Grundig Concertboy 1100

[Sinewave]

For a little while the radio would be a bit crackly and poppy until it's warmed up a bit, to the stage where it takes a while to get going, now it's almost dead with a feint crackle when moving the tuning.

I'm having a good read of some of the other threads on these sets, but to get me started in the right direction I'm wondering if anyone has any pointers whilst I start opening it up.

Thanks.

[Leon Crampin]

Change the smoothing electrolytic for a 2200uF 25V type - it's overrun on 250V mains. Note the three negative connections. Free off and oil the geared tuning gang spindle bearing. Clean the switches with Servisol or similar. Check that the perspex tuning scale has not come unglued from the front of the case, fouling the pointer.

The AM RF alignment will benefit from a tweak, usually confined to shifting the aerial coils slightly on the rod. Use the Grundig alignment instructions only - some UK trader sheets are incorrect. The IF and discriminator alignment will be OK unless previously disturbed.

Finally, check the output stage quiescent current as per the instructions. Note the supply voltage required when you do this.

Good sets, which work really well when properly set up.

Leon.

[Sinewave]

Thanks Leon, this was a superb sounding set indeed, so hoping to sort it.

With regards to the issues, they exhibit on battery as well as mains power.

[Tim]

I have a couple of Grundig “boy” series radios both with an intermittent crackle. I haven’t looked at them for some time, but I think I had narrowed it down to the RF/IF sections. Possibly “ green spot”?

[paulsherwin]

These are all classic bad Lockfit symptoms. Any transistors are suspect. Does the 1100 use a BC464/BC465 pair for the output stage?

[Leon Crampin]

No lockfits in this chassis. Unexplained crackles, if not switching, can be due to noisy bias diodes. The one in the IF can is hard to reach. A scope on the IF bias line usually reveals this fault. The transistors themselves are reliable.

Leon.

[paulsherwin]

Fair enough Leon.

[Tim]

Ah, thanks Leon. I’ll try to remember to check my Grundigs when I next have a play with them.

[Sinewave]

I'll check the transistors anyway. In the meanwhile, thinking of time and warming up I started checking capacitors.

Pulled this one out, that ought to be replaced.

I've got a drawing, but it's so bad I can hardly make a thing out.

[poppydog]

That looks likes glue on that cap, I have quite a few grundigs (including 3 concertboy 1100s now)that have caps that are glued to the board . I have a melody boy 500 that had problems almost identical to yours, it turned out to be very dirty/fluffy switch contacts. Servisol 10 was used to clean them but just make sure you don't get any on any wax as it will dissolve it..

poppydog

[Sinewave]

It's a very powdery/crystal like deposits, they don't appear to be glued. I just need to check them out with a meter though whilst they're out.

[rojosuiza]

Those sets have little printed circuits standing upright on the main board. Resolder all the joints carefully. Very often a nice, quick fix.

[Sinewave]

Originally Posted by rojosuiza

Those sets have little printed circuits standing upright on the main board. Resolder all the joints carefully. Very often a nice, quick fix.

Indeed, I noticed that the pads lift easily due to the flexibility where the boards connect, some have needed re doing. Yet to just finish testing the capacitors and transistors, then clean up the switches etc and then see.

[Boulevardier]

Just keep your fingers crossed that you don't have to get to any of the IF components - they're all inside that steel box which covers the small sub-pcb. I had a fine old time with my Elite-Boy getting that box off to work on the FM ratio detector!

Mike

[Sinewave]

So, I tested the capacitors and transistors and they checked out fine.

I also have given the 90 degree connecting boards a good clean up where the pads solder together. I de-soldered them, cleaned the flux residue up and re-soldered them.

I couldn't really find any faults apart from what looked like some bad joints, so I powered it up on the bench and it's now working, which is a nice result. Whilst I have all of the parts out I've been giving the casing a good clean up as it's a bit grubby in places. I've removed the metal trims from the top where the controls are as it was loose, so just trying to remove the glue residue from it before gluing it back in place.

[Boulevardier]

Did you manage to get inside the IF circuitry screening box?

Mike

[Sinewave]

So far know no reason to.

[Sinewave]

So just cleaning the speaker grill out with that Desolv-it foaming de-greaser cleaner. Very good stuff, so good it's taken the Grundig badge off the plastic

Ooops

[Leon Crampin]

Check the speaker coupling capacitor whilst the chassis is out. If it's an orange epoxy potted type, it will be under capacity, spoiling the bass response. The smoothing capacitor is inadequately rated at 16V, the set needs a 25V type to work reliably on 250V mains.

When you finally assemble the case, be careful where the back hooks in at the top that you gently engage the rather strange connector for the rod aerial. It's easy to crack the pc board if you are not careful.

Glad progress is good - if you want full AM performance, the aerial circuits will need peaking at the designated frequencies on the dial. FM alignment should be OK.

Leon.

[Sinewave]

Originally Posted by Leon Crampin

Check the speaker coupling capacitor whilst the chassis is out. If it's an orange epoxy potted type, it will be under capacity, spoiling the bass response. The smoothing capacitor is inadequately rated at 16V, the set needs a 25V type to work reliably on 250V mains.

When you finally assemble the case, be careful where the back hooks in at the top that you gently engage the rather strange connector for the rod aerial. It's easy to crack the pc board if you are not careful.

Glad progress is good - if you want full AM performance, the aerial circuits will need peaking at the designated frequencies on the dial. FM alignment should be OK.

Leon.

Hi Leon,

Speaker cap, is that the 1000uF 10V cap? If so, yes that is an orange epoxy, interestingly the set does have good bass response though.

Mains smoothing, I'll see what caps I have in stock.