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Discussion in 'Cabinets & Speakers' started by Kelia, Sep 15, 2019.
beat you to it, ironballs, third line, post#48.
yet you keep calling it voltage doubling and pronounce false information to readers
- and im completely unconvinced by your vague and illogical explanation of how these marshall amps obtain their H.t, and why it isn't voltage doubling.
why don't you answer the simple questions in post 57?
by avoiding questions like that , which are relevant ( and the key to the whole matter ) to me, at least it appears as if you have absolutely no clue whatsoever.
you're telling people to go and educated if they want answers, then provide answers of your own which make absolutely no logical sense or give a clear direction to anything.
What question? The one that had nothing to do with a voltage doubling circuit?
I'm intrigued by John's passion on the subject.
Is there a way to verify if it is in fact a doubler circuit? Can that be checked with a multimeter for example (I don't plan on poking anything in high voltage quite yet, I'm just curious)?
It may be a dumb question, but I appreciate your patience.
As I said before, go get educated.
don't believe me, ken fischer or anyone else who claims its voltage doubling...look at the question in post 57...its all you need.
get out a tape measure..use your eyes...50 watt power transformer is the same size as 100 watt power transformer post 671/2? to 1981...voltage doubler power transformers are much smaller ( than simple full wave designs ) by virtue of design
again fender twin output transformers dont usually blow, many 100 marshall o/t's blow because of voltage doubling and these flyback spikes.
"This is just something I am interested in, a hobby of sorts."
yeah, measure a power transformer from one of these amps ..youll read approx 180- 0 180v from the secondaries.
how do you get from 180vac to 475vdc?...voltage doubling.
Yes. I have said that before. That does not mean I have no education/knowledge. I come to this forum because I like it, the people and the electronics of amplifiers/guitars.
No, not voltage doubling.
Marshall used the entire of HT secondary of 350-360 VAC of a higher wattage power transformer for the bridge rectifier which is the same as PT HT with no center tap having the same voltage.
Look at an older common 50W Marshall which always uses a center tapped power transformer and the HT has 350-0-350, that would equate to 700 VAC across the entire HT secondary, but those handle a lower wattage so therefore lower current rating.
So in both cases using 350VAC the power supply would develop about 470VDC for the B+ rail.
Only recently has Marshall started to utilize bridge rectifier setups in some of their lower power designs.
Without looking at every Marshall 100W just this moment I would say that every one of them has a bridge rectifier setup.
The biggest thing to note to those who do not have a full understanding of electronics is that the bridge rectifier requires no center tap whereas the full wave rectifier does require a center tap with the same voltage level on both sides of the center tap.
A voltage doubler rectifier, a bridge rectifier and a common full wave rectifier are all different and are setup different with specific required types of components while producing the same outcome.
Anyone who has electronics education would recognize what Marshall did in those amplifiers, not voltage doubling.
I didn't read all 4 pages of comments so forgive me if this was discussed, but just buy a used Weber Z-Matcher for like $100
You can set the input to 8ohms and the output to 5.3 ohms and be done with it.
I own one of these and it makes life so much easier when you have a bunch of cabinets and like to mix them.
- you can do that, and you can do that for years( decades), but not here you can't.
do that here and your amp blows up.
this forum is like a black hole in time space where no thing you say is actually how it is because of voodoo myths.
- of course you can mismatch, enjoy your amp.
ironballs, ive read your response, and it simply doesn't make any sense, it doesnt prove anything except perhaps you've been scanning the internet for answers that you cant come up with yourself.
That wouldn't matter for example, if you'd attempted to answer the simple questions in post 57, and you were trying to use someone elses words to justify an idea of your own in relation to answering those questions.
You wont address those questions ( simple, simple questions ) because to do so goes against your theory.
in response to those questions, you said something like,' they have nothing to do with voltage doubling'
- answer them anyway...it's not rocket science.
it shows me that you know at least something about using your eyes and your brain instead of just scouring the internet for answers.
your exceedingly rude response to smokeydopey when you didn't have the time to scour the internet for answers you didnt have, is rather self-explanatory, and ironic.
How can YOU come here into this forum and answer ANY question when you, yourself, have no formal education in electronics ( just a hobby of sorts..)?
Being rude to me is one thing, and I'm almost certain the moderators would thank you for it, but why type something like that out to someone just looking for answers?
To simply go and tell someone to go and get an education if they want answers, because you cant provide those answers is actually the epitome of rudeness in a internet forum ( especially as you also state this is ' sort of a hobby' for you), and frankly shows me that I can and simply should, ignore everything you type out.
The ratio of naysayers in this argument of whether voltage doubling is used in marshalls I believe is probably 1( no voltage doubling) : 25 ( voltage doubling).
if you want to prove what you believe, i say that YOU ( solely based on your responses, and lack of responses so far) need to get an education, you haven't got a clue, a single clue ,and internet research is only getting you so far.
hint- the reason you cant find the money shot that buries the long standing observation that marshalls used voltage doubling since ( 1967?) when that first one appeared with twin voltage doublers, is because it's not there.
So every Marshall built after 1967 +/- uses voltage doubling? JMP's, 800's, 900's, 2000's, Jubes, etc...etc....?
Is there anything we can see in a schematic that shows voltage doubling components?
no, not every marshall
i believe its from 67 1/2? to 1981, only hundred watters.
ive tried to find them before, but had difficulty.
so, can a schematic show the voltage doubling circuitry?
I have a 1981 JCM800 2203 and would like to know if they used voltage doubling. how can I do this?
i just had a look for you, yes it does use voltage doubling.
its called a full wave bridge voltage doubler.( with a centre tap that goes to filter caps..marshalls little variation)
- carefully match your speaker load if you want my advice.
Please note he will still tell you that it is a voltage doubler.
Here is the schematic for your 1981 2203. Notice the stacked power supply filter capacitors with balance reference to the actual PT secondary instead of using the normal balancing resistor setup (not a voltage doubler).
Now here is a later version 2203 without the center tap reference used (states unused on schematic). It is basically the same power supply except for the power supply filter capacitor configuration. These are paralleled and not stacked.
Now here is a reissue 2203 with stacked power supply capacitors using balancing resistors in parallel. Again the same basic power supply.