Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Balticnoiseforge on July 21, 2021, 03:30:09 am
-
Iam building a clone of a Hiwatt dr201.
But iam having trouble finding a good choke.
Tried mouser etc and best i could find was 4H 225mA.
I dont know what original is specified as more than it is a 4H.
The transformers i bought can handle up to 1.3a on each filament, abit overkill but they are sold as dr201 transformer.
Iam building the x4 kt88 version with x4 preamp tubes, but may add one more for fx loop.
But problem iremains, cant find a 4h with enough mA, is there anyone that knows where to find one? I would need 250mA+ to be safe if i calculated the draw right.
Or is there any other "tricks" to make a choke withatand more mA?
-
here's a couple, bigger henries is not a bad thing as long as your RC times don't get crazy long
EDCOR - CXC Series Power Chokes (edcorusa.com) (https://www.edcorusa.com/cxcseries-1#/specFilters=47m!#-!414!##!419)
-
here's a couple, bigger henries is not a bad thing as long as your RC times don't get crazy long
EDCOR - CXC Series Power Chokes (edcorusa.com) (https://www.edcorusa.com/cxcseries-1#/specFilters=47m!#-!414!##!419)
Talked to a guy that said original dr201 choke is 10H @125mA, 115ohm
That means i could get away with using the 4h 225mA choke.
4H i got from mark Huss hiwatt schematic homepage.
Current draw of a x4 kt88 + x4-5 ecc83 must be higher there, also that both HT filaments is above 1a feels odd.
Link to attatched .Gif image
https://hiwatt.org/Schematics/DR_200wPS.gif
-
The Hammond 159s (https://www.hammfg.com/files/parts/pdf/159S.pdf) is rated 4H @225mA. That's way more current than needed for the DR201.
-
The Hammond 159s (https://www.hammfg.com/files/parts/pdf/159S.pdf) is rated 4H @225mA. That's way more current than needed for the DR201.
Oh okay - well then it should work, also have one of those at home.
What i dont understand is that the "replica" transformers are over 1a on both HT wires.
Was quite cheap for being such big transformers tho.
Tube town dr201
Technical Data:
Primary: 115, 230 & 240 V @ 50 Hz
Sec. 1: 0V - 178V @ 1,3 A
Sec. 2: 0V - 288V @ 1,3 A
Sec. 3: 6,3 V C.T. @ 9 A
Sec. 4: Bias 50 V @ 200 mA
-
What i dont understand is that the "replica" transformers are over 1a on both HT wires.
The HT secondaries need to supply a LOT of current because the plates of 4 x KT88s require a LOT of current. However, the choke only needs to handle the much smaller screen current of the KT88s plus a few mA for the little tubes. The heavy KT88 plate current does not flow through the choke.
I'm moving this topic to a more appropriate forum where it will get much more exposure.
-
Alright, slightly confusing for me - only built 50watt simple amplifiers etc, or well nothing like a PSU here.
Probably doesnt understand chokes fully either - in my head all current that goes to anodes rail would have to travel through choke - making it need more. But probably missing something, Will be some good goodnight reading.
-
Realised where i was thinking wrong, KT88 anodes is fed from HT1... Duh 😅 - thanks!
-
Since i got a Hammond 1590s at home.. is it worth using?
As i understand the henries of it will increase if it is not running close to the 225mA, but how much? Could anyone guide me to a place where i can learn that?
Also the less ohm is not something to worry about if iam not wrong? Also adding a series resistor would not make much sense.
OR is it worth ordering another choke that is closer to 4H @~125mA, 115ohm
-
Since i got a Hammond 1590s at home.. is it worth using?
1590S??? Is that a typo? Earlier you said you have a 159S. Just use it.
You should not fret over the fine details. Go to the Valve Wizard's website (http://www.valvewizard.co.uk/index.html) and read the section on Power Supplies-- Smoothing and Filtering.
-
Sluckey: yes that was a typo! Ok cheers, yes i have read alot of his stuff - but Always good to come back there once in a while because after some building you grasp more of what he actually means etc. 😅
Yeah maybe to focused on fine details, after this i will try doing a low w build from scratch trying different things etc - probably educatuional.
-
You could contact mhuss and ask him for advise on chokes. He's an active member at The Amp Garage (https://ampgarage.com/forum/index.php). Just send him a personal message. Check back often for his reply. The email notification does not work.
-
Sluckey: yes that was a typo! Ok cheers, yes i have read alot of his stuff - but Always good to come back there once in a while because after some building you grasp more of what he actually means etc. 😅
Yeah maybe to focused on fine details, after this i will try doing a low w build from scratch trying different things etc - probably educatuional.
Did you end up using this choke? The 159s? If so, how did it work for you? I have one that I'm restoring and the choke was destroyed from shipping. Hiwatt recommended a 5H choke (sorry, don't remember the number), but it's caused me to have to move the PT in order to accomodate for the size and now I'm picking up static which I believe is coming from this massive choke being so close to the output tube which is picking up some of the magnetic field.
I know this is an old post, but I'm hoping you're still active.
-
What is the current rating of your massive choke?
-
What is the current rating of your massive choke?
It's the 193L, 5H, 300mA. Originally, I was thinking it had to withstand 750V, which I later realized is not the case, because it feeds HT2/HT3, so it really could do 500V and be ok.
-
Voltage shouldn’t be an issue usually. Despite the published rated voltage, Hammond told me that they’re all tested at 1kV.
It seems that a 300mA choke may overkill for 4xKT88 g2 and the preamp though? Eyeballing the KT88 info, I’d suspect half that may be ample.
-
Voltage shouldn’t be an issue usually. Despite the published rated voltage, Hammond told me that they’re all tested at 1kV.
It seems that a 300mA choke may overkill for 4xKT88 g2 and the preamp though? Eyeballing the KT88 info, I’d suspect half that may be ample.
So in other words, the 159S would be more than sufficient and the size is a much better fit, allowing the PT to go where it's supposed to and the smaller choke should have a much smaller EMF, which shouldn't interfere with the output tube. Moving the PT to it's original location would also eliminate this as a possibility for introducing noise into the preamp. Either the choke or the PT are introducing noise, but not sure which one. Either way, this seems to be the better option. Thank you.
-
Sluckey: yes that was a typo! Ok cheers, yes i have read alot of his stuff - but Always good to come back there once in a while because after some building you grasp more of what he actually means etc. 😅
Yeah maybe to focused on fine details, after this i will try doing a low w build from scratch trying different things etc - probably educatuional.
Did you end up using this choke? The 159s? If so, how did it work for you? I have one that I'm restoring and the choke was destroyed from shipping. Hiwatt recommended a 5H choke (sorry, don't remember the number), but it's caused me to have to move the PT in order to accomodate for the size and now I'm picking up static which I believe is coming from this massive choke being so close to the output tube which is picking up some of the magnetic field.
I know this is an old post, but I'm hoping you're still active.
No dont worry! The choke worked fine, had no issue with magnetic disturbance or such - and i did build the 200w on a Hiwatt dr103 chassi so even less space i believe.
-
No dont worry! The choke worked fine, had no issue with magnetic disturbance or such - and i did build the 200w on a Hiwatt dr103 chassi so even less space i believe.
Good to know, thank you! I guess I'll be ordering this today! Now I just need to figure out what I'm going to do with the 193L I already purchased.