TW Express -Pacific transformers and voltages

[rhinson]

when specing at n.l., they usually add a few volts extra to compensate for idle drop. rh

[RJ Guitars]

It seems that we are attempting to match the exact transformer voltage and/or the exact B+ voltage on a few measured and documented Wrecks, without documenting and tweaking the voltage on the actual plates of the tubes? Tell me if I am wrong but it seems the dropping string and plate resistor values are always the same no matter what the transformer voltage is.

They have done extensive work at reviewing and documenting this on ODS amps over on the Dumble Discussion pages, and it is common to make resistor adjustments to dial things in to given voltage values on the plates. There does not seem to be an equivalent reservoir of information or concern for this practice here on the Trainwreck side of the fence.... is that true?

We know that resistor values vary and also that the plate voltage will change with each tube swap, so it seems inadequate to simply declare a critical voltage for a transformer but pay no attention to how that voltage differs at the tube?

Do we have a table of ideal plate voltages?

Does the transformer voltage matter more than the plate voltages?

rj

[Richie]

There does not seem to be an equivalent reservoir of information or concern for this practice here on the Trainwreck side of the fence.... is that true?

It does sound like it,but if you use the right transformers,then you should be in the ballpark with the voltages. I know some amps,people may bias different,or maybe a different tube might change the voltage a little, but i think you'll still be within 5 to 10%. And here in the USA, the wall voltage may be much different state to state,and that to would change things.

I have made a few wreck amps that used about 455 to 460 plate volts.
And i did adjust the dropping resistors to have the PI and preamps come out to the correct voltages. But yeah, probably not much info on things like that on the wreck amps.

As far as the topic, it seems the poster may have got a PT for the rocket/liverpool instead of the Express. Although the pacific don't have a recto tap at the moment that i know of.

[M Fowler]

The poster got his trannies directly from Pacific for 220v/240v for an Express based on them stating that these are the correct TW Express PT/OT for the Express.

Even the PT I got from Allyn has two voltage taps, they can't be just 300-0-300 only.

Mark

[rhinson]

The poster got his trannies directly from Pacific for 220v/240v for an Express based on them stating that these are the correct TW Express PT/OT for the Express.

Even the PT I got from Allyn has two voltage taps, they can't be just 300-0-300 only.

Mark

the original poster only got a 240v trannie, from his post---he didn't say the trannie had a 220v tap or had dual windings so that you could get 220v. and the very next poster said the voltages he's getting are correct with putting 220v (his wall voltage) on a 240v winding. there was probably some misunderstanding involving his wall voltage when he ordered the trannie orginally and just got the wrong one. pacific may not have a specific "export" version of this on file, although they should make make a standard one and keep in on file-----just like they have for the boutique amp companies they make stuff for. if you put the correct voltage on the pri, you'll get 300-0-300 n.l. for the main hv sec winding.
rh

[M Fowler]

@Paulster
Thanks for your data, my target is to get the one from schematics.
We'll find a way:-)

So, if anyone will use this PT from Pacific with code 32310:
primary 240V
secondary 280-250-0-250-280
...with 220V supply from wall outlet you won't get B+1 395V!
I'll check with 240V supply instead of 220V.
It's 10% difference, hopefully it'll match 585V AC sec. and 395V B+1.
You'll get report end of week.


regards

It seems that Reverbus has yet to try the 240v tap.

Mark

[Roe]

how does the trannies sound comparred to the ceriatone trannies?

[M Fowler]

Roe,

I see you list some nice amps.

In my case a Ceriatone built Express it is bright and frigging loud.

The Express I built has a nice darker usable tone for my purpose and still loud but I can use the brite switch with this Express. I actually can with my Ceriatone after I changed the tone caps t0 .033 and 500pf to 250pf I think, its been a while.

[dartanion]

Ceriatone transformers will work fine, however the OT is tonally not up to par with either the Heyboer/Toneslut or Pacific OTs. They have a Marshallesque quality to them that is not very Train Wreck-ish.

The Ceriatone PT works fine, however the square bell covers and how the chassis is drilled for the PT makes the PT interfere with using a standard Tolex cab from the many different cab builders. Unless you specify no back panel and no cleats for the back panel. Maybe things have changed from a few years ago, but maybe not.

Nik's kits are a tremendous value and he provides good customer service. If you want to do a Ceriatone Kit, I suggest the kit without transformers. This saves a bundle on shipping, and you get to choose which transformers to use.

[M Fowler]

Gabkits is the stock cabinet builder for USA market of the Ceriatone amps including the Express.

I did indeed have transformer spacing problems with my Gabkit cab which Gabkit said they told Nik about my problem and others that he needs to move the tranny over a bit. It is a tight squeeze and hits the back panel mouting block on the side of the cab. I modified my mounting block to fit and it is still a tight fit.

I plan to make a new cab more TW tradional and use another 17 inch chassis in that Gabkit head cab. Recycling is good right.

Mark

[dartanion]

FWIW, I communicated this issue to Nik a couple of years ago. I modified one cab by changing the cleat, then on the others I just relocated the PT and OT so there would be no clearance issues. These were kit builds that I was contracted to build, so it was simple enough to just eliminate the issue. Alternatively, I am sure StageCraftGear, Gabkits, Swanson, Mather and others would be happy to build cabs without back panels and rear cleats. Might even save you some bucks.

