My attempt at a Grid Bias Battery - UK Vintage Radio Repair and Restoration Discussion Forum

batterymaker1 · 15th May 2008, 4:55 pm

Around February, one of the regulars here asked me if I could make a replica 9 volt grid bias battery. I told him cautiously that I might be able to, but I'd have to do some research. On this side of the pond, grid bias batteries used fahnstock clips, so I needed to find a match for the wander sockets.

Turns out I already had it in my stockpile. I make packs for Zenith Trans Oceanics, and I fabricate the connector plug using four pieces of brass tubing. I also had a Vidor set that has a new set of wander plugs, so I test-fit the plug to the tubing: perfect fit.

A wander socket plate was made using a strip of circuit board and six brass tubes. The tubes were split in half on one end, their ends splayed and soldered to the board.

Then I dummied up a cover. I didn't have any decent Eveready Winner graphics, but I found a couple of really sharp Drydex GB pix, and since one of them had been shot dead-on, I blew it up and cleaned it.

A cover box of the correct size was assembled and was lined with adhesive tape. The box was then filled with wood blocks, and the socket plate was laid upon the blocks. I took a couple of small clamps and pressed the box cover tightly against the insides. Then I mixed up a small batch of Alumilite resin, tinted black, and poured it over the socket plate. Within minutes, I had a decent reproduction of a "tar top."

Another piece of circuit board was cut to mount the AA cell holders. Originally I experimented with metal AA holders, because most of the plastic ones I've used are of terrible quality. Turns out the metal ones wouldn't do the job either, so I found my solution in a couple of 3 AA holders. I managed to carefully solder a few wires onto the springs, adding the proper voltage taps. The holders were fastened to the board and their wires brought up to the top.

Here's where the fun began--how to attach the socket plate to the distro board? With this kind of application--attaching a vertical board to a horizontal board--I've used a system of angle strips made from sheet brass. Two were cut to size and attached on opposite ends of the distro board with screws and nuts. The socket plate had no mechanical fasteners
and so it was soldered directly to the strips.

While that sounds easy, it ain't. I had a devil of a time getting the plate aligned right. Too far to the left or the right meant that the entire assembly wouldn't fit into the cover. On top of that, the surface of the plate was not level, so I was soldering at all sorts of wild angles. I'm not proud of the kludgy look of the assembly, but here's the final result--it works. Wires were attached to the remaining solder pads, and I was able to get proper voltages from each tap.

Can I think of any improvements? Absolutely. If I ever do another one, I'm going to mount couple of screws into the socket plate, then do the Alumalite pour. From there, I can make elongated holes into the sheet brass strips and adjust the fit and finish accordingly.

The wander socket tar top is at an angle on the finished product, but based on pix I've seen, the originals had the same characteristic. So, I may have succeeded in accuracy without trying!

Bill

Sean Williams · 15th May 2008, 5:06 pm

Bill,

I am constantly amazed by the quality of your repros!

i am sure it takes many hours of hard work to create the artwork used in the cases, and to come up with suitable ideas for battery holders.

Excellent Work!

Cheers
Sean

batterymaker1 · 15th May 2008, 5:13 pm

Thanks. This is one I wish my quality were better. More like, I wish I planned it out more thoroughly--almost painted myself in the corner.

Robert Darwent · 15th May 2008, 6:03 pm

Quote:

Originally Posted by batterymaker1

The wander socket tar top is at an angle on the finished product, but based on pix I've seen, the originals had the same characteristic. So, I may have succeeded in accuracy without trying!

Quote:

Originally Posted by batterymaker1

This is one I wish my quality were better.

Hello Bill,

You're being far too hard on yourself there with your comments about quailty. I think the repro is top notch, a really first-class effort, well done!

As you say, pictures of original GB batteries are usually at an angle at the top. I've yet to see one perfectly straight anyway, and the cover graphics are just superb. So all in all your repro looks perfectly authentic to me!

In my opinion, mission accomplished! A job expertly done!

Regards

15th May 2008, 4:55 pm	#1
batterymaker1 Heptode Join Date: Apr 2006 Location: Indianapolis, Indiana, USA. Posts: 674	My attempt at a Grid Bias Battery Around February, one of the regulars here asked me if I could make a replica 9 volt grid bias battery. I told him cautiously that I might be able to, but I'd have to do some research. On this side of the pond, grid bias batteries used fahnstock clips, so I needed to find a match for the wander sockets. Turns out I already had it in my stockpile. I make packs for Zenith Trans Oceanics, and I fabricate the connector plug using four pieces of brass tubing. I also had a Vidor set that has a new set of wander plugs, so I test-fit the plug to the tubing: perfect fit. A wander socket plate was made using a strip of circuit board and six brass tubes. The tubes were split in half on one end, their ends splayed and soldered to the board. Then I dummied up a cover. I didn't have any decent Eveready Winner graphics, but I found a couple of really sharp Drydex GB pix, and since one of them had been shot dead-on, I blew it up and cleaned it. A cover box of the correct size was assembled and was lined with adhesive tape. The box was then filled with wood blocks, and the socket plate was laid upon the blocks. I took a couple of small clamps and pressed the box cover tightly against the insides. Then I mixed up a small batch of Alumilite resin, tinted black, and poured it over the socket plate. Within minutes, I had a decent reproduction of a "tar top." Another piece of circuit board was cut to mount the AA cell holders. Originally I experimented with metal AA holders, because most of the plastic ones I've used are of terrible quality. Turns out the metal ones wouldn't do the job either, so I found my solution in a couple of 3 AA holders. I managed to carefully solder a few wires onto the springs, adding the proper voltage taps. The holders were fastened to the board and their wires brought up to the top. Here's where the fun began--how to attach the socket plate to the distro board? With this kind of application--attaching a vertical board to a horizontal board--I've used a system of angle strips made from sheet brass. Two were cut to size and attached on opposite ends of the distro board with screws and nuts. The socket plate had no mechanical fasteners and so it was soldered directly to the strips. While that sounds easy, it ain't. I had a devil of a time getting the plate aligned right. Too far to the left or the right meant that the entire assembly wouldn't fit into the cover. On top of that, the surface of the plate was not level, so I was soldering at all sorts of wild angles. I'm not proud of the kludgy look of the assembly, but here's the final result--it works. Wires were attached to the remaining solder pads, and I was able to get proper voltages from each tap. Can I think of any improvements? Absolutely. If I ever do another one, I'm going to mount couple of screws into the socket plate, then do the Alumalite pour. From there, I can make elongated holes into the sheet brass strips and adjust the fit and finish accordingly. The wander socket tar top is at an angle on the finished product, but based on pix I've seen, the originals had the same characteristic. So, I may have succeeded in accuracy without trying! Bill Attached Thumbnails __________________ Just playing with high voltage....

15th May 2008, 5:06 pm	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: My attempt at a Grid Bias Battery Bill, I am constantly amazed by the quality of your repros! i am sure it takes many hours of hard work to create the artwork used in the cases, and to come up with suitable ideas for battery holders. Excellent Work! Cheers Sean __________________ Engineers make things work and have spare bits when finished

15th May 2008, 5:13 pm	#3
batterymaker1 Heptode Join Date: Apr 2006 Location: Indianapolis, Indiana, USA. Posts: 674	Re: My attempt at a Grid Bias Battery Thanks. This is one I wish my quality were better. More like, I wish I planned it out more thoroughly--almost painted myself in the corner. __________________ Just playing with high voltage....