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

[Hulk]

I'm working on another Gyraf Pultec - can I use two 2x12 30VA 220V toroids for the PSU??

 

[Hulk]

[quote author="Hulk"]I'm working on another Gyraf Pultec - can I use two 2x12 30VA 220V toroids for the PSU??[/quote]

Anyone??

 

[gyraf]

Hulk,

Look at the schematic:

It lists two 220:12V transformers, at 1.5A

I don't understand your question?

Jakob E.

 

[Hulk]

ehmm :roll:

I even build a Gyraf Pultec a few months ago and still I can ask without thinking :shock:

 

[martthie_08]

I've been looking around to find an answer for this smart ass question, but haven't been able to find anything, so here I go:

why does the line voltage get stepped down to 12V and then back up to 230V? Yes, the 12V are for heater I know, but I live in Europe, so couldn't I just rectify the 230V voltage coming out of my socket (with a fuse in between of course) for the B+ current and save a couple of bucks for the second tranny? I guess not, and I guess it it is dangerous or won't work, but can anybody tell me why?

 

[gyraf]

..would kill you if you touched chassis, as your psu 0V would be hanging off the mains voltage..

In the old days, some television sets and radios were done like this, because it saved an expensive power transformer. But these units HAD to be in all-insulated (wooden) cases, with no input/output connections referring to the chassis (antenna input was via a smal, cheap HF-transformer)

Don't even think of doing audio equipment like this..!

Jakob E.

 

[martthie_08]

bingo, that clears it up! Pretty crazy they did back then, but with all wooden enclosures, nice... Thanks Jakob.

 

[Hulk]

Can I use 220u/350V ELKO's for the Gyraf Pultec PSU - I don't know the difference between electrolyts and ELKO (if there is a difference)????

 

[gyraf]

same-same

 

[martthie_08]

In german, ELKO is an acronym for "ELektrolytischer KOndensator", so it is an electrolytic capacitor...

 

[cwatkins]

Hey it occurs to me that my grounding problem on the quad ssl is basicly the same problem I had here, is there a way we can bridge the 12v (it's dc after the rectifier right? could you potentionally connect them together there and save youself the 3rd transformer?

 

[Hulk]

I'm thinking about re-building my mono Gyraf Pultec to a dual Pultec with stereo pots and switches - I'm using Amveco 12V, 2,1A and Triad 6,3V 2A for the PSU - could I use just those two trafo's to power two Pultec's or will things "get too hot" :roll:

 

[yosh]

Does anyone know of someone who stocks the Amveco 62062 (or the 62072 or 62082 for that matter) other than Digikey?

The rumor is that Digikey won't have any for another 5 months or so. I want to buy two.

Thanks!

-Josh

 

[kafka]

Looks like Digikey also has plenty of the 62082's in stock.

Also in stock are the 62083-5, the 62075 or 62071, and the 62061 and 62064, which you should be able to use with only minor tweaking to the circuit.

 

[yosh]

You're right!

I don't know how I missed that. Thanks!

-Josh

 

[W DeMarco]

Hey Guys,

Just finished of my passive EQ build and Im noticing that the LM317 heatsink is real hot. Almost to hot to touch. Hurts after about half a second. It seems hotter than the tube right now. Is this normanl?

Thanks

Will

 

[gyraf]

LM317 will shut down by itself if it gets too hot. Try calculating the power dissipated as heat - that will show you if things are alright..

 

[W DeMarco]

Thanks Gman,

I also found that my audio signal got squashed when it reached the 1M resistor next to the bypass switch. Very low amount of gain after that switch. Not sure why but things are not acting properly. Any ideas?

Will

 

[W DeMarco]

Gyraf

Not sure how to make the calculations you we're speaking about. I left it running for several hours and it did not shut down. I get the feeling that its alright. Its hot but doesnt burn me.

I'm gonna get back inside later this week. I'll report finding then.

W

 

[gyraf]

I left it running for several hours and it did not shut down. I get the feeling that its alright. Its hot but doesnt burn me.

This is probably alright then - don't worry too much about it..

Jakob E.