Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
Apparently in run 4, the 7J7 was replaced with a 6J8. I can find the pinouts on the 7J7, but I can't find anything on the 6J8. Does anyone have not only the pinouts of the 6J8, but how it should be wired? I'm replacing resistors around that tube, and R29 keeps heating up. Don't know if the radio ever worked or not. Caps have all been replaced. There is also a 150ohm resistor added to the plates of that tube, but I'm not sure where as I don't know the pinouts. Can someone help me out?
Posts: 7,260
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
http://www.radiomuseum.org/tubes/tube_6j8.html
Check voltage on triode plate (29) nom 150vdc if low check for shorts and #29.
Terry
Posts: 1,824
Threads: 114
Joined: Jul 2014
City: Sneedville, TN
Here is data on the 6J8 http://www.radiomuseum.org/tubes/tube_6j8g.html . And here is the 7J7 http://www.radiomuseum.org/tubes/tube_7j7.html . They are electronically the same tube, but based differently, and the 6J8 uses a cap.. Hope it is of help
(This post was last modified: 05-30-2015, 06:56 PM by mikethedruid.
Edit Reason: added 7J7 link
)
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(05-30-2015, 06:48 PM)Radioroslyn Wrote: http://www.radiomuseum.org/tubes/tube_6j8.html
Check voltage on triode plate (29) nom 150vdc if low check for shorts and #29.
Terry
That was one of the first things I did, and I noticed the voltage was about 90+. But how would low voltage make the resistor heat up?
Pat
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(05-30-2015, 06:50 PM)mikethedruid Wrote: Here is data on the 6J8 http://www.radiomuseum.org/tubes/tube_6j8g.html . And here is the 7J7 http://www.radiomuseum.org/tubes/tube_7j7.html . They are electronically the same tube, but based differently, and the 6J8 uses a cap.. Hope it is of help
Thanks Mike,
That's what I needed. It's a start.
Pat
Posts: 7,260
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Hmmmm... Seems like you got 60v missing. Pull the tube and see if it going up to 150v if so may have a bad tube or something is causing it to haul down a lot of current (incorrect voltages on the grid or cathode).
Terry
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(05-30-2015, 07:29 PM)Patrick Wrote: (05-30-2015, 06:48 PM)Radioroslyn Wrote: http://www.radiomuseum.org/tubes/tube_6j8.html
Check voltage on triode plate (29) nom 150vdc if low check for shorts and #29.
Terry
That was one of the first things I did, and I noticed the voltage was about 90+. But how would low voltage make the resistor heat up?
Pat Whoops. Engaged mouth (or fingers) before brain. Forgot my basics.
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(05-31-2015, 06:32 AM)Radioroslyn Wrote: Hmmmm... Seems like you got 60v missing. Pull the tube and see if it going up to 150v if so may have a bad tube or something is causing it to haul down a lot of current (incorrect voltages on the grid or cathode).
Terry
I think that my biggest problem is that it's been almost 50 years since I've done basic electronics work. I had forgotton who Kirchhoff was, amongst others. Time to get the old textbook out.
Posts: 7,260
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Don't forget MURPHY too. I don't think he's in the book.
Terry
Posts: 347
Threads: 34
Joined: May 2007
City: Raleigh, NC
I recently finished a 40-190 with the same 7J7 to 6J8 change. The schematic shows only the 7J7, but in mine, the wiring and components to the 6J8 were the same as the shown on the schematic, taking into account the connection to the 6J8 grid cap wire instead of a grid pin on the base.
John Honeycutt
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(05-31-2015, 03:13 PM)Raleigh Wrote: I recently finished a 40-190 with the same 7J7 to 6J8 change. The schematic shows only the 7J7, but in mine, the wiring and components to the 6J8 were the same as the shown on the schematic, taking into account the connection to the 6J8 grid cap wire instead of a grid pin on the base. Mine has a 150 ohm resistor from pin 6 of the 6J8 to ground. Maybe that's why the 4.7K (R29) is getting hot. Even with the 6J8 pulled, I get 140V before R29, and less than 5V after it (right on the tube socket pin).
