#31
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Thanks. Yes, they are all 105C rated caps
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#32
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#33
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Cool, are you replacing them all?
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#34
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Oh no. Just the 7-pin socket that broke in the upper left obscured by my hand. I have four more Predicta sets to restore though and they have some damaged sockets too so I stocked up.
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#35
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How long has the restoration took?
__________________
Looking for zenith cobramatic parts -johnny the raster master! Last edited by radiotron; 09-12-2012 at 07:57 PM. |
Audiokarma |
#36
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The first post is dated Aug. 19th so it's been about 3 weeks so far.
I popped out the K6 network to do a little testing. It's tough to do because of the internal parallel and series combinations, but I here's what I found. There's a 47K and 4.7K in series between pins one and 2 for a total of 51.7K. I measured 70.7K. Between pins 2 and 7 I should have 3300pF but measured around 4300pF. Seems to me those are pretty far off and I should replace this network. I'll pop out K2 next and see how it measures up. |
#37
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The other networks showed similar results so I decided to just replace them all. I was curious about the internal construction and dissected a couple. The resistors are just carbon powder and the caps look like ceramic cylinders.
I rebuilt the K4 network using plastic caps and metal film resistors on a little perf board. The 0.0015 uF cap is rated for 2,000 volts like the one next to it on the main board. Parts for the other neworks will arrive in a couple days. |
#38
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Looking good!
That's looking great Bob,
You are making me want to eventually try a predicta but I will need to work up to it with some easier sets first, that I have in the wings. I like how the networks are looking on the board. I have my eye on one that is within driving distance if I win the auction, but I would never have one shipped. If I win it will have to be on display for a little while until I get up the nerve to give it a go. Tom Last edited by n2bew; 09-12-2012 at 09:54 PM. Reason: spelling, of course |
#39
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I like the solution to the networks, since you could not do what you did on the T&C. Looking forward to more updates as always!
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#40
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I ordered my parts from Mouser as usual, but made a mistake when choosing shipping options. I usually choose FedEx Ground if I'm in a hurry (2 days) or US Post Office (3-4 days) if I can wait a bit.
This time I choose a new option - a rather generic "Standard Shipping". When I received a shipping confirmation, it turned out to be UPS. I later did a package track with UPS and discovered they had farmed it out to the Post Office with an ETA of 10-14 days!?! If I had just chosen the Post Office in the first place, I probably would have received my parts by now. Instead, I'll be lucky to get them next week |
Audiokarma |
#41
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Not to worry! It won't take that long...
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#42
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The service is called 'UPS Mail Innovations' and my package ETA is 9/17. If I had gone with FedEx ground it, would have arrived a week sooner at about the same cost.
Do a web search on 'UPS Mail Innovations review' and you'll find plenty of nasty feedback. |
#43
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After the Predicta is assembled, can you get access to align the IF transformers?
Carl
__________________
CW 1950 Zenith Porthole - "Lincoln" |
#44
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Not very easily, but the cables are long enough that you can slide the chassis out a bit to make adjustments easier.
I'll probably align it while it's out of the cabinet entirely though. |
#45
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While waiting for parts to arrive, I took care of some other items.
The rebuilt electrolytics have been installed. Also, the germanium power rectifier module has been replaced with a terminal strip and two 1N4007 silicon rectifiers. Last edited by bandersen; 09-14-2012 at 02:58 AM. |
Audiokarma |
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