Help me with Chandler Tube Driver??

[timrichter9]

Hey all-

I found a cream colored 80s (??) Chandler Tube Driver (four knobs with yellow caps).
It has a AC power source but there has been some issue in the past.
The wall wart box was cut apart and it appears that the transformer inside it has
had the leads touched up with a soldering iron. This appears to be the original wart
as it says (CHANDLER on it and has 24v output).

Here's the rub. I may be stupid, but my other wall warts have two wires coming from
them and a diagram telling me which is positive and negative (inner or outer).

This thing has three wires that lead away from the transformer. I am scared to
plug it it, as the box was taped back together with black electrical tape.

The transformer wires look good.

Why are there 3 wires on this beast? If I check the output of the tranny by carefully plugging it
into an isolated 120v AC source, what should the voltages be?

Looks like there are three taps on the secondary (duh....explains the 3 wires)

Thanks
Tim

[g1]

There are DC supplies and AC supplies. The DC type will be marked for positive and negative. AC type have no polarity. Does the plug that connects to the unit have 3 terminals (like tip, ring, sleeve)? It is probably an AC supply, you can measure for AC volts, the 3rd wire would be the center tap. So you would have 24VAC, with 12VAC on either side of the center tap.

[timrichter9]

There are DC supplies and AC supplies. The DC type will be marked for positive and negative. AC type have no polarity. Does the plug that connects to the unit have 3 terminals (like tip, ring, sleeve)? It is probably an AC supply, you can measure for AC volts, the 3rd wire would be the center tap. So you would have 24VAC, with 12VAC on either side of the center tap.

actually it is a two prong wall wart. Inside the wall wart, the two prongs are soldered to the leads of a small transformer and that transformer has three taps. The "cord" that comes out of the secondary has three wires that go inside the unit.

Is this giving +12vDC and -12vDC being a 24v transformer with a grounded center tap?

Thanks

[52 Bill]

Is this giving +12vDC and -12vDC being a 24v transformer with a grounded center tap?

Thanks

Is there circuitry inside the transformer box? If this is a DC supply there will be a rectifier bridge and at least two filter caps.

If there is no circuitry then the supply is an AC source and the power supply circuitry is inside the pedal box.

[mrwendel]

I have one of these myself...the adapter is in fact a 24V center-tap AC adapter. It should measure ~12VAC from the CT to each of the other wires. I don't have my original adapter anymore to tell you what the colors are...my replacement is green=CT, blue and brown 12VAC.

[timrichter9]

Yes (to the response above), the transformer is actually inside the black plastic "wall wart" part of the AC supply.
the transformer was sticky taped to the inside of the box with the two blades (that go into the wall outlet) sticking
though the backside of it.

Can you tell me how you made a replacement? (to the poster below)?
Did you cut open the wall wart portion and put a new transformer in the wall wart?

I have one of these myself...the adapter is in fact a 24V center-tap AC adapter. It should measure ~12VAC from the CT to each of the other wires. I don't have my original adapter anymore to tell you what the colors are...my replacement is green=CT, blue and brown 12VAC.

[mrwendel]

I tried to open the wall wart but decided that I would mangle the case so much that I wouldn't want to use it anymore when I finished so I stopped working on that. I found a replacement by the specs. I ended up with a Condor wall wart: 24VAC ct 400mA. The wall wart is soldered directly to the pcb so all the rectifier/filtering components are on the same board as everything else. You probably could 'fix' the wall wart since I'm sure it's just a transformer there, but not sure you'll save much $ compared to just buying a replacement and soldering the 3 wires. The thing you have to think about (for this or the other thread on possibly putting the transformer in the case) is that you have to have enough current from the xformer for the tube heaters. It's also possible to modify the board/circuit to use a more standard 2-wire AC adapter but for me it wasn't worth the mods after I found the direct replacement.

One other thing...I've found that this particular model of the Tube Driver is different than all of the schematics that I've found on-line. I never completed backing into the schematic after tracing the board...but did enough to convince myself that I wasn't looking at any of the circuits that I had found online.