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Messages - phatt

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Just remove CR1 & CR2 for clean.
Or you could wire up a switch to switch those 2 diodes in or out of circuit for clean or dirt.
With diodes out of circuit you will find there will be a lot more clean but being a small amp it will still distort when volume is high.

Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« on: February 09, 2020, 06:52:38 AM »
Oh yeah,, Enzo mentioned Crosstalk,, Humm.
Try turning the Od Ch volume off as well as the Clean Ch volume.
Does the clean still bleed through?
Just a hunch? Phil.

Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« on: February 09, 2020, 06:42:00 AM »
As for attachments,, just remember to check the file size limit.
It's shown under attachments.
"Allowed file types: txt, jpg, gif, png, zip, pdf, mp3
Restrictions: 12 per post, maximum total size 15360KB, maximum individual size 5120KB"
I often have to reduce images before posting.

Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« on: February 08, 2020, 09:16:44 AM »
OK then,
Try a temporary wire from the pot solder terminal (ground end) now wire that to the main common of the Power supply. (Usually the big filtercaps) Or just strait to the chassis. Does that fix it?
That is the only way you can be sure it's truly at ground.
Not all PCB's are well designed and depending how the tracks are laid down and how far around the ground track takes to get back to PSU common can effect the actual ground.
I got caught with something similar,, a reverb that would not turn completely OFF,, drove me nuts.  :trouble

Guitar News / Re: It's 2020, and Germanium Fuzz pedals still sound awesome
« on: February 08, 2020, 02:40:16 AM »
Thanks Joe,, Well not my thing and it sounds just like all the other fuzz boxes I've ever heard/Played. Always hated that sound as it just trashes an otherwise good sound.
The kids obviously love em and they are still getting rave reviews. The circuit has been rehashed many times over and it still sounds crap to me  xP
 but each to there own opinion. :tu:

Amplifier Discussion / Re: Peavey Stereo Chorus NEW noise problem
« on: February 08, 2020, 02:32:03 AM »
My thoughts if useful,
Maybe post the schematic will help.
Sounds like you might have 1 or 2 issues.
The buzz behind the note might be *Crossover distortion*, the bias in the power stage might need adjustment. (or as Enzo said dodgy supply)
Re, Killing buzz by touching strings might be a grounding issue.
Schemo would be a huge help.

Amplifier Discussion / Re: Marshall Lead 12 testing and repair questions.
« on: February 07, 2020, 03:13:08 AM »

If the bases of Tr1 & Tr2 are as stated then it's a fair bet the most likely problem is the Output Tr's.

but maybe check this first before you swap out parts willie nilly;

Lift (unsolder) the input side of C8 (it's the input to power amp) now use your walkman or any audio device that has line/headphone output.
You should hear a reasonable medium level CLEAN sound.
If the sound is severely distorted or very low volume then it's a fair bet the power transistors are shot or TR3 is dead.

Amplifier Discussion / Re: marshall G30R CD clean channel volume problem
« on: February 07, 2020, 03:00:42 AM »
The most likely problem is the Volume pot is not grounded.
Several possibilities; the Volume pot itself might have cracked the ground pin,,or a cracked track,, a cracked or cold solder joint on the PCB.
Use plenty of light as these cracks are often hair thin and hard to see.

Amplifier Discussion / Re: Vox Mini 3g2
« on: February 03, 2020, 07:54:35 PM »
Hello Max & welcome,
                Disconnect the speaker wires at the speaker and check with a meter it should read somewhere between 4 and 8 Ohms if it's working.
If you don't have a meter then tap the terminals of the speaker with a 9Volt battery,, you should hear a click/pop and the cone will move. if no sound then the speaker is likely blown.
Don't leave the battery connected for a long time.

Amplifier Discussion / Re: Marshall Lead 12 testing and repair questions.
« on: January 31, 2020, 05:17:24 AM »
Wow...okay.   So my readings...

