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Messages - phatt

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Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« on: April 05, 2020, 03:59:55 AM »
OK,,, if you say so but as there are only two wires exiting the mains cord (Brown & Blue) then it's highly unlikely that it is earthed. xP
Normally the Earth wire (Green and Yellow in my country) goes direct to chassis and bolted with a lock washer.
Another thing that may not be obvious is the use of Step down Tx's.
Although the 240v side is Earthed some units don't carry the Earth through to the 120v output and that can go unnoticed until someone gets zapped. >:(

If it were my amp I'd be checking there was continuity between Earth pin on cord and Chassis. Only takes a quick check which could save your life. 8|

The Earth pin/Chassis continuity is the first thing I check when I open an Amplifier.
Stay safe, Phil.
(Never rely on visual inspections)

Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« on: April 02, 2020, 09:54:56 PM »

Take it to a teck shop, they will know where to source a new Tx. while you are there it looks like you have NO MAINS EARTH. ouch!!!
The tecks can install a new power cord with Chassis EARTH.
These things can be a Death trap without an earth.  :loco

Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« on: April 01, 2020, 09:24:09 PM »
Wire taps won't be inside the Tx.

With power cord removed from wall, Follow the incoming Mains wiring.
the sequence will be something like this;
Fuse> switch> THEN look for a tag board or block connector with mains wires that also go to the Tx.

If the Tx primary has dual winding's then there will be at least 4 mains wires between the block con and the Tx. (not to be confused with the secondary wires)
You may even find the numbers on the schematic are also printed on the tags.

Like I said; Take a picture of that section of the amp and post it, that will speed up the answer much faster than us trying to guess it all. hint.  8|

Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« on: April 01, 2020, 07:29:02 AM »
The transformer in the schematic specifically states "Export Model".
That is not what the OP has.
HUM :-\
Yeah maybe you are right JazzP but the OP would be wise to check before spending money only to find it was a simple wiring swap.

That schematic shows both Local and Export Tx's wound with 2 winding's.
Local TX is tapped in Parallel delivering 120v while Export is the same TX but tapped in series giving 240V. (well that's how I read it?)
The note under Export Model implies the Tx is the same you just have to reconfigure the wire taps.
I'm not familiar with that particular amp but I do know that a lot of gear was wound for both 120/240.
Some older gear came with a rear panel mechanical switch usually next to the power cord and fuse.
But some gear had to be opened to access the taps.
Maybe *Ratsapprentice* could lift the lid and take a picture of the Tx. :tu:

Amplifier Discussion / Re: Ampeg Vh140c power transformer replacement
« on: April 01, 2020, 12:04:24 AM »
   If the schematic is correct for your amp then it is already able to run on 120/240V.
You will need to change over the input wiring which is circled showing which taps.

If you do not have experience with this then don't try to swap it over yourself.
Doing so could destroy the whole transformer and blow the amp as well. i.e. smoke and flames. 8|
Get a teck to do the change over.
Cheers, Phil.

Amplifier Discussion / Re: Customized Kustom 12 Gauge
« on: March 31, 2020, 09:10:46 AM »
Regards Speakers.
 Years ago i read an article in a El magazine, I can't recall details now of course but the writer made the observation that it is better to design from the speaker back to amplifier.
He was referring to hifi but over the years I've come to understand why he made that observation.

The reality of this Amp/speaker thing is complex.
Many pages on guitar forums are filled with Spk debates and observations.
I can tell you that even though many amp circuits might look similar one only has to alter a 20cent passive in a circuit and it can have big impact on the outcome.

Much like Valve shootouts, they always give me a giggle.
Someone swaps a whole lot of valves in a particular amp circuit and gives an observation of which one is best.
Even some educated folks entertain this stuff.
Yes in one particular amp circuit Valve X might work better than Valve Y.
But that does not mean that valve X is better for every circuit. In another circuit design the opposite might be the case.
Same goes for speakers.
I may have told this little story before but years back a mate brought me his Trademark 60 combo.
He said do whatever you can but if it does not work I'll dump it. It's way wrong, too harsh, brittle. Dist ch is not usable.
After a few days of pondering what could be done I decided to try a few old speakers I had laying around.
OK the Hot rod Eminence special design speaker that was in the trademark might have higher SPL and make the amp sound a lot louder than another similar 50 watt chip amp design but those big name fancy pants drivers that promise so much will often peak at higher freq and hence sound Louder. (they know the kids will often buy the loudest unit) ;)
Problem with that is they are excessively bright when using heavy distortion, All sweetness is lost when you do that.
To overcome that issue one would have to dig deep into the circuit and change a lot of stuff.
As Trademark goop all the circuitry that I would need to change,, well it's just not worth all the fuss when all that was needed was a more balanced (Flatter SPL freq response driver)
My mate could not believe the huge difference.
the speaker was a $10 junk sale purchase. 8|

Just my observations,, Phil.

