Startup Issues...EDIT: FIXED

[ChrisM]

Finished my 50W ODS. Only thing left unconnected right now is the OT`s secondary taps.

When I use my light bulb limiter and a 60W light bulb I get a bright light with the main`s turned on. It stays bright and does not dim.

I disconnected the heaters to see if that was the issue. The light still was bright.

Here is what I have found so far...
- There is continuity between the heaters
- The AC bias wire has continuity with ground
- The B+ has continuity with ground

I removed the B+ wire going from the diodes to the first filter cap. I then tested again. The B+ still has continuity with ground.

I then thought maybe my connections are internally shorting with the xformer`s shield. So I disconnected the shield ground connection... Still I have continuity to ground.


Any help appreciated...
Thanks...

[Structo]

Hmmm, that is a puzzler.

Good thing you used the light bulb limiter.

How about this, disconnect all secondaries on the PT and test again.

Is this an international PT with multiple primaries?

[ChrisM]

Hmmm, that is a puzzler.

Good thing you used the light bulb limiter.

How about this, disconnect all secondaries on the PT and test again.

Is this an international PT with multiple primaries?

Ya that was my next thought, check the PT without anything connected to it.

This is a NA PT. It is the same one #124 uses. It is a Hammond, AES sells it.

[ChrisM]

Fixed the issue, kind of an odd find.

For the 12V transformer the primary leads are quite short. So because of this I added a little 3 tab terminal strip. I soldered the primaries to the lugs than ran wires from there to the other primaries and what not. Anyways one of the lugs was making contact with the chassis as it was tilted to the side. Repositioned the strip and it was fine.

Used a 60W then 100W light bulb, everything seems fine. Voltages seem ok for no tubes in and a light in series.

Going to add tubes next...

[Guitarman18]

ChrisM wrote:

For the 12V transformer the primary leads are quite short. So because of this I added a little 3 tab terminal strip. I soldered the primaries to the lugs than ran wires from there to the other primaries and what not. Anyways one of the lugs was making contact with the chassis as it was tilted to the side. Repositioned the strip and it was fine.

If I understand you correctly; IMO I would make your tag strip a little longer so that you can use 2 screw fixing, rather than worry if it will tilt in future. Two screws will give it more stabilty. Primaries accidently touching the chassis is something to avoid at all costs!


Cheers,

Paul.

[Structo]

Yeah, that was kind of a freak thing, huh?

I agree with Guitarman,
Need to stabilize that wiring in case the head gets bumped or something.
Not everybody treats their equipment gently.

Remember some day, most likely somebody else will own that amp.

[ChrisM]

ChrisM wrote:

For the 12V transformer the primary leads are quite short. So because of this I added a little 3 tab terminal strip. I soldered the primaries to the lugs than ran wires from there to the other primaries and what not. Anyways one of the lugs was making contact with the chassis as it was tilted to the side. Repositioned the strip and it was fine.

If I understand you correctly; IMO I would make your tag strip a little longer so that you can use 2 screw fixing, rather than worry if it will tilt in future. Two screws will give it more stabilty. Primaries accidently touching the chassis is something to avoid at all costs!


Cheers,

Paul.

Ya I agree.

The problem actually wasn't the terminal strip after all. Found the real issue, o well it is fixed.

[Structo]

So what was it so we can all learn from it?

[ChrisM]

It's lame with a capital L.

The B+ runs right near the AC main's ground. The ground connection uses one of those star grounding terminal lugs. Anyways the wire was close to this lug and the lug tore it a bit, I guess it tore the wire when I was tightening. So ya B+ shorting right to ground.

I moved the wire and put some tape on it for now. I will replace it later.

I am facing other issues now. Low output but at least the amp is passing signal to the speaker.

[mlp-mx6]

Keep an eye on your power xfmr. B+ straight to ground should have tripped your fuse. Your xfmr may be compromised. Just keep an eye on it.

[ChrisM]

Keep an eye on your power xfmr. B+ straight to ground should have tripped your fuse. Your xfmr may be compromised. Just keep an eye on it.

It wasn't direct contact and it wasnt long. Would the lighbulb have helped prevent harm?

[heisthl]

Keep an eye on your power xfmr. B+ straight to ground should have tripped your fuse. Your xfmr may be compromised. Just keep an eye on it.

On a 60 watt bulb you could probably leave the shorted amp on for a week and not hurt anything.