Need troubleshooting help - 2nd build. mini wreck 4-4-0

[amplifiednation]

Hey Guys,
I got a 4-4-0 all wired up to go and with a couple obvious miswires caught by cliff I corrected my fuse wiring and will be putting in an artificial center tap when i get out of work.

So here's whats going on.

I got no activity on the bulb limiter, no glow, no flash, nothing. It was like it wasn't even there.

I am getting 125V ac mains on the IEC, fuse, and on the mains toggle. When i flip the power switch I show DC voltage over 300 (I think it was like 380) after the ss rectifier diodes. I get nothing on the filaments. When I flip the standby, that DC current should flow through the switch and connect it to the first Filter (I thought)...instead when I flip the switch all that DC voltage dissapears....and I can't find it anywhere else, not on the caps, tubes, nowhere.

Will the articificial CT make the heaters get some voltage?

Any other thoughts before I get home today? I don't think I'm far off on the amp, I was pretty careful putting it together.

Please don't mind the messy layout, I drilled everything myself and obviously didn't quite do enough planning. I've learned my lesson!! I can clean up long runs if you see it neccessary, Cliff already suggested shortening the runs from the board to the pots...easy enough.

Thanks in advance!!

[Bruciep07]

Are your heaters wired properly? It's hard to tell from the picture, but it looks to me as though you have it mixed up and are sending one leg to the pilot lamp and the other leg to the heaters. That would show no potential across the heaters when measured with a DMM. Do you have the proper voltage at the heater resistors? Also looks like the jacket on the yellow heater wire going to the pilot lamp is cut.

[amplifiednation]

It is hard to tell!! ha, no they are wired properly, I put that run in for the pilot lamp after. I have each side running to the tubes, and the same two sides for the light. I do not have a ground reference though...i think that might be why they aren't showing any power? I dont' know. There is nothing even at the green wires right out of the PT.


that yellow wire got a little burnt by the iron getting to close. this PVC is hard stuff to work with.

[Bruciep07]

Will the articificial CT make the heaters get some voltage?

No, just reduce "hum", should still have around 6.3V when measuring between the 2 green heater wires...

There is nothing even at the green wires right out of the PT

Try disconnecting the green heater wires and measuring them, if you have voltage then your problem is wiring somewhere after the artificial center tap... No voltage and your problem is the PT or wiring leading to it...

[Firestorm]

What power transformer? Getting nothing on the green wires right out of the PT tells you something ...

[Fischerman]

Are you sure the center tap is connected (i.e. grounded) properly? It's hard to see where everything goes. I see the red/yellow wire from the tranny to that 100u capacitor on the board, then a black wire to the can cap but can't see where that other black wire (that goes through the hole in the board) goes.

Try drawing a schematic (just of the AC, switches/fuse, rectifier, first filter cap, including all grounds) exactly as you have it wired (don't reference the actual schematic, draw it yourself by only looking at the amp).

EDIT: Also, not sure if I'm seeing this correctly but it looks like you have a ground rail on the board (those short spans of black wire) that is grounded at the input jack end...and then also grounded to the speaker jack. If that's a standard speaker jack then it should already be grounded to the chassis just by bolting it in. In any case, two paths to ground from the same place is a ground loop and should be avoided. This wouldn't cause your power problem, it's just noise thing. If the above is not the case....ummm, nevermind (goodnight rosanne rosanna danna ).

[amplifiednation]

Its a Hammond 269EX I believe. I will have to disconnect the green wires from the resistors and check. I do not have a CT or artificial CT on the heaters. I will add that this afternoon. I knew I should have brought the amp to my office!!! haha. I think I might have a bad standby switch. I'm getting good voltage on the switch but when i "switch it on" the voltage doesn't go anywhere. Continuity tests show there is good connections through there.

The ground on the pre amp board is just a bus...the ground going to the speaker jack is from the OT and back to the board for the negative feedback loop.

[amplifiednation]

I think i figured out the issue for the heaters.

Are those two resistors supposed to go to ground? That would mean the heater wires should be connected directly to the PT's green wires along with the resistors?

I have the heaters going through the resistors which i think is blocking the AC.

that isn't what the schematic says though. I'll have to get home and do some testing.

[Cliff Schecht]

Those resistors I figured were to drop the heater voltage a bit. They won't block AC, that's capacitors .

[Fischerman]

Are those two resistors supposed to go to ground?

Those .1 ohm resistors are supposed to be series, definitely not to ground. They are there because those Hammond trannies are rated for 115vac (IIRC) so all the voltages are too high. Without them you'll prob have 7vac or a little more on your heaters (depending on your wall voltage), the resistors just knock it down closer to 6.3vac.

Still not understanding that extra wire from the speaker jack. Is that speaker jack isolated from the chassis? The NFB comes from the non-grounded end of the OT (and the NFB resistor is sized for a particular impedence tap on the OT).

[Cliff Schecht]

They sure look in series to me..

Also I noticed that extra feedback wire and forgot to mention it. What is this?

[Fischerman]

They sure look in series to me..

Also I noticed that extra feedback wire and forgot to mention it. What is this?

I prob wasn't clear Cliff. They are in series as they should be and definitely not to ground (which they are not in the pic).

To me it looks like there is a wire from the ground tab on the speaker jack to the ground bus on the board which, if this is the case, does nothiong but make a ground loop (IF that speaker jack is not isolated). The NFB wire is supposed to connect to that 5k6 resistor on the board (which doesn't appear to be connected to anything). The NFB wire should come from the non-grounded end of the OT but I don't know which OT tap is supposed to be used.

[amplifiednation]

Ok...

Thanks guys.

I got home and totally removed those resistors. The Hammond I got has primary at 125, and the heaters are rated at 6.3 so I don't think I need them.

Moved NFB wire to the proper location (good catch). I got confused on the layout.

I am not getting any power out of this PT. I've got full AC to the switch and to the primary's at 125V.

Bulb limiter...no activity, no flash, no glow, nothing. I checked the bulb, it's working.

I can't get any AC off the heaters or the secondaries. I was getting 380mV DC off the diodes but that the only place I can find any trace of electricity other than the power switch.

Ideas? I am not blowing fuses.

Also, tried a second standby switch.

pic...

[amplifiednation]

I found the issue. There is no neutral coming off the IEC. I did continuity tests with the plug and there is earth, and there is hot, but no neutral.

I was testing the AC on the switch and on the IEC and the only place I'm getting 125V AC is when I test using the chassis as ground. I think I overheated the terminal and it melted and came out a little bit, because my joint looks fine (and i remember this happening).

I'll have to wait and get another IEC plug tomorrow.

Should I shorten up the preamp runs to the pots? I couldn't figure out what was best, a long wire dropping off the board, or a short wire running straight to the pot?

[Cliff Schecht]

Get the amp working first. That's something you can clean up later IF it's an issue. You might just need to move a few wires around to get things stable, maybe not even heat up the iron (only the chopstick will tell ).