View Full Version : Resistors for Predicta


Tony F
01-04-2017, 09:12 PM
Hello All, I normally do radios, and not tv's. So I'm going to start on pulling this 10L43 mainboard and replace everything (well caps, resistors, and couplates) Anyway, are carbon comp resistors preferred over metal film? (if so,..why) or is it ok to use metal film throughout this set ? Does it have anything to do with frequency stability, drift ? Other factors, than just replacing all the caps and maybe just out of spec resistors. I really want to do this right. Being in Canada, we just have to jump through more hoops than you guys in the U.S. and we end up paying more than twice for everything ( parts, shipping and duty hassles). I normally deal with Dave at JustRadios, but he doesn't have all the different resistor values and the one supply place in town leaves a lot to be desired.
Thanks !
Tony

bandersen
01-04-2017, 10:16 PM
Metal film are superior to carbon comp. Virtually no temperature drift and widely available in all values and wattages. I've had no problems using them in Predictas or any other set. Metal oxide are pretty good to.

Tony F
01-05-2017, 07:45 AM
Thanks Bob, I appreciate your expertise. I have gone through the set and checked every resistor and matched it up with the ones on the schematic. Most match, but not all. There are maybe 6 or 8 that seem to be way off in value. I don't mean the resistor changing value over time, but the color code not even matching the schematic. I take it, these were probably production changes and I should be replacing these with the value that is in there and not with the one shown on the schematic ? There are quite a few that have drifted as well. One thing I did notice is a small crack and what looks like carbon tracking on the damper tube socket (6DA4) between pins 5 and 6. That is looking down at the tube socket (from the top of the board) and counting clockwise from the first pin right of the keyway.
As far as I can tell, everything is original except for R54 (390 ohm) and cap C20 (.022 @400). They have been tacked on above board.
I like your idea of putting the electrolytics on top of the board rather than restuffing the cans.
Tony

Electronic M
01-05-2017, 07:58 AM
Trust what is in the set unless you see evidence that it was previously replaced or that the resistors got overheated (which can discolor the color code paint). Might not be bad to order both possible values for parts that don't match the print. If the set don't work right and troubleshooting don't help changing the set from one rev of prod changes to another sometimes helps.

bandersen
01-05-2017, 09:49 AM
Yes, they did make production changes. Here is a two page Philco service bulletin describing some of them.

https://drive.google.com/file/d/0B37VOP1BSxbASW5SakFxSG1HTDQ/view?usp=sharing

Findm-Keepm
01-05-2017, 09:53 AM
Metal film are superior to carbon comp. Virtual no temperature drift and widely available in all values and wattages. I've had no problems using them in Predictas or any other set.

Better: :D:D:D:D

madlabs
01-05-2017, 11:12 AM
So is it recommended to make all of these changes? I'm not where I can look but I think my set has some but not all of these changes.

bandersen
01-05-2017, 11:18 AM
I wouldn't unless your set is experiencing the problem the change addresses.

Tony F
01-05-2017, 01:11 PM
Would you happen to know where this "DOT" is located that signifies the various production runs ? It says Run 2 is RED dot, Run 3 is ORANGE and Run 4 is YELLOW. I know this has the 3 watt R15A resistor. I will check for some of the other changes. I don't see any painted dots on any sheet metal. Thanks Bob,.. this is good info.
Tony

bandersen
01-05-2017, 02:47 PM
Better: :D:D:D:D

Well I don't know about all that - just passing along my experience as a EE and tinkerer ;)

Would you happen to know where this "DOT" is located that signifies the various production runs ? It says Run 2 is RED dot, Run 3 is ORANGE and Run 4 is YELLOW. I know this has the 3 watt R15A resistor. I will check for some of the other changes. I don't see any painted dots on any sheet metal. Thanks Bob,.. this is good info.
Tony

Sorry, I don't know. I reviewed pictures of several VOS boards but didn't see any colored dots.

madlabs
01-05-2017, 05:50 PM
Only thing I have seen is a stripe on the main circuit boards. One of mine has a yellow stripe and one has a green stripe, IIRC. Don't know if that has anything to do with the "dots" however.

ohohyodafarted
01-06-2017, 12:00 AM
Personal observations on carbon comps vs metal film resistors.

