|
Post by captainkevo on May 9, 2021 16:52:08 GMT -7
I purchased a year 2000 Maz 18 JR for my first Dr. Z amp and fell in love with it. I got home with it and immediately plugged it in and started playing. I played for 2 hours straight when all of a sudden the left channel input (I say left bc there’s no indicators or anything on the head to designate high or low or anything like that) stopped working. I’ve still got the hum of the amp coming through the speakers but no guitar volume. I checked the back to make sure all the tubes were glowing and everything looked okay to my untrained eye. I switched inputs and the guitar volume was back. I figured it had something to do with that input and I was too excited to worry about it at the time. I kept playing the right input for another hour or so and then it did the same exact thing. No weird noises when the volume came to a stop. No power surges that were obvious. Nothing stands out. So I shut the amp down and tried again later that night and the amp played fine through both outputs for about 20 mins in total before they stopped again. I have tried different cabs, cables, and guitars in every combination trying to whittle it down and it all goes back to the amp head itself. Any ideas? Please help.
|
|
|
Post by KeithA on May 9, 2021 17:23:07 GMT -7
Did you try a new/good 12ax7 in v1 (first tubes position)?
|
|
|
Post by captainkevo on May 9, 2021 17:24:58 GMT -7
I have not tried any new tubes or anything. To be honest I don’t know what I’m doing when it comes to that and this all happened last night.
|
|
|
Post by captainkevo on May 9, 2021 17:27:57 GMT -7
I should also say that if I crank the master up pretty good I can hear the guitar sound a little bit but I don’t want to damage the amp or anything so I didn’t do that for longer than a second.
|
|
|
Post by KeithA on May 9, 2021 17:33:55 GMT -7
Most times an issue like this is tube-related. That may not be the case here but it would be the best place to start/
This may help as well. Oh, and welcome to the forum.
|
|
|
Post by captainkevo on May 9, 2021 17:37:34 GMT -7
Awesome. Thank you for your suggestions. I’ll give that a shot tomorrow and see what I can come up with. Thanks! I didn’t realize I was entering a whole world by getting into these amps but man I’m glad I did. The community built around these amps is uplifting and a good testament to the quality of them.
|
|
|
Post by Jaguarguy (Mike) on May 9, 2021 18:34:32 GMT -7
Welcome to the Forum! A lot of good information and great people here! The trouble shooting guide is a good introduction to how to fix some minor issues - be safe when working on them - they can be dangerous if you mess around with the wrong parts!
|
|
|
Post by captainkevo on May 9, 2021 18:49:38 GMT -7
Welcome to the Forum! A lot of good information and great people here! The trouble shooting guide is a good introduction to how to fix some minor issues - be safe when working on them - they can be dangerous if you mess around with the wrong parts! Thank you! Excited to be a part of it all now. I am new to a lot of this. I got a blues JR 3 years ago as my intro to tube amps and all I really did was plug it in and play it. I’ll need to watch some how to videos and all of that fun stuff before I dig into anything or crack anything open. after watching the video posted on this thread Dr. Z said that if the ht fuse is blown the power light will still stay on, which mine is doing. I think that’ll be my first stop.
|
|
|
Post by captainkevo on May 9, 2021 19:11:33 GMT -7
Both fuses appear to be in good shape.
|
|
|
Post by runninwiththerevil (Matthew) on May 10, 2021 9:06:03 GMT -7
You aren't in much of a danger if it comes to most stuff on the external. You're actually in better shape with an amp like Dr Z compared to a modern Fender. So much of the Fender stuff is mounted directly to the board you need to be careful you don't crack that. But especially tubes in a hand wired amp. Just make sure you are unplugged and the tubes are cooled. Pre amp tubes aren't very expensive and it was one of the first ways that I messed around with "mod's". Order a couple of the standard 12ax7's, and then poke around and see what other fun ones people like and if it's in the budget add one of those too. I ended up with a vintage GE 12ax7, and found it made a huge difference is some various designs. The Carmen Ghia loved that in V1. I have a Maz now, it made more of a difference in V1 on the Maz 18 than the 38, but maybe not as much as it did for the Ghia.
