Zener to trim 30v please

[rogb]

Hi
I have just fired up my 50w build and all is well apart from the B+. I have the MC 40-18029, line voltage 244v AC, 374-0-374 on the red secondary, so about 20v too high. B+ is 495v loaded. 493 on the plates of V4-5. Bias 30.5 mV.

I am adjusting the dropping string to get the B+3-5 down a little ( V1 pin 1 was 217v now 184v ) but I think I need to get a zener on the CT.

I have had a good look through Mouser but I am having trouble finding a suitable zener with the right power dissipation and reverse cathode.

I have a Mouser order going in soon so any help would be appreciated if you have used the zener method before.
Thanks

[markusw]

On a recent 100W build I used a couple of 1N5333 5W 3.3V Zener diodes in series on the CT to drop the voltage. I mounted them on a small PCB.
They do not get warm at all.

Regards,

Markus

[rogb]

Thanks Markus, how about I order some of these:
http://uk.mouser.com/Search/ProductDeta ... 1N5347BRLG

10v 5W zeners and mount them say 3 in series to a little board then heatsink it to the chassis?

[M Fowler]

I'm used to old style (DO-3) through hole 50w 30v reverse zener diode by NTE. Now days they have different style available.

http://www.mouser.com/ProductDetail/NTE ... tosHxdc%3d

Which you can find at Newark and other places. http://www.newark.com/jsp/displayProduc ... 90220|plid|

[rogb]

Mark, I was just emailing Mouser with that part number!
not available in my area WTF???????

[markusw]

Thanks Markus, how about I order some of these:
http://uk.mouser.com/Search/ProductDeta ... 1N5347BRLG

10v 5W zeners and mount them say 3 in series to a little board then heatsink it to the chassis?

I guess that 10V 5W Zeners should be able to dissipate the heat too. I have a tendency for overkill which is why I used 3.3V 5W Zeners.

I'm used to old style (DO-3) through hole 50w 30v reverse zener diode by NTE. Now days they have different style available.

I completely forgot about using a panel mount Zener. The reason why I used the string of Zener diodes was that I wanted the flexibility to adjust the voltage depending on the number of zeners used.

Regards,

Markus

[Structo]

I used a 50w stud mount Zener on my little 6V6 Rocket.

The PT is from a organ and it was about 30v high.

Man, that thing gets pretty hot.

Don't skimp on the power rating!

[rogb]

I just heard from Leanne at Mouser and they won't ship NTE parts outside the US - no explanation.

I registered with Newark and went to pay the $27 for the part NTE5268AK but it said shipping would be added later with no indication of the cost so I cancelled that one for now.

Guess I will just have a high plate voltage for now, B3-5 on the PPS is good, though.

Sounds great too

[rsi]

There's a couple of places (non-Mouser) I have bought high power stud mount zeners from, if you are having problems. I have no idea why they wouldn't ship an NTE part to the UK.

These 2 places will have something you can use.

www.expediters.com

You need to have a part number to find things at Expediters.

http://www.surplussales.com/index.html

You can browse by type here.

[rogb]

There's a couple of places (non-Mouser) I have bought high power stud mount zeners from, if you are having problems. I have no idea why they wouldn't ship an NTE part to the UK.

These 2 places will have something you can use.

www.expediters.com

You need to have a part number to find things at Expediters.

http://www.surplussales.com/index.html

You can browse by type here.

Thanks I have contacted Surplus Sales for a shipping cost for 1x 50w 30v Zener. 1N3324RB


Thanks again

[ToneMerc]

I just heard from Leanne at Mouser and they won't ship NTE parts outside the US - no explanation.

NTE currently doesn't have a UK distributor at the moment looks like, not sure if that has anything to do with it. You might want to try Farnell, I believe this is the cathode case equivalent to NTE5268AK.

http://uk.farnell.com/solid-state/1n332 ... tt=1n3324b

TM

[rogb]

I just heard from Leanne at Mouser and they won't ship NTE parts outside the US - no explanation.

NTE currently doesn't have a UK distributor at the moment looks like, not sure if that has anything to do with it. You might want to try Farnell, I believe this is the cathode case equivalent to NTE5268AK.

http://uk.farnell.com/solid-state/1n332 ... tt=1n3324b

TM

Thanks TM, it needs an "R" to denote reverse polarity.
I already looked at that from Farnell but they charge £16 ($25) shipping for one item if it is not UK stocked. plus $24 for the part
Hope to hear back from Surplus sales -$15 plus I hope a reasonable shipping charge.

[M Fowler]

http://modulusamplification.com/DIODES- ... ?sid=12886

[rogb]

Thanks Mark, I hope to go with the 50w stud zener as soon as I hear back from the surplus guys.

When this gets buttoned up I am starting on the Marshall 50w - gonna ABY the 2 50w amps

[rsi]

Weird, as it turns out, i have a 1N2824B sitting on my desk.

I think it's a 50W 33V stud mount zener.

If you strike out with Surplus Sales let me know.