In small signal circuits where current is not an issue I have never had any problems with metal film resistors.

HOWEVER: I can't say the same is true in B+ power supply circuits. In old sets I have seen situations where 2W and 1W carbon comps were being pushed to their wattage limits. I have had more than one metal film self destruct under circumstances where the original ckt design was probably using a resistor that was under powered. In my experience metal film resistors will not tolerate overheating as well as a carbon comp.

As a result I have been using high quality NOS carbon comps in everything I rebuild. You never know when the original design might have been using a resistor that was under rated, and my experience is that carbon comps seem to tolerate abuse better.

Most high quality carbon comps have pretty good value tolerance and in old tube ckts the added accuracy you gain with metal film doesn't affect circuit function to any appreciable degree.

And besides, carbon comps are period correct, if you are into that sort of thing.

bandersen
01-06-2017, 09:49 AM
I should have mentioned I generally double the wattage when I replace resistors. 1W for 1/2W, 2W for 1W etc.

I use the PR01. PR02 and PR03 series from Vishay. They are a reddish brown rather than bright blue and the color bands are bright and clear. The 2W are similar is size to the old 1/2 watters.

Also very reasonably priced. Often as little as $0.02 each on sale. Available at Allied Electronics, Mouser and Digi-Key, Newark etc.

http://www.alliedelec.com/search/results.aspx?term=pr01

http://www.sm-elektronik.pl/galerie/2/28e7a56cd5c8ccaf14ed2f22489baec412385.jpg

Findm-Keepm
01-06-2017, 10:28 AM
Well I don't know about all that - just passing along my experience as a EE and tinkerer ;)

You forgot author / preservationist-custodian......:D:D

madlabs
01-06-2017, 10:47 AM
You forgot author / preservationist-custodian......:D:D

Hey! Where can I get a copy? Just looked and don't see one for sale.

Kamakiri
01-06-2017, 11:23 AM
I should get me a copy and leave it on my bench for people that ask me if I learned how to work on TVs and radios by watching Youtube videos :whip:

Crist Rigott
01-06-2017, 12:12 PM
You forgot author / preservationist-custodian......:D:D

Hey, where can I get a copy!

Kevin Kuehn
01-06-2017, 12:22 PM
Hmm. Apparently cabin fever is setting in a little early this year. ;)

Electronic M
01-06-2017, 12:23 PM
IIRC that cover was someone's photoshop gag creation.

Kevin Kuehn
01-06-2017, 12:28 PM
I figured that much. It's the motivation that concerns me. Must be just a pick on Phil and Bob day. ;)

Crist Rigott
01-06-2017, 12:49 PM
What! I was really looking forward to getting a copy and having Phil and Bob sign it. Just think a signed copy.....sigh.

Findm-Keepm
01-06-2017, 01:45 PM
I figured that much. It's the motivation that concerns me. Must be just a pick on Phil and Bob day. ;)

Ancient post of mine, I just like to praise Bob's restoration efforts when I can. All in jest.

http://www.videokarma.org/showthread.php?t=249404

dtvmcdonald
01-06-2017, 01:48 PM
My comment on resistor types:

First, I always try to replace carbon comp resistors with modern film ones
that are the same physical size, not smaller. Modern film ones always smaller for the same rated wattage , which means at rated power they will get hotter: not good!
And this looks more authentic, even if they are bright blue.

Second ... some modern film types in fact have spirals of resistor element.
This won't cause a problem at audio or NTSC video frequencies ....
but most certainly can and will in VHF/UHF tuners. At 41 MHz IF frequencies,
I have no experience so can't make a statement.

Findm-Keepm
01-06-2017, 06:49 PM
Second ... some modern film types in fact have spirals of resistor element.
This won't cause a problem at audio or NTSC video frequencies ....
but most certainly can and will in VHF/UHF tuners. At 41 MHz IF frequencies,
I have no experience so can't make a statement.

