martthie_08

stepdown 230V --> 220V ???
« on: July 12, 2005, 04:54:31 PM »
how can it be done? a transformer? have never seen one of those...

what I am doing: Racking some old TAB V-series preamps and they really like to see the 220V they were designed for. I know there are commercial racking products (from hestudiotechnik.de, for example) that have this built in.

what have I done so far: Hooked it up to 230V, sounded great, no problems.

thanx for any help!!!
cheers, Marten


EZ81

stepdown 230V --> 220V ???
« Reply #1 on: July 12, 2005, 05:51:48 PM »

martthie_08

stepdown 230V --> 220V ???
« Reply #2 on: July 13, 2005, 05:46:31 AM »
hey EZ81, that looks great, thank you! I will definetly have a go at this, there is only thing I am a little worried about: In Germany you can plug a power connector both ways into the ac main socket, so you never know which is hot and which is neutral. I am not 100% sure if the circuit you posted cares for this at all, I think it doesn't matter, but could anybody comment?

Great! Marten

Steffen

stepdown 230V --> 220V ???
« Reply #3 on: July 13, 2005, 07:55:37 AM »

peranders

stepdown 230V --> 220V ???
« Reply #4 on: July 13, 2005, 08:15:34 AM »
230-220 isn't much. You probably don't have to worry at all. Plugging 240 VAC "nominal" into an old 220 V amp would maybe cause trouble.
/Per-Anders

gyraf

stepdown 230V --> 220V ???
« Reply #5 on: July 13, 2005, 08:42:48 AM »
Yes, but some of the old V-modules are said to be quite sensitive to mains over-voltage..

Jakob E.
..note to self: don't let Harman run your company..

Mark Burnley

stepdown 230V --> 220V ???
« Reply #6 on: July 13, 2005, 09:47:29 AM »
Yep,

I've got overvoltage readings somewhere of some tests I did on V72/V74/U73's. The V72 and V74 units were rated at 220V, and the incoming UK mains was 245 average. This didn't affect their operation in the short term, but the U73 sounded awful, until I variaced the mains down to the specified 220V. The U73 seems very susceptible to input voltage.

I usually install a 240>220V transformer if there's a set of Vxx/Uxx items, or otherwise mod the HT and LT supplies to use larger resistors on a single for-the-UK unit.

Mark
O_O tape is life O_O

martthie_08

stepdown 230V --> 220V ???
« Reply #7 on: July 13, 2005, 10:05:39 AM »
Steffen, thanks for the link, but unfortunately, the tranny won't do 220, only 215. But that leads me into the right direction, at least now I know what these puppies are called. It's really hard to look for something you don't know the name of.

peranders, yes for guitar amps or the like it isn't that much of a problem, but I wan't to do it right for my V-racking project.

Jakob, this is what I've heard as well and if other folks are doing it, I want to have it as well. Interestingly enough, hestudiotechnik claim that they "limit" the line AC to 220V?! Regulators involved? Anyone have a "Neue Heimat" they can open up?

Mark, where do you order those 240>220V transformers? I have had no luck with RS or Reichelt, where I usually get what I'm looking for...

thanks to all!

Steffen

stepdown 230V --> 220V ???
« Reply #8 on: July 13, 2005, 10:18:12 AM »
V76, for instance, is specified for 220V +5/-15% supply voltage. you are safe with 215V. the problem with the reichelt trannies is the strayfield. you need good shielding or put it external. I racked 2 V76 supplied with this trafo, works fine...but had to put it outside the chassis.

steff

Mark Burnley

stepdown 230V --> 220V ???
« Reply #9 on: July 13, 2005, 10:48:39 AM »
Hi,

I use a standard mains transformer with a 240>230>220>200V tapped primary. I usually buy these as nos on the surplus market.

You connect the mains input to the e.g. 240V winding, and then connect the Vxx mains input to the 220V tapping. The primary is acting as an autotransformer, dropping 20V. Mains Neutral is common to supply and load. If you're lucky, you can use the secondary winding for phantom/lamps etc if you're doing a racking.

