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Messages - phatt

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1
Amplifier Discussion / Re: Ibanez TSA30 - buzzing
« on: November 12, 2019, 08:52:26 AM »
This might help;
https://www.ssguitar.com/index.php?topic=4011.0
Read second post by Bajaman.
Cheers, Phil.

2
If the Amp works (makes music as intended) then unlikely replacing transistors will fix it.
hint, Use Enzo's logic,, bang your fist on the amp and see if you can get it to pop.
If so it would point to a mechanical problem, i.e. a cracked solder or similar issue.
If something has been ripped out then look for hairline cracks in that area.
Phil.

3
Tubes and Hybrids / Texas tone made simple
« on: October 24, 2019, 12:23:19 AM »
Hi all,
I've been messing with this for a few years so thought I'd show folks this simple trick.
If you are lucky enough to own an old BF Fender or similar Valve amp from that era this may help. This is unlikely to work with a lot of amplifiers made now days (both SS and Glass) but I have had some success with my all SS setup,,so some experimentation may be required to work with your particular SS setup.

The Video should be fairly clear for those who understand the basics of how tone is created.

Note the audio circuitry in my little camera compresses quite hard so you won't hear just how much the bass splatters when the trick is bypassed at high volume,
When engaged you will loose perceived power but the whole point of doing this is to get the amp running at full volume without the bass splattering, read clean headroom. 8|
With those old amps the bass is big and sounds full at low volume but the bass collapses with many of those old valve circuits if you try to get to full volume,
Even worse if you have overwound PU's. xP

So here is what just one small cap can do when used in the right place.
Keep in mind this is all done on the cheap,,So no Tx special pu's and the small amp is old valve radio junk.
the pu's in this guitar are 4k ceramic (read,, about as cheap a copy strat as you can buy)

Enjoy, Phil
https://youtu.be/mWI45ng1SIY

4
The Newcomer's Forum / Re: I want to ask a question
« on: October 11, 2019, 07:23:27 PM »
There are likely quite a few small amps like yours that don't have short circuit protection on the output, so likely you have blown the output transistors.
Pull the chassis and take some pictures of the internals and some here might know how to fix the issue.
Phil.

5
Amplifier Discussion / Re: Fender 85 tone help
« on: October 01, 2019, 07:54:06 AM »
A lot of those mid price range amps are often a hit and miss affair.
Often clean is ok and drive channel can be anything from a duck fart to a screeching cat but as for that smooth sweet OD you mention,,,well I've never found one that works for that sound.

You could just use the clean channel and go try some OD pedals,, and maybe an optical Compressor.
If I'm looking at the right schematic the second ch has an optical limiter which would likely help the compression effect you need to get the clean channel onto a sweeter OD. But that is major rewiring with no guarantee it will work.
I can post a simple Hi pass filter you could wireup as a test to see if it helps but the Amp must have a lot of bass for it to work well.
It's just 2 resistors and a cap in front of the input.
Phil.

6
This is a bit silly R1 at 10 meg is just insane for Elguitar,, only useful for a passive piezo PU.  I meg is miles high enough. Even try 470k.

Also add some series resistance between C1 and input,,unless you want to pick up radio stations. try at least 1k~10k
I doubt you will get useful distortion out of this circuit if that is what you hope. :-X

Personally there are far better circuit designs some likely floating around on this very forum,, too busy ATMo but others here might help out.
Phil.

7
Amplifier Discussion / Re: Z-MATCHER 100W IMPEDANCE MATCHER
« on: September 13, 2019, 09:12:11 PM »
I'm not the expert but logic suggests that as there is no HV & Hi Z primary (as in Valve output Tx) then the Z matcher would not need to be as big.
I would assume it's just a low Z matching Tx with switching taps.

Have a look here not quite the same thing but obviously uses rather small Tx but still rated at 100Watt and only $30. Before you ask,,I have no idea if this would work for Valve guitar Amps. :-\
https://www.walmart.com/ip/100W-In-wall-Stereo-Speaker-Volume-Control-with-Impedance-Matching/198934342
Phil.


8
Maybe check the trim and pot wipers are actually in contact with tracks.
That can stop it from working.
Phil.

9
The Newcomer's Forum / Re: Lab Series L5 settings please?
« on: September 01, 2019, 10:40:36 PM »
Welcome to SS guitar. :tu:
I don't know the amp but too many variables to give meaningful answers.
Type of pickup SC or HB, Speakers used, pedals you might use. Many things need to be in place to make it happen.
You can try an eq pedal in front,, maybe even a Treble booster.

Be aware that one persons idea of *sounding like a Fender twin* might be very different to your idea. :-X

Schematic shows this amp has 2 inputs, top one has a passive type tone circuit which might prove to be more useful that the second input which runs an active tone with sweep EQ as well as that multi filter. (which I don't fully understand??)

The original Fender twins normally had a lot of bass at V1 & V2 while the input to power stages had a big bass roll off.
Change that cap from 1nF up to a 22nF and it will no longer sound like A Fender Twin.
It will just fart :lmao:
I use pedals to get my sound/tone/breakup and can run that into 3 quite different amps and still get a similar tonal outcome.
As much as I hate pedal boards I've realized that it's easier than trying to mod amps. (Sand or Glass)

On my Pedal board,
I use a tone circuit, a Treble booster and a compressor along with a simple OD setup.
This covers most of the classic rock/pop styles I play. If you are into heavy metal grunge then this would not work.
The tone circuit and Tboost are my own designs.
If you are into building pedals I can post them here?

