SVT classic transformer color code

[catstrat]

I have the schematics I need for this amp but I can't find any reference about the power transformer wiring color codes. Does anyone know the colors of the primary windings of the power transformer? I've looked all over and can't anything. Thanks.

[The Dude]

Is it this?

[catstrat]

Thanks. But it's blurred to the point I can't read any lettering. This amp has 6 wires going into ,what I believe,is the primary side. The chassis has two holes to allow the power transformer wires to pass through to the circuit. What I consider the primary winding is the hole closest to the back of the chassis. It has 6 wires. The secondary has 4 wires, 2 red and 2 yellow pairs. I think that is the secondary. It's the other hole in the chassis. Then there is the filament transformer with the wires coming off of the AC power entry module to it. I'm getting voltage out of the isolation transformer. I need to check the primary windings of the power transformer for an open winding. But with 6 wires I don't know which is which. The owner said he accidentally plugged into a 220 volt outlet. Don't ask me how he did it. Also I checked the voltage off the AC entry power board and I'm not sure if I'm getting voltage to the power tranny. That's why knowing the wire colors would help. Also it has the relay on the AC entry p c board for the fault circuit. Will that relay have any effect on the incoming AC voltage? Again thanks Dude for the diagram but it's pretty blurred.

[The Dude]

If you click on the picture it will expand and should be plenty legible at that point. No matter. If yours has 6 primary wires, it's not the right one anyway. Can you post what colors your primary has?

[g1]

Page 3 of the pdf shows the colours of the PT wires and the numbers of the tabs they connect to on the AC termination board.

[catstrat]

Thanks G1. I'll verify the colors tomorrow but what you posted looks right. I guess my question, which two colors tie into the primary winding? I want to check it to see if the winding is open. Does the primary have a center tap? Or am I totally overlooking something here that should be pretty simple to figure out ? Thanks Dude and G1.

[The Dude]

The primary won't have a center tap. It's most likely several taps for different voltages. I'm not sure if these colors match your particular amp/transformer, but see the last post in this thread. It might be what you have.

[The Dude]

Some checks:

1) No power applied, measure the resistance across the blades of your AC plug with the power switch on. Do you get anything? you should measure the transformer primary if nothing is open. If you measure infinity, either the primary or something before the primary is open.

2) With the amp unplugged and power switch on, meter from the blades of your AC plug to the transformer wires and find which wires are connected to the power cord. If one or both is missing, something is open in front of the transformer. If you find both blades of the AC plug connected to the primary, the primary is probably open. Double check directly across those transformer wires for continuity to verify.

You can figure out what's going on even without knowing the transformer wire colors.

[catstrat]

From what I can tell there is no AC voltage going to any of the wires for the power trans primary. I checked the thermistor and it's ok. Fuses and solder joints ok. Does the fault relay have anything to do with the primary winding of the power trans. Thanks.

[g1]

No. (edit: incorrect, appears relay does have to do with PT primary)
There does not seem to be a schematic showing the primary side, just that layout with the connectors.
You will have to trace out the wiring from the blades of the AC cord to the tabs that the various PT primary wires go to.

[The Dude]

Check also the solder on the IEC connector.

[catstrat]

I know a few days ago I did find a schematic on the power entry module. Drawn out showing where everything went,what did what. Now I can't find it again. It seemed to me that relay tied into the primary side. Before I open my big mouth anymore let me see if I can locate the schematic. I checked voltages again today and on one set of relay contacts I had full AC voltage. I removed that relay and I'm going to jumper across and bring voltage up via a variac and then see if I have any kind of secondary voltage. If I do that tells me the primary is good.Hopefully. I already resoldered the iec connector and every other solder joint on the board. I'll know more tomorrow. Thanks.

[g1]

Was it the SVT2 Pro schematic? Seems to have the right board number.
I don't understand why no one can draw up complete schematics anymore. Why not show the transformer?
Not sure what exactly is going on with the relay, but it has to get power from somewhere to engage, so if not from PT it must be from filament transformer. So sorry for saying earlier that it wasn't switching the PT primary, looks like it does.

[catstrat]

I found the schematic at tangible technology. It is titled SVT classic. I've heard the SVT 2 is close to the classic but since this schematic says SVT classic on it, I'll have to go by this one. I don't know either why it was so difficult to find. Thanks everyone. Let's see what I can do with this.

[Enzo]

You don't have any AC mains voltage on the primary of the main power transformer? Before going nuts, consider that an open primary would still have voltage present, it just wouldn't draw any current for a load.

The relay breaks the circuit to the power transformer, so does the standby switch. The main power switch powers the heaters, through the small fuse and through the thermistor. Note the relay is controlled by sensing the DC heater supply. Only if it sees that will it turn on the relay to enable the power transformer. No heaters, no high voltage.

The standby switch is nothing more than a power switch for the main transformer. If you are in standby it is normal for no voltage at the primary wires of the power transformer.

So you need the standby switch on AND the relay on for any voltage to reach that transformer primary. The AC heater supply goes to the preamp board, and is rectified and sent back for the relay circuit to sense.

SO...

Is the standby switch closing? And is the relay clicking on?


The SVT2Pro is the same board and circuit, they just crammed the speaker jack board onto the same page with it.