Make sure that the VA rating of the transformer is adequate, as all the load current has to be carried by the primary winding. And measure with a load attached the voltage at the tapping of the transformer before powering up your precious Vxx module!

Mark
O_O tape is life O_O


chriss

stepdown 230V --> 220V ???
« Reply #10 on: July 13, 2005, 05:38:14 PM »
when i did meaure my v72 connected to 230V I found the filament at 7V. that is 0,7V too much. something like 11%. not good, these ef804s are getting more and more expensive on - well you know where....
you could put a resistor in the power-line. i remeber i once found a formula to calculate the r on the forum of frihu.de, but you could also test it. somewhere between 150 and 300 ohms i guess. should have more than 1 watt though.

chris

PRR

stepdown 230V --> 220V ???
« Reply #11 on: July 14, 2005, 12:52:22 AM »
In Germany you can plug a power connector both ways into the ac main socket, so you never know which is hot and which is neutral. I am not 100% sure if the circuit you posted cares for this at all, I think it doesn't matter, but could anybody comment?

With that plan, it is possible to have 0VAC, 220VAC, or ~20VAC on the "N" pin.

If the original plugs were both-ways, the preamps were probably designed to not-care about some AC on the N wire. Most good gear does not care.

Otherwise, it may buzz. You'd know, because you would already have had to flip the plug to avoid getting 230VAC on the N line. Old US guitar amps worked this way: flip the plug for least buzz. With this adaptor, you have two plugs to flip, four possible ways, only one puts N at zero VAC.

Reminder: after building, check the output voltage before you plug anything in. With a 230V:12V transformer, you can end up at 230-12V= 218V, or at 230+12= 242V. If it comes out wrong, reverse the secondary winding.

For 230V:220 conversion, the transformer size only needs to be 10/230 of the total load. A 10VA core can carry a 230VA total load. Little preamps, the smallest power-iaon you can find is plenty big enough.

martthie_08

stepdown 230V --> 220V ???
« Reply #12 on: July 22, 2005, 05:03:21 AM »
I still haven't done any work yet, but thinking about it, I am sure now that I want do get it done the way Steffen did. btw. Steffen, I wanted to look at the racking of your V76, but the pictures aren't there anymore, so could you tell me how you mounted the "Trenntrafo"? Did you put it into an external box, or did you mount it on the outside of the rack chassis (like on guitar amps, for example)?

If anyone is looking for a big, cheap trafo with lots of voltages have a look at this one, at 8 kilo it is plain to heavy for my racking. I think with the 5 V Modules, the Steel Chassis and the cut up S67 mount, I will already be in the range of 20 something kilos :-)



thanks for all replies!!

Steffen

stepdown 230V --> 220V ???
« Reply #13 on: July 22, 2005, 07:29:09 AM »
Quote from: "martthie_08"
I still haven't done any work yet, but thinking about it, I am sure now that I want do get it done the way Steffen did. btw. Steffen, I wanted to look at the racking of your V76, but the pictures aren't there anymore, so could you tell me how you mounted the "Trenntrafo"? Did you put it into an external box, or did you mount it on the outside of the rack chassis (like on guitar amps, for example)?


the trafo was inside the box but produced too much hum . so  a external box was the easiest way to get rid of it. (the box already weighed a ton, 1-2 kg+ iron for extra shilding was unacceptable)

I´ve moved to another webhost. my old diy sites can be found here soon:

www.diygallery.de

at least the picture gallery is online already :
http://www.diygallery.de/Galeria/index.html

steff

martthie_08

stepdown 230V --> 220V ???
« Reply #14 on: July 22, 2005, 08:40:32 AM »
ok, thanks for the info Steffen. Nice gallery, your gear looks really sweet! What is inside the Pultecs? Are they based on the Gyraf pcb circuit / layout? Tube or transistor make up stage?


 

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