Its a voltage divider to set the voltage across the mosfet. So its the ratio that matters. Substituting 470K should have almost no effect on the final result. You are aiming for about 10V across the Mosfet.
Shoog
Cheers Shoog; your never far from your PC are you?
Not at the moment. I am on holiday and revising for an exam on Thursday, so I tend to hover. I've just switched my computer sound system over from a Gainclone to a valve amp and the results are very good, so I have the computer on for background sounds. What more could I want.
Shoog
Shoog
Hi JBS,
I have this transformer.
Not sure if you can see the details, this camera is rubbish. It has 36,0,36V and 0,40V secondaries. Its 68mm high on its side. I would say its 50-60VA. You can have it for postage if you would like it. Although I think it may be a bit low on voltage for you.
Other than that with your 70mm height you could use 2 or even four transformers to get the required voltage. Or a toroid, this does have the advantage of being able to add the heater windings without too much trouble.
Cheers Matt.
I have this transformer.
Not sure if you can see the details, this camera is rubbish. It has 36,0,36V and 0,40V secondaries. Its 68mm high on its side. I would say its 50-60VA. You can have it for postage if you would like it. Although I think it may be a bit low on voltage for you.
Other than that with your 70mm height you could use 2 or even four transformers to get the required voltage. Or a toroid, this does have the advantage of being able to add the heater windings without too much trouble.
Cheers Matt.
Attachments
Thanks Matt, thats a great offer but I've got a transformer for the tubes now:
--|MCF/T2950F|TRANSFORMER, 75VA, 2 X 50V | CPC It should give me about 70VDC at the rails. But thanks mate. It's the 6v heater supply I'm missing now, I can get one from the RS or Farnell trade counters next time I'm passing unless I stumble accross one before then.
What you studying Shoog?
--|MCF/T2950F|TRANSFORMER, 75VA, 2 X 50V | CPC It should give me about 70VDC at the rails. But thanks mate. It's the 6v heater supply I'm missing now, I can get one from the RS or Farnell trade counters next time I'm passing unless I stumble accross one before then.
What you studying Shoog?
Sorry, I forgot to say, you have a couple of LM3*7 regs from the old CA setup. Looking at the PS diagram they were living on the edge. 45V in? whoaa. I bet one or both are dead. Yeh they only drop 10V or so but unless they are HVT or HVK types they must have had a good ride.
Cheers Matt.
Cheers Matt.
yea it was edgy, I've picked up 3 faulty Cambridge audio amps in the last couple of years and it's always been a component working on the edge, rectifier diods, regulators and output transistors.Sorry, I forgot to say, you have a couple of LM3*7 regs from the old CA setup. Looking at the PS diagram they were living on the edge. 45V in? whoaa. I bet one or both are dead. Yeh they only drop 10V or so but unless they are HVT or HVK types they must have had a good ride.
Cheers Matt.
Career change. Took me a while to work out what I was good at. Science, problem solving and all things environmental. Having fun mostly.
Shoog
Good for you! It took me a while to realize I cant work in an office; changing to a field job after 8 years in an office was the best thing I ever did, I actually enjoy going to work now.
I'm Starting to think about the Rectifying circuit, I'll upgrade this over time towards the Eli Duttman design;
For the MK1 do you think I should go with just Capacitance or a CRC circuit?
Also Shoog, do you have any more info on getting a good choke out of a lighting ballast? Googling is not getting me anywhere!
J
For the MK1 do you think I should go with just Capacitance or a CRC circuit?
Also Shoog, do you have any more info on getting a good choke out of a lighting ballast? Googling is not getting me anywhere!
J
You don't want to lose any voltage so a CRC is a big no no. The amount of capacitance you have should give you adequate filtering (I hope), but if you can lay your hands on some lighting ballasts then they will improve matters a huge amount at almost no voltage cost. Basically all Florescent strip lights use chokes to prolong the current cycles out to give nearly smooth current. These are rectangular transformer looking things. Basically if you can find any redundant florescent lights there should be a nice little choke in it. This has a two point block terminal and is simply wired in series between your two capacitors. You will need a pair, one for each rail. Any size will be a huge help at these currents.
I salvaged some from the original CFL's which I had 10yrs ago - these were proper little chokes mounted in the bayonet fitting - they were great and small. I also go a pair from a specialist lighting supplier in Sheffield, and any decent lighting supplier should have them for about a £10.00 a go.
If you configure your caps as two series stacks in parallel, you can add in the chokes at any point in the future.
Good Luck
Shoog
I salvaged some from the original CFL's which I had 10yrs ago - these were proper little chokes mounted in the bayonet fitting - they were great and small. I also go a pair from a specialist lighting supplier in Sheffield, and any decent lighting supplier should have them for about a £10.00 a go.
If you configure your caps as two series stacks in parallel, you can add in the chokes at any point in the future.
Good Luck
Shoog
These are rectangular transformer looking things. Basically if you can find any redundant florescent lights there should be a nice little choke in it
Interesting to know Shoog because chokes are not available down here.
Also are these in the power supplies of desktop computers?
Maybe I should take a photo of one I have to identify the components and see if I can use any.
Cheers
No they are only in lights. The chokes that are in SMPS are very low inductance because they are designed to work at smoothing very high frequencies. Florescent light ballasts are meant to deal with raw mains power and so have relatively high inductance (but not great current capability).
For power amps I have had great success with using the secondary of a Microwave Oven Transformer. They are big and ugly - but they can cope with 0.5A of current which is quite spectacular really.
Shoog
For power amps I have had great success with using the secondary of a Microwave Oven Transformer. They are big and ugly - but they can cope with 0.5A of current which is quite spectacular really.
Shoog
For power amps I have had great success with using the secondary of a Microwave Oven Transformer. They are big and ugly - but they can cope with 0.5A of current which is quite spectacular really.
I just happen to have a broken microwave that's been sitting around for 2 years!
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