Tremolo failure...not...then again...

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lavrgs
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Tremolo failure...not...then again...

Post by lavrgs »

EDIT: I put the head up on the bench and the trem works...however I still think that the intensity knob should not reduce the volume so dramatically so I will need to investigate..

I'm going to guess that either some wire has come loose or V3 ( it's a Mojotone) is going south. I'm always a bit slow to get into stuff so I thought I'd write up my plan and see if there is something else I should be looking for.
The symptoms have been creeping in for about a month. Noisey whooshing sound that could be eliminated by a moderate thumping of the head cab and as of a few days ago the tremolo doesn't work...since I leave it almost off I may not have noticed when it stopped but as I turned up the intensity it did not increase...there was a noticeable drop in volume...
So the plan is to go in and measure voltages, wiggle, then swap V3 and see what happens...

While I'm in there I will take a look at the components in consideration of building a TMB Trem ala Joshs" plan. I will inspect the layout to see if his 3.75x12.1 board will fit. I do expect to start with a new chassis, the same size as the Mojotone, but I may as well get a sense for what to change.
Thanks in Advance.

Bill
Last edited by lavrgs on Wed 03/24/21 6:47 pm, edited 2 times in total.
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Bieworm
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Re: Tremolo failure

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lavrgs wrote:
Wed 03/24/21 12:21 pm
I'm going to guess that either some wire has come loose or V3 ( it's a Mojotone) is going south. I'm always a bit slow to get into stuff so I thought I'd write up my plan and see if there is something else I should be looking for.
The symptoms have been creeping in for about a month. Noisey whooshing sound that could be eliminated by a moderate thumping of the head cab and as of a few days ago the tremolo doesn't work...since I leave it almost off I may not have noticed when it stopped but as I turned up the intensity it did not increase...there was a noticeable drop in volume...
So the plan is to go in and measure voltages, wiggle, then swap V3 and see what happens...

While I'm in there I will take a look at the components in consideration of building a TMB Trem ala Joshs" plan. I will inspect the layout to see if his 3.75x12.1 board will fit. I do expect to start with a new chassis, the same size as the Mojotone, but I may as well get a sense for what to change.
Thanks in Advance.

Bill
Hey Bill.. why the same type chassis? It will definitely be very narrow with the PCB. And if you go the reverb route you'll need to add a tube socket. I buy blanks nowadays. It gives me more control and extends the building time, which means more fun. + the last chassis I bought was only 17.5€ for a blank dumble style type.
https://www.tube-town.net/ttstore/tt-ch ... -x-65.html

As for your tremolo problem, first try various 12ax7 tubes.. the circuit is very picky on tubes...some are noisy whoofers, others have a delayed start in oscillation.. you would be surprised about the difference in behaviour of the trem
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lavrgs
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Re: Tremolo failure...not

Post by lavrgs »

I have no problem workin' on chassis...
mill_chassis.jpg
The 17 euro blank sounds like a winner!...unless it's 60Eu to ship 8-) I'll check it out.
Now my trem problem is an intermittent 8=( but since it's on the bench it must be opened. I've had good luck with Electro harmonix tubes but If you have a preferred type I might get some
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Re: Tremolo failure...not

Post by Bieworm »

lavrgs wrote:
Wed 03/24/21 1:23 pm
I have no problem workin' on chassis...mill_chassis.jpg The 17 euro blank sounds like a winner!...unless it's 60Eu to ship 8-) I'll check it out.
Now my trem problem is an intermittent 8=( but since it's on the bench it must be opened. I've had good luck with Electro harmonix tubes but If you have a preferred type I might get some
I'm happy to see you don't fear the works!!
I use ehx too sometimes. Mostly use Tung-Sols though. For reverb tubes there's nothing like a good old sovtek. Very reliable tubes that can handle abuse without crapping out.
In my modern classic the Sovtek 12ax7 WA was the tube with the least of issues on the trem. But it's gotta be told that the voltages on that trem tube need to be very close to spec. I had a slow start oscillation problem that was solved by lowering the dropping resistor value after the cap can...not implying anything, but that was the cure then.
Dang, I'm jealous of your equipment. Love to own a mill and a spindle. Next on my list is a 3D printer. Imagine the possibilities...
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lavrgs
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Re: Tremolo failure...not

Post by lavrgs »

I'm happy to see you don't fear the works!!
I don't fear work at all...I just don't get to it...
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Re: Tremolo failure...not

Post by TriodeLuvr »

lavrgs wrote:
Wed 03/24/21 1:23 pm
I have no problem workin' on chassis...
LOL, that's nice to have! I had to make a decision about milling several years back when I realized my addiction to tubes wasn't going away. It was either buy a full-size knee mill with a lot of accessories for cutting shapes, or put together a benchtop CNC. I opted for the latter, because I wanted to cut precise holes for things like IEC inlets, D-Sub connectors, "D" fuse holders, etc. I also use it for engraving panels. The downside, of course, is that the limited reach means I can't usually mill all the holes on a chassis without repositioning several times. That can cause mistakes if I'm not very, very careful when programming. I'd love to have a larger mill for some of the work, but I'm out of room in the garage. Enjoy that thing!

Jack
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lavrgs
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Re: Tremolo failure...not

Post by lavrgs »

The mill has a bit of a story... I was able to use the machines at work but I could only get an hour or so after work...so I decided to see what I could find and while checkin' the "bay" I found a Tree J325 for 285 bux...4700 pounds of scrap steel just waiting for some work...600 for shipping, almost 900 to move it from my driveway and viola...well, there was some head scratching...but after selling off some parts that I was unable to use I have about 2200 into it and that money has be paid by a few jobs. I can understand the space problem...I call it TMS
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lavrgs
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Re: Tremolo failure...not

Post by lavrgs »

TriodeLuvr wrote:
Wed 03/24/21 3:52 pm
lavrgs wrote:
Wed 03/24/21 1:23 pm
I have no problem workin' on chassis...
I also use it for engraving panels.

Jack
I would be curious about the material you use for panels.
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Re: Tremolo failure...not...then again...

Post by TriodeLuvr »

Everything I build is aluminum, mostly 6061. The mill is a Taig that I bought "CNC-ready" way back when. I added stepper motors, a commercial controller and a DIY power supply. I also have a small benchtop Taig lathe that I use for making custom knobs, beauty rings (for tubes), custom nuts, standoffs, etc.

All my front and rear panels are engraved, then brushed and clear anodized. I do all of this in the garage. My anodizing tank is powered from a constant-current power supply that I also built myself. This methodology usually allows building a piece of equipment from start to finish without outsourcing. The cost and time required to paint and silkscreen custom pieces is horrendous now. I occasionally send out a chassis or transformer cover for powder coat, but that's rare.

Jack
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