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 Post subject: Re: Predicta restoration
PostPosted: Nov Sat 16, 2019 2:02 am 
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Location: Hampton Roads, VA
PM sent.

I put a temporary 1k pot with a 500ohm resistor in place just to get the vertical section working again, no longer having it collapsing. Still no audio or image coming through, what's the best way to isolate where it's coming from? The tubes check out, though some better than others. I have my scope with me, but not much else.


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 Post subject: Re: Predicta restoration
PostPosted: Nov Sat 16, 2019 3:40 am 
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As suggested above, a pot with a stop can be replaced by a regular pot of the same resistance with a resistor in series with it.

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 Post subject: Re: Predicta restoration
PostPosted: Nov Sat 16, 2019 6:51 am 
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Can someone confirm that C29 and R33 were pulled from 11L43 as well as changing bias resistor R34 to 150ohm? I was comparing resistances off of the SAMS and found this. Before I touched the set, I took photos of it, and both were missing, but I can't see R34.


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 Post subject: Re: Predicta restoration
PostPosted: Nov Sat 23, 2019 9:27 pm 
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Got the new vertical linearity pot installed. Finally got a picture, and was messing around with the horizontal frequency adjustment and the HV cut out. Powered down immediately and left to cool. Powered back up with no luck with HV. Horizontal oscillator is operating, and can be heard as the horizontal hold is adjusted. Any idea where to check? Sound is still operating, haven't begun to check voltages in the horizontal yet.


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 Post subject: Re: Predicta restoration
PostPosted: Jan Thu 09, 2020 10:07 am 
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I'm completely new to this and haven't done electronics work in 30 years so bear with me. I'm not stupid but lack recency of experience in this stuff and have forgotten much of the nomenclature. Yes, I'm fully aware Predictas aren't easy for even experienced restorers, I needn't be reminded. I'm pretty good at soldering and am quite experienced with a multi-meter. I constantly use one in working on automotive sensors and ECUs.

I picked up a Philco Barber Pole this past weekend with full intent on making it work. It only took me 10 years to find the right one, at the right price and close enough to "Pickup Only". I know I need to replace ALL the Capacitors and should replace all the resistors. Plus any other pieces parts that are out of tolerance. That's a given. I know I'm not the first, nor will be the last, to attempt to tackle Restoring a Predicta.

Has anyone a Parts list of Modern Capacitors, Resistors, etc. in relation to the Part Numbers on the Sam's Photofact Folder and recommendations on where to purchase. I've attempted cross referencing part numbers to no avail. The ones listed, for all manufacturers, are simply too antiquated to have current, direct references. I'd prefer to simply order the whole lot at one time from one place. There's only 35 Capacitors & 15 Resistors. That's not a lot to replace. I always have my replacement parts in place before disassembling anything.

If someone has a list, or link to a list, I'd sincerely appreciate them sharing. Thanks in advance.


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 Post subject: Re: Predicta restoration
PostPosted: Jan Thu 09, 2020 1:39 pm 
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You should probably start your own topic, but here is a BOM from digikey I used a few months ago. Please double-check against SAMS. I also found that a couple of the resistors had different values from SAMS when I came to replace them.

This is everything on the main PCB and all but a few resistors on the main chassis (and a couple of input diodes). It doesn't include anything from the IF and RF sections.

You should also get replacement couplates.


Attachments:
Bom_9L37.zip [1.92 KiB]
Downloaded 34 times

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 Post subject: Re: Predicta restoration
PostPosted: Jan Thu 09, 2020 7:19 pm 
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the BOM list will help tremendously. My sincere appreciation. Thank You!

Also, Thanks for the heads up in differing values. I cross checked the Sams & did find differences. How much of a factor would the differing values pose? I know in some applications things may be either larger or smaller than the recommended value and it poses no problem. In other applications the exact value is critical. Sometimes resulting in an "Earth Shattering Kaboom"!

If any of you have any recommendations on books or online resources to reeducate myself. I'd appreciate that too.

Again, thank you for the list!!!


Last edited by JPSummers on Jan Thu 09, 2020 8:27 pm, edited 1 time in total.

