Airline 62-9015-A

[angelodp]

Its an odd reading. It begins and 200K and slowly climbs to 311k right now and still slowly climbing? Ok leveled off at 311k I have been tacking in replacement resistors and caps for now... I suppose that is not ideal given the age of these original solder joints.

BTW this is the cap I used when all hell broke loose?

[sluckey]

Its an odd reading. It begins and 200K and slowly climbs to 311k right now and still slowly climbing? Ok leveled off at 311k

That's fine. Put the nonpolarized .5µF cap back in and leave it alone. Remove the lamp limiter. It has served it's purpose. Turn the amp on and measure the ***VOLTAGE*** ot pin 6. Compare to the schematic. What have you?

[sluckey]

BTW this is the cap I used when all hell broke loose?

That cap did not cause hell to break loose. Maybe you accidentally did something else while installing the cap.

[angelodp]

So pull the limiter, replace cap, and place all tubes in or just the rectifier?

A

[angelodp]

With just the rectifier I see 190v. I expected higher than the 90v on schematic, but is this way too high?

With Tubes 80v at 6 and 350v on tube plates, but its a sputtery mess. I did get the trem oscillating big time, but when it plays the volume controls do not make any difference. I cannot bring it down and it seems to be just running away... so i shut it down.

[sluckey]

Another thought. Is this the first time you have had the amp connected to the wall outlet without the light bulb limiter? If so, maybe the full B+ voltages have revealed a problem that was there all the while.

[Stevem]

It's very much time to troubleshoot this amp circuit by circuit.

Lets confirm that the output stage is ok.

Disconnect r30 from the filter node ( c27 ) then disconnect the wire from that same point that goes to r44.
When you fire up the amp without the lifter is all ok, if so then repower the Trem section.

[angelodp]

Gentlemen - Occim's razor. In a moment of frustration, I rebuilt the trem tube area, as it was very iffy as i had tacked in elements. Still a stumble scratchy mess, that only came up as I switched the standby off??

I decided to retrace my steps. I pulled the reverb tank back out and examined the area. I has inadvertently severed a shield ground from the verb/trem switch..... could that be it?? I doubted it. Then I took a closer look at the ground cable from one side of the verb tank, that I had soldered in (it was not connected when I got the amp),,,, wham there it was, the ground was leaning into the signal side and I had touched that with some solder. I unstuck that short and woohoo.... she's up and running ... Verb working... that Danelector swampy thing..... Trem working - I love it. Overall this amp is now a working unit. I am going to refurbish the cab and still need to check bias levels etc. I mean its sounding pretty good!!

Thanks for hangin with me and encouraging me on.

[Stevem]

It’s a hard lesson to keep in mind even when your doing a repair on a amp you have done 200 times before, that being only do one thing / mod at a time and triple check your work before moving on!

Away good to hear it’s up and running and that you stuck with figuring it out!

[angelodp]

Yes a good lesson. I also discovered that the one of the tube lugs on the 6AU6 was crumbling and so I replaced the socket. The standby on this amp is odd. With the standby switch closed the amp does not conduct and open is conducting. Can I do away with this standby? I read that many here do not believe that a standby is a useful item.

Question: The amp came with a cap strapped across the power cathode resistor. The schematic does not call for this cap. It had a 50/50 cap on there. I suppose I can experiment with different values and listen.

The amp does not have screen resistors - would you recommend installing them? 470ohm and also install 1.5k grid stoppers?

Also how much DC leakage is acceptable

C3- .06dcv
C2- .39dcv
C15- .20dcv
C16 - .08dcv

[Stevem]

A standby switch like that does not add to tube life, but one wired in the normal way does!
In particular it slow’s down mechanical brake down issues especially in output tubes.

[angelodp]

I see that this version has implemented a Master Volume in place of the standby switch. Hmmm.....

[angelodp]

Tried the Master set up, did not like it at all and pulled it back out.

I am wondering if it will work to install 1K Screen Grid resistors directly on both Pin 4 of the 6L6's? There are a lot of components hanging on those pins.

[sluckey]

I wouldn't bother. Since those tubes are running at such low voltages the benefit (if any) would be small. And it's so crowded around one of those tubes that you run the risk of unleashing the devil again.

You can put lipstick on a pig but it's still a pig.

[angelodp]

Copy that

Thanks