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 Just repaired a Channel Master CM7000 digital to analog NTSC converter box
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 Return to top of page · Post #: 1 · Written at 7:11:05 AM on 19 March 2020.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 766

I realise that Australia was a PAL country, and this digital TV to analogue NTSC converter set top box would not be useful in Australia. But having to replace bad electrolytic caps is worldwide.

In the USA and that corona virus has us mostly stuck at home. So, looking for something to do, saw this dead converter box, and looked on-line for fixes others successfully did. Said that replacing all the leaded electrolytic caps on the "logic" board (vs the power supply board). The box came alive after I did the caps associated with switching DC-DC converter circuits (the ones that take 5V and make 3.3V and another to 1.2V). As I didn't have 33μF 35V caps on hand, I used 47μF at 50V caps. These caps filter out the switching waveform, so the caps being bigger is of little concern.

Found this "answer" at another forum
here


 
 Return to top of page · Post #: 2 · Written at 11:06:44 AM on 19 March 2020.
Irext's avatar
 Location: Werribee South, VIC
 Member since 30 September 2016
 Member #: 1981
 Postcount: 400

I've repaired a lot of consumer devices (DVD players, set top boxes, music streamers etc, etc) with nothing more than a few electrolytic caps. All of them were destined for land fill.
The original caps were usually of very poor quality.
I replace them with 105 degree high quality caps.
I've noticed that often the first sign of trouble is the remote stops working then after a few months everything stops.


 
 Return to top of page · Post #: 3 · Written at 7:19:42 PM on 19 March 2020.
GTC's avatar
 GTC
 Location: Sydney, NSW
 Member since 28 January 2011
 Member #: 823
 Postcount: 6012

I realise that Australia was a PAL country

It still is.


 
 Return to top of page · Post #: 4 · Written at 9:37:33 PM on 19 March 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6349

Top breeders recommend it Smile


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 5 · Written at 12:09:58 PM on 20 March 2020.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1380

Haha... actually it was no good at all, it made my dog sick. Chum was much better.


 
 Return to top of page · Post #: 6 · Written at 5:35:43 PM on 20 March 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6349

When I was a kid I thought only Scotch terriers ate Chum.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 7 · Written at 5:41:44 PM on 20 March 2020.
Brad's avatar
 Administrator
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6349

WA2ISE's second paragraph reminded me of something the HRSA mentioned the other day, with regard to monthly meetings and auctions - slowly, but surely, all are being postponed due to many collectors not being as young as they once were - a valid point - and a case of what to do in the meantime.

I guess that for those collectors who only collect and prefer others to do any needed mending and restorations, it'd be a case of business as almost usual, but for those who like to be out and about, there's changes ahead.

It's probably just as well that the RadioFest was on last year. It would most certainly be cancelled if it were to be on in 2020.

Of course, whilst it cannot take the place of all collection, restoration and sales activities, this site won't be going anywhere any time soon.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 8 · Written at 7:00:44 AM on 21 March 2020.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 745

I have two of these CHANNEL MASTER set-top units; they were highly desirable after the mandated "D-Day" switch-off of analogue because they had an S-Video output - thus videophiles could avoid the well known picture quality limitations of Composite-video. So I got them while they were available!

After a while one unit became unstable, going into standby mode by itself.

I see the two caps you mention - seem easy enough to change (not like the 23 Chinese silver/black surface-mount infamous crap-caps also present on the main board - that is a worry!)

Mine says underneath "Made in Bulgaria" oops!

Also pointing to its Continental origin is the RF tuner/output modulator unit which says 'THOMSON' (France) - They own RCA and Telefunken - thus the licences to NTSC & PAL Shock


 
 Return to top of page · Post #: 9 · Written at 8:46:48 AM on 21 March 2020.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 766

NewVista, also take a look at the power supply, its caps are known to go bad, too. But changing out the leaded electrolytic caps should get your box working right again.

I like the CM7000 as it has S video. I used one of there to convert an old "notch filter" NTSC colour TV set into a digital TV set. Look at the bottom of my TV page here for details.


 
 Return to top of page · Post #: 10 · Written at 2:53:27 PM on 21 March 2020.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 745

That S-video/TV is an amazing project. Looks like it has all the correct delay compensation as well.
The work at RCA (picture on your webpage) reminds me of the research of Yves Faroudja, inventor of S-VHS, who no doubt collected licence fees on S-Video. The time I met Yves he had a booth at NAB in the 1980s which he manned alone and didn't seem to attract much attention: He was playing a movie to a large projected screen from a Pro Betacam SP player (component output) to his patented 'line doubler': It looked smooth like film and seemed free from motion smear, though I'm not sure what he had in the way of motion compensation back then?


 
 Return to top of page · Post #: 11 · Written at 2:12:38 PM on 23 March 2020.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 745

Also at NAB in mid 80s was prototype compatible RCA Widescreen NTSC TV that mixed signal for extended side areas with standard broadcast for 5:3 aspect ratio. The added side areas looked softer in character (viewers wouldn't mind, it was hoped, as most important picture information was in middle.) I wonder how many of these prototypes survive? Highly collectable!


 
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