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Discussion in 'Amp Tech Center' started by Achysklic, Oct 18, 2020.
The three pins together are pins 1,2,8.
Place your probes on the outside two of those three pins.
Good all green lights on pin 2 and 8
Looking like maybe a bad tube.
You have 5VAC heater voltage from the PT. The heater filament seems to be intact in the tube yet the tube does not rectify the AC voltage to DC voltage.
I order a new tube . Would the tube be bad even if the test good all green on conduct?
Ok not wanting another JJ tube after this wants a good rec tube to get
The tube is essentially two diodes. It needs the 5VAC heater to function. It appears the heater is intact and provided with voltage. It is not rectifying though.
I would find a 5y3 on ebay. either NOS or used. If you do not want to go that route I would probably buy another JJ unless a tube vender has a vintage tube at low enough cost.
Thanks for the help I appreciate it I’ll go on eBay and search for a NOS tube
I usually get the used ones at a much lower cost. Pretty much they work or they don't. They have a very long lifespan.
In the meantime...
I would suggest a couple of things to protect the rectifier and to help insure a quiet amp.
I would disconnect the HT and heater center taps and connect them as illustrated.
The HT CT (red/yellow stripe) creates less buzz when attached to the first filter cap negative terminal. (I have it shown connecting to the bias resistor/cap. If the wire is long enough try to get it to the filter cap.)
The heater CT makes for quieter hum when it is elevated. It is easy to elevate on a (5E3) cathode biased amp because of the approximately 20V bias voltage. (Elevated just means instead of using the 0 volt ground it is *grounded/elevated* to a higher voltage.) Simply connect the green/yellow CT to the junction of 6V6 pin8 and the bias resistor/cap.
The bias resistor (orange arrow) gets very hot. Move it toward the edge of the board so it will not heat the bias capacitor.
The red arrows pointing to the rectifier socket. Have a look at Rob Robinette's 5E3 mods site. There is a section - Rectifier 'Backup' Diodes. These diodes will help protect the rectifier tube. The tube doesn't have to work as hard = longer lasting tube.
Also in the 5E3 mods site there is *how to build a light bulb limiter*.
While your in there....
Good job *Eagle Eye* @D'tar .
I didn't catch those resistors in the wrong positions. That'll save some troubleshooting down the line!
I ordered new diodes and rec tube. This morning I wanted to get it one more shot I put the rec tube back in and turned it on this time the rec started to glow cherry red and got very hot I hurried up and turned it off.
No idea what would have caused that!
It’s like that tube ran away.
JJ5y3s are pretty robust and not too far off voltage drop like some others. You just got a dud. I wouldnt hesitate to get another. NOS or anos 5y3gt will serve you well and they are not super $$$.
it's hard to see on the pics ... but is V1 p3 bridged to v1 p8?
No it isnt,
But it is now...thank you I never notice the bridge on my diagram till you mentioned it.
I took the Rec tube back out it’s definitely blown now you can hear it rattle when you shake it.
Got a question, going back over wiring double checking. My OT is a classic tone 40-18022. On one side a blue, black , red wire on the other side a green and yellow wire all the diagrams I can find don’t show this color code is the black wire the same as the brown on robs diagram? And the yellow the same as the black?
With black going to v4 pin 3 and blue to v3 pin 3.
And green going to six jack and yellow to speaker jack?
Green to 6v6 plate
Red center tap to B+
Yellow to 6v6 plate
Black to output jack ground
Blue to output jack tip
I had that happen once when I didn't have the tang on the tube spigot in the slot on the socket base. I'd got the tube in wrong as it was a sloppy fit.