I was thinking of about 20mA per leg with 4 legs for both channels.  There is some additional current required on the negative rail, I forgot how much, but I used 22mA x 4 = 88mA per rail.  I then multiplied by 4 which is a reasonable factor for power requirements on the transformer.  Some would suggest 5x.

 

So 88mA x 4 = 352mA which would give approximately a 250VA rating (not counting the LV of about 18VA).  For the Blue Hawaii I use 350VA transformers and sometimes more. 

Thanks a lot.

I've been really busy today. Below is KGSShv converted to Carbon with some daughter boards. The big one on left channel is servo Kerry style. Amp has been running for one hour and it seems to work.

 

 

IMG_1407.JPG

Wow, I didn't know this was possible. I presumed the KGSShv Carbon was radically different?

how do ToroIDY react to returns? 

 

Not well.  They just shrugged off when I asked how come 10 units of the same design have so wildly different behavior.  They also just love to put short leads on everything for some fucked up reason. 

Not well.  They just shrugged off when I asked how come 10 units of the same design have so wildly different behavior.  They also just love to put short leads on everything for some fucked up reason. 

Do you have a better source for transformers then?

As far as lead length goes, I had a feeling it might cause problems and asked for specific lengths for each wire, and Toroidy delivered.

Hello,

 

here in Norway, we have Noratel that makes transformers. They are used by some of the guys in the Norwegian forums, and they are really happy with them. They make transformers for high end amp producers, but are expensive..I thought about asking them for a quote.

 

The specs should be:

 

Transformer 450v supply:

Primary voltage: 120v/120v

Secondary voltage: 2x 360v/2x 200mA + 2x 15v/2x500mA

 

Transformer 400v supply:

Primary voltage: 120v/120v

Secondary voltage: 2x 335v/2x200mA + 2x 15v/2x500mA

 

Have i got this right? Might be better and cheaper with separate LV transformers.

Hello,

 

I've ordered a transformer with the spec:

Primary voltage 0-115-230V 50/60Hz

Secondary voltage: 2x 360V @350mA

                               18-0-18V @1A

Because I'm going to build the carbon with the 20mA outupt. Should I change the value of the resistor from 5.1ohm/3W to 3ohm/3W?

Thanks.

one of hte other expensive options is paul holden, his transformers seem to be the real deal

Hello,

I've ordered a transformer with the spec:

Primary voltage 0-115-230V 50/60Hz

Secondary voltage: 2x 360V @350mA

18-0-18V @ 1A

you might want something closer to .1A

you might want something closer to .1A

?

Edited July 31, 201511 yr by insanity

Hmm. 2 x 360V @ 1 amp = 720 watt transformer, and that's without the 36 watts from the 18-0-18 winding.

Edited July 31, 201511 yr by JimL

I meant the LV winding doesn't need 1A

Past advice on the LV winding seems to have been 500-700mA. Not 1A, certainly, but quite a bit more than 100mA.

A parts question,

 

Resistor 806K should use high operating voltage like VR37? but can't found on mouser. Only found RN65 but all found only working<500V.

 

Or use same parts 787K used on HV's PSU?

 

Thanks!

Ah.  Pesky decimal point 

Hello,

 

I've ordered a transformer with the spec:

Primary voltage 0-115-230V 50/60Hz

Secondary voltage: 2x 360V @350mA

                               18-0-18V @1A

Because I'm going to build the carbon with the 20mA outupt. Should I change the value of the resistor from 5.1ohm/3W to 3ohm/3W?

Thanks.

 

In the models the 5.1 ohm resistor should have a cut off of around 112mA.  At 20mA per leg you should be consuming about 80mA/84mA per rail. 

 

This should be sufficient.

 

Also, I just wanted to mention that the LV rails consume less than 8mA per rail for the amp section.  The op amp for the servo will consume a bit more (5-10mA) so you really don't need that much from the transformer.  100mA is plenty.

I only use 500mA because the difference in cost is tiny and I like overhead from transformers. 

Agreed

My jrc 7[8,9]15 were pumping out -/+20 v when I fed them a 24vac transformer which was labelled 18, after replacing them once already. Are these regulators toast? I wanted to double-check before I fuck up the PCB pads from desoldering

They should have handled that but I've never come across that issue. 

Could some please explain how to calculate the voltage of the testpoints on the new kgsshv carbon boards? On earier version 0.8v was stated. But that was across a 100ohm resistor and not a 50ohm one. Furthermore I don`t know what current that translates to. 

 

thanks

NoPants,

No need to risk a board if your desoldering skills arn't  that great, just  cut the leads.

Parts are much cheaper than PCB's.

What's the input voltage going to the regulators.  Seems like they are toast, but I'm curious why you've had to replace so many times.  There may be something else wrong.

If the input voltage is the same as the output, then go ahead and cut the leads near the body.  It's easier to de-solder that way.  As a general rule you should not apply heat for more than about 3 seconds (4 is a max for me).  Less is of course better.

thanks for the tips Kerry, I've been doing that- unfortunately the pads still come off sometimes. As of right now I'm seeing -/+ 17 or 18vdc , I measured it at the outputs of the diode bridge. its only the 7915 that has real problems. 7815 is showing the correct voltages

My jrc 7[8,9]15 were pumping out -/+20 v when I fed them a 24vac transformer which was labelled 18, after replacing them once already. Are these regulators toast? I wanted to double-check before I fuck up the PCB pads from desoldering

Other things to try...

Check the ground pin on the regulators  to see if they truly at 0V, best done directly on the section coming out of the package, the will account for any unseen PCB trace breaks, dry joints etc.

A 1/2W 500R-1K resistor on the output will pull a load current from the regulator, see if that gets it going.

Edited August 8, 201511 yr by b0bb