I do have experience at 1.03 and 1.09 GHz, and at the IF Frequency of 60MHz. Film types from Dale/Vishay (RLR05/07 series) work fine if the lead length is short. Yeah, hard to find and pricey for civilian/non industrial use, but usable nevertheless.

Polaraligned
01-06-2017, 07:06 PM
Same here. I always replace with a higher wattage modern film resistor.

Tony F
01-13-2017, 05:45 PM
I have a question about the main "fuse" in this set. It is open and has been by-passed with (2) 4.5 ohm 10 watt in parallel (making 2.5 ohms). I have removed all the "kludges". All I can find in my area is a 5 ohm 10 watt resistor. Is this ok ?, the next step up is 6.8 ohms.
Tony

bandersen
01-13-2017, 06:20 PM
Yes, that's fine. The original was 5.6 ohms. Note that a regular power resistor is not the same as the original fusistor. A fusistor is designed to blow open like a fuse if current is excessive. A regular resistor will get hotter and hotter but not open up until it's really roasting.

I suggest adding a fuse in series with it. 1 or 2 amp slo blow should do it.

Tony F
01-20-2017, 11:49 AM
I am wondering how critical the small cylindrical capacitor is on the top of the tuner (labeled L2, C204) that has the 6.3 volt brown wire running through it to the heater of the 6X8 tube is. The reason I ask is while I was replacing the .22 mfd paper cap on the top of the tuner, I had noticed that someone in the past had removed the wire for the pilot lamp. It is missing totally, and only the 6.3 volt brown wire is there. There was a solder blob and what was left of the pilot lamp wire broken off down in this 5 pf cap. I was using a needle with my solder sucker and soldering iron to extract the remaining wire. I managed to crack the cap down the side. I see that the remaining half is ok inside the sheet metal of the tuner, the top half is still there (it cracked, but did not break off completely) When I put my ECG capacitance meter on it I don't get anything compared to the others on the tuner. My goal was to install a pilot lamp wire with lamp and holder. Is this cap there just to extract any remaining "junk" from the 6.3 volt line before it hits the tuner circuit ? I guess the only way I will know is when I finally fire up the set I don't get anything through the tuner. I guess the only place to get one would be out of a scrap tuner ? It is listed as #30-1268-1 :tears:
Tony

mrjukebox160
01-20-2017, 11:57 PM
This might be a different chassis from yours but is shows that cap as C222 and is 1000mmf

http://www.earlytelevision.org/pdf/Philco_H3410-Predicta-Princess-Sams-466-1.pdf

Tony F
01-21-2017, 09:15 AM
Hi, On the link to the Sams you posted, the capacitor I'm referring to is C204 (it is shown in the photo of the top of the tuner). It has the 2 wires running through it. In my case there was only one wire. I was trying to add the 2nd wire for the lamp when it cracked. It is a 10L43 chassis. It comes up on page 5 of the pdf document. Also, the Philco service data seems to show it better on the schematic in regards to the 6.3 volt line than the Sams does.
Thanks !
Tony

Tony F
01-21-2017, 01:56 PM
Mrjukebox160, you are correct. It is indeed a 1000 pf cap. Although the one listed is not the one shown in the picture ! Obviously an error on Sams part. The schematic does not match the photo part number. Sorry, I was scratching my head.
I had another question regarding the networks. I've watched a lot of Bob's videos on the Predicta's. Is K2, the only network (vertical section) you have to use 1000 volt caps on ? I know the one cap on the chassis board C14 .0015 mfd is the only one rated at 1000 volts, and the cap on the network (1500 pf) is directly connected to this cap. Will a 2200 pf @630 Volt poly on K2 go "poof !" ? Can you get away with 630 volt caps for the other networks ? I ordered 1000 volt mica caps from JustRadios, but his micas stop at 1000 pf. You then half to use the poly series. I ordered 3 -1300 pf @ 630 Volt 1% for using with the 2 - 47K resistors on the K3 network (also vertical section). I know his "regular" micas are only rated for 500 volts.
Tony

mrjukebox160
01-21-2017, 07:45 PM
Oddly, on the Sams that network is shown as K5. I don't know how much A/C is getting through C14. The spikes might be too high for a 630 volt cap.

