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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

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Old 14th Dec 2018, 10:43 am   #41
Hybrid tellies
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Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
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Default Re: Hacker Sovereign II RP25B

This has been an interesting read, well done for finding that inter mute fault. I have repaired a few RP25B's over the years for friends and family and after many years of service they are still going strong.
Welcome to the Hacker owners club.
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Old 14th Dec 2018, 5:00 pm   #42
Panrock
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Default Re: Hacker Sovereign II RP25B

Having caught the Hacker bug, I couldn't resist having a closer look at its audio amplifier board this afternoon. I was curious if it was set up right. Could I make the quality still better?

First thing, for no good reason I replaced the poor old 400uF output coupling capacitor, probably blameless, with a brand new 470uF. Well, it might have dried up a bit over half a century?

Next, to check the output pair's standing current. This was found to be over 4mA. It was simple to adjust for the correct 3mA. Once I had done this, I checked the mid-point voltage, which was dead-on the 8.9v specified - so no further adjustment needed. (The batteries were both giving exactly 9v.)

Lastly, I checked the battery drain when idling, set to VHF. This was no longer 25mA but had decreased to 23mA, which can be considered correct.

But was it worth it? Well, under these circumstances, where one believes one must have improved it, and with my 68 year-old cloth ears, well yes... it really does sound slightly clearer and more sonorous. I now know it is set correctly too, which counts for something.

Steve
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