Schematic for TC2240 EQ?
- Thread starter jlarcombe
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sismofyt
Well-known member
I have. You can get an original service manual if you pm me your adress :grin:
sismofyt
Well-known member
Actually it could be vintage as they have been in production for like 25 years. Dunno if they still make 'em. I've fixed and modded dozens of those btw. What's wrong with yours?
Service manual would be fantastic - PM to follow.
The sound cuts out intermittently on the bottom channel - seems to be something dodgy with the connection between the filter board and the amp board but I can't find any shorts or discontinuities with a meter. The pots on both channels are pretty crackly (I get the impression my unit has seen rather heavy use on the road..). I might try to replace the gain pots at least. Also I seem to remember that the metering is knackered on the bottom channel too.
It's a pretty decent 'surgical' EQ I think (the preamp section is slightly weird though).
Thanks again,
James.
The sound cuts out intermittently on the bottom channel - seems to be something dodgy with the connection between the filter board and the amp board but I can't find any shorts or discontinuities with a meter. The pots on both channels are pretty crackly (I get the impression my unit has seen rather heavy use on the road..). I might try to replace the gain pots at least. Also I seem to remember that the metering is knackered on the bottom channel too.
It's a pretty decent 'surgical' EQ I think (the preamp section is slightly weird though).
Thanks again,
James.
sismofyt
Well-known member
Yes, probably the PSU connections. The pots are crappy and the preamp useless. Decent eq.. I have some notes buried .. uhmm.. somewhere. I'll get back to you. Don't by parts from TC btw. They too expensive :evil:
I like the low-end eq on the TC1140/2240 eq's - they're very useable for drums. The mid and high tends to get "hard" when boosting, specially with high Q's. And this unit has very high Q's at it's max.
A very good upgrade for these is changing the quad opamps in the filter board section (they're unnamed in old versions, TL074's in "high-speed" versions). If you put in MC33079's instead, you have a much gentler and more useable eq.
Oh, and btw, The TC1140 schematic:
http://img56.photobucket.com/albums/v172/gyraf/TC1140_schematic.gif
Jakob E.
A very good upgrade for these is changing the quad opamps in the filter board section (they're unnamed in old versions, TL074's in "high-speed" versions). If you put in MC33079's instead, you have a much gentler and more useable eq.
Oh, and btw, The TC1140 schematic:
http://img56.photobucket.com/albums/v172/gyraf/TC1140_schematic.gif
Jakob E.
Jakob,
Very interested to hear about the MC33079 upgrade for these TC EQs. When you say a 'more gentle' EQ, are you referring just to the sonic quality, or is the range of available Q reduced by this modification? I do like the fact that you can wind up the Q really high on these units - very useful for salvaging an electric guitar.
Thanks,
James.
Very interested to hear about the MC33079 upgrade for these TC EQs. When you say a 'more gentle' EQ, are you referring just to the sonic quality, or is the range of available Q reduced by this modification? I do like the fact that you can wind up the Q really high on these units - very useful for salvaging an electric guitar.
Thanks,
James.
sismofyt
Well-known member
What Jakob said :thumb:
You may as well just mod it when you're fixing it :wink: I send the manual today..
You may as well just mod it when you're fixing it :wink: I send the manual today..
[quote author="jlarcombe"]Jakob,
When you say a 'more gentle' EQ, are you referring just to the sonic quality, or is the range of available Q reduced by this modification?[/quote]
The function stays the same, only the sound becomes actually useable also for mids and high.
The 33079 simply distorts significantly less at high gains. And high gains are needed in this circuit. The reason for the distortion rising heavily with frequency in the eq is the gain-bandwidth-product limitation. You run out of negative feedback gain, and without proper feedback to keep things tidy, the TL074 distorts REALLY bad - figures around 20% are mentioned.
The 33079 has much better "native" distortion figures, making it less dependent on a high GBP for keeping things sounding natural.
Jakob E.
When you say a 'more gentle' EQ, are you referring just to the sonic quality, or is the range of available Q reduced by this modification?[/quote]
The function stays the same, only the sound becomes actually useable also for mids and high.
The 33079 simply distorts significantly less at high gains. And high gains are needed in this circuit. The reason for the distortion rising heavily with frequency in the eq is the gain-bandwidth-product limitation. You run out of negative feedback gain, and without proper feedback to keep things tidy, the TL074 distorts REALLY bad - figures around 20% are mentioned.
The 33079 has much better "native" distortion figures, making it less dependent on a high GBP for keeping things sounding natural.
Jakob E.
:razz:
Is that pin compatible with TL074 also?
Is that pin compatible with TL074 also?
keeno
Well-known member
Jakob - have you replaced all the Tl074 or just a few? I think there are 16 pieces...keeno
All the ones at the filter PCB. The mainboard is alright - NE5534's, I think.
[quote author="gyraf"]A very good upgrade for these is changing the quad opamps in the filter board section (they're unnamed in old versions, TL074's in "high-speed" versions). If you put in MC33079's instead, you have a much gentler and more useable eq.[/quote]
is that an easy upgrade or do i risk totally scewing my eq as a beginner? I suppose i could use sockets so it would not be a problem if i risked only the opamps' lives...
is that an easy upgrade or do i risk totally scewing my eq as a beginner? I suppose i could use sockets so it would not be a problem if i risked only the opamps' lives...
You should at least be sure of your soldering/desoldering skills before taking on this..
Jakob E.
Jakob E.
modding went well 
is there an easy way to change the behavior of the bypass-switch? i would like to see whether it is bypassed or not.
there's a switch near the remote-bypass jack - could it be for that ? as i believe to understand the tc1140's schematics its only for the remote...
is there an easy way to change the behavior of the bypass-switch? i would like to see whether it is bypassed or not.
there's a switch near the remote-bypass jack - could it be for that ? as i believe to understand the tc1140's schematics its only for the remote...
The LED at the front should change brightness IIRC - less light when bypassed.
Jakob E.
smallbutfine
Well-known member
Other 'esoteric' quad opamps i like: OPA4227 (expensive...but a nice BB flavour) or OPA404 (very expensive, but also very good sounding - precision opamp). I use both as drop-ins without problems in some applications for TL074 without external parts change or PSU beef-up.
Kind regards,
Martin
Kind regards,
Martin
