too much power to faceplate?

I have a 1959 zenith console radio/turntable. It has 3 separate chassis, one for the amplifier one for the tuner and one for the turntable. I replaced all the electrolytics and paper capacitor with new ones and checked all the pieces against a schematic I have for it. It turns on and plays the radio and records just fine. The problem is, there is too much power running through the chassis and you get a light shock if I touch the record player arm or metal faceplate behind the dials. The chassis is used as ground for the radio and the faceplate is part of the chassis. The unit has a large transformer on the tuner chassis and two transformers for the amp board.

1. Is it common for units to use the faceplate where people put their hands as a ground?

2. what could be the reason for the power problem? the transformers?

Any advice is appreciated, thanks!

[Chad Hauris]

First make sure this is a transformer powered chassis where the power line is completely isolated from the chassis. If this is a series filament type unit you will need to use a different troubleshooting technique.
Check if there are any capacitors coupling the power line to the chassis...if so, I would remove them.
A good check would be to take an ohmmeter and measure between each of the power line prongs (unit unplugged) and the chassis. There should be no continuity at all. If there is, you have a leakage path, don't use the unit again till you fix it.

[Tom Bavis]

An ohmmeter won't always show leakage - it may only appear with higher voltage. Capacitors this old are suspect though - best not to plug it in until it's fixed.

Got a model number? We may be able to scare up a circuit diagram and point you to the problem part(s).

Zenith Mt1958, The Photofact packet i have has it and the schematic under Zenith Chassis 9H21LZ1/Z2, 3K01/01Z/01Z1/02. The 10 electrolytics I already replaced as well as a few paper, and black plastic tube ones with orange dips including the one the is before the transformer in the circuit. Aside from the changer motor, all circuits are powered by the other side of the transformer. There is one capacitor and resistor that connect the power to chassis ground as in the schematic. (.022MFD at 600V and 1 meg resistor) The is about 1.2 meg ohm resistance between the respective power prong and chassis.
The main transformer has two secondary's according to the schematic (Pri. 117VAC @.86A, Sec. 1 117VAC@ .19A DC , Sec. 2 6.3VAC @ 3.1A) I might be able to scan it if that would help at all.

[Tom Bavis]

OK, 0.022 uF is TOO BIG - current safety standards don't allow more than 0.7 mA leakage to chassis - this works out to 0.015 uF MAXIMUM. The 1 meg resistor is NOT a safety approved part, and an old cap is probably leaky. I would replace the cap with a .01 uF safety approved part (Y-capacitor with UL safety label) and eliminate the 1 meg resistor.

I just found the schematic for the amp... even worse! C19 is a .047 uF capacitor from line to ground. I suppose they expected you to just flip the plug over if you get a shock from the chassis - again, you MUST replace this with a smaller value, safety rated part - 0.01. C3 likewise is .047 uF, from line to the tonearm shield - reduce to 0.01.

It is possible (but unlikely) that the transformer has leakage to ground - you'd need an insulation resistance tester (I use my Sprague TO-4 cap checker) to measure it.

Ok, I have some safety caps on order. A couple of questions questions though:
1. What purpose does the resistor have? will it matter being absent from the circuit? (sorry, I'm a bit of an rookie when it comes to circuits still)
2. Would it be a good idea to get a 3 prong earth ground cord and ground the chassis?

[Tom Bavis]

The 1 meg resistor was to prevent a static charge from building up if an outside antenna is connected - grounding the chassis serves the same purpose, if it's even necessary - I doubt it. If you DO use a 3-wire cord, you might have to swap the two AC wires for minimum hum. Much easier with 2-wire - just flip the plug over.

No dice.
Sorry to be bother but I'm having fun with this and learning quite a bit.
I replaced the three caps to .01 rated y2 safety and removed the resistor. I replaced the plug cord end with a 2 prong polarized so it always is in the right direction.
When its plugged in and off it's fine (as long as its in the right direction)
When either the record player or radio are turned on i still get a tingle. When the record player is on the radio unit is not powered so I'm guessing its something to do with the amplifier section.

Would a bad tube possibly cause this? Considering there are only 3 might it be worth just replacing to find out.

[Tom Bavis]

The wire from the power cord that goes to the wide blade is neutral. This is the side of the AC line that these three caps must go to. If this line is switched, the switch must be moved to the opposite ("hot") wire. Easy enough to do in a 5-tube radio, but this may be a bit more involved... you may have to draw out the power circuit yourself to make sense of it.