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Old 24th May 2021, 9:58 am   #21
FERNSEH
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Using a DK32 as the frequency changer, a DF33 as IF amplifier and the 1D8GT as the audio amplifier the results are for a small portable radio quite satisfactory but not good enough for a table radio.
A complete redesign is called for.
To improve performance I've decided to use a different set of valves.
The frequency changer will be a DK40. The IF amplifier a DF91. The detector and audio amplifier will be a DAF91. Like the DK40 the output valve will be another special valve developed by Philips for high performance battery radios, the DL41.

DFWB.
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Old 3rd Jun 2021, 10:20 am   #22
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Default Re: Convert Bush DAC90 or AC91 to battery use.

This is the Philips designed circuit to be adopted for the all-dry battery Bush radio project.
Adaptor plates to be used in order the miniature valves can be employed in lieu of the octal valves previously fitted in the DAC90 chassis.

DFWB.
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Old 3rd Jun 2021, 12:14 pm   #23
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David thats a proper project with your adapter plates
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Old 3rd Jun 2021, 10:08 pm   #24
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi Bob,
The adaptor plates and valveholders now fitted along with a pair IF transformers which were removed from an Ultra YA series TV set.

DFWB.
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Old 4th Jun 2021, 7:43 am   #25
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Where can I order some adaptor plates David?
These seem to be the "in" thing these days.
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Old 5th Jun 2021, 6:57 pm   #26
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Default Re: Convert Bush DAC90 or AC91 to battery use.

H David looking what did you use to clean the chassis ? kind regards Bob
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Old 5th Jun 2021, 7:23 pm   #27
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi Bob,
Used a rubbing block and finished off with Brasso metal polish.
Hi Trevor,
the attachment shows a collection of brackets and adaptor plates.

DFWB.
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Old 8th Jun 2021, 9:42 pm   #28
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Frequency changer, IF amplifier and demodulator stages completed.
Coming up, the assembly of the audio amplifier and output stages.
Got to mention I prefer building sets that have octal valves instead of the miniature types on B7G bases. B8A not much better.

DFWB.
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Old 8th Jun 2021, 10:03 pm   #29
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Nice neat chassis.
Will be a cracking looking job when done.
Well done.
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Old 8th Jun 2021, 11:01 pm   #30
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi Trevor i second that looking forward to seeing the finished result
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Old 9th Jun 2021, 6:39 pm   #31
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David, a lot more drastic that Kylee20's range of modes to the DAC90a

Ed
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Old 9th Jun 2021, 7:49 pm   #32
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Exactly, Ed - I'm now feeling I barely scratched the surface!
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Old 9th Jun 2021, 9:50 pm   #33
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Kalee20 wrote: "Exactly, Ed - I'm now feeling I barely scratched the surface!"
And it's actually a Philips circuit design on a Bush chassis.
The audio amplifier wiring was completed this evening and now I have to summons up the courage to test the receiver. Can't afford any mistakes with this one. I reckon I've got the the only DL41 output pentode in the UK.
OK for DK40 octodes, I bought nine of those.

DFWB.
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Old 10th Jun 2021, 11:36 am   #34
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Default Re: Convert Bush DAC90 or AC91 to battery use.

The attachment shows that there is plenty space for the HT and LT batteries.
The output transformer was made by Ed Dinning to match the ra of the DL41 to the 3 ohm loudspeaker.
The idea for creating this set was the possibility Bush Radio might have considered making an "all-dry" version of the BA91.
To match the performance of that model was reason the D40 series valves were chosen rather than the more common DK91 and DL94 series of valves.

DFWB.
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Old 10th Jun 2021, 6:35 pm   #35
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David, let us know how it performs, especially on SW.

The wiring is also far too neat for a "production " set

Ed
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Old 10th Jun 2021, 8:55 pm   #36
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Default Re: Convert Bush DAC90 or AC91 to battery use.

"The wiring is also far too neat for a "production " set"
Hi Ed,
It's a special prototype model, unlikely to go into production.
Well the news is it works! Very good results on short waves which must be due to the choice of frequency changer valve, the DK40. This valve could be tried in the Zenith Transoceanic sets as replacement for the 1L6.
Plenty audio power, much better than receivers with the usual DL94 etc. Your output transformer is doing a great job.
Not so good is the ex-Ultra TV first IF transformer, it won't peak up properly on 465Kc/s. Intend to fit another IF transformer either the original Bush component or another ex-equipment part.
In terms of sensitivity the set should be as good as the AC91 but will audio output will never be as good as the mains models.

DFWB.
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Old 10th Jun 2021, 9:39 pm   #37
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David that is the price of DL41 going through the roof now
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Old 10th Jun 2021, 10:47 pm   #38
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi Bob,
I've seen the DL41 on sale from North American valve specialists.
Quite reasonable prices for the valves but high postal charges.

DFWB.
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Old 11th Jun 2021, 12:53 pm   #39
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Default Re: Convert Bush DAC90 or AC91 to battery use.

Hi David that is the problem postage charges and possibly getting walloped by import charges
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Old 11th Jun 2021, 5:09 pm   #40
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Default Re: Convert Bush DAC90 or AC91 to battery use.

UPDATE been to Davids shop to look at superb Bush / Philips Battery Valve Radio & it plays great even with no Aerial plugged in. Ed you are right the construction is very neat Kalee20 you should do this conversion . Going to start a new thread on another conversion that i discussed with David this afternoon kind regards Bob
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