Nice to get confirmation of my results.
I just thought, the winding insulation must be fairly substantial as it is designed to work with over a thousand volts. Handling a mere 130V should be a piece of cake, and heating is not a major issue.
Lifting the winding is easy, you will find a little metal stud on the side of the core with one end of the winding attached to it. Cut the winding at the stud, strip it back and use a little plastic joining block to terminate it. The winding is very thin - so attach the joining block to something solid - consider drilling out the stud and replacing with a mounting screw. Cheapest and best choke out there for a half amp supply.
The only problem I have with my next build, is I haven't got any spare voltage to burn in such a choke, so I can't do it - and thats a real bummer.
Shoog
I just thought, the winding insulation must be fairly substantial as it is designed to work with over a thousand volts. Handling a mere 130V should be a piece of cake, and heating is not a major issue.
Lifting the winding is easy, you will find a little metal stud on the side of the core with one end of the winding attached to it. Cut the winding at the stud, strip it back and use a little plastic joining block to terminate it. The winding is very thin - so attach the joining block to something solid - consider drilling out the stud and replacing with a mounting screw. Cheapest and best choke out there for a half amp supply.
The only problem I have with my next build, is I haven't got any spare voltage to burn in such a choke, so I can't do it - and thats a real bummer.
Shoog
rcavictim -
The L rating is very helpful. I can clearly see that I am way behind on the test equipment I will need for this hobby, although I do have a static inductance meter. Is there a particular MW oven wattage or xfrmr weight I should be looking for?
Not sure what you meant by:
What brand/model/source of toroids did you use in your amp?
thanks very much
The L rating is very helpful. I can clearly see that I am way behind on the test equipment I will need for this hobby, although I do have a static inductance meter. Is there a particular MW oven wattage or xfrmr weight I should be looking for?
Not sure what you meant by:
What brand/model/source of toroids did you use in your amp?
thanks very much
Still looking for a PT -
kevinkr -
After sleeping on it -- although I think there are times when using a dual primary as an iso xfrmr is ok - this instance is just NOT one of those times --too much current/power/heat involved here. So I am "back in the saddle" for a PT for this beast ... thanks Kevinkr for the sanity check
However, being the info "packrat" that I definitely am 🙂, is there any special fusing or construction tips you all could offer to minimize the effects of transformer failure and/or stress when using a dual primary as an isoxfrmr? thx again ...
kevinkr -
After sleeping on it -- although I think there are times when using a dual primary as an iso xfrmr is ok - this instance is just NOT one of those times --too much current/power/heat involved here. So I am "back in the saddle" for a PT for this beast ... thanks Kevinkr for the sanity check
However, being the info "packrat" that I definitely am 🙂, is there any special fusing or construction tips you all could offer to minimize the effects of transformer failure and/or stress when using a dual primary as an isoxfrmr? thx again ...
I think we are getting confused here. Your power transformer is OK for using the secondaries you have available to derive your +B so no issue there. Its a bit marginal but fine. You are not trying to use the primaries to derive your +B - I'm a little confused where that came in !
When talking of the MOT we are discussing using the secondary of the MOT as a choke. The primary is totally unused and will not present any problems at all. The wattage is not critical, but the higher the wattage is the more Henries that are likely to be preserved when the DC is on it. Any pulled transformer should do the job - they are all fairly much the same. The only issue to consider is that they are big and the bigger the wattage the bigger the transformer (they are also ugly and need to be inside your case and not on display.
You need to do a search of what toroidal suppliers are in your area. they are not all the same, but fairly much so. I have used Telcam and Multicorp brands successfully - and Farnell is my supplier - but that is no use to you in America.
Shoog
When talking of the MOT we are discussing using the secondary of the MOT as a choke. The primary is totally unused and will not present any problems at all. The wattage is not critical, but the higher the wattage is the more Henries that are likely to be preserved when the DC is on it. Any pulled transformer should do the job - they are all fairly much the same. The only issue to consider is that they are big and the bigger the wattage the bigger the transformer (they are also ugly and need to be inside your case and not on display.
