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Old 27th Apr 2017, 2:16 pm   #21
ms660
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Default Re: Grundig Party Boy 210E

Only electrolytic capacitors are polarized, polyester, paper, ceramic, silvered mica and anything else etc are not polarized but sometimes the outer foil connection end is marked with a line or a ring on some types.

EDIT: Post crossed.

Lawrence.
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Old 27th Apr 2017, 3:36 pm   #22
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Default Re: Grundig Party Boy 210E

These are the electrolytic capacitors.

C4 2uF Fm discriminator

C38 5uF AGC

C48 500uF

C49 1000uF Reservoir smoothing

C46 100uF TV1 emitter bypass/neg feedback

C51 500uF Audio output speaker
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Old 27th Apr 2017, 4:15 pm   #23
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Default Re: Grundig Party Boy 210E

I missed one C4 . before I go prising open the FM module to look at C4 would this cap give me all this trouble?
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Old 27th Apr 2017, 4:26 pm   #24
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Default Re: Grundig Party Boy 210E

C4 can be left alone, it is highly unlikely to have received any damage as it is isolated by the FM discriminator ratio detector transformer. The fault is more generalised as you have said it is on MW/LW as well.
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Old 27th Apr 2017, 4:52 pm   #25
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Default Re: Grundig Party Boy 210E

It might be worth measuring the voltage across C49 and C48 under fault conditions?

Lawrence.
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Old 27th Apr 2017, 7:25 pm   #26
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Default Re: Grundig Party Boy 210E

What would be the reasoning for this please?, and what sort of voltages should and shouldn't I be looking for? Regards Poppydog
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Old 27th Apr 2017, 7:29 pm   #27
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Default Re: Grundig Party Boy 210E

Just to see if the supply voltages are ok, it wouldn't take much time to measure them, with the fault condition coming through the loudspeaker and then again with the volume turned down to minimum.

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Old 27th Apr 2017, 7:53 pm   #28
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Default Re: Grundig Party Boy 210E

C48 QUIET: 8.39V
MOTORBOAT: 8.61V
C49 QUIET: 8.90V
MOTORBOAT:8.89V

All voltages taken with a 9v power supply regards Poppydog
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Old 27th Apr 2017, 7:59 pm   #29
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Default Re: Grundig Party Boy 210E

They seem reasonable as far as I know.

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Old 28th Apr 2017, 12:15 am   #30
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Default Re: Grundig Party Boy 210E

Without an oscilloscope to look at waveforms in various parts of the circuit this can be difficult to track down. An audio output could be taken from the DIN socket and fed to an external amplifier to check what is coming out of the IF stages after detection and before it reaches the radios audio amplifier input.
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Old 28th Apr 2017, 6:37 am   #31
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Default Re: Grundig Party Boy 210E

If this really does need a oscilloscope, then this is another one for the parts bin, because I don't have one. Never mind thanks for all the suggestions. Regard Poppydog
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Old 28th Apr 2017, 6:51 am   #32
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Default Re: Grundig Party Boy 210E

Sometimes new components can be faulty. As a last resort, have you tried going round and bridging all the electrolytics with a second capacitor, don't worry too much about the value, try a 47uf one. Do this to each electrolytic in circuit whilst the fault is happening just to see if it makes any difference.

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Old 28th Apr 2017, 8:11 am   #33
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Default Re: Grundig Party Boy 210E

Does this radio have the typical Grundig arrangement of press down two wavechange push buttons to get it into amplifier mode? If it does, is it well behaved in amplifier mode, because if it isn't your trouble is in the audio somewhere, so you can concentrate on this. Likewise, if the volume control is set on minimum does the tape recorder outlet work properly?. If it does work OK, does it only stop working properly when the volume is increased.

Are you able to test the thing with a high impedance something connected to the earphone jack (I assume it has one and that it disconnects the internal loudspeaker. This may indicate to you if the problem is caused by the current flowing to the loudspeaker.

In principle you need to try and divide the circuitry it section, find if the sections work correctly, and then try different combination of sections. You may be able to lift a resistor leg somewhere, and use a bench power supply to feed the RF stages to see if that makes a difference
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Old 28th Apr 2017, 10:15 am   #34
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Default Re: Grundig Party Boy 210E

Quote:
Originally Posted by poppydog View Post
If this really does need a oscilloscope, then this is another one for the parts bin, because I don't have one. Never mind thanks for all the suggestions.
The oscilloscope is a useful test instrument, but analysing the fault condition and trying to isolate sections will help locate the area that is causing the fault. As most people do not have an oscilloscope other methods have to be used, such as the one I suggested of taking an output from the DIN socket. The post by trsomian has suggested trying an output from the earphone socket with the internal speaker disconnected.
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Old 28th Apr 2017, 10:35 am   #35
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Default Re: Grundig Party Boy 210E

As an aside, if you do decide to scrap this I'd be interested in buying the case. I have a good working 210 with a damaged and unrestorable speaker grille.

Double check that you've fitted the replacement electrolytics the right way round, particularly C46.
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Old 30th Apr 2017, 10:14 pm   #36
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Default Re: Grundig Party Boy 210E

Whenever I see a comment like "without an oscilloscope" I think its 'curtain down time' I really would like to sort this as it still has excellent sound quality.

I have tried Crackles suggestion of bridging all of the electrolytics I replaced (100uf), none made any difference apart from C38 5uF, when I bridged that the motorboating slowed down a bit.

Trsomians suggestions were also tried, plugging in a din lead, made no difference even with the volume turned down or up - the motorboating and whistling still continued (from both radios). Also plugging in a lead into the earphone socket to an aux amplifier made no difference, still motorboating.

After all these tests I think I can rule out a problem with the output stage can't I?

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Old 30th Apr 2017, 11:36 pm   #37
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Default Re: Grundig Party Boy 210E

Hi Poppydog

Looking at the schematic, I would start with disconnecting the audio feed from the slider of the volume control, c45. This will allow you to narrow down the problem. No motorboating, then its down to the rf/if. Still motorboating, its the audio amp.

Having worked out where the fault lies, it will be a lot easier to advise you next.

Should it be the audio amp the then its down to either c48 - 500uf or c49 1000uf. But try feeding in audio from another radio just to make sure that you are not going up a blind alley.

Should it be the rf/if, then, switch to am and working backwards from the last if amp, grounding the base of each IF transistor with a 0.1uf to see what happens and think of emitter bypass and decoupling condensers. It may well be that you have a fault which has nothing to do with accidently switching polarity, who knows, but we're only talking 9 volts not 900 and silicon transistors after all .

Grundig radios of this era have a well deservd reputation for design, build and sound quality, so lets get this set working.

Chris
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Old 2nd May 2017, 11:08 pm   #38
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Default Re: Grundig Party Boy 210E

A small update as I have been very busy, following the advice from simpsons, C45 was lifted and the motorboating stopped so that means that the audio/output stage seems ok. So it is looking like the work I have just done in that area is ok as well. Radio on LW grounding base to emitter with the 0.1uf cap on BF184-II stops the motorboating but turns the sound into a FM type hiss with a distant station in the background, BF184-III it stops the noise completely, with a distant station in the background with the odd whistle. There are others to look at but they are all in modules, so I will have to look at how to get into them.

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