Decca Gypsy M1211 - Tiny Tim on the road...

It was a typical day in the Tiny Tim household. Spring was arriving fast, winter had been wrapped up and the sun shone through the window into Tiny Tim's eyes. He rubbed them and moved the blind to another angle before he commenced work again. He was cleaning the heads on a Grundig TK120 which didn't seem to have a lot else wrong with it. When it started working again he carried it from the bench to the kitchen cooking area and left it playing a tape, so he could listen to make sure nothing else would crop up on the unit. The newer machines were nicer to work on than the older Grundigs, which Tiny Tim never quite felt entirely happy with.

As he returned to his bench, the telephone rang. This scared little Tiny Tim out of his wits as he didn't like loud noises. He waited for a minute to see if Tinkerbell would pick it up. She shouted that she was busy and would he get it, so he gingerly picked the receiver up.
'Hello', he cautiously said into it. He didn't like the phone much as it was usually somebody from abroad telling him that his computer had a virus. Last time he was particularly rude and Tinkerbell had been cross at him for using such language.

'Hello there', said a female voice on the phone. 'Ah yer the man that mends old stuff?'. The voice had a southern USA accent.
'I try', Tiny Tim replied. 'What can I do for you?'.
'I'm Miss Applejack from Sweet Apple Acres', she replied. 'It's awful nice to talk to you. Granny Smith is in bed with some sort of bug and her old TV stopped working several months ago. Would you come and look at it, sugarcube.'
Applejack's a strong drink, Tiny Tim thought. He wondered if he could get some cider out of her if he went up for a look. 'When do you want me to come over?' he asked.
'Thank-you kindly mister, but as soon as possible', Miss Applejack replied. So, Tiny Tim nipped up immediately to see what he could do. When he knocked on the door of the large barn, the door was opened by a little girl with a red bow in her hair. It seemed she was called Missy Applebloom and he was soon rescued from her by her older sister, Miss Applejack.

'Thank-you kindly for coming sir', she said.
'Just call me Tiny Tim, everyone else does', Tiny Tim replied. 'Where's the set?'
Tiny Tim was taken to Granny Smith's room where she was trying to get a picture on a modern LCD set.
'Darn this modern Doo-Hickey', she was saying as she struggled with a remote. 'I wish my old one still worked. Should never have taken it to Bodgitt's''
Miss Applejack spoke up. 'This guy'll fix it Granny Smith'.
Granny Smith looked at him briefly. 'You're not from...'
Tiny Tim cut her off . 'No ma'am', he told her. 'Where's the set, as from what you just said, I think I'd better take it back to the workshop for a look over. I'll be in touch as soon as I know'.
Miss Applejack got the set and told Tiny Tim about it as he was taking it off her and putting it in the car. 'It had no sound', she told Tim, 'and when it came back it had no picture either. We weren't best happy I can tell you, sugarcube.'
'I'll bet', Tiny Tim told her as he started the car. 'Call you later.'
Miss Applejack went back up to the orchards as Tiny Tim drove off. The set he had in the back was a Decca Gypsy, Model M1211. It had definitely been worked on by somebody who didn't know what he was doing, so Tiny Tim decided to tackle the job in the rational way, which would be a first for him.

With it nicely placed on the bench and the back cover down (not off on these as the two circuit boards are mounted on the back cover!) he did what he usually did and apply mains to the set. A raster appeared and there was no sound at all. This set is from the era before sound was muted when there were no line or frame pulses, so there should have been a noise.

On applying a signal, there was still no sound and the line and frame were well off. Judging by the flicker on the screen, the frame was at the wrong speed. Tim already knew where the line and frame hold controls were on these sets so he got a small screwdriver and set them both midway, then using the screen as a guide, set them up properly. There was a severe hum bar, the picture was tearing at 50Hz frequency and when the tearing reached the bottom of the screen, the frame hold would be lost.

Then when he knocked the bench, the picture size and brightness went down further still. He found that by gently turning the power supply pot it would return, but still with the hum bar.

He got his trusty (and cheap) Maplin meter out and it said that the power supply was low. Switching it to AC he measured 25v AC ripple on an LT supply. He checked the panel on top of the transformer and found four diodes, fitted as a bridge and rather untidy. This looked a rather badly worked on area, so he snipped out the four diodes and with his meter, found out which two of the four pins were AC and which were + and -.

With the area cleaned up somewhat, he got a bridge rectifier unit and connected it up. As the level here might affect the tube heaters, he took the base off the tube and then switched on the set. There was still no sound, but he carefully turned the voltage control to 15 volts on the LT line, turned the set off, reconnected the tube base and switched on. He now had a stable picture but still no sound. So Tim found some screws (Many were missing!) and put the board into place before moving to the other board.

The tuner and video were OK, so he went for the sound side. The sound on these sets comes from 2 IC's. These were black beetles which were always a mystery to Tiny Tim, as they simply sat on the PCB and did things without lighting up. The output is a TAA611B and the Pre-amp, Limiter and Demodulator is a TBA750. Going for the input of the TAA161B gave a nice test tone through the speaker, so it was safe to assume that was OK. Going for the Volume Control, on pins 13 and 14 proved the last part of the TBA750 was OK.

The TBA750 had been changed already, so he tidied that up and looked with an accusing eye around here. The next thing back, connected to the chip, was L20, which went between pins 8 and 9. The coil had a capacitor and a 2k2 resistor across it, but with there being a coil here, then the reading across here should be less than 2200 Ohms. A lot less. It was over 2k.

Switching the set on and giving it a signal, the sound burst through when a 0.01uF capacitor was put across pins 8 and 9 of the TBA750. Removing the cover of L20 revealed the problem. One end of the coil was disconnected, so the sound could not pass. Tim couldn't see where it had come from, so he soldered it to the end of of the capacitor C62, which was also in the can.

Now sound burst through, so Tim refitted the cover and screwed the board down. Just to be sure, he left the set on for a few minutes. During which time the LT appeared to be going up and down of it's own accord. The setting of the LT control appeared to vary when the board was tapped. So Tiny Tim did what he should have done earlier. He cleaned and re-tensioned the fuse and holder and did the dry joints on the print side of the board.

Now the picture stayed steady and the sound was rather good, Tim thought. He gave the set a clean and polish and nipped up with it smartish. He had been ill himself and without a TV he would have gone mad. Besides, he wanted some cider.

Miss Applejack was frightfully pleased to see him as he got the set out of the car.
'Av yer done it?', she asked him.
'That I have',Tiny Tim replied. 'Where do you want it?'
The set was installed in Granny Smith's room and they left her watching Countdown. Tim broached the subjects of pay and cider. Miss Applejack paid him and sent her brother, Big Mackintosh, to get a couple of bottles as a thank-you.
'Would you like a glass before you leave?', Miss Applejack asked. Tim immediately said yes, and half a bottle later, he was on the floor...

Tim woke up in bed at home, with Tinkerbell looking over him. His head hurt and the room seemed too bright.
'Ah, you're awake', Tinkerbell stated.
'What...', he began, his head all muzzy.
'Miss Applejack brought you home. It seems you tried their cider.', Tinkerbell told him.
'Oh yes, I was delivering a TV', he said as it all came together in his brain. 'I've got a terrible dry mouth. Any chance of a cup of tea?'
Tinkerbell looked at him for a moment before she spoke. 'One sugarcube or two...'

Cheers,

Steve P.