The fact that you have this issue after it heats up seems to point to a tube that obviously still heats up, but is on the way to failing.
|
|
|
Post by captainkevo on May 10, 2021 13:18:41 GMT -7
So I just got back from a local shop. I took the amp up there to run some diagnostic tests on it and we replaced all of the tubes one at a time to try and sus it out. Doesn’t seem to be the tubes in the pre or power section so we’re moving on to the rectifier tube next. They didn’t have one in stock so they’re going to order one and try that out. If that doesn’t work we have a really good local amp tech here who is going to take a look at it.
|
|
|
Post by KeithA on May 10, 2021 13:47:36 GMT -7
So I just got back from a local shop. I took the amp up there to run some diagnostic tests on it and we replaced all of the tubes one at a time to try and sus it out. Doesn’t seem to be the tubes in the pre or power section so we’re moving on to the rectifier tube next. They didn’t have one in stock so they’re going to order one and try that out. If that doesn’t work we have a really good local amp tech here who is going to take a look at it. Do you have any Deoxit or contact cleaner that you can put on a cable end and clean all of the inputs (including the effects loop inputs)?
|
|
|
Post by GuitarZ on May 10, 2021 13:59:13 GMT -7
Do you have any Deoxit or contact cleaner that you can put on a cable end and clean all of the inputs (including the effects loop inputs)? Also, it could be a dirty tube socket. You can spray Deoxit in the little metal sockets and pop the tubes in and out. Or, for folks that might want to do this down the road, I found these tiny dental brushes: Amazon: Dental Brushes I didn't want to hit them with metal brushes and wanted to make sure the brush was smaller than the socket so that I didn't inadvertently expand a socket. The dental brushes fit the bill. My Marshall went quiet. I was just hearing a little bit of sound. I was troubleshooting tube by tube. I even hit the sockets with Deoxit early on (without the brushes). After a while, the volume was fine for maybe a minute or two after turning it on before going down to the 'little bit of sound'. I was searching for bad caps, loose solder connections, etc. I had to take a break for a few months. In the meantime, I picked up the brushes & figured I'd try cleaning the sockets again since a friend suggested that from the start. Popped it on to continue troubleshooting and was surprised to find the trouble gone. Good Luck!
|
|
|
Post by captainkevo on May 10, 2021 15:16:28 GMT -7
Do you have any Deoxit or contact cleaner that you can put on a cable end and clean all of the inputs (including the effects loop inputs)? Also, it could be a dirty tube socket. You can spray Deoxit in the little metal sockets and pop the tubes in and out. Or, for folks that might want to do this down the road, I found these tiny dental brushes: Amazon: Dental Brushes I didn't want to hit them with metal brushes and wanted to make sure the brush was smaller than the socket so that I didn't inadvertently expand a socket. The dental brushes fit the bill. My Marshall went quiet. I was just hearing a little bit of sound. I was troubleshooting tube by tube. I even hit the sockets with Deoxit early on (without the brushes). After a while, the volume was fine for maybe a minute or two after turning it on before going down to the 'little bit of sound'. I was searching for bad caps, loose solder connections, etc. I had to take a break for a few months. In the meantime, I picked up the brushes & figured I'd try cleaning the sockets again since a friend suggested that from the start. Popped it on to continue troubleshooting and was surprised to find the trouble gone. Good Luck! I do not have any as of right now. The shop still has the amp and is going to try the rectifier tube before moving on. But that will be my next step once they try that out and we eliminate that. thank y’all so much for all the juicy info.
|
|
|
Post by captainkevo on May 11, 2021 18:29:44 GMT -7
Quick update-
For reference the amp had been worked at some point in its 21 year life span and the work was a little shoddy.
Got a call from the amp repair tech in my town and it was a number of things. -The input jack was loose (Don suggested this may be the issue) -The power cable had been worked on and the splices were bad. -Dirty tube sockets (as suggested in this thread) -Rectifier tube was ba or at least going bad. -One of the pre amp tubes wasn’t exactly right (I can’t remember what the numbers were on it but I will have all the details once i get the actual completed work order) and it was pulling too much power causing it to short.
This is all off of memory at the moment but when the amp comes back in a week with the work order I will have more details.
|
|
|
Post by runninwiththerevil (Matthew) on May 11, 2021 19:58:13 GMT -7
Don't imagine any of that should set you back too bad. Glad to hear they got to the bottom of it for you.
|
|
|
Post by captainkevo on May 11, 2021 20:21:14 GMT -7
Don't imagine any of that should set you back too bad. Glad to hear they got to the bottom of it for you. Thanks! Were also going to go ahead and change out all the old tubes since they look like they’re very old as well. Actually kind of amazing how it all worked out. I bought it on consignment at a local shop and the owner of the shop called the guy who sold it on consignment and told him the situation and the guy is covering the cost of the repairs. Got to find a way to pay this kindness forward.
|
|
|
Post by headshrinker (Marc) on May 12, 2021 9:07:08 GMT -7
Actually kind of amazing how it all worked out. I bought it on consignment at a local shop and the owner of the shop called the guy who sold it on consignment and told him the situation and the guy is covering the cost of the repairs. Got to find a way to pay this kindness forward. Definitely a pay forward moment and another testament to the fact that Z owners are good people.
|
|