Thread: Baird Garrick
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Old 29th Jun 2018, 11:37 pm   #29
beery
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Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
Default Re: Baird Garrick

Hi all,
Yes, slow progress on the Baird again.

I was able to pay a visit to another TV collector who has the only working example of one of these sets that I know of, though his is actually a Lyric, which uses the same chassis. It worked quite well acutally
By taking some measurements on the working set I was able to ascertain that the non-original mains transformer in the radio section is indeed giving out too many volts, so I will have to replace it.

I've attached a photo of one of the smaller electrolytics from the radio chassis. These capacitors are hard to restuff especially when (as in the case of this capacitor) they are not held in place with a clamp. The only option seems to be to cut the capacitor length ways, though this means they never go back together properly. Anyway, you still can't see it when the capacitor is back in its original position.
I have now rebuilt all the capacitors in the radio section. One thing I found along the way is the poor standard of construction. Whilst all the solder joints are good, none of them are properly mechanically secured. Where wires and components join to solder tags they don't pass through the tag eyes, but are merely pushed against the side of the solder tag

I had to replace the smoothing choke in the radio section as I have taken the original to form the line output transformer. The original choke was 10H 170 ohms which is overkill, but it was really designed for the TV PSU which has an identical choke.
A replacement choke was given to me, but it measured 3H 68ohms. I wanted at least 5 henries and something nearer the right resistance. I unwound it and found it had 2080 turns of 31 SWG wire. Experience led me to pick two sizes smaller, so I filled the former up with 33 SWG, of which I managed to fit 3250 turns, which came out to 6H 155 ohms. In order to measure the inductance the core has to be reassembled together with the core gapping paper.
After putting the choke together I decided I really needed to clean and paint its rusty U clamp, so until the paint hardens I can't try it.

I now need to look at the problem of the mains transformer, before I try to solve the problem of mains hum on 405 line sound. The hum is not helped by the fact that the set does not switch off the audio when switching between radio and TV, it merely switches the heater supplies over from the radio RF/IF to the TV sound receiver.

I've removed the vision reciver from the TV section and this revealed yet more mouse droppings It also showed up a mystery, a missing valve which I assumed is an SP41 has a grounded top cap or grid, very odd.

I've also included a nice photo of the position of the contrast control. Not only have you got to remove the back and run the set with its nasty exposed mains EHT (more on that when I get an EHT transformer for it), but you have to reach right in and run the risk of breaking the CRT vacuum pip when adjusting it So why put it there, why not put the pot shaft sticking out of the rear of the chassis?? Answers on a postcard please.

That's all for now.

Cheers
Andy
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