mrjukebox160
01-21-2017, 07:49 PM
I now see there is a "second" K5 listed. Must be another misprint. It looks like 630 volt caps would work for the other caps. in the networks.

bandersen
01-23-2017, 01:03 PM
Hi, On the link to the Sams you posted, the capacitor I'm referring to is C204 (it is shown in the photo of the top of the tuner). It has the 2 wires running through it. In my case there was only one wire. I was trying to add the 2nd wire for the lamp when it cracked. It is a 10L43 chassis. It comes up on page 5 of the pdf document. Also, the Philco service data seems to show it better on the schematic in regards to the 6.3 volt line than the Sams does.
Thanks !
Tony

There seems to be some confusion regarding the Sams. The cap in question is C222 in the Sams, not C204. They mislabeled it on page 5.

It's a 1,000 pF ceramic feed-through cap. That's a type of cap commonly used to feed signals and power into a shielded box like a tuner.

Something like this may work if you need to replace it.
http://www.digikey.com/product-detail/en/tusonix-a-subsidiary-of-cts-electronic-components/2461-000-X7V0-102PLF/410-1043-ND/2079617

bandersen
01-23-2017, 01:09 PM
Oddly, on the Sams that network is shown as K5. I don't know how much A/C is getting through C14. The spikes might be too high for a 630 volt cap.

Some confusion between the Philco service info and Sams.

The networks are labeled N1-N7 by Philco and K1-K7 by Sams and the numbers do not refer to the same parts.

N2 is the same as K5 and is the vertical feedback. Yes, it is the only network that sees a voltage spike needing a higher voltage cap. 630 is more than enough for all the others.

Tony F
01-24-2017, 08:11 AM
Hello Bob, Thank-you for clearing that up ! I have a .0015 @ 1600 for that network. What about the 2200mfd that is used in the same network ? I have a 630 volt, but don't have anything at 1000V ? I will have to special order one if it is required. Also, I have replaced all resistors 1/2 watt with 1 watt, 1 watt with 2 watt. The only ones I'm questioning are the 3, 2 watt resistors R19, R40 and R45. These , I replaced with 2 watt ECG metal film, even though they are half the size of the original carbon comp ones. Nobody has any 3 watt metal film resistors in this area. I have left the WR4 (4100 ohm) and the R15A (5.6k 3 watt) one alone. I've pulled all 3 of the Can electrolyics and they all test good. Most are 20 to 30 mfd higher than the rating on the cans. I've pulled the solder from the traces on the board that cover up the holes where you added the 3 radial electrolyics to the board. Looks like I have to drill 1 or 2 holes (and run a small wire, like you did) to mount them. Also, did you mention that you used 1N5408 diodes to replace the original (34-8048-2) diodes ? It seems to be slowly coming together. I just wish the last person in this set didn't hack it up so much.
Thanks again for your valuable input.
Tony

bandersen
01-24-2017, 10:04 AM
Take a look at the Philco service info. You can see there is 3.2 VDC and a 60 Vp-p signal on that 2200 pF cap. 630 volt is more than enough. 150 would even be fine. I did the same analysis on all the couplate caps and determined that 250 was fine for almost all. 500 covered the rest. Use 630 if you really want to play it safe.

I also use C0G ceramic caps. That's the type thats the most stable type of ceramic. Mica is fine too, but rather pricey for the larger sizes. I've dissected some couplates and they appear to be tubular ceramic caps except for the vertical integrator. That's some type of thick film hybrid module bult on a ceramic substrate.

I use the Vishay VR01, VR02 and VR03 series of 1, 2,and 3 watt resistors. I get them mail order from any of the major vendors. Dirt cheap, great quality and look sort of like the old carbon comps.

Yes, I use 1N5408 diodes exclusively for all my projects now. Rated for 3A and 1,000 PIV.

