Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Nov Thu 23, 2017 4:30 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 55 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Wed 27, 2017 3:15 pm 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11845
Location: San Jose, CA USA
Yes, that 6X5 is toast.

_________________
Tom K6VL


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Wed 27, 2017 3:48 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 629
Location: Pewaukee, WI
Yeah, change the 6X5.

Personally I'd recommend removing it and making a solid state replacement by bridging the heater with a 10 Ohm 10W resistor and connecting two 1N4007 diodes in place of the tube diode sections. 6X5 tubes had a tendency to short and cause damage to the sets they were installed in so I usually convert to SS to avoid worry.


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Wed 27, 2017 4:47 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 669
Location: Crystal Bay, NV
The brightness of the picture tube will depend on the condition (emission) of the tube and the application of the correct voltages on the grids.
The high voltages cannot be measured without a special probe (allowing voltages over 4000v), However, a common technique to see if the HV is ok, takes only a screwdriver with an insulated handle. Holding the screwdriver by the plastic handle, touch the blade to the top of the 1B3 tube. You should be able to draw a blue arc of about a half inch. If the arc is less than that, the high voltage circuit may be to blame. This would be a good test to make before and then after the fade.

Hallicrafters used a very overworked 6C4 tube for the high voltage generation. I have not had any problem with the coil, but I see that others have. Look at the components around the 6C4 if the high voltage is insufficient. You may want to try a different 6C4 tube. Tube testers are not all that useful and substitution is always a better test.

Don't worry too much about a 10% resistor that now is 20% off. Most are not that critical. Really bad ones will be off by more than 20% (there may be exceptions to his rule).
======
Ron


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Thu 28, 2017 7:23 pm 
Member

Joined: Oct Thu 23, 2014 5:15 pm
Posts: 37
I managed to find a 10 ohm 10 watt cement wire wound power resistor and two in 4007 diodes. To convert to solid state I would solder the 10 ohm resistor across the tube socket between pins 2 and 7 and then solder the diodes between the cathode which is pin 8 and terminals 3 and 5 which are connected. Are the in 4007 diodes parallel or in series? Negative marking goes to cathode I assume.

Thanks!


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Thu 28, 2017 9:07 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 629
Location: Pewaukee, WI
Resistor between pins 2 and 7 is correct.
Assuming your set matches page 24 of the PDF below and pins 3 and 5 are factory hard wired together at the socket under-chassis, you can use a single 1N4007 in this particular TV chassis.
http://www.earlytelevision.org/pdf/hall ... er-tv1.pdf

In the original Halicrafters chassis design they wired the 2 plates (each plate is rated at 250mA) together to get more current (500mA or less) safely out of the tube.... a 1N4007 is rated for 1A of average current (double what the TV is going to draw through it) so a single 1n4007 should be more than sufficient.
1n4007 data sheet: http://www.mouser.com/ds/2/149/1N4007-888322.pdf BTW it is a 'One N 4007' not an 'in 4007'.
6X5 datasheet https://frank.pocnet.net/sheets/127/6/6X5.pdf

Cathode is the striped end. https://en.wikipedia.org/wiki/Diode#/me ... _en_fr.svg


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Thu 28, 2017 10:23 pm 
Member

Joined: Oct Thu 23, 2014 5:15 pm
Posts: 37
Thank you Electronic Memory!

I went ahead and wired the 10 ohm 10 watt resistor and the two 1N4007 diodes and tested the set on the dim bulb tester to be certain. All looks good. I used two 1N 4007 parallel with stripe towards cathode. My set is the same as the T 54 and have been using the same schematics provided in your link.

I really appreciate your help! Going to power up the set now and see what happens.


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Fri 29, 2017 4:28 pm 
Member

Joined: Oct Thu 23, 2014 5:15 pm
Posts: 37
I did the screwdriver test to the plate cap of the 1B3 and saw very little arcing, maybe 1/8th inch. The 1B3 is new, and the 6C4 looks fairly new. It's an RCA, logo and all lettering look new. The other 6C4 looks identical but there is no logo or any lettering visible on the tube, I could barely read the 6c4 on the glass. I switched the two 6C4's and saw no difference in the arcing. I went through the high voltage cage when replacing the capacitors. There are only a few resistors here and they were within specs. The high voltage coil is very delicate, I broke one of the wires at the top where it connects to a 5K6 resistor. I think my solder connection is good as i tested for continuity between the start of the winding and the finish where it connects to the two terminals. I get 21 ohms. Not looking forward to removing the coil and cleaning / baking the thing. Any suggestions are greatly appreciated.

Thanks!