You need to do a search of what toroidal suppliers are in your area. they are not all the same, but fairly much so. I have used Telcam and Multicorp brands successfully - and Farnell is my supplier - but that is no use to you in America.
Shoog
OK - I think I see the miscommunication - here was my original thinking.
However Shoog convince me to use a separate Heater source which could change this to the following -- right?
Primary #1 115V mains in
Primary #2 NC
85VCT Driver stage B+; SS rectified (approx 210VDC )
39VAC Power section B+ SS rectified
16VAC Fan source
By my quickie estimation - the 39VAC taps will only yield about ~98VDC right? I didn't think this was NEAR enough for the 6080s - your schematic calls out 125V. So I just figgered these taps were NC.
Thanks Shoog - I got no problems with a little dumpster diving for the MOTs - size could be an issue though.
However Shoog convince me to use a separate Heater source which could change this to the following -- right?
Primary #1 115V mains in
Primary #2 NC
85VCT Driver stage B+; SS rectified (approx 210VDC )
39VAC Power section B+ SS rectified
16VAC Fan source
By my quickie estimation - the 39VAC taps will only yield about ~98VDC right? I didn't think this was NEAR enough for the 6080s - your schematic calls out 125V. So I just figgered these taps were NC.
Thanks Shoog - I got no problems with a little dumpster diving for the MOTs - size could be an issue though.
My understanding was that this was going to be for the output stage and the driver, tapping off each stage just after the rectification. Sorry if I missed you idea. The 39V winding could be used to generate a simple negative rail to reference the LM317 cathodes to. This allow for just 100V on the plates of the 6080's and a negative rail of -30VDC. This is quite economical.However it then makes it quite difficult to get your 170V for the front end from the same transformer.
As I said the power supply is the tricky bit.
Shoog
No problem Shoog - you are also very patiently dealing with a real newbie - here (AND an ex-English teacher too 😱). OK I will look for a Driver source.
On the toroid front - the easiest to access US supplier is Antek - however they very strategically (I am sure) have a "gap" in their VA offerings at precisely the specs all of you mention for these uses (i.e., in the 6v/6V and 18V/18V secondary ranges) (are YOU listening ANTEK?????) presumable to "protect" their OT offerings. (Antek - Transformers - Grid View[]=0)
However, they offer a full VA range for the 12v/12V secondaries (at least until I finish this post 🙄). Is there a secret decoder ring/master equation or definitive post about calculating the secondary voltage/VA requirements for the OPT and interstage toroids.
My "pest" alarm just went off - maybe it is time to back off this one.
On the toroid front - the easiest to access US supplier is Antek - however they very strategically (I am sure) have a "gap" in their VA offerings at precisely the specs all of you mention for these uses (i.e., in the 6v/6V and 18V/18V secondary ranges) (are YOU listening ANTEK?????) presumable to "protect" their OT offerings. (Antek - Transformers - Grid View[]=0)
However, they offer a full VA range for the 12v/12V secondaries (at least until I finish this post 🙄). Is there a secret decoder ring/master equation or definitive post about calculating the secondary voltage/VA requirements for the OPT and interstage toroids.
My "pest" alarm just went off - maybe it is time to back off this one.
Divide the primary voltage by the secondary voltage and then take the square of that number. Multiply by the impedence of your speakers and you are aiming for between 1K2 and 1K6 as your final result. For a 8 Ohm speaker you are looking at a 18V secondary for a 4ohm speaker you are looking at about 10V 11V or 12V. I believe I took an 18V transformer and unwound it to 11V for 4R speakers, but its so long ago I have lost track of what I did.
The VA ratings are not critical, except you probably doen't want to go below 50VA for the outputs. For the interstagers you want it to be as low as possible simply for sizes sake, and because the primary inductance is higher on smaller transformers which is good.