Tony F
01-24-2017, 10:57 AM
All good info, I know you touch on these various things in your videos. I'll guess I'll have to re-watch anything having to do with the Predicta line and pause to take note. I have a cosmetic question. Has anyone had to replace the grill cloth in any of the Predicta line that uses cloth on the front ? If so have you found a close (suitable) match and where did you find it. This one is totally destroyed. I've been searching E-bay and locally and haven't found anything close.
Thanks !
Tony

Tony F
01-30-2017, 02:39 PM
Has anyone run into this problem and is there an easy fix ? The 4 plastic "lugs" that are molded into the back of the picture tube cover are stripped. They must have had quite a workout in their lifetime. 3 are completely stripped, one is almost. I've thought of drilling them out slightly and epoxying some 8/32" nuts on the backside and using a couple of longer machine screws instead of the metal plastic thread screws, or are plastic "heli coils" available ? or maybe a plastic insert ?
Tony

madlabs
01-30-2017, 07:22 PM
How about those plastic thingies they sell for putting screws in sheet rock and what not? I think they used to be called "mollies"? Just cut the flange end off. I was lucky, only one of mine was completely stripped so I just left it. I'ts not like they are likely to come flying off anyway, except maybe when moving the set.

Tony F
02-14-2017, 02:45 PM
I thought I'd post a photo of the networks that I just finished. The only one I had to put a 600 pf mica on the backside was N3 because of lack of room on the front. I would have loved to have used smaller components like the ones Bob uses in his. Just had to work with what I could get up here. The local electronics store closed a few months ago and hopefully will be back at a new location soon. I also picked up a Blonde Holiday with a 21" screen over the weekend. It is in pretty good shape, missing the horizontal knob and the tuning knob is broken where it goes on the shaft. Looks like someone had the main board out a long time ago but didn't change too much. A few black beauties are split open. They did a sloppy job, also there is a booster on the picture tube, so I'm not sure what that means as far as the shape of the picture tube goes. I don't have a picture tube tester. I mounted some of the electrolyics on the main board but still need a 100mfd to complete it. I installed 2 new octal sockets. The others, I just tightened the pins on them. I ended up using 3- 1300 pf polys for N3 rather than 2- 1200's and a 1600 pf in the middle. The total capacitance was about 50 pf under 4000. Using the 2-1200's and the 1600 would have put it about 50 pf over 4000. Hopefully it will be close enough. I just have to coat them with epoxy and make them look rusty like the originals.
Tony

bandersen
02-14-2017, 03:06 PM
Your N3 caps should be fine. I used three 1500s in the last few I made. Looks like those are polystyrene caps ? I understand those don't like the heat when soldering but are very stable.

Tony F
02-14-2017, 03:37 PM
That's nice to know Bob. Yes overkill,.. I know now. Maybe on the next one I'll end up using 1/2 watt resistors and 500 volt micas instead of 1 watt resistors and 1000 volt micas. Being my first, i wasn't sure. After watching tons of your videos looks like the only critical cap was the 1000 volt job on N2. It is kind of confusing as the test point on the vertical tube looks like only 260 volts. I know you talk about the spikes though. The polystyrene is new to me too. They were the only size the JustRadios had that was close to the needed values. He had 1300's at 1%. I kept the leads as short as possible on the backside and some of the solder joints were quite close to them with no hint of melting. I can see that if you were to get your iron close to them they would melt. So far so good.
Tony

bandersen
02-14-2017, 03:55 PM
Nothing wrong with overkill. Better than using underrated parts and having to pull the board again! Interesting that JustRadios has a wide variety of styrene caps at 630 volts. I was under the impression they weren't made anymore or hard to find. They are a bit pricey but not quite as much as mica.

