Eden wt 400 issues

[Enzo]

When you "check" those zener diodes, did you just subject them to the diode test on your voltmeter? The only real test of a zener is to run current through it and see if it "zenes" at the 12v. it may act like a diode just fine at the voltage your meter uses. That doesnlt mean it works as a zener.

[Jazz P Bass]

I simply love that technical term.
"zenes".

[Enzo]

Ah well, my degree is in communication, sometimes I try to make it work for me.

[ibanez7]

wt 400

Hi guys thanks for all the help,I'll check those vlaues and get back to you with the readings

[ibanez7]

Eden WT400

Hi Guys,
Think I've found the problem,its the 12v zener (D13),it shorted,but I cant recognise the value on the part,it looks like 1n4742 or 1n4142,any help? once i replace it hopefully tonight I'll give my results,thank you again

[Jazz P Bass]

1N4742 is a 12V 1 watt zener diode.
1N4142 is a schottky diode.

[J M Fahey]

1N4742 12V zener

[ibanez7]

Eden WT400

Hi there,
I've replaced the tip32,the two zeners the 12v and 15v,replaced the caps c9 47uf and c36 1000uf,and also the 1n4003 diode,last check i did was on the tube socket.here are the readings. on the tube socket.if this might be of any assistance,still getting 11.1v on the heater,is that enough?

Voltages from
4 to 9 = 5.5v
5 to 9 = 5.6v
1 to 3 = 59.4v
6 to 8 = 59.5v
2 to GND = -3.4v
7 to GND = -3.4v

[J M Fahey]

Excellent.
11.1V will work but is a bit low; I always found a "12V" Zener there a bit low, specially since you lose at least 700 mV through the TIP base.
Use it as-is, but whenever possible replace that Zener with the next higher up ¿¿1n4743???.
My bread and butter Zener is 1N4744 which is 15V, so I guess the intermediate one *should* be what I suggested, anyway Google it.
Congratulations, don't forget to post your results.

[ibanez7]

Wt 400

Hi there thank you for your response,one more question,where would I put my dmm meter leads to set the bias voltage on this diagram

[J M Fahey]

As stated on the schematic, DMM scale 200mV DC , Black to (B) point which is where the 2SA1494 emitter joins a .5 ohm power resistor; Red to (A) point, where the 2SC3858 touches a .5 ohm power resistor.
You are measuring the voltage drop across two power resistors that are in series.

[ibanez7]

WT 400 PSU Board

Hi There,
the pSu board on my wt400 has four 4700uf 80v caps,would I benefit by replacing them with 10000uf 80v,by giving me some extra headroom/output?

[J M Fahey]

It may pay, *only* if the new ones are the same size (or almost so) , meaning they drop in, no major surgery.
The difference will be audible (a better PSU never hurts) but not that much.
More power? A little, not noticeable.
Most notable will be cleaner bass. You might even *think* there's less of it, because of reduced ripple.

[ibanez7]

wt400

Is there any mod I can do to get just a little more headroom/ouput?

[J M Fahey]

Use bigger, meaner, louder speakers. What are you using now?