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Old 17th Mar 2021, 7:54 pm   #1
FERNSEH
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Default Convert Bush DAC90 or AC91 to battery use.

Received a message from a client asking if I had a Bush BA91 for disposal.
My answer was no and that I've also been on the lookout for that particular model. The BA91 is housed in a near identical cabinet to the DAC90.
BA91 has three waveband coverage, Long, Medium and Short.
How about this idea? Convert a DAC90 or better still a three wave Bush chassis to 2volt valves. The valve line-up in the BA91 is: KCF30, KF35, KBC32 and KL35, all octal types. The KCF30 might be difficult to find but the electrically similar Mazda TP25 could be considered, or if there is space for it, the huge Mullard KK32.
A chassis from a junk SUG3 is an alternative.

DFWB.
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Old 17th Mar 2021, 8:32 pm   #2
Nuvistor
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Default Re: Convert Bush DAC90 or AC91 to battery use.

You certainly set yourself some challenges David.
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Old 17th Mar 2021, 9:54 pm   #3
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Default Re: Convert Bush DAC90 or AC91 to battery use.

I like it!

Many people, of course, are doing it the other way round - making mains power supplies for battery radios...
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Old 17th Mar 2021, 10:36 pm   #4
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Default Re: Convert Bush DAC90 or AC91 to battery use.

I’ve actually got a chassis from a Bush battery radio here that looks about DAC90 sized! I was planning on reviving it and seeing if it would fit into the cabinet of a DAC90. I think it was probably from one of the Bush wooden cased battery portables, can’t remember the model though.

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Old 18th Mar 2021, 9:41 pm   #5
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Default Re: Convert Bush DAC90 or AC91 to battery use.

This Bush AC91 can be considered for conversion to battery valves.
We are even thinking about employing 1.4 volt valves with the rather special DK40 as the frequency changer. Bush did use the DK40 in an export model, possibly the only UK made set to do so.

DFWB.
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Old 19th Mar 2021, 10:23 am   #6
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Quote:
Originally Posted by FERNSEH View Post
The valve line-up in the BA91 is: KCF30, KF35, KBC32 and KL35, all octal types. The KCF30 might be difficult to find but the electrically similar Mazda TP25 could be considered, or if there is space for it, the huge Mullard KK32.
A chassis from a junk SUG3 is an alternative.

DFWB.
My BA91 has the TP25 fitted. Whoever did it has neatly added an International Octal conversion base to the TP25 (making it taller since the Mazda Octal base is still attached to the valve) but it means that a KCF30 can be plugged straight in should one become available. The KCF30 seems to be quite rare now.
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Old 19th Mar 2021, 11:41 am   #7
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Default Re: Convert Bush DAC90 or AC91 to battery use.

In fact the Mullard KCF30 is a re-based Mazda TP25 and it's likely this will be the frequency changer valve we'll use in the modified chassis. An alternative if there is space to accommodate it is the huge Mullard KK32.
https://www.radiomuseum.org/tubes/tube_kk32.html

DFWB.
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Old 19th Mar 2021, 2:57 pm   #8
slidertogrid
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Rather than altering a nice original set why not run it from an inverter if battery operation is needed?
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Old 19th Mar 2021, 5:17 pm   #9
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Ed Dinning has found a scrap SUG3 chassis for the project. It's got the three waveband coil pack which is just what we need for the BA91 recreation.

DFWB.
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Old 24th Mar 2021, 9:33 pm   #10
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Quote:
Originally Posted by Sideband View Post
My BA91 has the TP25 fitted. Whoever did it has neatly added an International Octal conversion base to the TP25 (making it taller since the Mazda Octal base is still attached to the valve) but it means that a KCF30 can be plugged straight in should one become available. The KCF30 seems to be quite rare now.

As requested by another forum member, here are some photos of my BA90 before restoration. In particular it shows the modified TP25 mounted on an IO base converter.

I had to do a lot of work on this set including repair of an IF transformer core and get the output transformer rewound.

There were no battery leads fitted to my set so I had to make some up.

The batteries were not fitted internally. There was a matching 'battery box' that the radio stood on but I've never seen one.
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Last edited by Sideband; 24th Mar 2021 at 9:46 pm.
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Old 25th Mar 2021, 1:13 pm   #11
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Found one serviceable 465Kc/s IF transformer and the search is on for another.
At least this project will give a chance to find a use for a KK32 octode frequency changer valve. The origins of this valve go back to 1930s as the KK2.
https://www.radiomuseum.org/tubes/tube_kk2.html

DFWB.
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Old 25th Mar 2021, 1:55 pm   #12
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Quote:
Originally Posted by Sideband View Post
here are some photos of my BA90 before restoration.
To avoid confusion, that is supposed to say BA91! It looks so much like the DAC90 I automatically call it a BA90.....
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Old 26th Mar 2021, 3:29 pm   #13
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Default Re: Convert Bush DAC90 or AC91 to battery use.

I have a Bush BA91 which is a very good performer and uses the Mullard K Series 2 Volt Octal valves, The SW reception is outstanding for a battery set.

If you look at a Bush BA11 this was the Wooden version of the BA91 you will find that it uses all 2 Volt Mazda Octals ie: TP25, VP23, HL23DD & PEN25.

Many years ago I saw a BA91 at the NVCF at The National Exhibition Centre
that was fitted from new with this line up. The only difference was that it was made in Dublin at the Bush Factory there.

Trevor.
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Old 26th Mar 2021, 9:50 pm   #14
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Default Re: Convert Bush DAC90 or AC91 to battery use.

This is my BA91 that I listed on the Radiomuseum website.

Regards
Trevor.

https://www.radiomuseum.org/r/bush_ba91.html
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Old 26th Apr 2021, 9:39 am   #15
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Default Re: Convert Bush DAC90 or AC91 to battery use.

If 1.4volt valves were to be employed it would be possible to fit the the batteries inside the cabinet.
Possibly a chance to use the 1D8GT diode-triode-pentode. The output transformer can be fitted under the chassis.

https://www.radiomuseum.org/tubes/tube_1d8gt.html

I doubt if ever Bush Radio considered this valve being a firm that almost always chose Mullard as the supplier of valves and tubes.

DFWB.
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Old 30th Apr 2021, 8:43 pm   #16
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Default Re: Convert Bush DAC90 or AC91 to battery use.

The attachment shows the suggested 1.4volt valves for the battery Bush radio receiver. The DK40 octode was employed at least once in an Bush export receiver. There should be sufficient space for a small HT battery.

DFWB.
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Old 12th May 2021, 7:33 pm   #17
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Have settled on the American 1D8GT to serve as the second detector, audio amplifier and output valve. Employing this valve instead of the usual DAC32 and DL33 will free up more space for the batteries.

DFWB.
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Old 14th May 2021, 11:47 am   #18
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Correct IF transformers fitted and the wiring of the frequency changer and IF amplifier stages done.
Coming up next, the detector and audio amplifier.
Very simple circuit design, no need component group boards.

DFWB.
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Old 22nd May 2021, 9:36 am   #19
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Default Re: Convert Bush DAC90 or AC91 to battery use.

The under chassis wiring completed and the receiver is undergoing initial tests.

DFWB.
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Old 22nd May 2021, 12:27 pm   #20
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David looking good you should put a video on youtube with it working kind regards Bob
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