UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

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

Closed Thread
 
Thread Tools
Old 24th Apr 2017, 10:38 pm   #1
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Grundig Party Boy 210E

After a reverse polarity incident a while ago on my battery operated Grundig Party Boy 210E it’s been playing up ever since. A symptom included when switched on (with PP9) it was motorboating (‘farting’ noises) but if you switched it on and off a couple of times it would be ok. A few weeks later after connecting my Grundig TN4 power supply to it it hummed loudly and the output transistors gave up the ghost. These were replaced and other components were checked in the output stage. The problem I have now is if a fresh PP9 is connected or a power supply is used at 9v the radio howls, whistles and motorboats especially on LW right across the scale and a little on FM although MW seems ok, however it still picks up stations very well. What I did find was if I connected it to my bench power supply at 9v and then slowly wound it down I found that at around 8v all the noises stopped and it’s perfect. Can anybody please point me in the right direction with regards to where I should be looking? As this is one of my favourite radios and is used a lot it’s taking priority over everything else.

Regards
Poppydog
poppydog is offline  
Old 24th Apr 2017, 11:06 pm   #2
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Grundig Party Boy 210E

Are you saying it's had reverse polarity applied? If so, there will be lots of knackered electrolytics inside.
paulsherwin is offline  
Old 24th Apr 2017, 11:20 pm   #3
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

Quote:
Originally Posted by paulsherwin View Post
Are you saying it's had reverse polarity applied? If so, there will be lots of knackered electrolytics inside.
Yes Paul it has. There doesn't appear to be many electrolytics in this radio, there is a awful lot of those oblong polyprope caps though. Regards Poppydog
poppydog is offline  
Old 24th Apr 2017, 11:30 pm   #4
julie_m
Dekatron
 
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
Default Re: Grundig Party Boy 210E

Multiple capacitor failure certainly would cause all manner of instabilities. Electrolytic capacitors can lose capacitance when reverse-biased even if they do not explode, so it might be prudent to replace them all -- but do them one at a time, testing after doing each one, to avoid introducing new faults by miswiring.
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments.
julie_m is offline  
Old 25th Apr 2017, 8:09 am   #5
trsomian
Hexode
 
Join Date: Oct 2010
Location: Box End, Beds. UK.
Posts: 271
Default Re: Grundig Party Boy 210E

How long was the reverse polarity applied for, because if it was very brief the capacitors may have survived OK. I don't know the circuit for these, but in some radios Grundig used a zener as a shunt regulator for the RF stages, which when the supply is reversed will be a forward biased diode, thus preventing much reverse voltage appearing on that part of the circuit. The series resistor might have overheated though
trsomian is offline  
Old 25th Apr 2017, 8:49 am   #6
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

The reverse polarity lasted as long as it took me to pull off the battery snaps after hearing the speaker pop, however it was tried again not long after but was disconnected quickly till eventually working out what was wrong. Just one more thing, when replacing the output transistors they were drawing around 4.5 ma at idle. I didn't increase this to the 8.5ma as is specified. Apart from the noises it still sounds very good. I will look at those electrolytics tonight Regards Poppydog
poppydog is offline  
Old 25th Apr 2017, 10:30 am   #7
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Grundig Party Boy 210E

If the OP transistors are underbiased they will produce crossover distortion at low volume levels, but if you're happy with the sound then it won't do any harm.
paulsherwin is offline  
Old 25th Apr 2017, 3:49 pm   #8
GeoffK
Heptode
 
Join Date: Mar 2016
Location: Essex, UK.
Posts: 602
Default Re: Grundig Party Boy 210E

The output bias current is 5.5mA not 8.5mA at 7.5 Volts. 4.5mA will be ok but could be set to 5.5mA.
__________________
Geoff
GeoffK is offline  
Old 25th Apr 2017, 10:20 pm   #9
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

All aluminium electrolytics have been replaced (there were only 5), they were all put in my Chinese tester and according to that they were acceptable, even though one of the axial caps was starting to reveal its contents on one end (I was hoping that was the one). The radio is still making the same noises, I've obviously upset something but what and where? Before anybody says it - I haven't been twiddling . With regards to the output transistors (AC187/188) current at idle can anybody confirm what the current should be as the sheet I've got says 8.5ma at 7.5v, however its not good print so the 8 could be a 5! Not that its going to make any difference to my whistling/farting noises.

