View Full Version : New enthusiast

02-07-2016, 03:23 PM
Hi I am looking forward to being a member of this community. I am a novice with no electronics background. I just acquired a 1953 Capehart 21 inch BW in good cosmetic exterior shape. Model number7h214M, serial number 578928. Chassis CX-37-1 and R 02 - 03. In note with disappointment that there is a Comet EC-63 picture tube brightner installed.

Any advice? Specifically
-How to test picture tube
- Schematics available?
-What equipment do I need.
- Any other relevant matters I am not aware of?


02-07-2016, 03:37 PM
From the Ad. I will post more detailed pics soon

Electronic M
02-07-2016, 03:53 PM
A monochrome TV is the second (first would be a color TV) most complex consumer market tube era electronic device, and not a good first electronic project for anyone. I'd highly recommend that you find a cheap common AA5 tube radio and make that your first project....It will teach you skills that will provide a foundation and help you on the TV.

As for the TV.
You will need to buy a CRT tester, or borrow one from someone local who has one. You can't accurately test the quality of a CRT any other way.

Google "Sam's Photofact" that should bring up their site where you can search the chassis and or model numbers, that search if it yields results should give you a Sam's number. You could buy the schematic from them, but it is usually much cheaper elsewhere.

Bare minimum you need a DMM(or VOM), soldering iron, schematic for your project, and to have the tubes other than the CRT tested (again buy or borrow a tester). Tools that are nice to have, but non-essential for TV work include B&K 1076/1077 analyzer, oscilloscope, variac, test CRT/CRT test jig, and a few other things.

Remember on tube equipment made before 1960 the primary failure mode is electrolytic and tubular paper capacitors, tubes and resistors occasionally are bad too, but they don't fail in mass like caps. Post 1960 equipment tends to have better quality capacitors, and often 'shotgun' capacitor replacement consumes more time and money then diagnosing the problems and replacing the 1-4 parts per problem.

Google "Phill's Old Radios" he has some good information on capacitor replacement on his site.

02-07-2016, 04:19 PM
looks like its in Sams set 203, but thats one I'm missing

Bill R
02-07-2016, 05:45 PM
You might want to start with some AA5 radios. This will help you learn to follow the schematics, and you will gain soldering practice. You will need an isolation transfromer and variac for safety and to bring the chassis up to power slowly. A good soldering gun and a DMM are about the minimum. Start simple so that you do not get discouraged or overwhelmed by television.

02-08-2016, 09:26 AM
Welcome! I can't add to the excellent advice already given.

Have fun!

02-09-2016, 09:39 PM
That is a nice looking tv you have !
I think if you take your time, and don't try too much all at once, you should be able to
handle making this tv your first electronics project.

There is one thing you already know..... With the brightner on the tube, you already
know it's got a weak picture tube. You don't need to buy a tester for that..... Once
you get the guts going, you will be able to evaluate the picture tube, and decide if
you want to get a replacement. And yes someone most likely will be able to get one.

Did you plug it in and fire it up..? No Smoke ? tubes light up..?
A lot of these sets had a fuse on the B+ power supply, that's what runs most of the
circuits. If the tubes light, and you get no picture, or sound of any kind, then you
may have some minor power supply problems.

Did you look at the power plug, ? look at it full length, any cracks in the insulation?
if so replace it.....

There are lots of tv repair books on ebay, they have titles that include "basic tv repair"
and stuff like that..... Some were written for the home owner who has decided he's
going to figure this thing out.... Those are good books to begin with.... People who
actually repair tvs began with this kind of book....

You will need a meter, get a $30. one off ebay. Or get an education on meters, and get
an older one that was expensive when new. I got a replacement Beckman 330 off ebay
for $20. and when I got one new in '83?? it was over $300. You can find good well
taken care of tools for a good price. Don't go nuts, you would not want to smoke a $100.
meter.... There are very very good youtube videos about basic electronics, and how
to use meters and other tools.... I wish they were around when I was learning this stuff....

Take your time, people here will answer your questions....

Good luck.


