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Old 4th Aug 2018, 10:21 pm   #1
Philips210
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Default Hacker Sovereign models.

Hi.

I have been checking my Hacker collection and in particular the various Sovereign models:

Sovereign RP18 (2 off)
Sovereign II RP25 (3 off)
Sovereign II RP25A
Sovereign II RP25B
Sovereign III RP721/MB and
Sovereign IV RP77 MB

There are considerable differences between the Sovereign and Sovereign II models but what I was wondering was, what are the differences between the RP25, RP25A and RP25B for the Sovereign II models?

Regards
Symon.
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Old 4th Aug 2018, 10:45 pm   #2
Paul_RK
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Default Re: Hacker Sovereign models.

Hello Symon,

Well, some of the most apparent and consequential differences between the RP25, 25A and 25B happened between rather than at the change of models: for instance, the switch to all silicon RF transistors in the course of RP25 production, and the addition of a DC power jack before the change in model designation from RP25A to RP25B.

For the simplest answer to your immediate question, though, the RP25 became the RP25A with the change of FM tuner from type T304 to T309, and the RP25A became the RP25B when the FM IF board changed from one employing all discrete transistors to a board using the TAA920 IC.

The Sovereign III's history was quite complex too, at least as regards cosmetic options, with at least seven variants coming to mind:

Battery-only RP72, tunable only to 101 MHz
Early RP72MB, tunable to 101 MHz
Later RP72MB, tunable to 104 MHz
Black dial RP72MB, tunable to 104 MHz
"Jade" RP72MB in green suede, tunable to 104 MHz
Rosewood Sovereign RP721MB, again with black dial, tunable to 104 MHz
Golden Sovereign RP722MB, tunable to 104 MHz.

And the Sovereign IV exists in Maidenhead and Bournemouth versions: Bournemouth sets have a redesigned and plainer top panel which doesn't mention the "IV".

Corrections to my shaky memory would of course be welcome.

Paul
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Old 4th Aug 2018, 11:45 pm   #3
mark2collection
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Default Re: Hacker Sovereign models.

The RP25B Sovereign II did indeed have an IC in the FM section, along with the DC power jack installed.

The RP25B also came with a voltage regulator circuit, so when the batteries were beginning to run low, the set still performed to spec.

Mark
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Old 5th Aug 2018, 12:09 am   #4
Radio Wrangler
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Default Re: Hacker Sovereign models.

Early RP25 had germanium transistors in the IFs and the AM front-end
later RP25 changed to lockfit silicon transistors in the IFs and AM front end
RP25B was a step further to an IC in the FM section. And also as said before, the plain dropper resistor was changed to a transistor regulator.

The RP35 Herald followed the change to silicon and used the same AM IF boards as the RP25 family. Just this afternoon, I had to dig into the RP25 manual update section in order to repair a late Herald.

David
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Old 5th Aug 2018, 11:06 pm   #5
Philips210
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Default Re: Hacker Sovereign models.

Hi

Thanks very much for your replies, there's some very helpful info there. Cosmetic differences between the RP25, RP25A and RP25B appear to be minimal unlike the Hunter model which saw several changes throughout its long production.

Regards,
Symon
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