Hey,
I got a 'Mains Transformer' for a Valve amp project I am working on from ebay, but I have little knowledge of testing mains transformers and was wondering if any of you can make sense of this Power Transformer for me
The writing on it is:
0 120 0 120
ANGLIA A53882
35 0 35
Apparently this transformer came from a 100w valve Sound city amp.
I need the outputs for this amp: Marshall JMP 2204
I was planning on making the 50w version as I have little money for all the valves and this is just a project of mine
Many Thanks!
I got a 'Mains Transformer' for a Valve amp project I am working on from ebay, but I have little knowledge of testing mains transformers and was wondering if any of you can make sense of this Power Transformer for me
An externally hosted image should be here but it was not working when we last tested it.
The writing on it is:
0 120 0 120
ANGLIA A53882
35 0 35
Apparently this transformer came from a 100w valve Sound city amp.
I need the outputs for this amp: Marshall JMP 2204
I was planning on making the 50w version as I have little money for all the valves and this is just a project of mine
Many Thanks!
Yea, Dont think I said it was an output transformer, Sorry if I did!
I got slightly confused as the post by hidnplayr says about the 'output stage' But still...
Thats the only writing on the entire Transformer... I just need it for the Power Transformer in the Schematic.
I thought The power Transformer was meant to output a few hundred volts, something like 400... So I need to test it if the writing doesnt tell me what it outputs. I was a bit afraid to just wack 240 volts straight through it though!
I got slightly confused as the post by hidnplayr says about the 'output stage' But still...
Thats the only writing on the entire Transformer... I just need it for the Power Transformer in the Schematic.
I thought The power Transformer was meant to output a few hundred volts, something like 400... So I need to test it if the writing doesnt tell me what it outputs. I was a bit afraid to just wack 240 volts straight through it though!
Hi there,
no need for testing, the writing tells very clearly what will come out:
If you put in 120V (primaries parallel) or 240V (primaries in series) it will put out 70V center-tapped on the secondaries.
I think there's not much use for 70V in tube audio, except for a negative bias supply perhaps...
Greetings,
Andreas
no need for testing, the writing tells very clearly what will come out:
If you put in 120V (primaries parallel) or 240V (primaries in series) it will put out 70V center-tapped on the secondaries.
I think there's not much use for 70V in tube audio, except for a negative bias supply perhaps...
Greetings,
Andreas
Not necessarily. The available 70 VAC could be voltage multiplied by the type of circuitry shown here. Five stages should get the rail into KT88/6550 "territory". That 35-0-35 is quite adequate for powering a 100 W. "sand" amp. and should support 50 tube W. easily enough. BIG 'lytics are needed in the multiplier.
Hi there,
voltage multipliers are only useful if little or almost no current is required, and even then they need really huge, high-voltage-capable capacitors to keep ripple reasonably low. No chance to use them for current-demanding amplifier service. Parts would cost way more than a correctly dimensioned mains transformer.
Greetings,
Andreas
or you could buy another transformer with 30-0-30 secondaries, and wire the transformers back to back. That way you will get about 280 volts ac out, which, when rectified will produce the 400 volts you need for the Marshall amplifier. A 280 volt transformer will be quite rare on ebay, anyway!
However, if you don't know what you are doing, be aware 400 volts will be lethal! I will not accept responsibility, etc.
However, if you don't know what you are doing, be aware 400 volts will be lethal! I will not accept responsibility, etc.
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Andreas,
The 1/2 wave parallel design I linked has decent current capability, unlike the 1/2 wave series setup. Suitable caps. will not come cheaply. Some cost containment can be realized by taking advantage of the fact that the WVDC required increases by stage in the 1/2 wave parallel setup.
The 1/2 wave parallel design I linked has decent current capability, unlike the 1/2 wave series setup. Suitable caps. will not come cheaply. Some cost containment can be realized by taking advantage of the fact that the WVDC required increases by stage in the 1/2 wave parallel setup.
No, if you put a transformer with 30-0-30 on the 35-0-35 winding, the core of the second transformer will saturate!
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It's still next to useless. The voltage regulation will be horrible, and it's still a half wave design, and that means core magnetization, saturation, and xfmr poofage.
"Suitable caps. will not come cheaply". No, they certainly won't. The best thing to do with that 70Vct xfmr is to save it for a SS project, or sell/trade it for a proper xfmr that will provide more appropriate voltages/currents for a hollow state project. It probably won't cost more than the capacitors you reference, and it'll work much better.
Ok,
I seem to have taken a *too* short look at it
- sorry for the mistake ... And of course voltage multipliers are useful in their applications. But for a guitar amp PS I would not go that way...The later stages will need large HV caps that do not come for cheap - a suitable mains transformer will not cost more. Why take the more difficult and parts-demanding approach here?
Greetings,
Andreas
You should be able to get a decent amount of music power out of it before saturation. (try and calculate it, 35V in 8 ohm)
You should use 160V or less on the anodes of the PL519.
the irony is lost...........
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