Dove right in! Help with RCA 21-D-8628

This was with tweaking everything throughout the day.

[Electronic M]

Originally Posted by BandDirector

This was with tweaking everything throughout the day.

It's looking better but did you go through the resistors in the vertical yet?... there's probably several off tolerance resistors and those can prevent proper linearity and height adjustment range.

Originally Posted by Electronic M

It's looking better but did you go through the resistors in the vertical yet?... there's probably several off tolerance resistors and those can prevent proper linearity and height adjustment range.

*sigh, I haven't. I need to do that, resistors are still foreign to me. I am struggling to understand how they work. I will google how to read the color bands. I did visit my closest Fry's to pickup several packs of resistors of various values.

It'a just another step at this point, I'm a bit weary.

[DavGoodlin]

Dont give up, Im working on a '60 Philco console and just resigned to replace all the "quality" caps and resistors they used just like RCA did.

Originally Posted by DavGoodlin

Dont give up, Im working on a '60 Philco console and just resigned to replace all the "quality" caps and resistors they used just like RCA did.

Oddly enough, I shouldn't have replaced the electrolytic used for the 3 panoramic speakers, it was working just fine. After messing with it I tore the original 8" center speaker leads and spent 2 hours trying to remedy it. Then the inevitable "pop" once I put the speaker set back in!

[Electronic M]

Once you memorize the color code resistor checks are quick and easy. Read value multiply by usually 1.1 or .9 for %10 tolerance then touch your DMM leads to the resistor and see if it's in range...you could print off a color code chart to have on hand...there were also paper color code "calculators" with wheels with colored edges and mostly covered faces there'd be a hole in the face cover such that when the edge color was lined up a number would be in the hole in the face cover.

Originally Posted by BandDirector

Oddly enough, I shouldn't have replaced the electrolytic used for the 3 panoramic speakers, it was working just fine. After messing with it I tore the original 8" center speaker leads and spent 2 hours trying to remedy it. Then the inevitable "pop" once I put the speaker set back in!

Speaker crossover caps are not high failure and usually not dangerous to other parts when they do fail unless you run at very high volume. Speaker crossover caps are usually non-polarized and should not be replaced a single with polarized lytic. (You can make a non-polarized lytic with 2 polarized lytics of 2x capacitance connected anti-series meaning series with the 2 positives or 2 negatives connected together).
Almost every RCA is prone to the speaker terminal rivet breaking off... just one of that brands quirks.

The rivet did fail, and I tried to make a electric tape line wall so that the leads don't make contact with any metal. The lytic was a polarized 10 mfd 450 volt, so it was extremely high voltage, the spec calls for 8 mf at 10 volts. I have a 4.7 mf at 50 volts floating around.

[Yamamaya42]

Originally Posted by Electronic M

Once you memorize the color code resistor checks are quick and easy. Read value multiply by usually 1.1 or .9 for %10 tolerance then touch your DMM leads to the resistor and see if it's in range...you could print off a color code chart to have on hand...there were also paper color code "calculators" with wheels with colored edges and mostly covered faces there'd be a hole in the face cover such that when the edge color was lined up a number would be in the hole in the face cover.



Speaker crossover caps are not high failure and usually not dangerous to other parts when they do fail unless you run at very high volume. Speaker crossover caps are usually non-polarized and should not be replaced a single with polarized lytic. (You can make a non-polarized lytic with 2 polarized lytics of 2x capacitance connected anti-series meaning series with the 2 positives or 2 negatives connected together).
Almost every RCA is prone to the speaker terminal rivet breaking off... just one of that brands quirks.

once taught , you NEVER FORGET!

https://en.wikipedia.org/wiki/List_o...code_mnemonics

The one we were "programmed" with is the 5th down on "Offensive and vulgar" list!

[Kevin Kuehn]

Originally Posted by BandDirector

The rivet did fail, and I tried to make a electric tape line wall so that the leads don't make contact with any metal. The lytic was a polarized 10 mfd 450 volt, so it was extremely high voltage, the spec calls for 8 mf at 10 volts. I have a 4.7 mf at 50 volts floating around.

Usually you can use a machine screw with a nut to replace the rivet. I'm assuming the cap was the high pass crossover for the tweeters, in which case it needs to be close to original micro-farads for the frequency roll-off to be correct. Voltage not so critical. But the large speaker should sound pretty decent by itself.

Question- so how do you know what kind of problem the tv has if the lower part of the image is compressed, and the top lines are spreading further from each other? It would seem both height and lineirty (sp?) is still troubled. Since the image can't yet fill the screen via height, and when it does the flicker returns (linerity) and a duplicate/triplicate image appears, and dims.

So both are needing tracing the resistors, if replacing all the capacitors created the problem? Is that the logic here?

[old_tv_nut]

The linearity and height generally interact to a greater or lesser extent depending on the design, so trying to say it's one or the other may not help diagnose it. It's a vertical sweep problem, so you need to check components in that section whether they are attached directly to one control or the other.

[Electronic M]

Replacing the capacitors didn't create any problem (unless you used the wrong capacitance or made a wiring mistake during replacement).

Carbon comp resistors are very prone to drift in value with age and extremely prone to drift with moisture or humidity...resistors for the most part fail in ways that prevent the set from working while also reducing the risk of other parts failing in a chain reaction, but caps tend to fail in ways that damage other parts.

Some collectors (Christ Ricotta for example) change all resistors and capacitors as preventive maintenance, but most of us do the caps first and for the half of TVs where there are resistors bad enough to prevent proper opperation go back and find the bad resistors.

BTW: have you checked and or substituted the vertical stage tubes yet. If you haven't do it before the resistors because it is quicker and easier.

[Electronic M]

Originally Posted by old_tv_nut

The linearity and height generally interact to a greater or lesser extent depending on the design, so trying to say it's one or the other may not help diagnose it. It's a vertical sweep problem, so you need to check components in that section whether they are attached directly to one control or the other.

Any resistor connected to the vertical tubes could be causing the issues the same as the ones on the height and Lin pots. The nice thing about working off a Sam's schematic is that the components for each stage are grouped together with signal in out and power connections marked so on any given stage you can easily say "it's gotta be in this cluster of 6-30 components".

I have swapped the tubes a few times, will do it again later this evening to double check. I have made a list of the resistors and their capacities/wattages/variance level and will draw my own schematic that is more blown up than the one in my service manual. I did not purchase any of the needed resistors, instead I bought all the wrong values! But I'll keep them. PW500 is the vert/height board

This blow-up may be easier to read on my end!

Swapping tubes didn't work