What's on your work bench?

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Re: What's on your work bench?

Post by NippleWrestler »

this monster. Trying to fix Clarry's 'fix' from 3 years ago when he did something bizarre.

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Re: What's on your work bench?

Post by Slowy »

Bloody hell! A signal would die of old age before it got through that.
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Re: What's on your work bench?

Post by NippleWrestler »

Slowy wrote: Sat Feb 20, 2021 2:15 pm Bloody hell! A signal would die of old age before it got through that.
You've never worked on an amp until you've worked on a Mesa Boogie.

This is a 1997 Tremoverb. Mesa designed it as the flagship of the flagships. It's the only Mesa ever to feature the blues mode and, to me, is the best amp produced by one of the greatest amp manufacturers.

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Re: What's on your work bench?

Post by robthemac »

NippleWrestler wrote: Sat Feb 20, 2021 3:26 pm
This is a 1997 Tremoverb. Mesa designed it as the flagship of the flagships. It's the only Mesa ever to feature the blues mode and, to me, is the best amp produced by one of the greatest amp manufacturers.
Completely agree! Hard to find in NZ.

Your amp? Or just working on it?

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Re: What's on your work bench?

Post by StrummersOfThunder »

i hope thats hot glue

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Re: What's on your work bench?

Post by NippleWrestler »

robthemac wrote: Sat Feb 20, 2021 9:11 pm
NippleWrestler wrote: Sat Feb 20, 2021 3:26 pm
This is a 1997 Tremoverb. Mesa designed it as the flagship of the flagships. It's the only Mesa ever to feature the blues mode and, to me, is the best amp produced by one of the greatest amp manufacturers.
Completely agree! Hard to find in NZ.

Your amp? Or just working on it?
Yeah man is mine. It was my holy grail amp for years and one came up for an insane price but the tremolo wasn't working and the old seller didn't know why. I lived with it for 4 years before deciding to have a look and there's some interesting stuff going on in there, a whole bunch of homebrew 'mods' that I'm working my way through.

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Re: What's on your work bench?

Post by Jay »

StrummersOfThunder wrote: Sun Feb 21, 2021 5:22 am i hope thats hot glue
Ejaculation of hot glue once upon a time...
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Re: What's on your work bench?

Post by vinylguy »

You are a brave man to tackle that one. Hope you have a variac to test it with when you first power up. Makes my current amplifier project look awfully lame (a bit like my soldering skills...)

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Re: What's on your work bench?

Post by NippleWrestler »

vinylguy wrote: Sun Feb 21, 2021 8:43 am You are a brave man to tackle that one. Hope you have a variac to test it with when you first power up. Makes my current amplifier project look awfully lame (a bit like my soldering skills...)
No need for a variac here, I'm just restoring it back to stock. The amp already works fine, just needs a bit of attention.

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Re: What's on your work bench?

Post by RectifiedAmps »

Soldering mesas always reminds me of:
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Re: What's on your work bench?

Post by Optical »

NippleWrestler wrote: Sat Feb 20, 2021 10:48 am this monster. Trying to fix Clarry's 'fix' from 3 years ago when he did something bizarre.

What's the issue with it? Let me know if you need a hand
From memory the trem circuit was a 555 timer controlling an LDR on the tone stack output

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Re: What's on your work bench?

Post by NippleWrestler »

Optical wrote: Mon Feb 22, 2021 9:31 am
NippleWrestler wrote: Sat Feb 20, 2021 10:48 am this monster. Trying to fix Clarry's 'fix' from 3 years ago when he did something bizarre.

What's the issue with it? Let me know if you need a hand
From memory the trem circuit was a 555 timer controlling an LDR on the tone stack output
Cheers man. When I went round to test the amp about 4 years ago form the old owner there was this horrid wubwubwubwub pulse coming from the amp. The guy, quite shocked, took it to Clarry who then disconnected the tremolo by jumping the circuit and also removing a 600v cap for reasons I'm not quite 100% on.

Although a good guess it didn't solve the problem so the guy took it to Rockshop whom, say what you like about, are the mesa techs for New Zealand. Turns out the problem was a loose joint around v4 which they spruced up. $400 in repairs later and I got the amp, sans tremolo, but since I have a company making pedals, one of which is a tremolo, it was fine.

But, I know more now than I did then and wanted to see if I could restore the amp to stock since I knew the trem wasn't working and it's a big part of the appeal of this amp (and explains the Tremoverb name since it has both tremolo and an enormous reverb tank). So I had a look inside, hence the photo of the guts. There's some 'interesting' things going on. Clarry jumpered some stuff to some other stuff which removed the trem from the circuit, it looks like someone else added a trimpot in series with the bias switch (which would bring down the voltage to the tubes I think), some bits needed tidying up. The 555 timer is apparently ok since if I do rotate the speed knobs there's a faint clicking that corresponds with the pot so I think the IC is fine.

So, ipso facto I need a new ldr and a new cap. The ldr I have to source from xvive via eBay, my amp tech buddy is helping me with the cap and since he's a bit of an amp nerd just wants to look for himself at the bizarre jungle of schematic that is a Mesa Boogie amp.

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Re: What's on your work bench?

Post by robthemac »

So this is going to be your personal amp for a while?

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Re: What's on your work bench?

Post by Optical »

Sweet.. The trimpot on the bias is probably worth keeping - means you can bias up any tubes, not just mesa brand tubes.
The tremelo LDR is AC coupled to the preamp with a 100nF cap, removing that would disable the tremelo, but not sure if this is your issue.
If you have a scope you can put that across the tremelo LDR light side and see the control voltage fluctuating, maybe a voltmeter could see it too if the speed is set low. Assuming the control voltage is ok, then it should hopefully just be a matter of connecting the resistor side of the LDR back up to AC couple between the preamp / fx return and ground. Actually the PI input is more accurate as the trem circuit sits after the reverb and fx loop stages!
Cool amp for sure

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Re: What's on your work bench?

Post by NippleWrestler »

Optical wrote: Mon Feb 22, 2021 2:58 pm Sweet.. The trimpot on the bias is probably worth keeping - means you can bias up any tubes, not just mesa brand tubes.
The tremelo LDR is AC coupled to the preamp with a 100nF cap, removing that would disable the tremelo, but not sure if this is your issue.
If you have a scope you can put that across the tremelo LDR light side and see the control voltage fluctuating, maybe a voltmeter could see it too if the speed is set low. Assuming the control voltage is ok, then it should hopefully just be a matter of connecting the resistor side of the LDR back up to AC couple between the preamp / fx return and ground. Actually the PI input is more accurate as the trem circuit sits after the reverb and fx loop stages!
Cool amp for sure
There's much better ways to change the bias which is something I have planned. You can use any tubes anyway, it just voids the warranty (but that expired 20+ years ago).

There's a lot I haven't gone into but there's parts missing, pads pulled, and jumpered stuff all around the ldr. I basically have to rebuild the tremolo section and I'm 99% sure the ldr is cooked.

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