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Post by edmardell on May 29, 2012 1:39:27 GMT -7
Mornin' guys,
I haven't been able to find out the root of this problem for ages now. When I use the ghia with the brakelite on four clicks, and I use my pedals; compressor adding a slight boost, a booster and a drive pedal, which also boosts, every now and then if I pick the strings hard my signal will drop really low for about half a second and then come back on again. It's like someone's coming over and turning the volume down then up again, and sometimes there's a light pop sound when it drops.
Any ideas? It seems to do it when the volume is on about 10o clock no matter what click the BL is on.
I tried about 3 months ago changing the output valves which I thought sorted it, but alas, here I am again.
Any help would be incredible.
Thanks Ed
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Post by benttop (Steve) on May 29, 2012 5:33:51 GMT -7
What troubleshooting have you tried? What I'm getting at is, are you sure it's the Ghia and not one of the pedals?
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Post by bluzman on May 29, 2012 8:36:07 GMT -7
With the BL on 3 or 4 that sounds to me like you're hitting the front end really hard and you're getting sag from the power tubes, as you are attenuating about -9 to -12db. The power tubes are doing their thing but the pedals are playing a role. I've been playing with compressors lately one into another into a boost and I can get that even with the BL on bypass. Sometimes, especially with a nice circuit like a Ghia, the power tubes saturating are all you need. Try less pedals and/or less attenuation along with less compressor!!
When you start getting the natural tube sag, it is compression and a compressor is kind of redundant depending on how it is being used.
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Post by edmardell on May 31, 2012 5:51:39 GMT -7
Hi Guys,
Thanks for taking the time to reply me - I had my amp tech take a look at it and he thought it was probably overloading the first tube, it was too much for it to handle. When I told him that it was an ECC83 he said he was certain as it's a much higher gain tube than say an '81. So I popped an ecc81 in and hey presto, no cutting out.
Lucky! I have a gig tonight that I can't mess up on!
Thanks for all your help, really appreciated.
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Post by edmardell on May 31, 2012 16:38:54 GMT -7
That top post seemed so optimistic.
Gigged the Ghia. Absolutely fine for the first set, second set the dropping out returns until I finally turn off all pedals, and it's still doing it. I look in the back and one of the EL84s is glowing blue, obviously had its day.
Just what IS this problem!? I've had it since about July last year, Buddy Whittington was playing through it and it happed to him (I know.) and he mentioned something about the projective filter? Since then I've had the EL84s replaced. The preamps. The Rectifier. Nothing sorted it.
Overall very disheartened. Really thinking about looking elsewhere for an amp if I can't pin this problem soon, hate to say it!!!
SO I thought I'd rectified the problem. Alas, it returned and completely ruined the second set for me, I had to use my back up through the PA which I really didn't enjoy it.
If ANYONE has any further ideas, please please help me out here.
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Post by headshrinker (Marc) on May 31, 2012 17:35:26 GMT -7
I had a similar thing happen in a fender amp and it turned out to be a bad ground. I'm guessing you have ruled out a bad cord. If not try a known good one. on both ends of your board. Does it do it when you are not in the board and go into the amp straight? If not it might be a problem with one of your pedals or the board cords. If it only does it at 10:00 on the volume you might have oxidation at that point in the pot. Try cleaning the pot with deoxit. Lastly since you said one of the tubes was bad has it done it since you changed the power tubes. It could have been that tube going. I have had tubes that work for a bit, screw up and then work again when they are going.
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Post by benttop (Steve) on May 31, 2012 19:23:55 GMT -7
That top post seemed so optimistic. Gigged the Ghia. Absolutely fine for the first set, second set the dropping out returns until I finally turn off all pedals, and it's still doing it. I look in the back and one of the EL84s is glowing blue, obviously had its day. Just what IS this problem!? I've had it since about July last year, Buddy Whittington was playing through it and it happed to him (I know.) and he mentioned something about the projective filter? Since then I've had the EL84s replaced. The preamps. The Rectifier. Nothing sorted it. Overall very disheartened. Really thinking about looking elsewhere for an amp if I can't pin this problem soon, hate to say it!!! SO I thought I'd rectified the problem. Alas, it returned and completely ruined the second set for me, I had to use my back up through the PA which I really didn't enjoy it. If ANYONE has any further ideas, please please help me out here. Buddy was talking about the conjunctive filter. Have your tech call Dr. Z and get the lowdown - he should be able to fix it or rule that out.
