gyraf pultec build in the 110v (us) and transformer heat

[cwatkins]

Does anyone have part numbers/sourcing information
for the transformers used on their builds of the gyraf
pultec in the US, that doesn't overheat after say a 4 hour
session?

I've tried several transformers and although it all works, they
just get way to hot and eventually burn out. I've built two boards
now and I did see a couple other people mention heat issues,
so I'm hoping I've done nothing wrong, but that maybe somebodies
figure it out.

I'd love to rack this thing and build a couple more, but I fear one
day I'll leave it on overnight and comeback to a molten wad of goo.

 

[pucho812]

have you tired installing a fan. can get them small and cheap.

ON my bom that I have try

LL5402 Lundahl Transformers. can get them from KandKaudio in the states.

 

[cwatkins]

I mean the power transformers, the audio output transfomers are fine.

And as far as a fan goes, there is only one in the control room, and it's
quiet and not on very often.
and I'm still going for a quiet transformer if at all possible.

but fan's in the control room, over my dead body.

I built a machine closet for that, but to open the door to adjust
the eq, is not gonna work, plus it's not exactly cool in there.

 

[pucho812]

doh. MY bad. try this

http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=196&M=62062

 

[cwatkins]

Well, I looked at those but there are no 6.3v?

 

[cwatkins]

Eureka!

Yes, You can use two 62082's (I'm sure the smaller one in chuck's spec will work too, I suspect.) Just use the second one in series on both sides,
plug it in so that: it's set for 220 and you use the "center tap", I guess
(I was guessing, and it works.)

No noise, no hum, no heat.

So pleasant!

And not near as messy as the pc mount either! I think it was that the 110v ones were saturating, and that pcmount one must not quite have
had it or something? don't know but the 62082 with center tap in series
nailed 230v right off, which I couldn't get to save my life with the other
transformer and has no heat or noise whatsoever. Plus now there is no
circuit noise either.

Yes!

 

[gyraf]

Good we got that one sorted!

 

[ChuckD]

Ah ha!!!

I just replaced mine as decribed above and no more heat!!
No more hummm (well really not an audio hum but a chassis vibration)

Great ! Thanks for solving this one.

-ChuckD

 

[cwatkins]

I'd be really interested in what your noise floor is.

 

[Zee1usa]

I am going to buy some power transformers soon for my 2 units.

It is great that you discovered that 2 transformers works to eliminate heat and noise.

Should'nt I just be able to find a single transformer that can handle a higher current rating...lets say double of what the 1 will do?

:? Z

 

[cwatkins]

I asked gyraf about that...but..

They all looked like $100+, I was going to go that route, didn't really find one that had 220v and 6.3v.. then someone
pointed out using the same transformer's we already had and I'm like, well, that's great but they don't do 6.3v..

then I went back to the manual and went, well, screw it, I'll be dangerous, lets try to center tap this sucker backwards and get 6.0v and it was sweet. I'd never seen myself get anything near 220v out of those two transformers..

I'd shocked myself so many times at the 300v out of those caps, blown up the bottom of the board, the rectifiers, burnt out transformer, I was *going* to make it work.

Now I just have a tinyweeny bit of noise a little gain issue.. But I suspect everyone else probably will have perfect units. I'm a bull in the china shop newbie, It will always be rev2 of a build of mine before it's absolutely perfect.

 

[Underthebigtree]

Hi folks -

I'm nearing initial completion of my Gyraf Pultec, and am ready to wire up the 2 Amveco 62082 transformers. I'm still a bit fuzzy on how this wiring is supposed to go. Could anyone who has successfully wired this pair of trafos give a wiring diagram, or perhaps simply a description of which wires go where by wire color?

Many thanks,

Nick

 

[cwatkins]

I just recently answered, last week, I don't have the post handy though.
probably should meta it it soon, the bugs are almost worked out...

 

[Zee1usa]

[quote author="underthebigtree"]Hi folks -

I'm nearing initial completion of my Gyraf Pultec, and am ready to wire up the 2 Amveco 62082 transformers. I'm still a bit fuzzy on how this wiring is supposed to go. Could anyone who has successfully wired this pair of trafos give a wiring diagram, or perhaps simply a description of which wires go where by wire color?

Many thanks,

Nick[/quote]

Hi nick,

My name is nick also. I was a bit confused at first , but soon realized that it was a very simple task. Look at the PDF document on Gyraf's website.
It shows very clearly how it wires up. 120VAC in to the first Xformer which is stepped down to 12VAC to the pcb then from the pcb 12V into the 12VAC connection on the second xformer which gets stepped up to 220.
I will try to make a diagram soon and post it.

Z

 

[Underthebigtree]

Found it, thanks. For this first one, I'm just doing a mono Pultec (stereo version after I get this one working), so I'll just use your description without the 3rd toroid. The part that confused me was about feeding 12V to a primary that wants 115V or 240V, in order to get 220. Then the light bulb went off and I realized that the trafo is being wired in reverse.

Thanks again,

Nick

 

[Zee1usa]

 

[Underthebigtree]

OK, for posterity's sake:

I've had it running for 3 hours using a 100W light bulb current limiter, and there are absolutely no problems. There is no hum, no audible noise, and it appears to be working perfectly the first time out of the gate - an absolute first for me in DIY. There is no residual heat thus far, other than the expected heat from the tube, which is the same level as in other tube gear I have. The difference between my Pultec and the one in cwatkins' pictures is that mine is balanced, using a Lundahl input trafo as well as the output. Perhaps this accounts for the lack of noise or hum.

Rather than doing it the way cwatkins described, I wired up my 2 Amveco 62082's according to the manufacturer's wiring diagram, to get the voltages required in Jakob's schematic. I ended up getting a solid 246V directly off of the 2nd transformer that didn't fluctuate more than .2V.

www.amveco.com/Miniature_Low_Profile_Transfers_2.htm

According to them, you wire the primary in parallel for 115V, and in series for 230V. You wire the secondary in parallel for 12V (actually measured as 15V), and in series for 24V, which we don't need in this circuit.

I thus wired it like so:

Transformer 1: Stepping down from wall voltage (115-120V) to 15V:
Primary: yellow and red tied together, to white (neutral) wall AC input
black and violet tied together, from power switch tied to black (hot) wall AC input

Secondary: green and brown tied together, and red and blue tied together, to get 15V. This is soldered to the 15VAC inputs from trafo 1 on the main board.

Transformer 2: stepping up the voltage from 15V to 245V:
Secondary: green and brown tied together, red and blue tied together. These are attached to the 15VAC outs on the main board.
Primary: we want the primary wired in series to generate the 230V (245V in my case), so we tied red and black together, and cover them with electrical tape. Then we wire yellow to one of the 230V ins on the main board, and violet to the other one. Works like a charm.

Hope this helps someone!

Nick

And P.S.: This thing sounds freaking great. Really, really, really good. Hats off to you, Jakob, for providing this for us. You are amazing.

 

[cannikin]

Hey Guys;

This is a little off topic but where do you pull voltage from to power a simple On/Off LED?

This always eludes me.

 

[gyraf]

..from the heater supply - remember the LED series resistor..

 

[cannikin]

Thanks Jakob,

Looking at the schematic that would be after the LM317 & the 470R resistor?

As you can imagine... I'm a little clueless..... :grin: