[catalin]

Hello community! My very first topic around here.
Looking for a PT for my KT88 project I found a interesting choice by tt Maj 100pw with a current rating at 600mA. I already prepared a 600ohm/300W bench and 1ohm/100W to test its rated capabilities for couple of hours but before starting to "toast" it I wanna ask: Any experience with this power transformer at nominal rating (600mA) ? It is a reliable one, please? Thank You.

[Laurent]

April joke? 

[catalin]

Hope not. I really built a bench to test full rated specifications, including a temperature probe. It is weird didn't found for this model no VA specifications regards power capabilities. Any thoughts, please?

[Laurent]

The voltage coming out of the main secondary in full wave recto is too low (356x0.71=252V dc). For EL34 in a JCM??
Or CT is not used and you work with bridge recto. Then you get for usable current less: 600mA x 0.62= 372mA dc.

[catalin]

Thanks for You input. It is not a JCM application. Actually not quite.It will be more like: 356V times 1,41 Vpk times 0,707 Vrms for a bridge rectifier. Nothing more falsch. As I know in real world  AC references are rms (230V mains are 325Vpk), so I'll be more conservative to expect more like 475-480V DC around.

[catalin]

I opened this topic cause for me this transformer looks physical small to dissipate almost 300w in secondary side. It was claimed more efficient, more linear, highly performance....but still, nothing can replace the iron mass, so I have my doubts.
This are the specs:
Pri: 120V, 230V, 240V @ 50Hz
Sec1: 356 VCT @ 600mA
Sec2: 6,3 VCT @ 7,5A
Sec3: 98 V @ 150mA
Sec4: 12,6 V @ 1A
I already ordered one so I can test it myself in few days,but if You have any experience with it will be greatly appreciated.

[bea]

Well, the core material and its geometry may have a significant impact.

BTW: 490V rectified is not too large. I would tend to use that transformer preferredly with 6L6 rather than KT88 - at those voltages the 6L6 will deliver almost the same power as KT88s (and slightly more than EL34 can), At half the price of the KT88.

[catalin]

I have some preliminary measurements. With 230V on the mains and 6.8A draw from heather winding I got 366V no load and 6.12 over heaters. With 580mA draw with 610 ohm load got 352.5V and 6V over heaters. This is a realy very good regulation,  less than 5%. I think I will wind one or two turns over isolation to raise the heater voltage to 6.3-6.5V. Further test to monitor temperature conditions will follow. Thank you.

...and forgot to mention: it is absolute quiet, I cannot heard it at all

[bea]

6V is still within normal tolerance for the heaters.

[Hardcorebastler]

This are the specs:
Pri: 120V, 230V, 240V @ 50Hz
Sec1: 356 VCT @ 600mA
Sec2: 6,3 VCT @ 7,5A
Sec3: 98 V @ 150mA
Sec4: 12,6 V @ 1A
356 * 0,6A = 214 VA
356V AC  * 1,4 = 498V DC mit Brückengleichrichter
214 VA / 498V DC = 0,4 A DC

[catalin]

Thank you.