Posts: 7,260
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Disconnect the wire from the socket (where the 4.7k is attached)and see if the voltage goes up. If so your socket has a internal short. If not check for shorted rubber wire going to the pushbuttons.
Terry
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(06-07-2015, 07:47 AM)Radioroslyn Wrote: Disconnect the wire from the socket (where the 4.7k is attached)and see if the voltage goes up. If so your socket has a internal short. If not check for shorted rubber wire going to the pushbuttons.
Terry
Thanks Terry,
I hadn't even considered a shorted socket. I did find a pic online of the 150 ohm resistor on the chassis. It is attached to an inuslated standoff screwed to the pushbuttons. I've circles it in red.
But I cannot find it on the schematic. The schematic show only two 150 ohm resistors, #34 and #60, which I can account for.
Pat
Posts: 7,260
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
After taking a second look I think I would unground that resistor. Circuit wise it doesn't make a lot of sense cause it will pull the plate voltage on the osc section of the mixer way down. Tube manual sez the triode section can take up to 250vdc which less than the chassis is providing. Is your 4.7K resistor in spec?
Terry
(This post was last modified: 06-07-2015, 09:11 AM by Radioroslyn.)
Posts: 365
Threads: 76
Joined: Oct 2014
City: Winter Haven, FL
(06-07-2015, 09:11 AM)Radioroslyn Wrote: After taking a second look I think I would unground that resistor. Circuit wise it doesn't make a lot of sense cause it will pull the plate voltage on the osc section of the mixer way down. Tube manual sez the triode section can take up to 250vdc which less than the chassis is providing. Is your 4.7K resistor in spec?
Terry Yes. I'm going to keep this radio, So I've replaced all of the resistors, and checked the new ones as I install them. I'll go eliminate the possibility of a shorted socket first, then go from there with your second suggestion. But only after another cup of coffee. It's almost 8 A.M. here.
Tanks,
Pat
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Philco 39-116 radio and remote
|
Hi Brad,
Thanks so much for the info! Do you happen to have the specs for the PT-86 transformer? I did not find a lis...RichG — 04:32 PM |
Philco 269 - 444 FIVE VALVE VERSION?
|
Thanks Arran;
If your set has five tubes/valves then it could be an A537, V537, or a U527, then again it looks like s...ChasL0001 — 11:07 AM |
Philco 29 or 45
|
29 chassis has a shadow meter while 45 chassis does not. Shadow meter is part no. 27 in the 29 schematic. compare it t...klondike98 — 10:32 AM |
Philco 269 - 444 FIVE VALVE VERSION?
|
Sorry, Chas.
Re the burns, I broke my first TV at the age of 3. Between my electrical experiments :yikes: (My mom wa...MrFixr55 — 09:07 AM |
Philco 41-221 Restored
|
Thanks for the compliment Richard. The tenite grille is original. A few of the horizontal slats were slightly warped so ...RodB — 08:44 AM |
Philco 29 or 45
|
Hello, I have just received a Philco lowboy where the tube layout label in the cabinet says 29 or 45. There is no label ...dconant — 08:29 AM |
Philco 41-221 Restored
|
Mr fixr,
That is great news I would love to see repo grille !!
I too have a very similar Philco but my cabinet has fab...radiorich — 08:22 AM |
Philco 41-221 Restored
|
Hi Rod,
I always tell people that my scars give me character. :wink: Great job on the radio. Is the grille origi...MrFixr55 — 08:00 AM |
Philco 269 - 444 FIVE VALVE VERSION?
|
It looks like the PENDD61 valve/tube must have failed, so someone replaced it with the EBC33, which is a double diode-tr...Arran — 04:29 AM |
Philco 269 - 444 FIVE VALVE VERSION?
|
Hello Chas. Radiomuseum has information on both sets.
Thanks Gary, lots of good info there.
Perhaps we'll ha...ChasL0001 — 02:23 AM |
Who's Online
|
There are currently no members online. |
|
|