Express Build

[steve_p]

So I just got an express build fired up.

Things seem pretty good, but is seems my voltages are a tad off. Any insight is welcomed. Don't mind the extra long OT lead on V5 or the pilot light not hooked up....

Wall Voltage: 120VAC
PT Secondary: 596VAC
B+1: 396.7
B+2: 380.7
B+3: 304.4
B+4: 287.1
B+5: 272.4

It seems a touch strange that my secondary is about 10V higher than the voltage chart lists as nominal, but the remainder of my voltages are all 10-20 Volts lower than nominal. Is this something I should worry about, or just play it and enjoy?

At the moment, tubes are RFT EL34s and a mix of JJ and Electro-Harmonix 12AX7s. Next step is to pop in some NOS goodies in the preamp.

Only played it a for a few minutes, but it definitely sounds good.....

Pictures:

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240438.jpg[/img]

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240432.jpg[/img]

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240433.jpg[/img]

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240434.jpg[/img]

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240435.jpg[/img]

[IMG768]http://i674.photobucket.com/albums/vv10 ... 240437.jpg[/img]

[cbass]

Waht is your voltage on pin5 of your power tubes?How much current are you're power tube s drawing?If they are biased hot that will pull your B+ down some.

[steve_p]

Bias is set at about 42mA.
Pin 5 measurements are about -38.5V.

Forgot to add one question to the masses:
Is it a problem to leave the 1ohm cathode resistors installed vs the Stock jumpers?

Thanks

[ampgeek]

Nice looking build!

No problems leaving the 1ohm installed. You might want to tighten them up a bit and/or put some heat shrink on the leads just to be safe.

You might also want to do a quick experiment. Measure the power tube cathode current on each side while playing. Many have reported (me included) an ~2X higher draw on one side when whacking out a power chord. My understanding is that this is normal. But..it is enough for me to want to rotate my nice, NOS EL-34s after each gig to get even wear!

Enjoy,
Dave O.

[martin manning]

You don't say which PT you are running, but from the lead colors I'm guessing Pacific. Your voltages look very similar to my recent Express build using that PT.

[steve_p]

Hi Martin,
Sorry bout that, I am using heyboer trannys for this build. I am using the
300-0-300 taps.

I can't remember off the top of my head, but what is the voltage on the pacific? I thought it was only 280.


Steve

[martin manning]

I measured 306 unloaded on the secondary I'm using, if I am remembering correctly. There are two sets of taps on the Pacific.