Grundig 110a GB radio

[boater sam]

Thanks Mark,

I will perseveriere and get to the bottom of it. I am only fixing this to give away, its not in my remit as collectable.

Getting deeply involved at present is difficult. I am working on a paste table covered in stuff, all spares and test equipment are still packed away since we moved into the bungalow last November, its has been a bit fraught since and not had time for any radios. The scopes and sig gens etc. are somewhere----------. Along with 100+ sets!
Emptying the workshop from the farm into a spare bedroom in a bungalow is a gallon in a pint pot.

I will check the other electrolytics, refit those I have disconnected and see what it does. With there being nothing on long wave and next to nothing on medium wave I may just settle for FM only, the artist I am giving it to wants a mains radio for background in her studio boat and it is better for a bit of modern junk to get splashed with paint than a collectable woody.

I am presently sitting in a scaffolding cage around the house waiting for the solar panel installers, its hard to concentrate!

[Mark Hennessy]

Sounds like a bit of a nightmare - radios are a useful distraction from that sort of thing! We had our roof done last year, so know what the scaffolding cage feels like. The kids loved it though - to them it was a giant climbing frame and they were quite sad to see it all come down.

FM-only sounds like a reasonable compromise. Ordinarily it would be nice to get to the bottom of it, but needs must. But at the very least, if possible, checking those 2 caps in the AM detector circuit would satisfy my curiosity.

I do have a bit of a soft spot for Grundig transistors, and have 6 of them, including a 110 and a 111. OK, they're heavily production-engineered with elaborate plastic mouldings for the chassis and PCB caps and inductors, and are almost impossible to restore cosmetically, but they are always very sensitive, and they do sound really good for their size - mostly down to using their own speakers and including a bit of EQ to help them. Sometimes they over-do the bass boost, but that's what the market liked at the time. Usually, they're not easy to work on, but luckily the electronics is pretty reliable. In contrast, I only own 1 Grundig "woodie", and I haven't had a chance to explore that yet. It takes up a lot of space, so I'm tempted to move it on...

[boater sam]

Sounds like a bit of a nightmare - radios are a useful distraction from that sort of thing! We had our roof done last year, so know what the scaffolding cage feels like. The kids loved it though - to them it was a giant climbing frame and they were quite sad to see it all come down.

FM-only sounds like a reasonable compromise. Ordinarily it would be nice to get to the bottom of it, but needs must. But at the very least, if possible, checking those 2 caps in the AM detector circuit would satisfy my curiosity.

I do have a bit of a soft spot for Grundig transistors, and have 6 of them, including a 110 and a 111. OK, they're heavily production-engineered with elaborate plastic mouldings for the chassis and PCB caps and inductors, and are almost impossible to restore cosmetically, but they are always very sensitive, and they do sound really good for their size - mostly down to using their own speakers and including a bit of EQ to help them. Sometimes they over-do the bass boost, but that's what the market liked at the time. Usually, they're not easy to work on, but luckily the electronics is pretty reliable. In contrast, I only own 1 Grundig "woodie", and I haven't had a chance to explore that yet. It takes up a lot of space, so I'm tempted to move it on...

Where would I find 2 of the 7v 35mA miniature bulbs for the scale edge illumination or is it easier to fit LEDs?

[boater sam]

Had an hour to spare so I checked C48 & C49.  Marked 6/47   8.4v, sheet says 5uf 6v  Duff, magic box thought they were diodes!

Replaced with all I could lay my hands on, 4,7uf 63v. Wired up the speaker and tested, it works on all bands, no hum, thanks guys for the directions.

Now I have to find some bulbs or fit a couple of  LEDs with the correct ballast resistors and restring that horrible cord drive. Somewhere I have some wire ended tiny bulbs.
My fine bead cord is not fine enough, it falls off the drum when the drive reaches the end and the spring tension lessens.  The original cord is less than 1mm in diameter and fits in grooves in the drum.
I will have to try fishing line if I can find some, not the sort of thing that I have ever had.

