|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
3rd Dec 2015, 10:45 pm | #41 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
|
Re: Grundig Concert Boy 1100
If the rectifier was miswired, with the - output and one of the AC inputs swapped over, it would have created a circuit from the transformer through the lamp and one of the diodes, which would have conducted on every alternate semicycle. The lamp should have protected everything, though.
Unsolder the bridge rectifier altogether. Follow the traces under the board from the transformer. Connect the two AC inputs of the bridge rectifier here. Connect the + output to the point so marked, and the - output (which, if not marked, may be assumed diagonally opposite the + output) to the remaining hole. The plates of the original rectifier could have had any of the following combinations:
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments. Last edited by julie_m; 3rd Dec 2015 at 11:03 pm. |
3rd Dec 2015, 11:30 pm | #42 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
I have now wired everything correctly and have no bulb when switched to BATT and no bulb when on mains. When the radio is switched on the bulb is very bright. Back to square one!
|
4th Dec 2015, 12:04 am | #43 |
Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,526
|
Re: Grundig Concert Boy 1100
No, not square 1. We now know that the rectifier is OK and the short circuit is on the radio side of the switch. My first two suspects would be C805 and the output stage of the radio (not in the available circuit clip). First try removing C805. If the bulb is much dimmer and the radio hums loudly, then C805 is faulty. If the bulb stays bright and the set hums, then probably the output stage is bad.
See how it goes........
__________________
....__________ ....|____||__|__\_____ .=.| _---\__|__|_---_|. .........O..Chris....O |
4th Dec 2015, 12:18 am | #44 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
|
Re: Grundig Concert Boy 1100
Can you run it on batteries? if so does it work. Whilst running the radio off batteries or a suitable external DC source check the idle current with the volume control set to minimum. If it's below 20mA then it should be ok but if it is higher then suspect the output stage. If this radio uses a transistorised output stage rather than an IC then the idle current may start off low but rapidly rise after a few minutes this indicates that the output transistors are leaky.
__________________
Simon BVWS member |
4th Dec 2015, 12:24 am | #45 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
Thank you very much for everybody that helped tonight but my teddy and bed are awaiting, so will have another look tomorrow.
|
4th Dec 2015, 3:59 pm | #46 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
probably should have done this from the very start but I connected up a 9v dc supply switched it to batt turned the radio on and im getting a very quiet heartbeat sound through the speaker.i also cannot find a c805 on my schematic only a c806. also to use it via battery side would I need to unsolder bulb and replace with the correct fuse? thanks
|
4th Dec 2015, 4:10 pm | #47 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Grundig Concert Boy 1100
C805 is shown in post 8.
If you switch to battery the bulb will be out of circuit as far as the radio's concerned, so it's immaterial whether you fit a fuse. Heart beat sound could be a sign of a discharged or overloaded battery. What's its voltage like on load?
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
4th Dec 2015, 4:32 pm | #48 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
the voltage is very erratic unreadable. numbers on meter going up and down very quick in time to the heartbeat sound
|
4th Dec 2015, 4:52 pm | #49 |
Rest in Peace
Join Date: Jan 2015
Location: Cottesmore, East Midlands, UK.
Posts: 858
|
Re: Grundig Concert Boy 1100
C805 on the Trader Sheet is the electrolytic capacitor connected across the bridge rectifier downstream of the on/off switch (see the clip of the cct diagram I attached to an earlier post).
You may need to watch out for component identifying numbers. The Trader Sheets were compiled by a third party by reverse engineering and sold to general radio repair shops. The labels they assigned to various components will probably not match the component numbers on the manufacturers service sheets - these would only have been issued by the manufacturers to their own dealers' workshops. Cheers, Frank NB - just noticed that C805, while it appears on the Trader cct diagram, does not appear in the component list or the location diagrams on the Traders sheets, and is probably a drafting error. From the large value, (2200uF) I'd guess that C805 is the one that appears as C806 on the component list. It lives on the main PCB among the output transistors. Last edited by frankmcvey; 4th Dec 2015 at 5:07 pm. |
4th Dec 2015, 4:57 pm | #50 |
Rest in Peace
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
|
Re: Grundig Concert Boy 1100
Up until today, I have always seen the AC connections at opposite coners on bridge rectifiers. Today I see the AC connections adjacent to each other on a diddy bridge rectifier in a switch mode power supply.
Just to keep you on your toes. |
4th Dec 2015, 5:29 pm | #51 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
frank mcvey on my diagram my 806 is where your 805 is. what would be the cause of my erratic meter reading whilst measuring the voltage with the radio switched on?
|
4th Dec 2015, 5:53 pm | #52 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Grundig Concert Boy 1100
All the C8XX numbered capacitors are concerned with the power supply. I reckon C805 and C806 are the same cap, one of them being a misprint.
It's going to be the 2200uF cap. Just disconnect one end of it and see what happens when the radio is battery powered. It's a smoothing cap and only really used when the set is mains powered.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
4th Dec 2015, 6:32 pm | #53 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
I've located the 2200uF cap, it's very odd looking I will try to disconnect it but it's looking like I'm going to have to disconnect the tuning cord assembly to get the plate with all the station numbers on it off. That tuning cord looks a pain.
|
4th Dec 2015, 7:19 pm | #54 |
Rest in Peace
Join Date: Jan 2015
Location: Cottesmore, East Midlands, UK.
Posts: 858
|
Re: Grundig Concert Boy 1100
With the back off, there are 3 screws to remove; two in the main chassis and one in the slider control bracket.
Free the tuning cap spindle from the dial drive pulley and you can ease out the chassis followed by the slider control unit. The dial drive remains in the cabinet. Before putting it back, completely close the tuning cap and wind the tuning scale all the way down to ensure that the tuning cap agrees with the dial indication. Best to do any fault finding and testing with batteries when the set is dismantled. Cheers, Frank |
4th Dec 2015, 9:50 pm | #55 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
ive desoldered the cap the it took a lot of heat to melt the solder the cap was red hot so if it wasn't us it probably is now.fresh batteries in switched on the heartbeat sound has gone there is a very faint hiss regardless of where volume is.when switched on the battery voltage drops down to 2volt.not much progress.
|
4th Dec 2015, 10:01 pm | #56 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Grundig Concert Boy 1100
If the battery is good and the voltage is dropping to 2V on load then you have a near short-circuit somewhere. Are any components getting hot?
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
4th Dec 2015, 10:30 pm | #57 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
Yes.the three that are screwed to the aluminium plate. AC187 is the only one I can read, that one is red hot and the other two beside it are warm. I can't seem to find them on the diagram
|
4th Dec 2015, 10:49 pm | #58 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Grundig Concert Boy 1100
AC187 is TR12. If that's heat sinked, then TR13 AC188 will be too.
Are these three lead transistors, or is the collector connection via the can?
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
4th Dec 2015, 10:56 pm | #59 |
Banned
Join Date: Oct 2015
Location: Cornwall, UK.
Posts: 849
|
Re: Grundig Concert Boy 1100
sorry I don't understand what you are asking!!
|
4th Dec 2015, 11:03 pm | #60 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
|
Re: Grundig Concert Boy 1100
Transistors generally have three connections. Collector, Base and Emitter. Where they're in a can bolted to a heat sink with two bolts, the collector connection is via the can and there are only two leads.
I was going to suggest disconnecting the transistor to see whether the battery voltage rises.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |