PT questions for an 18Watt Liverpool.....

[gtrcollectr]

I have a set of iron for an 18 watt that I am hoping to use for a 2xel84 liverpool. Here are the specs on the PT:

120VAC 60HZ Primary
5.0 VAC 3.25A Secondary (Rect.)
6.3 VAC 3.25A Secondary (Rect.)
6.3 VAC 3.25A CT Secondary (Filament)
570 VAC CT Secondary (285-0-285)

I am a bit concerned about the voltage being to high for 2xel84. I have seen that most liverpools are 4xel84 and seem to use the 260 volt PT. if needed what would be the proper way to get the voltage in the correct range for this amp. Is there a way to calculate the voltage at b1 with the 285 from the PT.

I have read up on the ot and it seems that the 18 watt ot will work fine for this build.


Thanks in advance..

[dartanion]

That will work just fine. The difference is going to be that your output will be higher than with a 260-0-260 PT. If you need to reduce the B+ some, you can always put a couple of zeners in series to ground on your HV CT.

[gtrcollectr]

Thanks, What kind of drop can expect from the zeners? I don't want to get stuck in a situation where I am forced to run NOS tubes because of the voltages.

[Buschman]

Are you going to use a tube rectifier? You can easily drop voltages with a 5y3 but the amp will sag a bit.
I've also found that some new production tubes hold up better than nos as far as plate voltage is concerned.

[dartanion]

It depends on what voltage zeners you are using and how much voltage you need to dump.

Using a tube rectifier like a 5Y3 will add sag, which may ruin the character of the amp. However it will drop voltage.

[gtrcollectr]

I am running a ss rectifier, I am hoping about to get 330VDC at B+1. I am building per Mark Abbots schematic , but in a 2 tube layout. So those are the voltages I am shooting for. If I need 330VDC and the PT is 285VAC is ther any way to calculate where I might end up after rectification? And if its way high what zeener I would need to use to get the required drop? I just want to get this right the first time......

Thanks Again

[paulruby]

Run a 5AR4 recto and you'll get about 350V. Use JJ EL84 and you're good to go. It'll sound great.

[paddy]

Hi there
I built a 2xEL84 Liverpool,had the same problem with higher than needed voltage on the secondary.I needed to drop about 60 volts DC and did this by using a couple of zeners in series with the centre tap.This works fine,just be sure to use sturdy devices that will handle the heat(mine bolt onto a small heat sink,mounted to the chassis.
As far as the O.T goes,I used a Heyboer 18 Watter and it sounds great

Cheers
Paddy

[withnail_jet]

Hi there
I built a 2xEL84 Liverpool,had the same problem with higher than needed voltage on the secondary.I needed to drop about 60 volts DC and did this by using a couple of zeners in series with the centre tap.This works fine,just be sure to use sturdy devices that will handle the heat(mine bolt onto a small heat sink,mounted to the chassis.
As far as the O.T goes,I used a Heyboer 18 Watter and it sounds great

Cheers
Paddy

Do you happen to have part numbers and a supplier you could share? I'm having problems sourcing the larger wattage ones (how many watts did you use?).

Thanks!

[paddy]

The part # for the zeners i used is BZV15-C30R.
It is a 30 Volt/15 Watt device.Place 2 in series to drop 60 volts.
I found mine in my junk box so i can't give supplier details sorry.
I just did a quick google search
and seems like they are still readily available.

cheers
paddy

[withnail_jet]

The part # for the zeners i used is BZV15-C30R.
It is a 30 Volt/15 Watt device.Place 2 in series to drop 60 volts.
I found mine in my junk box so i can't give supplier details sorry.
I just did a quick google search
and seems like they are still readily available.

cheers
paddy

hmm...I can't even find anyplace here that stocks that p/n. I'm assuming you're in the UK?

[paddy]

hi
try cavalierinc.com they seem to have them
cheers
paddy