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Post by pintail78 on May 31, 2012 20:17:36 GMT -7
I'm a really good amp tech, but hey send it to the doc and have his guys look at it. I would send and call about the problem, make sure its fixed.
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Post by edmardell on Jun 1, 2012 1:25:06 GMT -7
Thanks for the replies guys. All my leads are top quality, and depending on the gig I've used it with pedals and without. I just can't figure this out, like I said this was happening before and after I changed my output tubes, and the output tube that went up last night was about 5 months old. I don't run the amp hard enough for it to burn out that quick! Have a radio session on Sunday so will probably have to use a different amp altogether, which I don't want to!
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Post by bluzman on Jun 1, 2012 5:46:22 GMT -7
Thanks for the replies guys. All my leads are top quality, and depending on the gig I've used it with pedals and without. I just can't figure this out, like I said this was happening before and after I changed my output tubes, and the output tube that went up last night was about 5 months old. I don't run the amp hard enough for it to burn out that quick! Have a radio session on Sunday so will probably have to use a different amp altogether, which I don't want to! Gigging with the amp while using pedals and the BL at 4 to me is running it hard... not that the amp can't handle it, but the power tubes are being pushed. Try running the amp at a lower volume with the BL on 2 or 3. Another thing, double and triple check the wiring of the speaker out into and out of the BL to the speaker. Use De-Ox on the jacks. Also how old is the Ghia? Some older ones had a lower rated conjunctive filter capacitor. I had one that I needed to upgrade the cap on. If it's an older amp it may need a new filter. An easy fix for an experienced tech... nothing that you'd want to try yourself without being experienced inside of a chassis.
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Post by edmardell on Jun 1, 2012 5:54:58 GMT -7
Thanks for the replies guys. All my leads are top quality, and depending on the gig I've used it with pedals and without. I just can't figure this out, like I said this was happening before and after I changed my output tubes, and the output tube that went up last night was about 5 months old. I don't run the amp hard enough for it to burn out that quick! Have a radio session on Sunday so will probably have to use a different amp altogether, which I don't want to! Gigging with the amp while using pedals and the BL at 4 to me is running it hard... not that the amp can't handle it, but the power tubes are being pushed. Try running the amp at a lower volume with the BL on 2 or 3. Another thing, double and triple check the wiring of the speaker out into and out of the BL to the speaker. Use De-Ox on the jacks. Also how old is the Ghia? Some older ones had a lower rated conjunctive filter capacitor. I had one that I needed to upgrade the cap on. If it's an older amp it may need a new filter. An easy fix for an experienced tech... nothing that you'd want to try yourself without being experienced inside of a chassis. Hello mate, I actually didn't have the attenuator connected last night at all. It's an '06 model, I'm giving it to the tech to basically keep until he finds something wrong with it, I'll mention the conjunctive filter to him. Thanks guys!
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Post by prspastor on Jun 2, 2012 6:22:33 GMT -7
Don't give up on an amp or think that it is a "bad" amp just because you are having troubles. I think folks that end up selling an amp because of momentary issues regret it later on. I'm speaking from experience here. You have a highly serviceable amp there and it is fixable. Work the problem - it will probably be very simple. It is a great amp and will last you your whole life. I'd just send it to Dr. Z to have a look at. They'll take care of it... FWIW, it sounds like a tube issue to me. Tubes are absolutely terrible these days. Even a new, matched set that has been carefully screened can crap out in a few hours. Dr. Z has expressed deep frustration with tubes lately - makes his amps look bad when in reality it is the tubes that are bad. It also might be a cold solder joint on a socket that starts expanding when the amp is heated up after a while. Just things to think about with your tech. Hope you get it fixed soon.