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Fri 29, 2017 5:40 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 669
Location: Crystal Bay, NV
That sounds like a very weak arc on the 1B3. Maybe some other forum readers will comment on this. I would not suspect a bad coil. Have you replaced all the 6000v capacitors (six I believe)? Check the voltages on the 6C4, particularly the grid which should be quite negative: -30 to -40v.
=====
Ron


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Fri 29, 2017 8:06 pm 
Member
User avatar

Joined: Mar Sun 01, 2009 10:27 pm
Posts: 4206
Location: Ann Arbor, MI
Most TVs with larger screens have something like 12000 volts or greater on the CRT. This TV has 4000 volts. So the arc you will get will be quite a bit smaller than on other sets. So your high voltage, when the set is cold, may very well be OK.

_________________
Tom


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Fri 29, 2017 9:45 pm 
Member
User avatar

Joined: Feb Thu 17, 2011 11:27 pm
Posts: 10665
Location: Long Island, N.Y.
My repairman has worked on vintage TV's of all kinds since the '60's. He gave me the advice of a cooling fan in these early Hallicrafters and was not surprised at how well it worked for me when I tried it. Baking the coil is a tough job and does not always cure the issue to boot, but good luck with that. Heat is the culprit on these particular sets.


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Sat 30, 2017 3:56 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11845
Location: San Jose, CA USA
1/8" arc sounds about right for this set. So your High voltage is working reasonably well, at least at the time you measured it. Fade may cause it to droop quite a bit as the set warms up.

_________________
Tom K6VL


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Sat 30, 2017 7:36 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 669
Location: Crystal Bay, NV
Notice that there is an adjustment (trimmer cap) on the HV. It may make a difference that you can see on the CRT itself.
Still think that an 1/8" arc seems pretty anemic for 5000v.
=====
Ron


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Sat 30, 2017 9:04 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 669
Location: Crystal Bay, NV
You can make a simple high voltage probe for only a couple dollars. Here's what you need: A voltmeter (VTVM or FET with an input impedance of 10 Megs or more), ten resistors of 10 Megs each and one resistor of 100k, and a piece of tubing to put the resistors in, and small nail for the probe. 1/2 watt resistors are fine, but don't use tiny resistors. Hook all the resistors in series with the probe connection at one and a ground clip at the end of the 100K resistor. Hook a tap wire on the ungrounded end of the 100K resistor: The tap connects to the voltmeter. If you use a 5v scale on the voltmeter, this is multiplied by 1000 and reads up to 5000v. The current draw will be about 50 micro amps at 5000v, which is about the load of the CRT with average brightness. Turn the brightness all the way down to get an accurate reading (don't want the crt load to be added to the probe load. Be sure to have the ground clip connected to protect your voltmeter.

If this is for a one time project, you can dispense with the probe and just hook the resistors up temporarily to the set. Should cost between 2 and 5 dollars total.
====
Ron


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Sep Sat 30, 2017 9:54 pm 
Member

Joined: Oct Thu 23, 2014 5:15 pm
Posts: 37
Thanks Ron, Tom and others,

My set is not exactly like the one here: http://www.earlytelevision.org/pdf/Hall ... s_91-6.pdf. Looks the same but there are a few differences

One odd thing is that I do not get anything on the screen with the brightness turned down. It's fairly bright turned all the way up, but as I turn the control down the top of the screen goes dark with a sharp horizontal line that moves down as I turn the control down. Before I even turn the control 1/3rd of the way down the screen is completely dark. I did try running the set with a fan blowing into the high voltage cage with the top off, brightness turned up all the way and no fade after 15-20 minutes. Contrast seems to work okay, that can be turned all the way down and softens things.

When turning the set on it takes a few minutes before I see anything on the screen and it starts to glow dimly at the very bottom of the screen then a bright line appears at the bottom and gradually moves towards the top. There is a very rapid flickering and horizontal lines but no snow. I'll try to post a few pictures. No signal running into the set yet. There is one 680 pf. cap that goes from pin 1 of the horizontal amp to pin 5 of the horizontal oscillator that I have not replaced. Could this be my problem?


Top
 Profile  
 
 Post subject: Re: Hallicrafters model 505
PostPosted: Oct Sun 01, 2017 12:48 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 11845
Location: San Jose, CA USA
A few possibilities here: These sets sometimes do not like having the brightness turned all the way up. That can cause the high voltage to collapse and the raster blooms. What you may be seeing is the raster becoming smaller as you turn down the brightness. Try adjusting the width and vertical size controls to see if they affect what you are seeing. Also the vertical and horizontal centering. In general, try playing with the centering, size, and focus controls along with the brightness. You should see a nice sharp raster (with individual scan lines visible) if you don't have the brightness to high and you have good focus. You should have a nice rectangular raster that does not reach the edges of the round tube face.

It would not be unusual for there to be nothing on the screen with the brightness all the way down.

And finally, these sets may not have enough gain to really show good "snow" when there is nothing connected to the antenna input.

_________________
Tom K6VL


Top
 Profile  
 
Post New Topic Post Reply  [ 55 posts ]  Moderators: 7jp4-guy, Mr. Detrola Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 11 guests



Search for:
Jump to:  


















Privacy Policy :: Powered by phpBB