[reverbus]

As prommised, here is report with Pacific transformers TW Expr.:
PT 32310
OT 25525

Mains AC (wall outlet V=220V) - increased with variac:

1.
(Measured with standby switch on, no input signal)
Mains to pri.: 230V (not high enough)
Output on sec.: 567V
B+1 378V
B+2 364V
B+3 290V
B+4 273V
B+5 259V
Heaters=6,38V
Bias -32,3VDC/43mA

2.
(Measured with standby switch on, no input signal)
Mains to pri.: 240V (O.K.)
Output on sec.: 598V
B+1 391V
B+2 382V
B+3 303V
B+4 284V
B+5 269V
Heaters=6,65V (hopefully not too high?)
Bias -32,9VDC/43mA
*Plate&screen voltage EL34 (JJ): pin3=391V; screen pin4=373V
*Plate voltage PI V3 pin1=189V; pin6=189V
*Preamp plate voltage V1 pin6=177V; pin1=201V; V2 pin1=253V

This is now closer to schematics.
So, using Pacifics PT 32310:
Their schematics shows pri.240V/ sec.:280-0-280
If you connect 240V to primary you'll get close to 600V on secondary.
If you connect 220V or 230V to primary, secondary voltage is not reaching 585V as from orig.schematics.
You need 240V, maybe volt or two less will also be enough to get 585V.
I'll build Vintage Voltage Adapter to boost Mains AC from 220V (Wall outlet) to 240V.

OT 25525 (6k6) is, as sounds, main reason for pretty big difference-comparing with sound before.
My Express is Ceriatone's, but both transformers were from our local supplier.
Amp is now less loud, sounds more chimy, more harmonics...I'm in right direction
Next step will be change of power tubes to Siemens NOS, and playing with V1,V2,V3.
Finaly - capacitors - waiting for Allyn's shipment.

regards

[rhinson]

As prommised, here is report with Pacific transformers TW Expr.:
PT 32310
OT 25525

Mains AC (wall outlet V=220V) - increased with variac:

1.
(Measured with standby switch on, no input signal)
Mains to pri.: 230V (not high enough)
Output on sec.: 567V
B+1 378V
B+2 364V
B+3 290V
B+4 273V
B+5 259V
Heaters=6,38V
Bias -32,3VDC/43mA

2.
(Measured with standby switch on, no input signal)
Mains to pri.: 240V (O.K.)
Output on sec.: 598V
B+1 391V
B+2 382V
B+3 303V
B+4 284V
B+5 269V
Heaters=6,65V (hopefully not too high?)
Bias -32,9VDC/43mA
*Plate&screen voltage EL34 (JJ): pin3=391V; screen pin4=373V
*Plate voltage PI V3 pin1=189V; pin6=189V
*Preamp plate voltage V1 pin6=177V; pin1=201V; V2 pin1=253V

This is now closer to schematics.
So, using Pacifics PT 32310:
Their schematics shows pri.240V/ sec.:280-0-280
If you connect 240V to primary you'll get close to 600V on secondary.
If you connect 220V or 230V to primary, secondary voltage is not reaching 585V as from orig.schematics.
You need 240V, maybe volt or two less will also be enough to get 585V.
I'll build Vintage Voltage Adapter to boost Mains AC from 220V (Wall outlet) to 240V.

OT 25525 (6k6) is, as sounds, main reason for pretty big difference-comparing with sound before.
My Express is Ceriatone's, but both transformers were from our local supplier.
Amp is now less loud, sounds more chimy, more harmonics...I'm in right direction
Next step will be change of power tubes to Siemens NOS, and playing with V1,V2,V3.
Finaly - capacitors - waiting for Allyn's shipment.

regards

yes if you put 240v on the pri. you'll get around 600v (ie---300-0-300) on the hv sec----this is what it should be. the schematic for the trannie lists it as 280-0-280@300 ma----in this case it means it'll drop to 280 on the hvsec ac if 300ma (full draw) is applied. this is just how some places choose to rate their trannies on their spec sheets. others may just give the n.l. voltage, etc. you should always ask them to build you one based on the wall voltage in your particular location----it would have been no problem for them to have put a 220v tap in there while they were winding it, or do a dual pri. with taps for several export primary hookup options. rh

[reverbus]

Thanks rhinson!
I didn't know that...
I was sure that at prim.240V - sec. will show 280x2=560V, as show their schematics.

PT is pretty warm at 240V pri. - it wasn't case before, with different one.
And one more info for Ceriatone's Ex. - both trannies are fixed in original holes - no changes needed. Only - PT is few mm fatter then prevouis one.

[paulster]

I think this also shows that it's essentially a 300-0-300V transformer as expected.

It's a shame that the European 230V 'standard' is only a standard in name and not implementation as you've got 220, 230 and 240V in different countries all labelled as 230V.

Not that it makes any difference for most consumer products that step the voltage down, but for those of us that step it up it makes a big difference!

My wall voltage is 250V in the quiet periods which is great for a really healthy dose of B+!