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Post by jkleinwilson on Feb 13, 2023 11:39:12 GMT -7
I have a 2004 Maz Jr. 18 that has become noisy when I pot up the cut and reverb.
The cut knob creates more of a hiss, while the reverb knob adds a hum. When they're both fully potted up, it has a synergistic effect and both noises get louder. When they're both all the way down, the amp is almost quiet -- just a quiet hum but otherwise good sound.
Everything is original except for a power tube replacement a few years ago.
I've tried deoxit/tightening on all of the pots, jacks and switches, which is the extent of my DIY skill set, but no real improvement.
Any suggestions for next steps?
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Post by purpletele on Feb 13, 2023 14:44:12 GMT -7
I would replace all of the pre-amp tubes after a good 19 year run.
However, I would start with V3 and see if that makes a difference and then go to V4.
I would bet that it is V3 or V4 causing issues.
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Post by mikeskory on Feb 22, 2023 2:20:26 GMT -7
Sorry to jump in but I see the post is recent. I'm having the same issues with a Maz 18 except the reverb is not working at all with the input jack. I can put a signal into the "in" of the reverb tank that works all the way out. I'm wondering about the reverb transformer. Do they ever go bad? But that's where it's leading me. (BTW I did replace the 12AT7 but the amp came in with a 12ax7 in place of the 12at7)
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Post by purpletele on Feb 22, 2023 18:23:56 GMT -7
Sorry to jump in but I see the post is recent. I'm having the same issues with a Maz 18 except the reverb is not working at all with the input jack. I can put a signal into the "in" of the reverb tank that works all the way out. I'm wondering about the reverb transformer. Do they ever go bad? But that's where it's leading me. (BTW I did replace the 12AT7 but the amp came in with a 12ax7 in place of the 12at7) Mike, A few questions so we can help diagnose your issue. 1. How old is the amp? 2. How long have you had it? 3. Did the reverb ever work for you? 4. You said that the Reverb is not working at all with the input jack. I don't understand what you are trying to explain there. Can you expand on that?
5. You state that you can put signal into the 'In' of the Reverb tank that work all the way out. Are you inputting a signal from a signal generator into the reverb tank? I don't understand, 'that work all the way out'. Are you saying you did get a signal out of the return?
Response
1. The reverb transformer can certainly fail, but that is unlikely. You can test for continuity to see if it has failed and that would indicate OL or Open Loop.
2. You can pull the reverb tank and check for continuity at the input jacks. That is a real simple and accurate test. 3. I would check for continuity in your cables. 4. It's possible that the Actual Reverb Pot has an issue as well.
If you provide the answers to the questions above, it might inspire an idea from someone else.
Brian V
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Post by mikeskory on Feb 22, 2023 21:02:50 GMT -7
A few questions so we can help diagnose your issue.
1. How old is the amp? I am not sure. It belongs to a customer of ours. I will check with him tomorrow 2. How long have you had it? I am not sure. I will check with the customer tomorrow 3. Did the reverb ever work for you? Yes it did work. 4. You said that the Reverb is not working at all with the input jack. I don't understand what you are trying to explain there. Can you expand on that? If I inject a signal through the input jack, the reverb does not work. As I turn up the reverb control I only get more noise.
5. You state that you can put signal into the 'In' of the Reverb tank that work all the way out. Are you inputting a signal from a signal generator into the reverb tank? I don't understand, 'that work all the way out'. Are you saying you did get a signal out of the return? Yes I injected a signal at the "In" RCA jack. That signal can be heard through the speaker including use of the reverb control.
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Post by purpletele on Feb 22, 2023 22:27:45 GMT -7
A few questions so we can help diagnose your issue. 1. How old is the amp? I am not sure. It belongs to a customer of ours. I will check with him tomorrow 2. How long have you had it? I am not sure. I will check with the customer tomorrow 3. Did the reverb ever work for you? Yes it did work. 4. You said that the Reverb is not working at all with the input jack. I don't understand what you are trying to explain there. Can you expand on that? If I inject a signal through the input jack, the reverb does not work. As I turn up the reverb control I only get more noise. 5. You state that you can put signal into the 'In' of the Reverb tank that work all the way out. Are you inputting a signal from a signal generator into the reverb tank? I don't understand, 'that work all the way out'. Are you saying you did get a signal out of the return? Yes I injected a signal at the "In" RCA jack. That signal can be heard through the speaker including use of the reverb control. Thanks for the response. I see why you asked about the reverb transformer. Maybe check for continuity on the reverb transformer leads. Now we scratch our heads and hope someone with greater wisdom can chime in.
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Post by mikeskory on Feb 23, 2023 4:45:34 GMT -7
...and why had the customer replaced the stock 12at7 with a 12ax7? Makes me think he was trying to compensate for the weak reverb. If I knew for sure if the Fender reverb trans would work I would buy one. They are only $20. The Mercury Magnetics Dr Z reverb trans is $55. 2/27/23 update. I ordered a Fender reverb trans supposedly for 12at7 use. I'll let you know. The customer seems to be MIA. Hasn't returned calls in several weeks.
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Post by mikeskory on Mar 15, 2023 4:21:24 GMT -7
The owner of the Maz 18 finally called. It belongs to a church. Was donated years ago and has been sitting in a closet. Story was that a previous tech could not get it working properly so it was donated. Not sure what they are going to do with it now. Thanks for the listening ear.-Mike
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Post by premiumplus (Dave) on Mar 15, 2023 11:25:45 GMT -7
If you've got a scope, follow the injected signal through...and here's a cool test for transformers: Transformer test
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