WEM Dominator/ Ch2 not working.

[Sea Chief]

Chaps-

Got a WEM dominator (mk1 bass it is, same circuit as mk3) here with a non working ch2.
Done the obvious tube swap from good ch1 and no joy.
Done giving the socket a damn good seeing-to also.

Nothing looks fried, or wires unsecure. Anyone know this amp? ideas where to start? thx SC.

[nickb]

Is this the one?



Do you hear any change at all when you twiddle the ch2 volume?
With the ch2 volume up what happens when you tweak the bass 7 treble controls?
Do you have any test equipment?

[Sea Chief]

Is this the one?

[ATTACH=CONFIG]25807[/ATTACH]

Do you hear any change at all when you twiddle the ch2 volume?
With the ch2 volume up what happens when you tweak the bass 7 treble controls?
Do you have any test equipment?

Hi nickb- yes thats the one great I was wondering how to get my one up.

Nothing happens tweaking Bass or Treble. Its a very dead sound/ zilch.

I do have a MM, and experience (but way moreso than knowledge of circuits). It does look fairly simple in there.

thx Chief

[52 Bill]

Nothing happens tweaking Bass or Treble. Its a very dead sound/ zilch.

The first test is to check for voltages. Check for high voltages on the plates of the preamp tube, pins 1 and 6. Then check for a small voltage on the cathodes, pins 3 and 8. The schematic is not marked, so compare the voltages to those of the working channel.

Make sure that you follow all safety guidelines when working on a powered on amp.

If the schematic is correct, then the driver/PI tube also needs to be checked. Try swapping that tube as well.

[Sea Chief]

Bill-all sorted..

I followed your checks & before even comparing to V1 (ok afaict) I read 0.08v on pin 1, and 346v on pin 6. So I followed my nose & read the pin 1 100k plate resisitor as open circuit/ plonked in a new carbon comp.. and ch2 good as gold!

{Blimey I wish all fixes were like this! 2 replies 1/2hr work, done... compared to my nightmare other amp: all of 5 weeks on it & still cant even find the prob!)

many thanks, SChief.

[eschertron]

Chief,

I am glad to read that your "satisfaction-to-time spent" ratio is increasing. You've had a few rough patches there.

[Sea Chief]

Indeed. I needed this fix! tbh the knowledge gained from my other pita amp threads meant I could apply some basic knowledge to this. Ie testing/ trying the plate resisitor 1st up.

Now tho its back to the pita amp.. shucks- what an utter arse.