here's what I have on it, the asterisk * denotes the phasing "dot" on the wiring diagram) On these trannies, the numbers are simply little tape tags, and not the plastic clips.

115VAC Primary:

1* Orange Lead, 115VAC
2 Orange Lead, 115VAC

HV Secondary, 720VAC, @300 mA

3* Gray Lead, 360VAC
4 Gray Lead, 325VAC
5 Gray Lead 55VAC (bias tap)
6 Gray Lead, 0VAC (cenrtre tap)
7 Gray Lead, 325VAC
8 Gray Lead, 360VAC

Filaments:

6.3VAC CT, 5A #1

9* Yellow Lead, 3.15VAC
10 Red Lead. 0V (CT)
11 Yellow Lead, 3.15VAC

6.3VAC CT, 5A #2

12* Yellow Lead, 3.15VAC
13 Red Lead. 0V (CT)
14 Yellow Lead, 3.15VAC

5VAC, 4A Rectifier Filament:

15* White Lead, 5VAC
16 White Lead, 5VAC

Yellow / Green Lead: electroststic shield, connect to chassis ground.

On the Trafomatic ST35 transformer, it has two 115VAC primaries, so it is good for 110-120 or 220-240VAC, 50 or 60 Hz.

1* and 2 (Orange Leads) are 115VAC primary #1
3* and 4 (Orange Leads) are 115VAC Primary #2

For 115VAC, connect 1* to 3*, AC input is across both pairs.

Connect 2 to 4.

For 230VAC, connect 2 and 3* together. AC power is across 1* and 4, the windings are in series.

I would GUESS that this is the same scheme as for your transformer's primary, but...

It is best to try it out first, using a 100 watt (approximately) incandescent light bulb in series, to act as a current limiter, and with no loading on any of the secondaries. If the lamp glows dimly (or less than full brilliance), then the phasing os correct, if it glows brightly, then the phasing is incorrect, and one of the windings must be reversed.

HTH

/ed B in NH .

[Quad]

Oh oh! It looks like they have multiple versions of the ST-70 PT.
The primary colors on the one I have are similar to the ST-35 one
posted by you. Thanks for the bulb tip on finding the "dotted" end
of the primary.

Boris of Vista Audio is out of the country at this time and will
be back in a week or so. I'll post the wiring info here once I
get it from him.

[EWBrown]

I believe this set of ST 70 trannies from Trafomatic were early versions, or perhaps from a custom order (I bought them from Roy Mottram a while ago, as a partially built amp on a large chassis plate). The leads were numbered with tape labels (except for a couple of missing labels, and those leads were easy to figure out). The earlier trannies had "weird" nonstandard color codes, the new ones seem to be following a somewhat more conventional lead coloring scheme, as apparent on Prasad's power trannie..

I've since stripped the amp chassis down, in order to make a couple of minor mechanical changes, and then will (sometime) get it back together, then completed. THis one will be a "work in progress" ...

/ed B in NH

[Quad]

For the record, here is the Trafomatic ST70 Power Tranny color code -

Orange wires labelled 1,2 and labelled 3,4 -
Two 120VAC primaries (phase dots on #1 and #3).
For 220/240V, connect wires #2 and #3 together so the windings are in series.

Two windings - green pairs with white center tap. - each 5A, 3.15V-0-3.15V,

Pair of Yellow wires - 5VAC, 4A filament

HV secondary winding - 300ma, 720V with the following taps
[Blue,Red,Gray,Yellow,Red,Blue] - [360,325,55,0,325,360]

Blue - 360V
Red - 325V
Gray - 55V
Yellow (labelled #0) - 0V Center Tap
Red - 325V
Blue - 360V

A Yellow wire with green stripes - Internal shield, connects to chassis ground.