02-11-2016, 08:53 PM
Squirrel boy that was very encouraging. I am learning things and hopefully I wont make too many blunders. I have not yet bought a picture tube tester but with a multimeter I tested the CRT heater for continuity. My meter came back at 1 which I think means no continuity. Am I shot out of the water? This TV looked very clean so I am hoping it did not have major issues. I haven't taken the chassisout yet because I don't know how to separate the CRT from the chassis safely, but I peeked underneath and it looks like its all original caps,no modern caps in there. What should I do next are there resaonably priced replacements for the 21fp4a CRT?

02-11-2016, 09:14 PM
One ohm is perfect. Your Crt's heaters are good. :thmbsp:

Electronic M
02-11-2016, 09:35 PM
Depending on the set the CRT is either mounted to the chassis or mounted to the cabinet. If it's mounted to the cabinet you should be able to unplug the yoke, CRT socket, and HV lead to remove the chassis. If the CRT is mounted to the chassis then the chassis and CRT must stay together until the pair has been removed from the cabinet. Chassis mounted CRTs normally separate from the chassis by pulling from the front (after fasteners and mounts have been loosened or removed).

This may sound a bit stupid but on chassis mount CRT sets if the mounts seem sturdy I don't bother removing the CRT for servicing, and simply turn the chassis /CRT assembly on it's side to service it.

02-12-2016, 09:21 AM
If you get the SAMs photofact for the set, they usually have some instructions for how the chassis and crt can be removed.

02-12-2016, 10:48 AM
Thanks everyone for the help and encouragement. I want to clarify a little on the test I did on the CRT. I looked up the schematic for the picture tube (Tung-sol spec sheet) and it said that pins 2 and 12 were the heater pins. Using a Cen-tech digital multimeter model 98025 (cheapo version that I got free from harbor freight) I set the dial to 200 ohms. Before taking the measurement the readout reads "1" to the far leftmost position, there is blank space (enough for maybe 3 digits) to the right and then the decimal point is visible. When I cross the leads the value settles at 1.3 ohms. this differs from the manual which states that the shorted leads should read zero ohms. I put a brand new battery into the multimeter. At any rate, with these settings, the value on the multimeter when reading pins 2 and 12 is the same as described above a 1 to the left of the readout screen and the decimal point to the far right. My thinking is that this means no continuity. When I take other measurements using this setting for example the fuse on the power supply that squirrel boy mentioned it seems to give a legitimate reading - 1.3 ohms. Any ideas on what this reading means - is it an indicator that the picture tube is bad?

As for the CRT mounting - I think it is chassis mount so I will take the CRT and chassis out as a Unit. I did order the SAMS from ebay and am awaiting arrival.

Electronic M
02-12-2016, 02:03 PM
There are a few possibilities regarding the heater continuity. You could be measuring the wrong pins....The heater wires to the socket are usually brown and black, and on 50's CRTs with the common 10BP4 style base IIRC the heater is always the two pins nearest the key on the bakelite center shaft.
There could be dirt or corrosion on the pins preventing a good reading (use the sharp tips of the test leads to scrape through it if that is the case).
The last good possibility is that the solder on the base pins is bad and needs to be re-flowed with a soldering iron.
If all those fail to give you a reading, then the CRT is probably bad.

You can also try light testing the CRT heater....As in get a 6V lantern battery or some such and connect it to the CRT heater and see if it lights.

02-12-2016, 02:47 PM
I was checking the wrong pins - the correct pins are 1 and 12 for the heater - on these I get about 2.7 so heater should be good right?

02-21-2016, 08:06 PM
I was checking the wrong pins - the correct pins are 1 and 12 for the heater - on these I get about 2.7 so heater should be good right?

Sounds good as far as that goes. A brightener would not be used
for a heater A.K.A. filament problem. From my earlier post:

CRT's almost always fail due to low emission. On a
B&W symptoms are dark pix, negative pix, streaking of
bright areas, slow warm up & overly bright whites with no detail or any
combination of.....

Best test is darken the room, turn down the bright & contrast.
If it looks a lot better its the CRT 99%.

Good news is you have a clean cabinet. As an old TV tech but NOT
a wood worker the guts are easily dealt with compaired to a
trashed cabinet. Good luck.

73 Zeno:smoke: