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 Post subject: Predicta Barber Pole Redux
PostPosted: Nov Tue 29, 2016 2:55 am 
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Location: Coopersburg, PA USA
Some of you may recall my thread on restoring a Predica Barberpole. I never got the picture satisfactory and am working on it now. When I restored it I replaced all paper and electrolytic caps, tested and replaced any bad tubes, and replaced any resistors out of spec.

Here is a picture of the movie Double Indemnity off of a DVD.
Image

Note the problems:
1. Picture is 'split' with some of the picture below and above.
2. Horizontal interference
3. Picture isn't sharp
3. Audio has a distinct hum also.

Wish you could see it in person, the picture doesn't really show the problems too well. I've fiddled with all the controls to no avail. Any ideas?

Also, does anyone have a test pattern DVD for sale? I know there's stuff on the internet, but I don't have a DVD burner.

Thanks Stan

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 05, 2016 9:03 am 
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Location: Powell River BC Canada
You have vertical fold over . The circuits involving the vertical height and linearity
controls should be examined.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 05, 2016 5:01 pm 
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Location: Albion, CA, USA
Double post. :oops:


Last edited by madlabs on Dec Mon 05, 2016 5:03 pm, edited 1 time in total.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 05, 2016 5:02 pm 
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Joined: Aug Thu 20, 2015 3:09 pm
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Location: Albion, CA, USA
I'm far from an expert but I have been working on my Predicta. I just got the sound working OK on mine, here is what it took for me:

Check the volume pot, mine was very scratchy and one wire was hanging by a single thread. I noticed that touching the pot reduced hum so I added a .01 cap to ground from the pot body and that helped. The 12CA5 was bad. Removed and cleaned the buzz pot, very hard to clean by just squirting deoxit into that one. Perform an audio alignment per the instructions in Sam's. My A11-12 adjustment can had a broken slug, I had to remove and replace. But now my audio is great!

As to the video issues, I leave that to those that actually have a clue. I'm still working on my horizontal linearity.


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 05, 2016 6:53 pm 
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Location: Waynesboro and Richmond, VA , USA
Did you rebuild the couplates on the vertical board? Those are known for trouble such as you are having.


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Tue 06, 2016 11:16 pm 
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Yes, I rebuilt the couplates.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Tue 06, 2016 11:34 pm 
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Location: Powell River BC Canada
Can you post the circuit of the sweep and damper section ?

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Thu 08, 2016 1:39 am 
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By adjusting the various controls I have a pretty good picture, so that part is closed. I also addressed some poor solder joints.

Now a new step in the saga. I broke the thermistor when turning the chassis over. TV still works if I jumper where the thermistor connects and bring it up slow on the variac to avoid the large startup inrush current. I understand from Phil's Old Radio site that a CL-90 from Mouser (or others) is a good replacement. But I have on hand a NOS Wuerth Tube-saver surgistor. Its ratings are 100 ohm starting, .2 ohm norminal, time delay 10 seconds, power range 100-300 watts.

I ordered a CL-90 from Mouser but in the meantime, would the Wuerth tube-saver be a good replacement?

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Thu 08, 2016 4:21 pm 
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Location: Chicago, IL USA
I don't get the power rating on that Wurth part. It's just for the series filament string which doesn't use anywhere near that much power. Perhaps it's designed to go in series with the AC supply to the whole set ?

The original Philco part is 400 ohms cold while the Wurth is 100 and the CL-90 is 120.
The CL-90 is OK but two Ametherm SL-221 in series would have been a better choice. The SL12-22101 is 220 cold so two in series is 440.

http://www.mouser.com/ProductDetail/Ame ... JzCx93c%3d


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Fri 09, 2016 3:55 pm 
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I ordered two of the SL-221 an will install them in series.

I now understand that selecting a replacement for the original is just finding the right number of ohms (cold) needed and possibly use more than one in series or parallel - just like dealing with fixed resistors.

I will continue to power on via variac slowly until I install the Ametherms.

Thanks, banderson.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Sat 10, 2016 3:12 am 
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Took the time to create a test pattern DVD. Makes things a lot easier. As you can see below, there are a few things wrong with the picture.

Lets start with the most glaring. You can't tell by the picture, because its wasn't happening just then, but I keep losing horizontal hold. Might stay OK for a few seconds up to a minute, but then I lose it. Adjusting horizontal hold knob will bring it back, but only for a short time.

What should I look for for this problem? Should I re-check voltages and compare with schematic?

Image

Thanks for everyones help so far.

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Stan Saeger
Coopersburg, PA
http://www.saegerradio.com/


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Sat 10, 2016 6:26 am 
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Stan Saeger wrote:
Took the time to create a test pattern DVD. Makes things a lot easier. As you can see below,
there are a few things wrong with the picture.

Lets start with the most glaring. You can't tell by the picture, because its wasn't happening just then, but I keep losing
horizontal hold. Might stay OK for a few seconds up to a minute, but then I lose it. Adjusting horizontal hold knob will
bring it back, but only for a short time.

