B&K CRT 400 and 465 Restoration Help(almost complete!) - Videokarma.org TV - Video

Kawooa · #1 03-01-2016, 10:58 AM

So quite awhile ago I bought the 400 to test my early 50's 17bp4 CRT to see if I can move along in that project before starting. Just in case the tube as bad I didn't want to do a bunch of work first then find the tubes bad. But I never bothered fixing the tester up as I needed to buy three ne-48. At over $5 a pop ouch. But I finally did it. Testing it vs my 465 shows it low on emission. The 400 shows under 300ua(mostly 280 or lower) when the 465 shows 320ua minimum. My mom got me the 465 a month or two ago and I replaced the electrolytics and it shows my tube good. It has a weird "glitch" when I switch from emission back to shorts then heater adj then back to emission a few times the needle moves up to show even better emission for my tube! I got it as high as 420ua before I stopped! Haven't check every resistor yet to replace any possible bad ones. I'm mostly here about the 400. But of course I want the 465 working great too. I just haven't felt up to the task of checking 2 dozen resistors.

I'm planning on selling the 400 for a decent amount as all the non restored ones go for 50-100. Could ask a decent amount on a already fixed up and fully working one. But I need to sort out that low reading. Could it be the tester is just a lacking and sucky model that will always be this way? I replaced out the selenium recifier with a silicon diode and a 200ohm 5w in the power line in. I'll include a picture of my schematic modified to show such. I also installed a 1/2a fuse in the power line as well. I even replaced my 40kohm 10w resistor with another until I found out I made a mistake measuring the ohms and took my new 40k out. Why waste if the old was good the whole time?

When I have my variac putting ac voltage into the tester at about 120-125 (normal for houses) my filament voltage is good at 6.3-6.4v with my rectified voltage at 160ish. The schematic lists 170vdc. Should I try taking my 200ohm resistor out and see if that makes a difference? I can bridge it with a alligator clip for testing. I meant to put the resistor on the other side of the diode just before the electrolytic but a mistake was made. Well it works anyways. The resistor never gets hot telling me it doesn't draw much current. It also says how I don't have to worry about another hot resistor as my 10k-10k-40k combo resistors get hot enough as is. They are rated 10w but drop about 8. Genius idea on the manufactures part.

Sorry if I ramble too much. Want to be as complete as possible on the model 400 since I want to sell it and thus have it as safe and accurate as possible.

Ps- don't nag about using an isolation transformer. I already am, it's connected into the wall then into my variac then into the tester. I can get about 148vac max out of that combo!

Kawooa · #2 03-01-2016, 11:02 AM

I'll post pictures of my testers and their insides later. I've already opened them up like 10 times in the last two days. I'm just tired of opening them.

Electronic M · #3 03-01-2016, 03:04 PM

That 200 ohm seems kinda high for that application. I'd try bridging it.

Your CRT sounds like it's good enough to produce a watchable picture (at least if it is not in too bright a room).

jr_tech · #4 03-01-2016, 05:50 PM

Quote:

Originally Posted by Kawooa

I'm planning on selling the 400 for a decent amount as all the non restored ones go for 50-100. Could ask a decent amount on a already fixed up and fully working one. But I need to sort out that low reading. Could it be the tester is just a lacking and sucky model that will always be this way? I replaced out the selenium recifier with a silicon diode and a 200ohm 5w in the power line in. I'll include a picture of my schematic modified to show such. I also installed a 1/2a fuse in the power line as well. I even replaced my 40kohm 10w resistor with another until I found out I made a mistake measuring the ohms and took my new 40k out. Why waste if the old was good

I think that you are being overly optimistic...if you examine the SOLD list on eBay, you will find that very few have *actually* sold for more than 10 bucks!

http://www.ebay.com/sch/i.html?_from...p2045573.m1684

I think I paid about $15 for mine, which included shipping, and it worked well.

jr

Kawooa · #5 03-01-2016, 10:03 PM

Tomorrow I will try bridging the 200ohm and retesting. As for my tube I don't how well it does. I wanted to get a tester to determine if I would move forward on a old majestic tv as a project. If the tube was bad then I would do no work. But if I didn't test and did all that work well then I'm screwed. Since the tube seems good then I will move forward as soon as some other "project" or more appropriate is shelf dust cleaners. They help keep the dust off the shelf by collecting it themselves. How nice of them.

Kawooa · #6 03-02-2016, 10:03 AM

Shorting past the resistor only increased my voltage 1.5-2 volts. I let the tube "cook" for like 5 minutes and it seemed to increase the reading up but it didn't ever pass 300. I still wonder why it's reading low compaired to the 465. With the the 465 if I set the heater voltage then connect the tube the voltage drops to 5.5v and it acts the same as the 400. I wonder since this is a set voltage off the transformer if it is dropping down for the tube. I don't notice much off the power light which is off the 6v windings. It reads 6.3-6.4. But maybe the tubes getting a little more resistance along the way then the power light. I may try cleaning my life test button as it may be slightly poor contact. Since the life test just disconnects the heater and puts voltage on the cathode and grids.

Kawooa · #7 03-02-2016, 10:09 AM

Here's a picture of the 400's innards. Look at all that messing wiring. The two orange capacitors are 0.22uf 630v in series for a 1200v 0.11 capacitor. That's the closest I could get to 1000v 0.1uf. I didn't have a 0.1uf 1000v on hand and didn't feel like purchasing some. Maybe I'll change them out one day if I don't or can't sell it. Maybe is the key as most likely I never will bother.