new express power up problem/question

[pinkmarkos]

hello- I have just finished wiring up my express and I was hoping someone with experience can help me troubleshoot some things. this is my first ever build so I'm not a skilled troubleshooter yet. these are the voltages i've got so far:

Mains: 122 VAC (The pilot light comes on)
Secondaries: 304 VAC at each yellow PT secondary (this is OK right?) The build guide states I should be getting 585 total here.
B+1- 420 VDC
B+2 - B+5- I am not getting any voltage at all- not sure why...
Heaters- V1 pin 1- 3.1 VAC, V1 pin 9 3.1 VAC- this is OK if it adds up to about 6.3 right?
Max negative bias voltage- -35VDC
I am not getting any voltage at all anywhere else (i.e. plate or screen voltages)
Does the amp have to be off standby to measure the voltages accurately? I haven't taken it out of standby yet. I will post pics ASAP- hopefully tonight.
I hope this is enough information for someone with experience to help me troubleshoot.
Also, I thought I had the impedance switch wiring figured out, but my only question is this- on the layout there are two black wires from the lug behind the the 16ohm lug- one goes to the speaker jack and it looks like to the other one goes to a lug behind the other 16 ohm lug. On the switch, there is no lug behind the other 16 ohm lug. It is impossible to see where it goes on the francesca pics, and I cant tell from the schematic. I don't want to fry mt OT, so any help would be much appreciated.

[guitarsnguns04]

can you post any pics? as far as the impedence switch there are jumpers on to other lugs and a 100k fb resistor on the 8 ohm tap..not sure if thats what you are referring to though..good pics would be very helpful for your build

[guitarsnguns04]

also you could you specify if you have tubes installed or not..are you using a light bulb limited at startup etc

[billyz]

The Standby switch must be closed to allow voltage to the rest of the circuit.

[paulster]

Billy is correct. The standby switch is placed between B+1 and B+2 so you'd expect to have B+1 and negative bias only with the amp in standby mode.

The negative bias is always active to ensure that your bias voltage will be there before the B+ hits the tubes.

[gearhead]

Need to measure between the secondaries, and not each one to ground. Same as with the heaters.

Without the standby, all you have is current going to the first set of power caps, which charges them up, and the heaters.

When you flick off the standby, there will be a slight drop in the B+1 voltage, and will get measurable voltages on the other B+'s.

Suggest you go through the no-tube, light bulb limiter routine.

[johnny riff]

pinkmarkos wrote:Heaters- V1 pin 1- 3.1 VAC, V1 pin 9 3.1 VAC- this is OK if it adds up to about 6.3 right?
The heaters are pins 4-5 and pin 9 on the pre-amp(12ax7)pin 1 is the plate.you might want to check the pin out for the 12ax7.yes they should add up to 6.3v+/- a 1/10th or so.

[fishy]

First ever build.... cool , welcome to the club.
Make sure you understand what you are going to do before you flick the switch. That is just as important for an experienced builder as it is for a first time builder.

Regarding the impedance selector. It sounds like you are confused over the Stackpole switch.
If you refer to the posted layout in the files section, it should clear things up for you.
If you are using a different style of switch and are confused on how it needs to be wired, pictures will really help.

In general, pictures of your build will give people the opportunity to sanity check your build which might save you time and money.

[pinkmarkos]

wow= thanks for all the feedback. you guys have answered a lot of my questions. first- i must be having some kind of pinout dyslexia or something- yes i am measuring the heaters at pins 4 and 9 at V1. i have not installed any tubes yet, and i am not using a light bulb limiter. i tried to use one, but i must have wired it up incorrectly (fireworks), so i decided not to use it.
so now- i have 610 VAC between the secondaries and 6.5VAC at the heaters. as far i can tell, this is actually where i should be without power to the rest of the amp. i will try to get some pics up soon- i can't find the cord for my camera. warning- first build alert- lead dress not the greatest, but i think it looks not bad overall. not as good as most of the other amps i see on the forum, but i'm not going for aesthetics here.
i believe i have the impedance switch hooked up correctly- but my only question is where is the other end of the white jumper in this pic? (not my build) - otherwise i am understanding this. thanks again for the help

[pinkmarkos]

here are pics- like i say, obviously a first build, but i traced the layout twice and i don't think i missed anything, but i easily could have. thx

[johnny riff]

the build doesn't look that bad,nice job.check out what you have at the plate pin3 on the octals as well as the control grid pin5. there wants to be negitive voltage(bias)-30 or more.

[pinkmarkos]

i am getting -29 VDC pin 5 on the octals

[pinkmarkos]

hello again- thanks all for the assistance already rendered.
i have now installed tubes with no major problems except for voltages on V1 and V2 that are way too high (these are known good tubes BTW)
here're the voltages i'm getting (with expected in parenthesis):
V1a plate VDC 353(210), cathode VDC 10.7 (1.9)
V1b plate VDC 353(182), cathode VDC 5.78 (1.5)
V2a plate VDC 354(267), cathode VDC 6.1(2.
V3a plate VDC 230(190), cathode VDC 42(41)
V3b plate VDC 238(193), cathode VDC 42(41)
V4+5 plate 412 (415), screen 406(397) , bias VDC max -36, min -27
all heaters 6.3VAC
B+1 413 (420), B+2 408 (405), B+3 through B+5 353 (317, 298, 283)
Is it possible the problem could be with the 9K1 resistors somewhere? Everything seems to check out before that, and I'm not getting any voltage drop across R27 or R28. I will switch them and the jumpers out, hopefully this will help the voltage problem. Any input would be very appreciated- Thx

[paulster]

You haven't got your jumpers going diagonally the wrong way when working on the underside of the board, have you? That would move all of the B+ points up one stage effectively and leave the B+5 resistor out of circuit.

If you're not getting a voltage drop across at least one of what I assume are the 9K1 resistors then this could be it.

[guitarsnguns04]

you should get some heatshrink on the leads on r18 and r19..pin 5 on the power tubes. They could ground easily and actually may be shorting to the output jack in the pic above..hatd to see though. I agree though..check jumpers on r26-27-28 best of luck and keep us posted