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Ibanez TSA30 Schematic and PCB Layout

Started by Gustaf, May 06, 2016, 03:31:52 PM

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Gustaf

Here is the circuit diagram and PCB layout for Ibanez Tube Screamer Amplifier TSA30.

Thanks to vitrolin for sharing!

BR,

Gustaf

bajaman

Thanks - extremely helpful - these amplifiers have been a curse to fix from day one - I have seen many with the same intermittent buzzing fault - almost pulled what is left of my hair trying to fix the suckers. The fault is capacitor C20, a 470uf 25v filter capacitor - I replaced this with a 2200uf 25v type - problem fixed ! Hope this helps anyone else out there :)

phatt

Thanks Bajaman, handy to know little details like that. :tu:
I wonder why they run the preamp heater filaments at 10 volts ???
Phil.

J M Fahey

I also wondered that the first time I saw it.
Not sure whether calling this weird or plain stupid.

They use a single regulator, here shown as a 10V one, to power both filaments, which require 12V (in fact, 12.6) and the Tube Screamer, which requires 9V .
So somebody finds himself very intelligent because he "split the difference" and saved one regulator  :loco, using a single 7810 instead of one 7812 (which to be perfect requires a diode to ground at the grund leg so it outputs 12.6V) PLUS a 7809 for the TS.
Maybe they gave him a bonus for the incredible savings  :duh

Personally I´d use a 7812, and increase the value of the resistor feeding the TS (R46) from 220r to about 1k2, which should give it poorly regulated 9V , more like a 9V battery would do.

phatt

Thanks for the detail,,Yes I guess it's no surprise as everyone is trying to scratch out every last cent.
I figured it would run fine just by changing the reg to 12Volt and the TS circuit would sound much the same.
Phil.

Mprall00

Reviving because I need to know - did anyone swap the regulator without changing r46? Haven't verified everything in the path is rated over 12.6v so thought i would check if anyone already did it. If so, did it change the sound?

phatt

I don't have that Amp but a read of the schematic tells me it will matter little as 12 volts is still within the 16 Volt cap ratings.
I doubt you would hear any difference in the sonic result.
Though V1 will last longer if heater is running 12Volts :tu:
Phil.

Mprall00

Quote from: phatt on October 13, 2018, 08:49:58 AM
I don't have that Amp but a read of the schematic tells me it will matter little as 12 volts is still within the 16 Volt cap ratings.
I doubt you would hear any difference in the sonic result.
Though V1 will last longer if heater is running 12Volts :tu:
Phil.

Thanks! Along with making v1 last longer, might it reduce the hiss? It adds white noise as I turn up the volume currently.  It seems to be coming from v1 as it disappears when I pull v1. I replaced the coupling caps and grid and plate resistors with metal film 1 watt resistors. Decreased the grid to 10k while I was at it. Reduced the hiss some but still not as quite as my tsa15... that amp has proper power to the preamp so wondering if it would help with noise too...?

phatt

No way to really know without an A/B test circuit. :-\
But I'm guessing that with the Valve preamp section running wide open and then gain at 1C3A you are bound to have some hiss.

You can always reduce R4 and 5 too a more sane 100k that will reduce some excess hiss but be aware that U3A is active even when the TS part is switched out.
As far as the Valve section goes it's a Marshall/Bassman type circuit but volume is after tone stack which means the preamp is full on all the time so hiss will be evident even at lower setting of volume.
R17 could be made as a pot for preamp gain, that might have worked better.

Sorry I can't think of anything else,
Phil.

Mprall00

Quote from: phatt on October 16, 2018, 08:31:37 AM
No way to really know without an A/B test circuit. :-\
But I'm guessing that with the Valve preamp section running wide open and then gain at 1C3A you are bound to have some hiss.

You can always reduce R4 and 5 too a more sane 100k that will reduce some excess hiss but be aware that U3A is active even when the TS part is switched out.
As far as the Valve section goes it's a Marshall/Bassman type circuit but volume is after tone stack which means the preamp is full on all the time so hiss will be evident even at lower setting of volume.
R17 could be made as a pot for preamp gain, that might have worked better.

Sorry I can't think of anything else,
Phil.

Awesome. Thanks for the advice!

g1

Once I worked on a tube mic that had a higher noise floor because the heater voltage was too high.  Bringing the heater back down to 12.6V had a noticeable impact.
Try it and find out, it's probably something that varies from case to case as far as how much difference it makes.

Mprall00

Quote from: phatt on October 16, 2018, 08:31:37 AM
No way to really know without an A/B test circuit. :-\
But I'm guessing that with the Valve preamp section running wide open and then gain at 1C3A you are bound to have some hiss.

You can always reduce R4 and 5 too a more sane 100k that will reduce some excess hiss but be aware that U3A is active even when the TS part is switched out.
As far as the Valve section goes it's a Marshall/Bassman type circuit but volume is after tone stack which means the preamp is full on all the time so hiss will be evident even at lower setting of volume.
R17 could be made as a pot for preamp gain, that might have worked better.

Sorry I can't think of anything else,
Phil.

Hey.  The gain knob pointer was great.  Got it on 50k right now and seems to have good range.  I actually bypassed the entirety of the solid state front end now on a switch and it sounds way better.  Most of the noise is gone and it sounds much clearer now. 

I have another question.  Is this how I would add a presence control?  5k pot in series with a 100nf cap coming off between r25 and c16?

phatt

Sorry but
Unless you tell us Where Exactly in the circuit have you inserted the new input,,it's all meaningless?
could be  VR9?  or at R33?

Forget the presence idea,, bad for the PI stage. xP
Phil.

Mprall00

Quote from: phatt on January 28, 2019, 01:10:32 AM
Sorry but
Unless you tell us Where Exactly in the circuit have you inserted the new input,,it's all meaningless?
could be  VR9?  or at R33?

Forget the presence idea,, bad for the PI stage. xP
Phil.

I just added an input jack with a 1meg resistor and went straight in to cn3b which eliminated the TS, boost, and solid state always on gain.  Actually took that whole input PCB out for now, which means the "effects loop" does nothing now. 

Replaced r17 with the 50k pot for gain.  It sounds good now.  Incredibly loud.  It was oddly quiet stock for 30 watts - quieter than my blues junior by a good bit.  But its not pedal friendly really now.  Thought I could tame some highs by cutting back the presence maybe?  Or maybe adding a tone control earlier between v1 and v2?

Just learning and experimenting with this one.  Will take any advice.  Thanks!

phatt

You could replace R72 with 560k and change your new gain pot with 250k.
Also replace R4 and R5 with 100k,, that will back off the gain.
Is R13 (56k) still in circuit?

You can alter the tone stack might help back off excess treble.
Make C23 100nF and C22 22nF might work,, not sure how well but suck it and see.
Phil.