Firestone 13G3 Television - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

rogerdup · 17th Jun 2018, 5:35 pm

Hi David,
Sorry for the delay responding. Was not at home this WE.
I use an RCA RF generator and a 625 lines broadcast decoder to feed the Firestone TV antenna. The vertical stability is good.
The sawtooth was observed on an oscilloscope. I am thinking of increasing a little the 0,1 mf capacitor decoupling the 1st 12SN7 anode to the ground, and also perhaps to act on the 27meg resistor. I have no time right now to do that, but this week.
The image on the crt is spread on the upper part. potatoes like.
Roger

rogerdup · 21st Jun 2018, 4:21 pm

I am in the process of replacing all the 7 pins sockets of the three IF stages and video and sep. with ceramic quality ones. The originals are very poor quality: false contacts and bad grounding. This set appear to have been an economic model.

FERNSEH · 21st Jun 2018, 8:50 pm

To improve performance of the frame timebase on 50Hz TV systems the ramp forming capacitor C63 could be changed from 0.05mfd to a slightly higher value, say 0.056mfd or .06mfd. There will be a slight reduction in the amplitude of the waveform.

DFWB.

rogerdup · 22nd Jun 2018, 1:54 am

Hi David,
On the Firestone 13-G-3 schematic, this capacitor is 0,1mfd. So I would have to try to 0,15mfd.
The schematic extract you are refering to is for the TV149 I think. The time bases of the 149 are very different from the Firestone.

usradcoll1 · 23rd Jun 2018, 5:10 pm

Quote:

Originally Posted by rogerdup

I am in the process of replacing all the 7 pins sockets of the three IF stages and video and sep. with ceramic quality ones. The originals are very poor quality: false contacts and bad grounding. This set appear to have been an economic model.

Tele-tone, the builder of the set was only in business for a few years to compete with the larger firms on the lower end of the product lines, mostly building private label sets such as yours.

rogerdup · 24th Jun 2018, 12:12 pm

Thanks for the info. I replaced all the 7 pins sockets and put new 6au6 along all the IF chain. I have to re-align because the image is very dark as if too much contrast. The brightness at the max. All voltages are corrects.
Lot of stuff remain..

rogerdup · 28th Jun 2018, 4:41 pm

hello friends,
Hereafter some photos of the full restoration I achieved on the Firestone 13G3. I completely re-cabled the IF stages, detector, video and sync sep. changing the original sockets for ceramic ones. Almost all resistors and capacitors have been replaced in those stages. Did the same for the time basis. All tubes have been replaced by new ones, only left in place the 7JP4 crt. Changing also the antenna cable.
I hope to receive in short the three 270pf capacitors link inter-stages IF.
A realignment has been necessary, but still need a fine tuning after the link capacitor replacement.
On the photo the three big Tesla can capacitors 2x100mfd/450v.
The bad news: up to now, NOT found the knobs for this set ..

Roger

FERNSEH · 28th Jun 2018, 5:18 pm

Hi Roger,
After replacing those cheap to make SRBP valveholders with good quality replacements you will experience a dramatic improvement in performance in terms of stage gain and ease of alignment.

I have here a GEC BT5144 TV which was made 1949/50. Force feed it with the powerful signal from the Aurora and the set will display a well contrasted picture. Perhaps replacing those poor quality valveholders with better ones might well improve the gain of the RF amplifier stages.

DFWB.

rogerdup · 28th Jun 2018, 6:27 pm

Hi David,
Glad to hear from you!
Yes, I experienced very good result picture quality wise after replacing the tubes sockets, and I completely eliminate grounding problem inter-stages .
The images are so good now, that motivates me to replace also the link capacitors to have the set functioning as new.
I will put picture shots when all is in place.

rogerdup · 22nd Jul 2018, 9:13 am

Hello gentlemen,
I successfully restored my Firestone 13G3 Tv and hopefully get very nice pictures. The only thing that bother me is some white lines on the picture and I don't remenber what is the cause and how to eliminate them. Somebody can help?
Thanks,
Roger

Nuvistor · 22nd Jul 2018, 9:25 am

They are probably flyback lines, I.e, when the frame scan returns from bottom to the top of the screen.
Having to turn the brightness up due to a weak CRT or video signal can cause it. There others but TV’s started to include flyback suppression circuits to blank of the CRT during the frame flyback period.
A simple circuit can be added if there is not one already installed, if one is then check the components.
A photo would confirm if it is this problem.

rogerdup · 22nd Jul 2018, 12:35 pm

Hi Frank,
This is effectively what I supposed concerning the flyback spot. The Firestone has been a relatively cheap set and looking at the schematic, I don't see any flyback spot supression circuit. On the other hand, the Very High Voltage is obtained based on an 12SN7 oscillator.
The good point: the 7JP4 crt seems to be in good condition offering nice contrast. Not so bad for an electrostatic type of tube. I will try a screen shot to show the default.