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 Post subject: Re: Predicta restoration
PostPosted: Jan Thu 09, 2020 8:03 pm 
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I left them with the SAMS - I seem to remember they were in the audio section and the audio is fine. OTH I have what appears to be a ground leak issue with the horizontal sync so who knows? I think that is likely to be something else though.

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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 9:46 am 
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wiscojim wrote:
Zsuttle wrote:
Oh, sorry, to clarify, I was asking on the SAMS if there was a good way to differentiate from the mica and ceramics in the parts list. (Eg for next time) They group them together and the only way I actually know how to tell them apart is by physically looking at each one, which makes it a pain if I have to order anything.
All you would need is an old supplier catalog from Sprague, Centralab, Aerovox or one of the other substitute brands listed to look them up by part number to identify their characteristics. For example in the Cornell-Dubilier column shown below, once you find what designations such as BYA and CUB stand for you would be able to quickly know the types of capacitors they are.



Attachment:
ppcl.jpg


.

would anyone happen to have or be able to share the "Secret Decoder" for Cornell-Dubilier, Aerovox or Sprague? I think they're still in business but parts & inventory systems change a lot in 60 years. I'm having similar issues with parts Identification and cross reference. Thankfully, someone shared their Digi-Key shopping list w/ me but there's a LOT more I need to order. Thanks :)


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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 11:28 am 
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Ok folks I found a good Resource for Predicta Capacitors & Resistors. a 1963 Sprague Catalog. It contains many of the components in the Sam's Photofact Manual. Now if I can figure out how to upload it. Here's a Link if I can't get it uploaded.
http://www.technicalaudio.com/pdf/Elect ... EM_E30.pdf


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Sprague_capacitors_1966_REM_E30.pdf [22.9 MiB]
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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 6:39 pm 
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With a bit more experience you can identify the type of vintage capacitor construction by looking at them.
Also you can be able to make pretty good guesses to the type of capacitor by looking at the parts list.
Capacitors 1000 pf (uuf) (0.001 uf) or less can be ceramic or mica, mica is frequently has a tolerance of 5% or better.
Capacitors greater than about 1uf are usually electrolytic.
In between those extremes the capacitors are usually paper or film (plastic). In later equipment some are ceramic.
You really only have to replace the electrolytic and paper for the first go round.
The limits are not absolute.
This webpage shows some typical appearances.
https://www.antiqueradio.org/recap.htm#identifying

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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 7:19 pm 
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Thanks for the link. :) I've read through that and it's very helpful. The issue I have w/ the Sams is that the values could be uf, mf or uuf without differentiation except by type of construction. I haven't pulled out the chassis yet to identify each one. Even then, some are more difficult to figure out than others. It also seems Philco used a unique banding system for identification, at times. I think you're right, with some experience identification will be easier. Til then I'll have to rely on matching values to order pieces parts.


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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 7:40 pm 
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Sams always put the lytics (which are the only caps rated 1uF or higher) in the first few C ID numbers of the parts list and you can distinguish them from micas as Sam's will only list the voltage for lytics. So the cap before the first on the list list without a voltage listed will be the last lytic. After you pass the lytics caps with a decimal (0.01 for instance) are always uF. Caps without a decimal are uuF (which is a dead notation that has been replaced with pF). In some older sets mica caps 1000pF (=0.001uF) or larger are often actually paper caps hiding in mica shells) and in sets of that age and newer some caps as high as 0.02uF can be ceramic. Most modern caps (and bumblebee caps of the 50s which used resistor color code instead of text) are labeled in Pf with the first 2 numbers being the value and the 3rd being a power of ten multiplier. look at the Wikipedia page for SI measurement prefixes and it will give you an idea of how to convert between mili, micro and pico.


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 Post subject: Re: Predicta restoration
PostPosted: Feb Tue 04, 2020 7:56 pm 
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The rule of thumb I used compiling the BOM was that if the capacitor had a voltage rating, it was a paper cap, otherwise it was ceramic/mica. The two exceptions are C46 and C47, which have voltage ratings in the KV.

The electrolytic caps are listed separately.

BTW, I would add R54 (820K) to the BOM. This resistor failed on me after a while which stopped the vertical hold working.

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