You have to experiment a lot before you find what works.
And for bedroom players don't assume the fantastic sound you hear at low SPL will equate to stage stardom,, At high volume it most likely will turn to crud.
Phil.

10
Amplifier Discussion / Re: Zener vs IC regulator for the preamp section
« on: August 30, 2019, 11:41:58 PM »
Who told you zeners are unstable?   A zillion guitar amps use zener regulated supplies for the op amps.
Maybe i should have said that generally IC regs are more reliable?
I don't recall having to replace any IC reg circuits I've worked on. But you have many more years of experience than myself.
In my limited experience I've had to fix a few Zener regulated circuits.
Maybe not so much the fault of the Zener but the way it's implimented.
I can't recall exacts now but I recall a couple of SS Amps where the zeners have run so hot it delamed the copper track,,Overheating and killing the Electro beside it.
If only a little more thought went into layout and stand off the zener from the PCB it would have been ok?

Also after replacing the Zeners in my old faithful SS Laney twice in the first~5 years I ripped them out, replaced with ICreg and has given no issues in the last 10+ years.
Phil.

11
Amplifier Discussion / Re: Zener vs IC regulator for the preamp section
« on: August 30, 2019, 10:22:48 AM »
Zener or IC reg will make no difference to any *Organic mojo*
These are SS amps and without any form of OD the amp will have no feel.
these trick have to be done in the preamp stages.
to get power stage rattle in SS power amps you need to have years of practice at building gear.
I use an old Laney keyboard amp which is rather basic and *Sterile* by itself but all the tricks are in the pedals I use, easier and cheaper than trying to reinvent the wheel of Valve power stage compression and all the other mojo that goes into that.

I have 6 pedals on my board 3 are brand names and 3 are my own designs.
This covers all my needs from clean to heavy OD. I don't play metal or like so I only need the classic rock which is often just a bit of compression and rattle. Some call this the edge of break up.

as to regs,, IC regs are trouble free and would have better regulation.
Phil

12
OK good to hear you are ok with it.  :tu: sorry i missed the point but I did have one young chap who almost blew himself up assuming the circuit did not need a transformer and wanted to plug it directly to mains. xP

The Headphones might be powered from the preamp hence it works ok to that point.
Sounds like a power stage problem.
Things to try;
number one, with meter set to DC Volts check if there is any DC voltage on th output,, report the result,, it should be very close to Zero DC.
Look for hairline cracks in the solder pads, use a magnifying glass in sunlight to find them.

It may have a Zobel network on the output (google it if not sure),, normally a cap and resistor across the output.

check for any overheating caps or resistors on the power amp as these parts can drift after years of service.

pock around with a wooden chop stick and gently wiggle parts and see if you can get the sound to change.
That may give clues as to what parts are failing.
Sorry We can't be much help.
Maybe take pics of the guts and post ,, that may give clues for folks here to help.
Phil.

13
If you bypassed the Mains transformer and you are STILL ALIVE to talk about it then consider yourself very VERY lucky.
NEVER bypass the transformer of an amplifier. :trouble :trouble :trouble :trouble

I doubt the amp has been as lucky as you,, as the much higher voltage would have most likely destroyed the circuit and likely not worth fixing. :'(

I'd advise you to get help from a qualified tech shop to check out if it's worth fixing.
Phil.

14
If you have 20VDC across the speaker terminals then (as Enzo has already noted) the chip is likely fried.

Disconnect that speaker until you get zero volts on the output otherwise you could burn up the voice coil.

Check to see if the Zobel network on the chip output has signs of over heating, a sign there is instability,, possibly bad layout, circuit design.
If so then others here may know what is wrong.
The Zobel is the series resistor and cap across the output.  It should be as close as possible to the output terminals of the Power chip.
If there are signs of discoloration (overheating) then check that resistor is within tolerance.

To the best of my understanding the LM1875 will work,, though you may have to replace the zobel.
TDA2050 data shows 2R2/2Watt and 470nF,, while the data for LM1875 shows 1R and 220nF.

I just did a search on TDA2050 and spider 2 and 3 seem to have a habit of blowing.
so maybe bad design or maybe counterfeit chips.  :-X
hope that helps,, Phil.

15
Amplifier Discussion / Re: Gallien Krueger 800RB
« on: August 20, 2019, 02:22:45 AM »
Well have you checked the voltages on the schematic?

https://elektrotanya.com/gallien-krueger_800rb_sm.pdf/download.html

If that 5 Ohm resistor at R57 is running hot then I believe that is a sign that there is Hi Freq instability.

What is the DC reading at idle?
Then how much does it drift as you increase power?
I'd haz za guess the issue is early in the signal path.
If C11 is stuffed that may send it into oscillation.
A scope here would be the best way to tell you what is going wrong.

Also don't forget to keep a keen eye on simple things like dried /cracked solder pads.
Phil.

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