UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Closed Thread
 
Thread Tools
Old 6th Aug 2020, 4:26 pm   #1
SeanStevens
Octode
 
SeanStevens's Avatar
 
Join Date: Sep 2009
Location: Bath, Somerset, UK.
Posts: 1,033
Default Zenith Trans Oceanic H500. Mains potential at Volume Control

I've just popped this poor radio out of its case to see if the repairs to the rexine are within my capabilities (they are not!).

I tried the radio while out in the garden and using an external mains socket. It worked fine so I went to turn it off and got a tingle! Upon measuring from the metal stem of the volume/on/off switch to ground it showed 247v on the AC scale of my DVM.

I'm guessing it is a live chassis - but is it wired up backwards? Surely the metal volume pot shouldn't be + mains?

When I say ground, I mean the black lead stick into the gaps in the paving slabs.

SEAN
__________________
There are only 10 types of people, those who understand the binary system, and those who don't.
SeanStevens is offline  
Old 6th Aug 2020, 4:38 pm   #2
wd40addict
Octode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,515
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

Yes, it's live chassis! The original US mains plug on the vacuum cleaner style sprung reel was reversible...

What plug is fitted to yours, has a previous owner wired a UK plug backwards?

Another good safety feature was that the 90v HT battery connector is male, the female is on the radio end - what were they thinking?
wd40addict is online now  
Old 6th Aug 2020, 5:51 pm   #3
SeanStevens
Octode
 
SeanStevens's Avatar
 
Join Date: Sep 2009
Location: Bath, Somerset, UK.
Posts: 1,033
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

It has a UK plug on it.

I'll swap it around and check again (with a meter!!!)

Cheers

SEAN
__________________
There are only 10 types of people, those who understand the binary system, and those who don't.
SeanStevens is offline  
Old 6th Aug 2020, 6:29 pm   #4
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

According to a schematic I'm looking at, one side of the mains isn't connected directly to the chassis it's connected to the chassis via a 0.047uF and a 330k in parallel, on mains HT-ve isn't chassis.

On battery HT-ve is chassis, so far as I can make out.

Lawrence.
ms660 is offline  
Old 7th Aug 2020, 7:18 am   #5
SeanStevens
Octode
 
SeanStevens's Avatar
 
Join Date: Sep 2009
Location: Bath, Somerset, UK.
Posts: 1,033
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

Odd, I tried it in the house on a known good ring main - same result.

I've swapped the plug around - checked and it is now less lethal!



SEAN
__________________
There are only 10 types of people, those who understand the binary system, and those who don't.
SeanStevens is offline  
Old 7th Aug 2020, 7:51 am   #6
wd40addict
Octode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,515
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

Lawrence is quite right, the chassis connection is not direct. It's a while since I've been inside mine, but obviously it's still safer if the CR go to neutral rather than live. Mine still has a US plug, but I've marked it so I know the right way round when plugged into a standard shaver adapter.

On my T-600 you have to have a US mains plug or you can't switch to battery operation.
wd40addict is online now  
Old 7th Aug 2020, 8:29 am   #7
SeanStevens
Octode
 
SeanStevens's Avatar
 
Join Date: Sep 2009
Location: Bath, Somerset, UK.
Posts: 1,033
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

So although not direct, you would expect 243v? That is what I measured. I took a photo and one of it in the kitchen. I didn't want to be the earth, so I stuck the black probe into the first thing I had to had, a lettuce. I got only 23v with a poor earth!

SEAN
__________________
There are only 10 types of people, those who understand the binary system, and those who don't.
SeanStevens is offline  
Old 7th Aug 2020, 8:47 am   #8
wd40addict
Octode
 
wd40addict's Avatar
 
Join Date: May 2009
Location: Stevenage, Herts. UK.
Posts: 1,515
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

Yes, the 330k // 47n will certainly give you a tingle and if you measured the voltage with a DMM with high input impedance you'd see virtually the full 240v. The capacitor reactance is only 67.7k @ 50Hz and that's before considering any leakage it may have developed over the years.
wd40addict is online now  
Old 8th Aug 2020, 5:43 pm   #9
usradcoll1
Heptode
 
Join Date: Mar 2017
Location: Cedar Grove, Wisconsin, USA.
Posts: 823
Default Re: Zenith Trans Oceanic H500. Mains potential at Volume Control

Quote:
Originally Posted by wd40addict View Post
Yes, the 330k // 47n will certainly give you a tingle and if you measured the voltage with a DMM with high input impedance you'd see virtually the full 240v. The capacitor reactance is only 67.7k @ 50Hz and that's before considering any leakage it may have developed over the years.
Your set must have the optional adaptor to operate it from 240V mains. There was a special socket on the top of the chassis that it is plugged into.
First thing I would do is replace the 47NF with a 1000 or 1600 volt modern cap. We don't have that problem, as we only use 120 volt mains.
BTW, the Tolex outer covering is usually in rough shape due to carless handling and usually treated as luggage. Even here, it's hard to find a real well cared for example.
Dave, USradcoll1.
usradcoll1 is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:40 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.