B to E = -.59 v
B to C = +19.73 v

B to E = -.56 v
B to C = +18.49 v
Test point voltages are referenced from Ground.
So black probe on Common/Ground/Chassis, then with Red probe check the test points.
Then post your readings.

*when probing TR2, B to C, it puts a hum to the speaker.  Sounds like 60hz.

Cannot determine "junction" of R15 and R16.

not important, just check the test points you can find.

Signal tracer?  Are we talking about inputting a low-level audio signal and testing for it at IC pin 1?

Yes you can inject a low signal into certain points on the circuit to find the offending part.
but I would be checking you have close to correct voltages at those test points on the poweramp first.

Amplifier Discussion / Re: Marshall Lead 12 testing and repair questions.
« on: January 30, 2020, 12:10:52 AM »
Measure your DC supply voltages,,Might be a good place to start.
IF? the schematic I'm reading is the correct one,, then you should have ~20-0-20VDC for power amp and about ~15-0-15VDC for preamp.

The test point voltages are written on the schematic for the power amp section.
The Emitters of Tr1&Tr2 should be -.7Volts,, Collector of Tr1 should read +18Volts.
Junction of R15&R16 should read -9Volts.
If one of those readings is way off then that will help folks work out what'sup. :tu:

Schematics and Layouts / Re: guitar amp diagram revision help
« on: January 26, 2020, 07:44:48 AM »
Thanks Joe, yes I was fairly certain that was the case. :tu:

Yeah I get your point about the fun of building your own rig,,,,but you have to buy and build everything. xP
Yes a kit is a good way to go, assuming you are talking just a power amp kit?
BUT you still have to pucha$e; a speaker, transformer, face plate, knobs, maybe some paint and vinyl covering,, add speaker cloth, a cab handle, rubber feet, corner caps.
Then you have to design a circuit from scratch that may end up no better than a $40 bargain from a second hand store. The circuit posted is a small 10/15Watt basic circuit and these can be found on landfill sites if you hunt around and you may even get lucky and pickup a whole amp for nicks. (well that depends on where you live I guess)
Having built a lot of amps from kits and from scratch,, I can tell you that the chance of success at first attempt is very low. Even worse if it's a first attempt. :-X

On the other hand ""IF"" *Watermelon33* has played an amplifier that uses this EXACT Design and it delivers the sound he wants,, then yes it then makes logical sense to build one because you have already heard the result.

My advice would be buy something cheap and back engineer it, you will learn a lot faster and avoid the eternal frustration of building a circuit only only to find it sounds nothing like what you hoped for.
cheers, Phil.

Schematics and Layouts / Re: guitar amp diagram revision help
« on: January 24, 2020, 07:39:05 PM »
BTW, X1 is NOT a buffer. As for distortion, just adding diodes won't work well, you would need to add an extra stage to get a reasonable outcome.
You could add an input buffer stage and alter X1 to work like the link *Joecool* noted above.

Also, I believe the TDA2050 is no longer made, though you could use LM1875, others here will know more.

The reality of this is that you it would work out a lot cheaper and many times easier to just purchase a small amp. xP

That would be a waste of a good malt whisky.
Your tone would sound a lot better if you drank the whole bottle. ;)

Tubes and Hybrids / Re: 12 v tube preamp
« on: January 17, 2020, 08:59:30 PM »
hi Flester,
AFAIK, Tiny Terror is all valve running on high voltage.
I have no doubt that running Valves on low voltages will work but I doubt you will do much better than SS pedals.
The big thing with Valve rigs is the High voltage and the way in which the supply is delivered to each stage.
I think the term is  High Impedance supply, these sag as power is increased giving the classic compression feel. There are of course many other things that make all valve amps do the magic but just altering the values of the drop resistors in the supply chain changes the way the whole amp responds to how you play.
I doubt that will happen if running an AX7 at 12Volts.

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