FERNSEH · 22nd Jul 2018, 12:51 pm

Hi Roger,
is the signal from the final video amplifier supplied to the CRT modulating electrode via a capacitor? If it is then the addition of a DC restorer will solve your problem. We know that AC coupling of a video signal results in the loss of the DC component thus causing the the black level reference to move up and down according to picture content.

Refer to page three in the topic about DC restoration and modifications to an Ultra TV set that didn't have this circuit refinement: https://www.vintage-radio.net/forum/...d.php?t=145083

DFWB.

rogerdup · 22nd Jul 2018, 3:02 pm

Hi David,
Yes there is a 0.25mf capacitor from to the video anode to the CRT cathode. I will go to the thread you refer to..
Thanks,
Roger

FERNSEH · 22nd Jul 2018, 3:19 pm

Hi Roger,
check out Augus25's essays about the addition of DC restoration to his electrostatic deflection TV set. He employed a 6AL5 tube to clamp the positive going sync tip to the reference level.

Refer to page 4 post No. 64.

DFWB.

rogerdup · 22nd Jul 2018, 3:24 pm

David,
I get lost among all those messages refering to the DC restorer question.
I have to deal with the Firestone 13G3 schematic, and find difficult to add a 6AL5 tube in the voltage heater Stream. I would prefer to use a diode. Do you have the schematic of the Firestone at hand?
Thanks
Roger

FERNSEH · 22nd Jul 2018, 3:39 pm

Hi Roger,

I have no schematic for the Firestone but I'd imagine the method of coupling the video signal from the anode of the video amplifier tube to the CRT modulating electrode will be through a capacitor. Certainly it will not be a direct connection. It's almost certain to be the CRT cathode that receives the video signal, although it is not unknown to use the grid (wehnelt). If that's the case the video waveform will be positive going.
Edit: Hi Roger, if you can post up or send me a copy of the video and CRT circuits I can then study it and make a suggestion where to fit the DC restorer.

A silicon diode will be OK.

DFWB.

rogerdup · 22nd Jul 2018, 3:44 pm

Wait.. I will pass a piece of the Firestone schematic..

rogerdup · 22nd Jul 2018, 4:14 pm

Hi David here is the part of the Firestone schematic. Where do I put the diode?

FERNSEH · 22nd Jul 2018, 5:25 pm

I've introduced a DC restorer diode between the brightness control and the right side plate of C43. The series resistor R42 can be bypassed. An additional resistor having a value of 1Mohms is connected across the diode, it's an essential component for the correct operation of the sync pulse clamp circuit.
Compare my suggested modification with the Argus25 circuit.

Look forward to your comments.

DFWB.

17th Jun 2018, 5:35 pm	#41
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television Hi David, Sorry for the delay responding. Was not at home this WE. I use an RCA RF generator and a 625 lines broadcast decoder to feed the Firestone TV antenna. The vertical stability is good. The sawtooth was observed on an oscilloscope. I am thinking of increasing a little the 0,1 mf capacitor decoupling the 1st 12SN7 anode to the ground, and also perhaps to act on the 27meg resistor. I have no time right now to do that, but this week. The image on the crt is spread on the upper part. potatoes like. Roger

21st Jun 2018, 4:21 pm	#42
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television I am in the process of replacing all the 7 pins sockets of the three IF stages and video and sep. with ceramic quality ones. The originals are very poor quality: false contacts and bad grounding. This set appear to have been an economic model.

21st Jun 2018, 8:50 pm	#43
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Firestone 13G3 Television To improve performance of the frame timebase on 50Hz TV systems the ramp forming capacitor C63 could be changed from 0.05mfd to a slightly higher value, say 0.056mfd or .06mfd. There will be a slight reduction in the amplitude of the waveform. DFWB. Attached Thumbnails

22nd Jun 2018, 1:54 am	#44
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television Hi David, On the Firestone 13-G-3 schematic, this capacitor is 0,1mfd. So I would have to try to 0,15mfd. The schematic extract you are refering to is for the TV149 I think. The time bases of the 149 are very different from the Firestone. Last edited by rogerdup; 22nd Jun 2018 at 2:02 am.

24th Jun 2018, 12:12 pm	#46
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television Thanks for the info. I replaced all the 7 pins sockets and put new 6au6 along all the IF chain. I have to re-align because the image is very dark as if too much contrast. The brightness at the max. All voltages are corrects. Lot of stuff remain..

28th Jun 2018, 4:41 pm	#47
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television hello friends, Hereafter some photos of the full restoration I achieved on the Firestone 13G3. I completely re-cabled the IF stages, detector, video and sync sep. changing the original sockets for ceramic ones. Almost all resistors and capacitors have been replaced in those stages. Did the same for the time basis. All tubes have been replaced by new ones, only left in place the 7JP4 crt. Changing also the antenna cable. I hope to receive in short the three 270pf capacitors link inter-stages IF. A realignment has been necessary, but still need a fine tuning after the link capacitor replacement. On the photo the three big Tesla can capacitors 2x100mfd/450v. The bad news: up to now, NOT found the knobs for this set .. Roger Attached Thumbnails

28th Jun 2018, 5:18 pm	#48
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Firestone 13G3 Television Hi Roger, After replacing those cheap to make SRBP valveholders with good quality replacements you will experience a dramatic improvement in performance in terms of stage gain and ease of alignment. I have here a GEC BT5144 TV which was made 1949/50. Force feed it with the powerful signal from the Aurora and the set will display a well contrasted picture. Perhaps replacing those poor quality valveholders with better ones might well improve the gain of the RF amplifier stages. DFWB.

