37-61 Issues - Printable Version
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RE: 37-61 Issues - Tgace459 - 05-18-2016
Well. Im thinking its either the 6f6g tube or the pins....I wigggled the tube from the top and it came back on but as I tried to adjust the tuner (specifically when I went all the way over to the low end of the dial) "pop" it died again.
Interesting enough the 3 pin is the one I had to soldier a couple of wires too and the solder job isn't spectacular. Maybe a cold joint?
RE: 37-61 Issues - morzh - 05-18-2016
Could be.
But like we said before, bad tube/bad contact (dirty socket, bad soldering, loose tube's pins). Just inspect, clean, resolder. And test the 6F6 just in case. I do not like untested tubes.
RE: 37-61 Issues - Tgace459 - 05-18-2016
Thanks! I feel better knowing that I'm closing in on a solution and that this radio CAN work.
RE: 37-61 Issues - Radioroslyn - 05-18-2016
I'm with Mike the plate volt is WAY HIGH at 400 something volts. The 6F6 should load the hv line some but it seem the that isn't happening... Acts like the tube heater (the part that lights up) is burned out. Max plate voltage for the 6K7 isn't anywhere near 430v more like 300v. Make sure pin 8 of the 6F6 is grounded and you should see some -voltage on pin 5 of the 6F6 too. About -10 to -15v.
Terry
RE: 37-61 Issues - Tgace459 - 05-18-2016
(05-18-2016, 03:16 PM)Radioroslyn Wrote: I'm with Mike the plate volt is WAY HIGH at 400 something volts. The 6F6 should load the hv line some but it seem the that isn't happening... Acts like the tube heater (the part that lights up) is burned out. Max plate voltage for the 6K7 isn't anywhere near 430v more like 300v. Make sure pin 8 of the 6F6 is grounded and you should see some -voltage on pin 5 of the 6F6 too. About -10 to -15v.
Terry
The tube does light up. Could a loose pin connector explain the wonky voltages?
RE: 37-61 Issues - morzh - 05-18-2016
Yes. We've been pointing to that for awhile. Why don't you:
1. Clean the socket.
2. Make sure the Cathode pin IS grounded reliably.
3. Can you check the tube?
The likely culprit is the Cathode pin. It can explain high voltage at the plate and SG pins. As well as intermittent operation.
When the radio is powered and the tube is in, take a thin awl-like instrument (insulated handle and a thick sturdy needle) and try to move the Cathode pin or establish contact between it and the socket.
If does not help, do the same for other pins.
Be careful, 400VDC is not a pleasant thing to be zapped with though as Edison/Brown proved, safer than the equal value AC.
RE: 37-61 Issues - Radioroslyn - 05-18-2016
As Nipsey Russell use to say "Oh Ya"!
Terry
RE: 37-61 Issues - Tgace459 - 05-18-2016
10-4 when I get back home I'll get on it. I have a co-worker with a stockpile of tubes and a tester. She will probably just swap me one for one and give me a tested 6f6g.
RE: 37-61 Issues - Radioroslyn - 05-18-2016
In a pinch you can use a 6V6, 6L6, or 5881 to test it out. The 6L6 and 5881 do draw more heater and plate current.
Terry
RE: 37-61 Issues - Tgace459 - 05-18-2016
Well. I cleaned and resolidered and pushed and prodded and I can get it working for 20-45 seconds and then "pop" it goes out.
Interestingly... I cant get it to play again unless I shut the radio off for a few minutes. Its almost as if the tube goes out after it hits a certain temperature. Once I get it playing and it goes out I can't get it going again without turning the radio off then on again.
The ground on the cathode looks solid...wires are intact and firmly solidered.
RE: 37-61 Issues - morzh - 05-18-2016
Change it.
RE: 37-61 Issues - Steve Davis - 05-18-2016
Try re-soldering the tube pins
Steve
RE: 37-61 Issues - Tgace459 - 05-19-2016
Im considering a full socket replacement when I get my new tube. Correct me if I'm wrong but it looks like I'm going to have to drill out the rivets on the existing socket and use bolts on the replacement?
RE: 37-61 Issues - Radioroslyn - 05-19-2016
Yup that's how it's done. There are several types of sockets. Original is a wafer socket, cheap and not all that great. Molded socket are better. And there are ceramic sockets electrically have better insulating properties and are used in high frequency applications. Also some have slightly different spacing between the mounting holes, all pretty much use a 1 1/8" in the center. Wafer or molded are good choices for the replacement on your set.
Terry
RE: 37-61 Issues - morzh - 05-19-2016
Before you resort to the drastic measures
If the new tube works fine, there is no need to disturb the socket unless in your current effort to clean it and make it connect you mangled it.
I am yet to encounter a problem with these. (Loctal ones are a different matter altogether).