Guitar News / Re: Coronavirus hitting the music industry
« on: March 19, 2020, 08:05:08 AM »
The Elephant in the room; :o
It took ~~ 40,000 Yrs to reach 200 Million people on this planet
At the time of Christ it's estimated that it was a shade under 200Million.
By the 1830's we cracked the 1 Billion mark.
Less that 200 Years later we have hit the 7.8 Billion.
Now if that does not tell you the real reason for the worlds problem I don't know what will. 8|
Unlike the FAKE hockey stick curve presented by Al Gore this one is REAL.
Scroll down a bit for the graph,, scary :'(

There are people that suggest that the human population on Earth be limited to 500 million. The first place I ran across this was here:
It's interesting that they can't seem to be able to track down the people that paid to put these things up.

Thanks, Interesting find, I did not know about that one.
Maybe they wanted to stay anonymous as they would have been persecuted. 
Although a bit hard for us all to swallow it's a fair assessment as there is a limit to how many people the planet can sustain.

Amplifier Discussion / Re: Adding spring reverb to a 6V6 guitar amp
« on: March 19, 2020, 07:50:27 AM »
Assuming you have this new rev circuit on a separate board.
Then my first thought is,,,Check you have a ground path back to the main amp circuit?

Guitar News / Re: Coronavirus hitting the music industry
« on: March 14, 2020, 09:17:52 AM »
The Elephant in the room; :o
It took ~~ 40,000 Yrs to reach 200 Million people on this planet
At the time of Christ it's estimated that it was a shade under 200Million.
By the 1830's we cracked the 1 Billion mark.
Less that 200 Years later we have hit the 7.8 Billion.
Now if that does not tell you the real reason for the worlds problem I don't know what will. 8|
Unlike the FAKE hockey stick curve presented by Al Gore this one is REAL.
Scroll down a bit for the graph,, scary :'(

Anyone who is familiar with the world of Stock markets will likely know of the bell curve. It goes up and then crashes.
That graph shows it's about to fall over and crash. xP

I do realise that no Politician or world science geek is ever going to mention it in public but that is a reality that we as a species will ALL have to face in the not to distant future.

Regarding *Joecools* comments staying healthy;
Same problem as my fish aquariums when I was a kid,, once they breed and the tank gets over crowded then disease often takes over.
It's darn hard to stay healthy when the whole place is full of pollutants from being packed in a sardine tin while eating organically dead processed food. xP

We fall victim to bad health because we are feed crap food so hence our health in general is starting to fail us, especially in western countries.
If you buy packaged food from supermarkets then it's highly likely you are eating unhealthy highly processed crap foods.
Wheat was hybridized in the 40's and went world wide by the 70's. At that time the world was in famine and it solved a problem. That bloke got the nobel prize, but guess what?  We just kept breeding more people. Durh!!!
As the old saying goes you solve one problem only to find you just created a much bigger problem. opps!
Sadly modern hybrid wheat has a higher GI level than sugar. Sugar is 55 while white bread is in the~60's :o  **Ed opps,, Sugar is 59, Wheat is 69**
It's estimated that 1 in 4 people in the western world now have diabetes. (another Hockey stick curve)
Before sugar was refined and wheat was hybridized Diabetes was hardly ever noted. Now it's off the scale.
If you don't know, Hybrid wheat products of some kind are in nearly all processed foods, that's just about everything in packets, boxes or cans.
I have not used the bread or cereal isle for many years now and I'm in far better health than I have ever been.
Really good info is very very hard to find and you have to read a lot, Do your own research and stay away from doctors as they will make you sicker than you already are. 8|
I've had debilitating health issues since my teens and in the end I was forced to heal myself. It was a lot of work but I no longer live in fear of silly viruses.

