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Old 14th Oct 2008, 9:29 pm   #1
mark pirate
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Default Hacker sovereign - no am

Hi all, reading the latest threads on hackers has prompted me to build a decent example from the 4 lying round the workshop!
The set in question is a sovereign 2 rp25b, while it works well on vhf, it is dead on mw/lw, i have a am only herald rp35(working) to use for parts.
any ideas where the fault could lie? anyone had this fault?
P.S. i have no signal gen at the moment

Mark
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Old 14th Oct 2008, 9:54 pm   #2
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Default Re: Hacker sovereign - no am

Hi Mark,

The most likely culprit is the big Daly-branded electrolytic that smooths the supply to the AM side of things. Maybe 300uF?

There are a couple of threads here about this, started I think by Darren and Mike Phelan.

Nick.

EDIT... Just dug out my manual for the RP25B: Check for 6V across C24 (100uF) on the IF amp board 506. Replace the cap if it's low.
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Old 14th Oct 2008, 10:19 pm   #3
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Default Re: Hacker sovereign - no am

Hi Nick, thanks for the advice,
Quote:
Check for 6V across C24 (100uF) on the IF amp board 506. Replace the cap if it's low.
I just checked this, it is 5v on vhf & no reading at all? on am.
will replace this & report back.

Mark
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Old 14th Oct 2008, 11:06 pm   #4
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Default Re: Hacker sovereign - no am

Mark,

If you haven't already done so, check the wavechange (pushbutton) switches - squirt them with some Servisol contact cleaner if you can. Certainly on the Sovereign I (RP18) and probably on the Sovereign II, the supply to the AM & FM boards is switched when you change wavebands.

Mike
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Old 14th Oct 2008, 11:08 pm   #5
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Default Re: Hacker sovereign - no am

Mark, I'm being thick.

I was fooled because the manual refers to board 506 as the AM IF amp when in fact it's the FM one.

What I should have said is: check for at least 6V across C21 (350V) when switched to LW or MW on the 503A panel. This is the dodgy Daly cap I referred to earlier.

See Darren's thread here: https://www.vintage-radio.net/forum/...light=c21+daly

And Mike's: https://www.vintage-radio.net/forum/...r+electrolytic

Many apologies,
Nick.

Last edited by Nickthedentist; 14th Oct 2008 at 11:14 pm.
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Old 15th Oct 2008, 1:37 am   #6
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Default Re: Hacker sovereign - no am

I don't think it would be a Daly in an RP25B: just looked at three sets here and of those an RP25 has a Daly, a 25A a red TCC and the 25B one of those metallic pale blue looking fellows - are they ITT or Philips? A worthy suspect, though, whatever it is.

Paul
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Old 15th Oct 2008, 7:07 am   #7
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Default Re: Hacker sovereign - no am

Thanks Paul, you're a mine of useful info as usual .

Further to my above post, I meant 350uF not 350V (obviously!).

Sorry.
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Old 15th Oct 2008, 7:57 am   #8
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Default Re: Hacker sovereign - no am

No problem Nick, you did get the board no. right. Will check c21 later
Mike, yes first thing I did was to clean the wavechange switches, but as nick says, I think it is a cap problem, at least there are no nasty af*** transistors in this set.
Paul, you are dead right about the caps fitted to these sets, I think the blue caps are made by Philips.

Mark

Last edited by Darren-UK; 18th Oct 2008 at 10:29 am. Reason: Excessive use of emoticons.
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Old 16th Oct 2008, 9:13 pm   #9
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Default Re: Hacker sovereign - no am

Hi all, Nick,
Quote:
check for at least 6V across C21 (350V) when switched to LW or MW on the 503A panel. This is the dodgy Daly cap I referred to earlier.
I have now checked this cap & am getting exactly 6v across it on am,
any other things to look for before i replace the complete 503a panel

Mark
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Old 17th Oct 2008, 7:33 pm   #10
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Default Re: Hacker sovereign - no am

I just fixed an all AF11* sovereign with no AM but FM was good.

In truth, it actually fixed itself...I was fiddling around trying to find a faulty transistor and after about 15 mins it slowly came to life on MW but no LW and then LW recovered.

I assume the electrolytics were reforming...Peter
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Old 17th Oct 2008, 7:50 pm   #11
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Unhappy Re: Hacker sovereign - no am

Hi peter, you are a lucky man
Quote:
In truth, it actually fixed itself...I was fiddling around trying to find a faulty transistor and after about 15 mins it slowly came to life on MW but no LW and then LW recovered.
I have given up trying to find the fault, i am in the process of replacing
the entire 503 board from a scrap set, will report back when finished

Mark
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Old 17th Oct 2008, 7:57 pm   #12
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Default Re: Hacker sovereign - no am

Hi Mark,

HANG ON!!! It might not be the 503A at all. And you might have to re-align the set if you swap panels.

Have you got the manual?

On AM, the audio leaves the 503A board at the junction of R14 and R16. Try injecting a signal here (wet finger?) to see if you can hear a hum in the speaker.

Try measuring voltages around the transistors T2/T3/T4 on the 503A board. Note that the manual quotes them with respect to HT+ which it later says is +6v with respect to chassis (i.e. they're measured WRT the +ve side of C21).

Also, have you measured any voltages around the AM "front end", i.e. around TR1, BF194 (on the switch board)? Again, measured WRT the 6V HT rail.

[The manual could have done with some proofreading (in addition to the AM/FM cock-up I mentioned before); sometimes these transistors are referred to as T1-T4, other times as TR1-TR4. Similarly, T1 appears to be on the switch board but the voltages page implies that it's on 503A ]

Nick.
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Old 17th Oct 2008, 9:27 pm   #13
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Thumbs up Re: Hacker sovereign - no am

Hi Nick,
Quote:
HANG ON!!! It might not be the 503A at all. And you might have to re-align the set if you swap panels.
Well, i have replaced the 508, And the set is now working well on am. Don't know what the problem is with the original board.

I have re-fitted it to the doner set & it is still well dead, the c21 cap is ok
& i have +6v on it, must be a dead transistor, anyway my set is now working well & just needs some cosmetic cleaning & fm aerial replaced.
Watch out for it on success stories soon.

Mark

Last edited by Darren-UK; 18th Oct 2008 at 10:30 am. Reason: Excessive use of emoticons.
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Old 17th Oct 2008, 9:37 pm   #14
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Default Re: Hacker sovereign - no am

Well done Mark!

N.
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Old 17th Oct 2008, 9:38 pm   #15
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Default Re: Hacker sovereign - no am

Quote:
Originally Posted by mark pirate View Post
..the doner set...
Well, I suppose it is Friday evening
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Old 17th Oct 2008, 9:51 pm   #16
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Default Re: Hacker sovereign - no am

Thanks Nick, i must admit, after that board transplant a kebab & a pint is well
deserved
Mark

Last edited by Darren-UK; 18th Oct 2008 at 10:31 am. Reason: Excessive use of emoticons.
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