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Post by Maddog on Jun 2, 2012 7:44:10 GMT -7
FWIW, it sounds like a tube issue to me. Tubes are absolutely terrible these days. Even a new, matched set that has been carefully screened can crap out in a few hours. Dr. Z has expressed deep frustration with tubes lately - makes his amps look bad when in reality it is the tubes that are bad. . +1000...I'm with Jon here......guessing you probably had a questionable tube from the day you bought the new tubes.....Tubes (especially EL 84's) are just a crap shoot these days..... Cheap fix tho....
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Post by BritInvasion on Jun 2, 2012 7:57:06 GMT -7
FWIW, it sounds like a tube issue to me. Tubes are absolutely terrible these days. Even a new, matched set that has been carefully screened can crap out in a few hours. Dr. Z has expressed deep frustration with tubes lately - makes his amps look bad when in reality it is the tubes that are bad. . +1000...I'm with Jon here......guessing you probably had a questionable tube from the day you bought the new tubes.....Tubes (especially EL 84's) are just a crap shoot these days..... Cheap fix tho.... Yes and yes.
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Post by Fiestared69 on Jun 3, 2012 6:14:08 GMT -7
I can't imagine using a ghia on a gig and having to use a breaklite on 4 clicks !!!!....... The power tubes are doomed to fail pushing them that hard ! I suggest getting a smaller amp (Maz 8) or a new soundman !!
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Post by Phil (aka Phil) on Jun 3, 2012 7:03:08 GMT -7
Just a few thoughts here..
First, +1 about the tube quality problem. The JJ EL84's in particular are not as good as they used to be. Try a couple of EH EL84's...those have been better lately.
One of my best friends (the smartest man I've ever known) told me once that you can always tell when a car was made by the quality of the parts used- in bad economic times the manufacturers "cut corners" on the parts and plastic quality to improve their margins. Tubes are made in Russia and China, and you're not only fighting the global recession, you're righting the whims of the mob (in Russia) and the Chinese government. It's a wonder we get good tubes at all.
Second- I've been troubleshooting and repairing antique radios and guitar amps for a long time...and in a very, very high percentage of the time it's a tube that's at fault. There's always the aforementioned jack oxidation, tube pin problems, bad caps or resistors, etc, but as a percentage those are in the minority. I was talking to Jim and Don at the Z shop a couple of years ago and they were telling me that the vast majority of the time when a Z amp is sent back for service a tube or tubes was all that was wrong. I've been amazed myself at times when I've substituted a new tube and had the problem remain only to try a third tube and have the problem resolved. This is especially true of power tubes like EL84's and "V1", the first preamp tube. Buying tubes from a known good vendor who burns them in and rejects the bad ones is a great start.
Third, in this specific case, while it's hard to diagnose over the Internet...my first instinct is that it's a tube, probably a power tube. Here's why. What you're describing is a power loss on a hard transient. If you look at the voltages involved in the amp, from front to back, the components near the "front" (input) of the amp and the associated connections are "rated" or built for a much greater voltage than the millivolts coming from your guitar or even the low voltage coming from your pedals or the preamp stage. It's hard to "overload" or cause a drop out like you're describing that recovers after a second only on a really hard transient in the preamp stage. It could be a bad preamp tube theoretically but I'm guessing not.
Then you've got the power amp section and the rectifier. In my experience the rectifier either works or doesn't at all most of the time. It could be a bad 5Y3 giving you the ultimate case of "sag" by not meeting it's current output spec but if it is it'd be the first time I've seen such a failure.
Then at the output you've got the conjunctive filter across the output. I'd definitely check that out. I think by 2006 Z had changed to the 600V snubber cap that's now standard but even that could have blown. However, it's there to smooth out the response of the amp, and even if it's blown I don't think it would cause these reported symptoms. That leaves the power tubes which except for new production rectos are the most problematic component. JJ's used to only be good to my ears for 300 hours or less...these days maybe a lot less.
Finally, Z has the best service in the business. I highly recommend sending it back to him for piece of mind. It's a world class amp that will be "right" once it leaves Cleveland after the short turn-around time.