28th Jun 2018, 6:27 pm	#49
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: Firestone 13G3 Television Hi David, Glad to hear from you! Yes, I experienced very good result picture quality wise after replacing the tubes sockets, and I completely eliminate grounding problem inter-stages . The images are so good now, that motivates me to replace also the link capacitors to have the set functioning as new. I will put picture shots when all is in place.

22nd Jul 2018, 9:13 am	#50
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	white horizontal lines Firestone tv Hello gentlemen, I successfully restored my Firestone 13G3 Tv and hopefully get very nice pictures. The only thing that bother me is some white lines on the picture and I don't remenber what is the cause and how to eliminate them. Somebody can help? Thanks, Roger

22nd Jul 2018, 9:25 am	#51
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: white horizontal lines Firestone tv They are probably flyback lines, I.e, when the frame scan returns from bottom to the top of the screen. Having to turn the brightness up due to a weak CRT or video signal can cause it. There others but TV’s started to include flyback suppression circuits to blank of the CRT during the frame flyback period. A simple circuit can be added if there is not one already installed, if one is then check the components. A photo would confirm if it is this problem. __________________ Frank

22nd Jul 2018, 12:35 pm	#52
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: white horizontal lines Firestone tv Hi Frank, This is effectively what I supposed concerning the flyback spot. The Firestone has been a relatively cheap set and looking at the schematic, I don't see any flyback spot supression circuit. On the other hand, the Very High Voltage is obtained based on an 12SN7 oscillator. The good point: the 7JP4 crt seems to be in good condition offering nice contrast. Not so bad for an electrostatic type of tube. I will try a screen shot to show the default.

22nd Jul 2018, 12:51 pm	#53
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: white horizontal lines Firestone tv Hi Roger, is the signal from the final video amplifier supplied to the CRT modulating electrode via a capacitor? If it is then the addition of a DC restorer will solve your problem. We know that AC coupling of a video signal results in the loss of the DC component thus causing the the black level reference to move up and down according to picture content. Refer to page three in the topic about DC restoration and modifications to an Ultra TV set that didn't have this circuit refinement: https://www.vintage-radio.net/forum/...d.php?t=145083 DFWB.

22nd Jul 2018, 3:02 pm	#54
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: white horizontal lines Firestone tv Hi David, Yes there is a 0.25mf capacitor from to the video anode to the CRT cathode. I will go to the thread you refer to.. Thanks, Roger

22nd Jul 2018, 3:19 pm	#55
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: white horizontal lines Firestone tv Hi Roger, check out Augus25's essays about the addition of DC restoration to his electrostatic deflection TV set. He employed a 6AL5 tube to clamp the positive going sync tip to the reference level. Refer to page 4 post No. 64. DFWB.

22nd Jul 2018, 3:24 pm	#56
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: white horizontal lines Firestone tv David, I get lost among all those messages refering to the DC restorer question. I have to deal with the Firestone 13G3 schematic, and find difficult to add a 6AL5 tube in the voltage heater Stream. I would prefer to use a diode. Do you have the schematic of the Firestone at hand? Thanks Roger

22nd Jul 2018, 3:39 pm	#57
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: white horizontal lines Firestone tv Hi Roger, I have no schematic for the Firestone but I'd imagine the method of coupling the video signal from the anode of the video amplifier tube to the CRT modulating electrode will be through a capacitor. Certainly it will not be a direct connection. It's almost certain to be the CRT cathode that receives the video signal, although it is not unknown to use the grid (wehnelt). If that's the case the video waveform will be positive going. Edit: Hi Roger, if you can post up or send me a copy of the video and CRT circuits I can then study it and make a suggestion where to fit the DC restorer. A silicon diode will be OK. DFWB. Last edited by FERNSEH; 22nd Jul 2018 at 3:54 pm.

22nd Jul 2018, 3:44 pm	#58
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: white horizontal lines Firestone tv Wait.. I will pass a piece of the Firestone schematic..

22nd Jul 2018, 4:14 pm	#59
rogerdup Retired Dormant Member Join Date: Jan 2018 Location: Chamalières, France. Posts: 167	Re: white horizontal lines Firestone tv Hi David here is the part of the Firestone schematic. Where do I put the diode? Attached Thumbnails

22nd Jul 2018, 5:25 pm	#60
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: white horizontal lines Firestone tv I've introduced a DC restorer diode between the brightness control and the right side plate of C43. The series resistor R42 can be bypassed. An additional resistor having a value of 1Mohms is connected across the diode, it's an essential component for the correct operation of the sync pulse clamp circuit. Compare my suggested modification with the Argus25 circuit. Look forward to your comments. DFWB. Attached Thumbnails