Regards
Poppydog
poppydog is offline  
Old 26th Apr 2017, 10:49 am   #10
Chicoull
Triode
 
Join Date: Dec 2016
Location: Elgin, Moray, UK.
Posts: 31
Default Re: Grundig Party Boy 210E

Hi, I checked the Radio and TV Servicing Book for 1971-72. the circuit diagram shows 8.5mA at 7.5V. It says to adjust R45 for 8.5mA at Link Point X.
Chicoull is offline  
Old 26th Apr 2017, 11:12 am   #11
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Grundig Party Boy 210E

The Grundig service sheet also gives the output pair quiescent current as 8.5mA.

Lawrence.
ms660 is offline  
Old 26th Apr 2017, 11:39 am   #12
GeoffK
Heptode
 
Join Date: Mar 2016
Location: Essex, UK.
Posts: 602
Default Re: Grundig Party Boy 210E

Yes the MW/LW version was 5.5mA.
__________________
Geoff
GeoffK is offline  
Old 26th Apr 2017, 11:57 am   #13
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Grundig Party Boy 210E

Quote:
Originally Posted by Hetrodyne View Post
Yes the MW/LW version was 5.5mA.
I'm confused now, is the OP's Grundig MW/LW or MW/LW and FM?

Lawrence.
ms660 is offline  
Old 26th Apr 2017, 12:18 pm   #14
Chicoull
Triode
 
Join Date: Dec 2016
Location: Elgin, Moray, UK.
Posts: 31
Default Re: Grundig Party Boy 210E

The 210E is LW, MW and VHF.
Chicoull is offline  
Old 27th Apr 2017, 8:45 am   #15
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

Thanks for the replies regarding the idle current, I may look to increase that this evening. Any more advice regarding the whistling and motor boating would be more than welcome. Regards Poppydog
poppydog is offline  
Old 27th Apr 2017, 9:12 am   #16
Hybrid tellies
Nonode
 
Hybrid tellies's Avatar
 
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
Default Re: Grundig Party Boy 210E

Have you checked the electrolytic across the main supply line? This will have suffered if there has been a power supply reversal. This will give the effects that you are getting if its blown open circuit.
I had the same problem when my friend connected up his Roberts R250 to a wall wart supply that had opposite polarity. It blew out the electrolytic cap across the supply and completely spit the case of the output IC.
__________________
Simon
BVWS member
Hybrid tellies is offline  
Old 27th Apr 2017, 1:42 pm   #17
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

Quick question, are these plastic/polyester type wima caps polarized? Regards Poppydog
poppydog is offline  
Old 27th Apr 2017, 1:47 pm   #18
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
Default Re: Grundig Party Boy 210E

Is there supposed to be a picture?

Only electrolytic capacitors are polarized.

Lawrence.

Last edited by ms660; 27th Apr 2017 at 1:52 pm.
ms660 is offline  
Old 27th Apr 2017, 2:03 pm   #19
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

No. Sorry do you need a picture? There are loads of them in this radio. I am getting replies saying check\ change "electrolytics". there are only 5 ,which have all been changed. My schematic is showing no more polarized caps, (looking at symbols on sheet) however on the pcb I can just about see under these wimas a neg polarity sign. googling polarized polyester caps is inconclusive. Regards Poppydog
poppydog is offline  
Old 27th Apr 2017, 2:15 pm   #20
poppydog
Banned
 
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
Default Re: Grundig Party Boy 210E

Quote:
Originally Posted by ms660 View Post
Is there supposed to be a picture?

Only electrolytic capacitors are polarized.
Just read your edit
poppydog is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 1:22 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.