Anyone familiar with the Ampex AG 440

Hi I have a worrying problem with my Ampex 2 track machine and thought if I give a description here as to what is happening someone may have an idea as to where to look to track down this problem.

So I have voltages coming off the grounds of this thing, all of 180V but assuming low amps as I only realized this when fiddling around in the patchbay. Touching the machine itself I never noticed so not really sure for how long this has been an issue.

1) Even with the machine turned off but plugged into the wall with power on I still get voltage to ground.
2) Disconnected everything from front control panel and still have problem so guess that's the area the problem is located.
3) Unplug power to front panel and only get 20V ?? but why ??
3) I can unplug power from directly after the power transformer and I get about 1 v. The power transformer is connected separately to the back of the wooden console of the tape deck.

Any ideas as to what is going on  ??

suggest you remove both .005 uF capacitors, C606 and C607, located in the control box,
which are line to chassis RF filter capacitors; sometimes referred to as "death caps".

Haha well named, thanks I will try that tonight.

OK removed the Death Capacitors but now left wondering if I am reading my multimeter correctly. Or if it is working properly.

When I discovered the problem I got a mild shock like 12v with Ampex connected to the patchbay so disconnected it and measured volts from Ampex ground chassis to the patchbay and got 180V. Noting I never got any shock from the machine itself but when I turned the machine off at the wall voltages had gone.
Now after removing the capacitors it's down around 140V but getting different readings depending of where I put the probe.


Can some one please recommend where I should measure if or what voltages are coming from the ground of my Ampex 440 ?

ground should be 0V unless I am missing something here. It's been quite a long time since I had anything to do with an apex 440...

as pucho has surmised, your AG-440 is not grounded.
presuming you are employing a 230 to 117 step-down transformer ?
measure the leakage from the 440 chassis to a known earth point,
reverse the power plug in some safe fashion and measure again.
terminate your AC voltmeter with a practical value resistor, 1000 ohms should work.
wire the power to the machine for lowest leakage.
now ground the machine.  if you have input transformers installed, there should be no hum issues.
grounding experts, be calm, both the neutral and hot are fused and on a  double pole power switch.

The schematic shows a 3-pin cord grounded to chassis.

Past owners have been known to cut the ground, in the cord or inside the machine. Check that!!

Is your wall-outlet grounded? Do not assume. Do not trust a 3-light checker too far.

The 440 does indeed come with a three wire power cord. It is 120 volt operation only, so if you are using it in a 240 area you will have a transformer on it. This transformer may have isolated the ground. You have already had a shock from this machine, by the way it WONT have been 12 volts. You have been lucky so far. GROUND THIS MACHINE IMMEDIATELY! If you dont know how, get professional advice.

OK thanks everyone turns out there was no real issue with the machine but did learn something very interesting .

The voltage I was measuring was as described as potential difference between the Ampex and by patchbay /outboard gear as the machine (as described above) does not share the same ground. The power plug that goes to the transformer has ground terminated .

This was causing me to get a mild shock when touching both at the same time and rectified by connecting the two grounds together.

Yes I had to call in an expert Better safe than sorry.