Shoog
The VA ratings are not critical, except you probably doen't want to go below 50VA for the outputs. For the interstagers you want it to be as low as possible simply for sizes sake, and because the primary inductance is higher on smaller transformers which is good.
Shoog
Well ... the interstage is where everything blows up. The "smallest" 55Ver Antek offers is *800VA* - didn't bother to look at the price. Think I am screwed. Hammond has a 10Kto90K interstage ($40US) whihc shows up in some 40's era 6080 schematic I saw but the Hammond xfmr has very bad low end specs - not good for bass.
The way it was going this amp was going to be ~100 lbs anyway 😉 - probably could have shut off the furnace in winter too 😀
The way it was going this amp was going to be ~100 lbs anyway 😉 - probably could have shut off the furnace in winter too 😀
Did you mean "take the square ROOT of that number". It does not work taking the square of the first term. thx.
Do a search on "Spud Shade ECL86" and look about three pages from the end. There is a source of transformers given. 120VA at 55V is the best they do. It also has a dertailed discussion on calculating the correct turns ratio.
Here the toroidal supplier;
Rapid Electronics - Electrical & Power
Shoog
Here the toroidal supplier;
Rapid Electronics - Electrical & Power
Shoog
Shoog -- I appreciate all your efforts kind sir --
However -- the shipping from Rapid is 4x the cost of the xfmrs (merch ~$20; ship ~$80) -- hard to stomach that I am sorry to say.
Have not found that list of suppliers nor formuli on my first pass through the thread you mentioned (tried several searches too). I will go thought it word by word tonight when I have more time. Maybe I will try google searching into the forum again - that is the only way I found the thread at all - the internal search engine only returned the message you posted with the name of the thread to search for.
thanks again -
thx again.
However -- the shipping from Rapid is 4x the cost of the xfmrs (merch ~$20; ship ~$80) -- hard to stomach that I am sorry to say.
Have not found that list of suppliers nor formuli on my first pass through the thread you mentioned (tried several searches too). I will go thought it word by word tonight when I have more time. Maybe I will try google searching into the forum again - that is the only way I found the thread at all - the internal search engine only returned the message you posted with the name of the thread to search for.
thanks again -
thx again.
Take the square of the turns ratio and divide by speaker impedance, you will get the primary Z. (I think 😕) That's how I did compute my parafeed OPT using toroidal transformer.
Found a Interstage on EBAY????
Hi Shoog --
Could you look at this EBAY toroid and access wherether is would served as the interstage xfmr for the 6as7 amp? Thanks a million.
High Power Audio Torroidal Transformer 100,55,-55,-110V - eBay (item 280411451895 end time Oct-24-09 14:37:33 PDT)
Hi Shoog --
Could you look at this EBAY toroid and access wherether is would served as the interstage xfmr for the 6as7 amp? Thanks a million.
High Power Audio Torroidal Transformer 100,55,-55,-110V - eBay (item 280411451895 end time Oct-24-09 14:37:33 PDT)
How about this bad boy (not a toroid) 3+1:1?? thx
http://cgi.ebay.com/TRIAD-A-89-A-AU...ptZVintage_Electronics_R2?hash=item35a457967a
http://cgi.ebay.com/TRIAD-A-89-A-AU...ptZVintage_Electronics_R2?hash=item35a457967a
How about this supplier;
15VA Power Transformer
15VA and an Canadian supplier
How ab out these for outputs - if you have 8ohm speakers;
Surplus Transformer
How about these nicely encapsulated ones for mounting on top of the case;
Printed Circuit Mount Toroidal Power Transformers
Or just one of the standard power range;
Output Voltage - 12VAC
Theres a start.
Shoog
15VA Power Transformer
15VA and an Canadian supplier
How ab out these for outputs - if you have 8ohm speakers;
Surplus Transformer
How about these nicely encapsulated ones for mounting on top of the case;
Printed Circuit Mount Toroidal Power Transformers
Or just one of the standard power range;
Output Voltage - 12VAC
Theres a start.
Shoog
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