Just picked up an early grey labeled, Phase inverter tube, 2x12 HD130 combo.......sounded amazing. All original....had a non name PI tube, TAD EL-34b power tubes. Played great at the used music store.....got it home.....sounded awesome for a one hour session! Quiet as a mouse at idle! Play always on low power to save power tube life.
Then, played tonight for about 10 minutes, left the room....came back to play...heard static....scrambled egg sounds too. Now all I get is no volume and LOTS of distorted sound. Also had a the dreaded "scrambled egg sound" thing going occasionally....replaced the PI tube with several none good tubes; same. I do not have spare EL-34's...these are lighting off fine and are not glow platting or looking a funny color...
Any ideas as to what this might be before I take her to a tech?
Bad power tube or tubes(s)? Something in the power amp part of the amp gone bad?
HELP?
Update, turned her on this
Update, turned her on this morning....now playing fine......
Help? Any ideas?
Cold Solder Joint
That sounds like a cold solder joint somewhere in the signal path. Try checking the input jack(s) and make sure the wire connections are solid. Re-flow with solder if any are loose. Also, clean the jack with contact cleaner like DeOxit. Good luck. -mgriffin
Thanks mgriffin.....any other
Thanks mgriffin.....any other thoughts out there?
distortion
Try cleaning output speaker jacks
AS well as the suggestion to
AS well as the suggestion to clean the jacks, you should clean the output tube sockets. A LOT of amps have been "fixed" with a shot of deoxit and a few wiggles. Mike.
Thanks all, .......anyone
Thanks all, .......anyone else?
Also, in addition to what's
Also, in addition to what's been stated above (again!) does it do it on BOTH channels? this would let you know if it;s just one side or the ohter and where you need to start looking. Mike.
both channels!
Yes, does it on both channels...
OK, that means it's
OK, that means it's somewhere in the finals so I'm back to my dirty sockets and the maybe the master volume control. Dirty master can do some crazy stuff. I really don't know what scrambled egg sounds are though. You got me on that one. Mike
Interesting, cleaned all the
Interesting, cleaned all the inputs and speaker jack with deoxit.....cleaned power tube sockets with deoxit. Played her again last night....
Started the distorted low volume stuff again, and I turned the master volume to 10, and it cleared up...
Sooooo, Master Volume pot dirty maybe??
It's worth a shot
It's worth a shot of cleaner spray to find out. Might as well clean all of the the other pots too. -mgriffin
Tried that....seemed to work.
Tried that....seemed to work....then it did this again.....then stopped again......driving me crazy!
What else?
Hi Woody, The cleaning process you've done has hopefully made the master volume pot less scratchy. This is a routine maintenance procedure and not always a fix for intermittent problems. It was worth the effort. Intermittent "features" like you describe can be a pain, but they usually can be traced to something mechanical in nature, that is expansion and contraction caused by heating and cooling. So the question is: does the amp work OK when first tuned on and then get nutty after it's warmed up? If yes, start looking for loose solder joints and/or cracked or burnt resistor(s) in the power amp section. Also, if you have a DMM, test the master volume pot. It should measure 1Mohm from end to end. Also verify that it smoothly goes from 0 ohms to 1 Mohm at the wiper when you turn the knob through it's full range. Since it's an Audio Taper pot, the change in resistance won't be linear but it should be smooth and not jumpy. If it tests good, move on to visually checking for cold/loose solder joints. Also check each resistor with your DMM and gently tap them to see if the readings jump around. Hang in there. Let me add one more thing. Do the tests I've described with the power off for safety. -mgriffin
I'm afraid you are going to
I'm afraid you are going to have to get it into failure mode and chopstick it. It sounds electro-mechanical-bad solder joint or corrosion SOMEWHERE. It's in the power section from your description so you are going to have to have it apart, get it to fail and then start tapping components SAFELY with an isolated tool (plastic, wooden dowel-NOT an pencil) and see if you can get it to muck up. If you had a audio probe it might go faster but who knows. With no diagnostic equipment, you are going to have to meatball it. If you don't feel comfortable around 700v, DON'T DO IT. Get a person who is comfortable around these voltages. Knowing it's in the final stages helps some so start tapping the driver connections and later. Mike.
I am afraid it is getting
I am afraid it is getting into the "take it to a tech" mode at this point....a little nervous poking around in there with the chassis pulled and on......
BUT, I have to say, it does
BUT, I have to say, it does this dist tone and low volume, sometimes. when it is first taken from stdby to on.....at first turn on, not after warmed up.....I can adjust the master volume back and forth and it goes away.....
COULD be a bad pot with the
COULD be a bad pot with the track worn off. No amount of cleaning will cure that. IF YOU'RE BRAVE, you can short from wiper to input of the master pot and take it out of the equation. That will eliminate it from the process and it will be wide open for the test and see what it does. THEN you would know if it was the pot. Mike
Well, I am back....this thing
Well, I am back....this thing just kinda worked itself out......Only rarely does that distorted thing when first cutting on from stby to on......rarely!. What I am hearing now is a SUPER CLEAN and wonderful sounding dry channel 1; and on the reverb side, channel 2, has at anything above small venue volume level, just a subtle bit of hair on it.....very, very subtle but it is there to the discerning ear. It sounds great, but not as super clean as channel 1.
Any thoughts about this?
Back up, still problems with a bit of distorted tone!
Well, I am back....this thing just kinda worked itself out......Only rarely does that distorted thing when first cutting on from stby to on......rarely!. What I am hearing now is a SUPER CLEAN and wonderful sounding dry channel 1; and on the reverb side, channel 2, has at anything above small venue volume level, just a subtle bit of hair on it.....very, very subtle but it is there to the discerning ear. It sounds great, but not as super clean as channel 1.
Any thoughts about this?
Other than tracking it
Other than tracking it through the IC path and HEARING where it starts (or seeing it) the only thing to try in a shotgun format is to try swapping the IC's one at a time to see if it's one of them. OF just blindly replacing them but that MAY not work as one MAY be overdriven by a bad cap shorted or open. Using a audio tracer would be my choice. Personally, I like a little grit. It gives you the best of both worlds. By the way, does it change gritty level with the reverb or without and does it CHANGE as you add reverb? Mike.
No change at all with adding
No change at all with adding or taking away reverb......sounds like I need to take her to a tech.....here is a pic BTW....