[Mark Hennessy]

Hi Sam,

That's great news - thanks for trying that and letting know the outcome

I've moved the posts about flicker and monitors, etc, to a new thread. It was perhaps my fault for taking it off-topic.

https://golbornevintageradio.co.uk/forum...p?tid=9339

But in terms of fitting LEDs to your set, it (the flicker issue) is something to consider. I don't know what bulbs the RF110 uses because I don't think I've ever looked inside mine, but I do know that the RF111 uses MES. Obviously a like-for-like replacement is easiest, assuming the light emerges where you need it to. Some scales are lit by the edge of the lamp, so an LED replacement might not be suitable, in which case some mechanical and electrical work is needed to fit a standard 3mm or 5mm LED in place. Again, I don't know the mechanical arrangements inside the RF110. I'd also take the supply from the DC side, to side-step the flicker issue. But some might prefer to not modify things, even slightly. I understand that.

If I remember which part of the attic my set is hidden, I'll take a look. I'm curious now...

This has reminded me of an almost on-topic tale. My step-dad had an RF111 that didn't work. He had a little electrical knowledge, and was good at hands-on stuff, but had managed to convince himself that the reason the set was dead was because the failed 7V bulbs had been replaced with 6V lamps! Naturally, he wasn't going to listen to 11-year-old me telling him that didn't make sense. We had the schematic - it was folded up inside - so I could explain it all, but still, he was never going to believe me!

A few years later I decided to take a look, and quickly found that the broken solder joints between the main PCB and the vertical PCB inside the aluminium can. The dial lamps were mounted on the top of this can, on a length of steel wire shaped to accept the plastic MES bulb holders. 30 seconds with the soldering iron, and I was able to proudly demonstrate the now-working radio.

I explained everything, and in his usual "I'm never wrong" fashion, he simply said "See - told you it was the bulbs!". Of course I said "but you said it was because the replacements were 6V, not 7V", but there was no getting through. No longer my step dad - that's been the case for 30+ years now - but we did get on a bit better after the radio incident, when he eventually got used to the idea that I'd overtaken him in this subject area. In fairness, I was grateful for what I was able to learn from him.

Happy days,

Mark

[boater sam]

There are two MES 7v 1w bulbs in rudimentary holders which are to light up the pointer and two tiny cap less?  7v 35mA bulbs on the edge of the translucent plastic dial backing panel in holders moulded in the panel. I have not yet managed to remove these, one is O/C but clear, the other is a silvered pearl,  plainly duff.

[Mark Hennessy]

Ah - OK. Funny how the schematic only shows one of each, but at least the different ratings are covered.

If those capless ones are like others I've seen in Grundig sets, they're like the 1.2W bulbs we used to find in car instrument panels. Those are still available. Whether they'd be bright enough on 7V is another question - given the difference in ratings they might be, albeit a bit yellow/orange - but at least they'd enjoy a relatively long life...

These look promising: https://www.easy-lightbulbs.com/products...ess-t1-1-2

No experience of the company, etc.

[boater sam]

Moved on.

I found some grain of wheat wire ended bulbs in my stock, soldered them into the holders on the tuning scale back sheet.

Then I had to face the restringing of the tuning drive.

 For such a simple system, it was inordinately difficult Several attempts resulted in the cord slipping off the drum when at the end of the travel. The grooves in the drum are very fine and my cord was a bit thicker than the original.
I pre-stretched a length of 1mm bead cord overnight and carefully threaded it round the pulleys and spindle before winding 3 turns onto the drum. After much cursing and several attempts I managed to get the drive to work and with the spring out of the way of where the pointer has to be attached which was the final hard part.
I soldered the light bulb wires back on and fitted the MES bulbs, refitted the tuning scale back sheet to the pcb and tested the set.

Everything worked, including the sneaky tone control. It is a pull/push on the volume control potentiometer and mains switch, very unusual but effective. Where one would ever find a replacement control is a moot point.
I wonder how many owners have never realised that there is a tone control on these sets?

Finished the reassembly and soak tested, all good.

So a tricky repair, a patience tester. I will deliver it to the recipient later, hoping to never see it again!

[radioman]

Well done Sam, rather you than me for that repair !

[boater sam]

Thanks to all for the encouragement and advice.
Its just taking the rough with the smooth and what you are used to.
I suppose in 1967 manufacturers were getting into their stride making stuff that was reliable and never intended to be repaired. It all started with the transistor, prior to that they made things that could be repaired quite easily because they did go wrong frequently.
If you think about the progress from valves to transistors and then the chip, valves lasted longer than all the others. I look inside modern stuff and weep, no chance of me fixing it, I can't even see some of the components!