Tony F
02-24-2017, 04:02 PM
I finally got around to applying the epoxy coating and some Red Oxide Primer spray paint to the networks. They are about twice as large (taller) than the originals, but fit the board with no problems. Next is to install them and reinstall the main board. Thanks for all the tips Bob. Hope you are enjoying your new "digs".
Tony

Tony F
04-25-2017, 12:46 PM
Well I finally got this Predicta up and running. Thanks to El Predicta for the replacement flyback and assorted parts I needed. I found a 3.2 ohm Emerson speaker to sub for the one that was missing. I thought I would post a few pics. I still need to play with the yolk a bit. The top left side (looking at the set) seems to be pulled to the center a bit. Maybe someone could tell me what I need to play with to fix it. Also, I'm still looking for some suitable grill cloth. In case you are wondering about the messed up grill cloth. I cut a square from the top quarter of what was there for a sample. The bottom 3/4 of the grill cloth was the way I acquired the set. The networks seem to work great. I also need some reproduction gold numbers for the dial as these ones are completely worn off. I thought about using a trim piece from a princess but the "Philco" logo would be sideways as it is painted on the back.
Tony

Tony F
04-27-2017, 09:56 AM
Could someone tell me if there is anything I can do to minimize or get rid of the retrace lines on this set ? From what I understand, it is or has something to do with the timing of shutting the gun off at the right time. It uses the 10L43 chassis and all caps and resistors have been swapped out (except for the tuner). They are pretty visible at the top 1/3 of the screen. Is there some value of a component I can play with, or is it just to be expected ?
Thanks !
Tony

bandersen
04-27-2017, 10:18 AM
They have a retrace suppression circuit. Looking at Sams 466-1 they pick a signal off the vertical output transformer and feed it into the brightness control. Check R26 and C27. They show a dashed line across R26 which I think means in some version it's shorted out. You might want to try shorting and unshorting that resistor.

BTW I note in your photos that the image is stretched vertically and doesn't fill horizontally ?

WISCOJIM
04-27-2017, 02:07 PM
BTW I note in your photos that the image is stretched vertically and doesn't fill horizontally ?Wrong aspect ratio selected on a converter box?

.

Electronic M
04-27-2017, 02:42 PM
Could someone tell me if there is anything I can do to minimize or get rid of the retrace lines on this set ? They are pretty visible at the top 1/3 of the screen.
Tony

Are you familiar with macrovision copy protection? It is common on DVD and VHS tapes and can cause what looks like a retrace issue on tube era sets.

IIRC Phill's old radios has a good write up on it.

Tony F
04-27-2017, 03:46 PM
Hi, I'm playing all recordings off of my popcorn hour with a 4 GB hard drive (Cloud media) hooked up to the set, through a radio shack modulator that has channel 3 and 4. I've tried swapping aspect ratios (on the popcorn hour)16:9 > 4:3. I've tried various formats. (That is the "bars" you see on either side of the picture). If I swap to the output of my satellite receiver it will output a full width picture without the bars, but the retrace lines are still there (even with no output source). So I'm back to Bob's advice about the resistor and cap combo. I've got a little digging to do. Thanks for the help so far.
Tony

Tony F
05-16-2017, 12:40 PM
Hi, I have a question about the vertical linearity on this set. I get lots of vertical height, the problem seems to be the width of the scan lines between the bottom half and the top half of the picture. The bottom half the lines have a lot of spacing between them, and the top half seems tighter together. If a man is standing with his waist in the middle of the screen his upper body and head is shortened up and his legs at the bottom are longer and out of proportion. The magnets on the back of the yoke only seem to have limited effect, when playing in combination with the vertical linearity control in combination with the horizontal controls. Sams shows (2) 680 ohm resistors R61 & R62 in parallel with the yoke coils. I didn't really notice them when I had the picture tube cover off. Are they located on the front of the black plastic yoke cover (where the magnets are) or are they located underneath this cover. Also, with C53 being a ceramic disc, should I think about replacing it as well ? Those would be the only resistors I hadn't replaced. All paper and electrolytics were replaced with the exception of the original ceramic disc caps. All tubes are NOS.
Thank-you
Tony

bandersen
05-16-2017, 12:48 PM
The resistors are under the cover, but I really don't think they will have any effect on linearity. I believe they are damping resistors to prevent ringing. I'd leave the cap alone too.

The magnets won't have much effect either. They are for centering and horizontal linearity correction.

The vertical linearity control should have a very, very noticeable effect. It also interacts with the height control so you'll need to go back and forth with adjusting them to get the best linearity at the right height.