Three prong question.... picture

[Garydean]

I'm not feeling this AC wire setup. There is a 3 position toggle on the faceplate with the center position being off, standby to the right (as you see it from this view) and "on" is in the left position (as you see it from this view). The white wire from the fuse holder goes to the PT.

Should I?

Remove the white wire from the fuse holder and remove the white wire (neutral) from the switch (#2 lug) and connect them? This would give me neutral straight from the AC cord right to the transformer.

Black (pos) leave as shown in the picture. Connect a new black wire from the other side of the fuse holder (where the white from the transformer used to be) and go to the switch where the white wire is on the #2 lug. This will be the only wire connected to the #2 lug which is the off position.

Result will be pos/black thru the fuse holder then to the switch. The brown wire on the standby side of the switch goes to the transformer. White/neutral straight to the transformer.

the different style standby switch has me a bit miffed.

thank you,

gary

[Enzo]

Here is a question to answer first: does the switch work now?

It is a plain old DPDT switch, center off, right? Looking at the photo, the top row of solder lugs is one switch SPDT, and the lower row is also a SPDT.

The switch action is simple. Center is off - amp is off. FLip the switch one way and the amp comes on warming up, but no high voltage to the circuits. We call that standby. Now flip the switch past the center off over to the ON position, and the high voltage is fed to the circuits. The only difference between ON and STANDBY is where the high voltage goes, or doesn't.

IN other words, the main AC is on either way, and the B+ is on only one way.

Looking at the photo, I see the mains white wire going to the center of hte top row. The the two ends of that row are wired together with the short orange wire, and the orange from the PT connected to them as well. Assuming the orange wire is one of the power tranny primary wires, this means that the orange wire will be connected to t he white mains wire with the switch turned either way. The black mains wire goes to the fuse, and a white wire from the other end of the fuse completes the circuit to the power tranny primary. SO far it seems we have a basic on off on AC mains switching circuit.

Now the lower half of the switch. A brown wire from the PT goes to one end of the switch, and a red wire from the center lug runs out of sight, presumably to the HV rectifier. With the switch centerd, everything is off, with the switch thrown one way, this lower half completes the circuit to the HV rectifier, flipped the other direction, nothing is connected so it remains without HV.

So unless I am not looking at it right, it ought to work as advertised. Flip the toggle towards teh end of hte chassis, and the mains comes on to warm up the tubes, then after a moment, switch it to the other end, and the B+ comes on too. Does it not do this?

And if it does do this, why rewire anything? Looks to me like someone had an amp with NO standby switch and just had to have one, so they did this so they had a standby without drilling a hole for a second switch.

From the center off position, flip the switch one way to warm up the amp, then a moment later switch it to the other way and the amp can be played.

[Garydean]

Great explanation Enzo. Yes it does work as advertised in the picture above. I wasn't sure if there were any safety issues with that wiring. Thanks for clearing that up for me.

ALSO

In the picture is a line to ground Cap off the fuse holder. I should be replacing that with a Y2 cap....no? As well as the filter cap next to it (parts on order).

Gary

[Enzo]

And the reason we want to replace it is...?

If that line cap is not causing trouble, why replace it? Your chassis is grounded anyway, I'd suspect the amp originally had just a 2-wire cord maybe? In general, I'd say, if the amp works, don't "fix" it.

[Garydean]

The amp is a late 60's Univox (Japan) bass amp. Originally it had a 2 prong cord. A few of the low value caps in the preamp are burnt. I'm gonna re-cap, put in tubes, as there were none, check voltages, bias and move it out. My friend wants to use it as a guitar head. I'm sure you run into the situation where a customer doesn't mind spending more money to fix an amp that's worth less than the repair. These heads in working condition with tubes sell for about $150. Tubes alone are going to run 60 bucks. Add caps and labor and there's the value of the amp.

there's no question here....just some FYI.

I appreciate your advice and thoughts as always.

Gary

[Rick Erickson]

In the picture is a line to ground Cap off the fuse holder. I should be replacing that with a Y2 cap....no?

No - Clip it out and throw it away. If I'm seeing it correctly, it's running from the black wire (hot) to your filter cap ground. Why in the world would you want to inject 60Hz pulses into your ground buss? Even if it was connected to the white (neutral) wire I would recomend removing it if you have a 3 conductor safety-ground AC cord. At best: it is a redundant ground path. At worst: it's a safety hazzard.

RE