Without the output Tx cutting all the fizz I don't see any great advantage.
SS power amps are DC coupled and hence don't cut the fizz generated by over driven stages. :'(
The OTx is part of the magic of Valve amps,, most of the great Valve amps did not use hi spec OTx's and so they smooth out the hi freq crud.
Valve pwr stages also cut very low freq because of caps (AC coupled circuits) and maybe some miller effect.
Most SS pwr stages (Especially ones like you mentioned) are dead flat,,, So unless you have an intricate understanding of how to circumvent all that then my advice is leave the SS pwr stage stock and do all the fancy stuff in a well designed preamp.
Or just research some pedals there are plenty out there 8|

Amplifier Discussion / Re: Peavey CS400
« on: March 10, 2020, 12:53:58 AM »
First check the DC Voltage at the speaker output?
If not very close to Zero then the circuit is faulty.
Yes could be HF problems.
If the amp is working (No DCV on output) then I'd replace the burnt components and see if they run hot. Better minds here will know more. :tu:

Tubes and Hybrids / Re: JTM60 Combo rectified diodes fried
« on: March 04, 2020, 06:34:13 AM »

Resistance across tip and sleeve with tubes in is 138k
I assume that is the resistance reading on the secondary of the output Tx?
Well if so then the output Tx is open,, sounds like a complete failure and taken out both tx's and power valves all at once. :'(
To the best of my understanding;
If the amp is trying to drive such a high output resistance (130k) then you may end up just repeating the same destruction. Never run a valve amplifier with a high or no load resistance you will blow it all (As above)
Pull the Valves and repeat the DC voltage testing, as you did before,, if they read ok then check the Output Tx.

The Newcomer's Forum / Re: JLH 1969
« on: February 27, 2020, 10:33:16 PM »
@ Loudthud,
Oh thanks for that,, I just realised that I was not logged on so did not notice the schematic,, durh me. :duh
well as luck would have it i have a pair of TIP142/147 and a few 2N7000.
Not about to build, just wanted to Bboard the circuit and see how it performs.
I'm not expecting the same Grind I get from my little 10 watt valve amps but if it gives a nice little rattle I might pursue it further.
I agree, pwramps sound good when driven hard but then I'm back to the SPL issue, even a 10Watt amp is often too loud for home practice. :-\
I assume there is no short circuit protection and only about 20 watt output??
thanks for your help, Phil.

The Newcomer's Forum / Re: JLH 1969
« on: February 24, 2020, 07:22:34 AM »
Hi Loudthudsy,
                     I tried to search for that MC12DAR circuit but got nothing meaningful.
I'm interested to try it out as long as it does not need unobtainium reverse wound diodes. :lmao:
I think my problem with trying to get SS PwrAmps to respond like a Valve PwrStage is that
Even if one can reproduce a tuby SS Pwr Stage one is still stuck with the same limitation as A valve pwr stage. That being, they only sound good when they are cranked up. I noticed this with some of the Peavy gear.
So having built quite a few amps now both valve and SS I just use pedals for all the dirt tricks and the amp is a clean simple SS PwrAmp.
I also have built a few ReAmp systems for myself and a couple of local players with quite stunning results.
A small 10w pp Valve amp driving a resistive load and line out to a clean all SS second amp.
This removes the limitation of having to play loud to get the magic OD of Valve pwramp.
So from bedroom to gig SPL's the sound/tone/dynamics are much the same.
BTW my resistive load is NOT the common 8 Ohm load on 8 Ohm tap which as you may already know kills the magic.
Thanks for posting the plots, very helpful.

No worries Lex, Happy to help. :tu:
Yes mate That is the program I use.
How fast you learn to use it depends on how much you already understand about electronic circuits.
But as I mentioned what's to loose because you can't blow anything up and you can't kill yourself by touching high voltage or burn your fingers on a hot soldering irons.  :lmao:
You will still need to read up on some of the basics of audio circuits, a lot can be found on the dub,dub,dub and help is also here of course. 8|

The program comes with a whole library of circuits for you to learn from, some of which will be useless for Audio but no matter just start using it and don't expect to understand it all in a few weeks. It took me 6 months to fully grasp what the hell I was doing and it does send you loco at times.  :loco
Be warned it's a highly addictive hobby, And I'm just so grateful for the friend who introduced me to simulations years back. Even though i already had a fairly good grasp of how amps worked, sims just saved me years of building land fill.
As they say "a picture is worth a 1,000 words"
check your pm's, Phil.

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