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

[old_coot88]

That's a timeless and venerable piece of gear. Are you zeroing the meter for the ohms measurements?

Originally Posted by old_coot88

That's a timeless and venerable piece of gear. Are you zeroing the meter for the ohms measurements?

I did before I ran the series of tests. I downloaded the manual/schematic Wednesday when it arrived. I followed the process to 'tune' it and I have only two days experience with it. The ac/dc probe came today, from a B/K unit, just a random eBay find. I have just begun this whole process in a random way. I don't really now what tools to assemble, so it is just a scavenger hunt as I make small steps. I don't even know what to call the probe's connection to the chassis, a screw type sort of coax?

I love the whole nature of this ordeal and I am hell-bent. Just need to stay calm.

Tools I have:

CRT tester
RCA Senior vtvm VoltOhmyst
B/K solid state 2-channel oscilliscope
B/K Dynascan 1070 (does not have test pattern)
RCA Bias Supply
HP VHF signal generator

Projects:

1957 RCA KCS116C 21"
Rangeaire AM/FM tube radio from 1964 - learning project radio

I have been told to put the tv chassis components back together, and to find a compatible transformer. A smaller project was advised to first tackle how to restore a tube electronic, hence the Rangeaire.

Problems:
I do not know how to measure resistance in ohms, therefore it will be difficult identifying the resistors I removed from the tv chassis.
I know how to callibrate the vtvm via the RCA manual.
I know how to setup the oscilliscope via the B/K manual.
I do not know how to measure a capacitor using my DMM, even assuming the cap is dead, I cannot pinpoint whether my reading is accurate. Therefore I cannot accurately place the old tv caps unless I can trust what is written on each one. They are clearly marked with volts and +- % for identification.
The tv crt is rated good.
The Rangeaire radio does work, a little low on volume but it does work. I can study and test the caps and resistors, tubes, and voltages to learn AC/DC measurements.

Now what?

[JohnCT]

Originally Posted by BandDirector

I do not know how to measure resistance in ohms, therefore it will be difficult identifying the resistors I removed from the tv chassis.

Order a fistful of brand new 1% film resistors ranging from less than an ohm to over 1 meg. With known good resistors of exact values, you can practice with your meter until it's second nature. Order resistors with the value printed numerically on them so you don't get confused with color codes. Known value resistors can also tell you if your meter is working properly..

In addition, you have to become familiar with ranges. For instance, a 680 ohm resistor is also known as a .68K resistor. A 820K resistor is a .82Meg, etc. Using known good resistors takes the guessing out.

I do not know how to measure a capacitor using my DMM, even assuming the cap is dead, I cannot pinpoint whether my reading is accurate.

If you're talking about a typical DMM that measures AC/DC voltages, resistance, and current, then you can't use such a meter. Some people use a resistance "kick" to determine a cap is good or not, but that's a waste of time. However, many newer DMMs though have a rudimentary capacitor function that checks for value.
If this is what you're referring to, then order a bunch of capacitors and learn the differences between pf, uf, and nf. NF was not used in the old days, but is more European than U.S.

There are on-line conversion calculators so if your meter says a capacitor is reading 68nf, you can plug that into a converter and find it's also known as a .068uf.

Most of these meters don't test for leakage as a good leakage tester must put the same voltage across the cap as it's rated for. For instance, a typical 0.05 400V cap may read .05 on a capacitor DMM tester, but become electrically leaky at 100V or more, well beyond the voltage a typical capacitor checker will test for.


John

[old_coot88]

Regarding the VoltOhmyst, you might have to re-zero it a few times until it warms up good.