What should I look for for this problem? Should I re-check voltages and compare with schematic?

Two possibilities come to mind. If the set has an AGC adjustment, it may be mis set. If you have too strong of a signal passing
through the IF strip the sync signal gets clipped off. The normal way to adjust the AGC is to adjust it in the direction that gives
more contrast until you hit the point that the sync gets messed up and then back off until the sync is stable.

Another possibility is that you have some mica caps going bad. Mica caps usually do not fail, but they do sometimes. Replace
any in and around the sync separator circuit and horizontal oscillator.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Sat 10, 2016 4:38 pm 
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Stan, the only real agc on this set is the local/ distant switch on the back next to the antenna terminals. Make sure it is set to local. If you still have issues look into resistors along the video if chain. Re the horizontal lock, I had the same issue with my Barberpole for awhile. The fix was to simply replace the tube. Been working great since. Give that a try. Also noting that the linearity if off but you should do fine straightening that out with the adjustment controls. Also keep in mind that when at normal operating temperature the thermistor had 4 ohms resistance. If you are running up your variac to full 117-120 volts the AC going in to the tube filaments will be slightly high and could affect tube emission. I'd strongly suggest that until your replacement part comes in that you place 4 ohms of resistance across the thermistor terminals where you have it temporarily jumpered. That may make all the difference with these conditions you are noting in the video. I've found that this chassis is kinda voltage sensitive .......

George
Easton, PA


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 12, 2016 4:39 pm 
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(Corrected width of picture to prevent horizontal scrolling)
George -
1. I have the local/distant switch on local.
2. When you say replace the tube to correct horizontal lock, which tube? 12DQ6 horiz output? It tests good.
3. Regarding resistors along video IF chain, I checked resistance at tube pins per Sams schematic, and all are within spec.
4. One thing I forgot from when I first went thru this set is the 5AM6 was replaced with a 6AM6. Made a mental note to order a 5AM6, but forgot. I wonder if this could be at least part of the problem. I put a WTB in the classified.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 12, 2016 5:36 pm 
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Joined: May Fri 29, 2009 4:35 am
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Location: Chicago, IL USA
9BR7 is the horizontal AFC tube. I assume you meant 5AM8 (600 mA filament). This is a series string set so using a 6AM8 (450 mA filament) is going to restrict the current through all the tube filaments and quite possibly enough to effect the operation.


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 12, 2016 5:40 pm 
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Location: Chicago, IL USA
BTW you can get a 5AM8 and many other tubes this set uses for $1 each from ESRC.

http://www.esrcvacuumtubes.com/dollar_days.html


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Mon 12, 2016 6:59 pm 
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Yes, 5AM8, not 5AM6.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Tue 13, 2016 2:23 am 
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Besides the horizontal AFC tube, the sync separator tube and the horizontal oscillator tube could cause problems. The horizontal output tube can not cause this type of problem. If replacing tubes does not help, do voltage checks on the sync separator tube. That tube needs to run with somewhat strange voltages as it needs to amplify only the sync part of the signal and reject the video part of the signal. In circuit resistance checks can not always show up a bad resistor, especially if the circuit has a combination of a very high value resistor and a low value resistor.

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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Tue 13, 2016 5:12 am 
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Stan Saeger wrote:
(Corrected width of picture to prevent horizontal scrolling)
George -
1. I have the local/distant switch on local.
2. When you say replace the tube to correct horizontal lock, which tube? 12DQ6 horiz output? It tests good.
3. Regarding resistors along video IF chain, I checked resistance at tube pins per Sams schematic, and all are within spec.
4. One thing I forgot from when I first went thru this set is the 5AM6 was replaced with a 6AM6. Made a mental note to order a 5AM6, but forgot. I wonder if this could be at least part of the problem. I put a WTB in the classified.


Well firstly my apologies, mistook your hold as vertical hold which my Barberpole exhibited. Your issue is horizontal. I'd still try swapping out the 9BR7 sync separator. That was the tube that gave me trouble, and yes, mine also tested good, but swapping out to another good tube resolved my issue.

Re the 5AM6 vs 6AM6, I believe the only operational difference is the heater voltage being 5 volts vs 6. Now, this COULD create all sorts of issues - - especially since you have already taken 4 ohms resistance out of the filament chain by jumpering the thermistor. I would insert 4 ohms of resistance into that circuit and try it again. I'd also swap out the 6 volt tube for the correct 6 volt tube as this will potentially affect performance of all of the tubes in the chain slightly.


Ive found that its the little stuff that'll get ya with these transformerless PRedicta chassies!

-George-


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 Post subject: Re: Predicta Barber Pole Redux
PostPosted: Dec Tue 13, 2016 3:53 pm 
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Location: Coopersburg, PA USA
Status:
1. Have a 6AM8 on order to replace the 5AM8 and a 9BR7. Will install when they arrive.
2. Have replacement for thermistor on order. Will install when it at arrives - should be today's mail.
3. Will check voltages for 9BR7 sync separator.

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Coopersburg, PA
http://www.saegerradio.com/


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