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Old 20th May 2020, 10:30 pm   #66
staticmind
Tetrode
 
Join Date: Sep 2019
Location: Aalborg, Denmark
Posts: 97
Default Re: B&O Capri 606 TV (17") restoration

As always, thank you very much for the insight on this. The AGC functionality makes sense.

I stumbled upon this site with an unbelievable amount of information Philips tuners:
https://www.maximus-randd.com/tv-tuner-history-pt1.html

My TV has an Philips AT7432 tuner. The schematic of it is also shown on the site as: https://www.maximus-randd.com/upload...uit_1_orig.jpg

Here it shows that there's a coil at the IF output going to ground. But in the TV's schematics I don't see that the coil is connected to ground - it is in series with the output, or am I interpreting this wrong? If there's a coil going to ground, it seems correct that I'm measuring 0 ohms, provided the coil has few turns.

The tuner is a rotating drum type with coils etched on multiple (10) PCBs. It was easy to take apart and reassemble.
The only thing I changed in the tuner was a few resistors that measured more than 15% out of tolerance, and then one crusty 820p cap. I still have the old components, in case it messes with the alignment. There are a couple of screws on the tuner chassis with loctite or paint. I know they are for alignment, so didn't touch anything here at all. The replacement resistors follow the same path, completely.

You're also right about the wire going between tuner sections. Thinnest layer of enameled wire I've ever seen, will investigate if there are any shorts here as well. I'll also get to check the shielded cable and 971H96.
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