Hello everyone,
Does anyone have any information on a Zenith (Sydney) Modulated Oscillator Model 512B?
I have just bought this unit but it is fairly sad inside and out.
My first question is about the batteries. It has 2 cables coming out which I guess are for 2 batteries. One has a 2 pin plug, the pins are 7/16" apart from centre with one pin bigger. The other is a 3 pin plug but only 2 are connected but this plug has been joined on. What voltages would the batteries have been?
My second question is about a green component inside. Somebody obviously had it apart and sat it down and broke a part. It seems to be a ceramic tube with a couple of turns of wire on each end. The ceramic tube is broken half way along. It has a red dot on it. I will try to post pictures.

Regards

The voltage will depend on the valve. If its a 3pin battery plug it was likely a 45V battery and may have had a dry cell filament battery?

If it has valves/s please list them.


Marc

It has 2 valves, IQ5 GT Radiotron is written on both of them.
What are my options for replacing a 45V battery?

Best (and only practical) option is five 9 volt transistor batteries wired in series.

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A valve a day keeps the transistor away...

I wonder if the + of one battery will clip into the - of the next?

As far as I remember they won't - not unless you like bent clips. It's much easier just to get one clip for each battery and connect via the wires as this needs to be done at any rate.

A word of warning to all - when assembling batteries that put out high tension voltages it is important to remember that under the right conditions these will bite. The connectors should be hooked together first, followed by the two end connections to the receiver then all connections insulated. Then and only then should an attempt be made to snap in the batteries.

One other option is using battery cradles, such as the one available from Jaycar, Cat #: PH9235, though this will require more space and wiring up is more difficult in most circumstances.

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A valve a day keeps the transistor away...

Oh yes they will (216) (MN104), collector I repair for has a few portable battery sets. It is not unusual to get 10 "cheapies" to make 90V

Put them together one up one terminal up, one terminals down (top to top ) & negative locks into positive. continue in a line like that, then wrap duct, or gaffer tape around them.

Get a dead one, decapitate it, break the cap in half & you have the negative & positive terminals.

1Q5 is listed as a beam output Tetrode max 90V plate. Dry cell battery filaments, which are polarised. Pin 2 is F+ and pin7 F-. Do not assume the chassis to be Negative, the thing may be "back biased"? there is an off chance that it may have a 4.5V "C" bias battery as well?

Normally we modify a battery holder to take two "D" cells parallel for the filaments.

Do not be hasty in trying to power it up. Work may need doing to it?

Marc

Sorry guys, I misread the question and thought the question related to battery clips being shorted to create links between 9 volt batteries all facing in the same direction. Faced alternately, yes they can be cascaded the way Marc explained. My apologies for that.

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A valve a day keeps the transistor away...

G'day Adrian,

This umit is a portable test instrument and is powered by two batteries, a 1.5v filament battery and a 45v HT batt.

eBay has two auctions for the types of battery used during the era, vis; an Eveready 745, a 1.5v battery which was comprised of about 9 higher type D cells connected in parallel to power the filaments and a multicell Eveready type 482 45v unit to provide the HT for the 1Q5's.

To look at photos of these batteries, go to eBay and search for numbers, 170711704740 and 180738092111, the enlarged images show the pin connections for the 45v unit.

One can substitute a couple of D cells wired in parallel for the 745 and 6 by 9v transistor batteries wired in serial as a sub for the Eveready 482, however their their useful life would be quite limited.

Another approach would be to make up a mains type power supply, but I wonder if this worth the effort unless you expect the unit to be used regurarly.


Cheers, Graham...

Everready now have available a 9 volter in their lithium range. These would perform better however buying enough for 45 volts would stretch the budget a bit.

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A valve a day keeps the transistor away...

If you really want to get excited, at http://tubesandmore.com/ you can still buy 45V Batteries.

Originally the cells were a longer "F" cell. The power to wieght ratio of newer technology cells should be better.

Someone in the HRSA (I think) Did make a module that produced that sort of B+, from a LV battery.

If you want to mains power it kits are available or you can make one easily.

LR8 is a good adjustable regulator up to 400V down to 5V at around 15ma. Used two on a split 45, 100V supply with no issues.

Marc

Marcc,
There is a cage inside going through the chassis and an insulated connection in the top. I guess this is for a 4.5V 'back bias' battery.
It is fairly corroded inside and the paper capacitors are flaky so I guess all of the electrolyte has leaked from them. The external battery cables have the insulation falling off of them so I will replace all of the above before powering on. There is also a broken part I need identified, I will try to Email the pictures this morning.

Gfr63,
Thanks for the info, do you have one of these instruments?
My powersupply only goes to 30V, I hope this is enough to test the unit. I intend to use this unit regularly so a transformer or rechargables may be what I use.
I will check the photo's out. Do you have any info on the internal bias battery?

Thanks everyone.

The proper "C" battery took wires with pins 1Q5 used 4.5 at 90V and could have used a battery similar to that used in an AVO 7x . From memory the "C" battery is around 3/4" wide & longish

Sometimes a 4.5V cycle battery was used. Took one of those out of a set recently (still have it), it was low on voltage. Unfortunately the warranty ran out Dec 1927.

Photo's may be of help?

Marc

Sorry about the delay, I haven't been able to log in for a week.

Brad, I have Emailed you some pictures to post here, although the quality is not good.

The first picture is of the broken green component with a red dot on it. Does anyone know what it is?
The second picture is of the possible battery holder.
The third picture on the bottom left shows the bottom of the possible battery holder and the broken component in the centre. Far left is space, then a shield. Maybe this was to hold a battery?
The fourth picture is of the external battery connections. One of these is wired in parrallel with the possible battery holder. Perhaps both batteries were internal and someone brought them both out.

Pictures uploaded.

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A valve a day keeps the transistor away...