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Post by edmardell on Jun 8, 2012 4:07:43 GMT -7
Thanks to maddog, prs, britinvasion & Fiestared & Phil for your replies. I've shown my tech the thread, he has had the ghia opened up and says it's amazing inside, so well made. Although he couldn't peg what was wrong with it!
Shown him the thread so he's going to go away, otherwise I will send her back to Z!
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Post by pintail78 on Jun 8, 2012 12:43:40 GMT -7
Could be the conjective filter, but I had one that just failed, I don't think they are an intermitant problem unless its due to a overheating/pushing to hard problem. Maybe it gets hot, the resistivity is lowered and the amp get even more pushed?
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Post by pintail78 on Jun 8, 2012 12:44:36 GMT -7
I would just change the filter out, its a pretty cheap deal. If its not that or a tube send it to the doc.
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swiveltung
Full Member
tracking number 770638390642
Posts: 219
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Post by swiveltung on Jun 9, 2012 11:20:19 GMT -7
I dont know about EL84's, but a blue glow is not a bad thing on 6L6's and 6V6's.... Love that neon glow!
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Post by jhumber on Jun 9, 2012 12:21:27 GMT -7
Hey Ed Sorry to hear the Ghia is giving you problems. Shout if you have any important gigs coming up and want to borrow my Maz 38 1x12....still going strong after 200+ gigs If I'm not using it, you're welcome to it. Cheers Jordan
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Post by mickey on Jun 16, 2012 9:32:44 GMT -7
Ed, did you get it fixed? What was the problem?
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Post by edmardell on Jun 20, 2012 9:26:33 GMT -7
Ed, did you get it fixed? What was the problem? Hi Mickey, hope you're well - and thanks Jordan, that's mighty fine of you to offer. I actually pickup up an HT40 the other day which I'll use for the function stuff, but the Ghia I want to use for the other band Well, the amp tech couldn't get it to go wrong which was irritating, however within 5 seconds of me playing it, I managed to get it to happen again. I thought I'd just go through a process of elimination and I swapped out the EL84s for some brand spankers, and apparently that's completely sorted it!?! I'm taking it to a rehearsal this week so that'll be the ultimate test, so we shall see. I'm just thinking that I probably burned through the power valves I had in it, considering in the last 2 months I have gigged almost every other night (Phew) and I pretty much had it attenuated to the max. We'll see. Thanks to everyone for your help, I'll post back in a couple of days! Ed
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Post by Phil (aka Phil) on Jun 20, 2012 12:57:21 GMT -7
What did uncle Phil say a few posts above? ;D
Hope you got it all sorted out!
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Post by mickey on Jun 20, 2012 23:28:18 GMT -7
Sounds promising Ed, hope it's sorted now.
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Post by edmardell on Jun 23, 2012 5:47:50 GMT -7
What did uncle Phil say a few posts above? ;D Hope you got it all sorted out! I know, I honestly didn't think it was that simple. I've gigged the amp now 3 times and it's been phenomenal. I ran it with the Blackstar HT40 just in case, but I had no problems. I actually swapped out the v30 for a T75 just to see what happened and for the style I'm playing (RnB, Soul, Pop) it's absolutely wicked. I actually put a 5751 back in as well and I couldn't be happier. This is actually the end of the saga, and something as simple as a valve swap. Everyone's been really helpful - I really appreciate all the advice you've given me. Now to get back to gigging! Ed
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Post by pintail78 on Jul 29, 2012 8:28:36 GMT -7
Z's are tough its always something simple, start with the tubes.....finish with a beer-when your done.
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Post by rickc007 on Jul 29, 2012 8:37:10 GMT -7
Late to the party, but I had this with a Mesa
turns out it's a preamp tube, and was kind of well know, v3 I think, memory is fading
But it's like if you have a crappy preamp tube there, the volume does this drop out thing, then it can come back
"Just" replacing the preamp tube doesn't necessarily clear it, replacing a crappy Mesa tube with another crappy Mesa tube, gives the same results Put a quality tube in V3 was the solution
Glad you found the problem child , intermittant problems are most annoying
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